View Full Version : ALTEC 846B Trouble/week sound?


blzatrl123
03-31-2007, 02:27 PM
I just picked up a set of Altec Valencia 846B at a estate sale with a Dynco 150 amp,Pat-5 Preamp,Se-10 EQ,Fm-5 Tuner, and aEmpire turntable M# nowhere to be found. WHERE DO YOU LOOK? All for $220.00. The gentleman had told me that everything worked, Make a long story even shorter. One of the Altecs sounded week.The Horn was not working and the woofers Had no bass responce. I tried to turn up the high freq control and nothing happen. I then remved the woofer face plate and on the woofer is a white paper tag with these numbers 50-03 030767-01 416-82 is this the right speaker?:scratch2: I then hooked wires to the woofer and got sound but it seamed week even at a higher volumes, Is this because the woofer is out of the box?Or is it bad ,then I hooked up wires to the 806-8a horn,Nothing,No sound. I am hopeing that the horn can be repaired? Any advise would be great. The other speaker is SOLID great bass and mids. I hooked up the speakers to my Concept 16.5 and man did that liven those babys up. I would love to keeps these speakers, I like the way they sound .

Zilch
03-31-2007, 02:51 PM
I am hopeing that the horn can be repaired?You'll want to send BOTH of the compression drivers to GPA for new diaphragms and refurbishing.

Before doing that, though, assuming you give a whit about Valencias, put on a pot of coffee and read this thread at LHF:

http://audioheritage.org/vbulletin/showthread.php?t=14690

Yes, the WHOLE thing.

[Work in progress.... :p:]

blzatrl123
03-31-2007, 03:37 PM
Will do give me some time to read.

dgwojo
03-31-2007, 03:55 PM
Nice find, sounds like the crossover caps could be suspect if the horn blew the diaphragm, an easy fix, the woofer has to be in the cabinet for any kind of response. Normally I can repair those diaphragms in an 846b, the woofers are normally 416-8A or 416-8Z, and the horn drivers 806-8A's, the 846B is one my favorites. Warning, if you unsure of what you're doing, don't mess with the horn driver diaphragms, maybe read this first!! GPA Small Format Diaphragm Instructions (http://www.greatplainsaudio.com/SmDrvrDiaRpl.pdf)

blzatrl123
03-31-2007, 03:57 PM
Very interesting, SO i guess i need to get a pair if EV-T35's And yes i hear what those guys ar etalking about.I could back off the horn. Who is GPA? I need this person. Thanks for all the help.ENJOY THE SOUND

Zilch
03-31-2007, 04:08 PM
Very interesting, SO i guess i need to get a pair if EV-T35's
NO!! T-35s rather suck as tweeters, actually, as is documented in that thread.

And yes i hear what those guys are talking about. I could back off the horn.Think about it. How could that be a solution?


Bottom line: Valencias suffer a HF deficit. Integrating tweeters, even good ones, is "problematic." They will play full range with different compression drivers and HF compensation such as was used in Altec Model 19. We are evaluating candidate "upgrade" drivers. The cost may be similar to that of refurbishing the originals.

Who is GPA? I need this person.Dgwojo linked you there, above....

DynacoDave
03-31-2007, 04:37 PM
I replaced the diaphragm in my 846B's horn. No problem, easy. Cost was 23.00 is 1994 from a local Pro audio shop. The hard part was finding a diaphragm that was not for a pa horn. I usually run mine bi-amped with an active crossover, fed with a ST70 on the horns and a MosFet 120 on the woofers. I'd keep em. Cheers, Dave

blzatrl123
03-31-2007, 04:49 PM
Hey DGWOLPA thanks , Then what woofer do i have. I looked again and I have 416-8z woofers, my horn numbers are diffrent you have 802-8a I have 806-8a. What is the diffrence? Also i should look into my crossover caps? Can does be tested with a meter? JBL I would be interested in that upgrade and how it works.
Excuse me for the lag i am new at this.

Thanks

blzatrl123
03-31-2007, 04:53 PM
Dynco Dave, I think I will, The EQ is missing a channel, i need to get it fixed.The system puts out some power, But my Concept 16.5 kills it,More power. Are there any members who know how to repair Dynco equiptment?

As I said I am new at this . I am learning. I didnt understand how you where running your amps. The lingo is new to me,But thanks anyway,

blzatrl123
03-31-2007, 05:01 PM
HEY guys i have to go back to work boss calling, I iwll look for a responce and thanks for the input i learned allot to day.

dgwojo
03-31-2007, 08:25 PM
Hey DGWOLPA thanks , Then what woofer do i have. I looked again and I have 416-8z woofers, my horn numbers are diffrent you have 802-8a I have 806-8a. What is the diffrence? Also i should look into my crossover caps? Can does be tested with a meter? JBL I would be interested in that upgrade and how it works.
Excuse me for the lag i am new at this.

Thanks
Hi, I corrected my thread, 806-8A is correct, 416-8Z and 416-8A are the same except the A has a magnet cover, just cosmetics!! I'd remove the acoustic loading cap in those horn drivers, add felt dampening and new caps in the crossovers, the highs will be just fine if you're using the correct diaphragms and the magnets on the horn drivers are still well charged. Let me know if you need help repairing the phragm, I've had good luck repairing them, Dave.

PS - GPA = Great Plains Audio, Bill Hanuschak GPA (http://www.greatplainsaudio.com/about.html)

http://i86.photobucket.com/albums/k98/dgwojo/Altec_846B_NoGrills.jpg

http://i86.photobucket.com/albums/k98/dgwojo/Altec_846B_Components.jpg

http://i86.photobucket.com/albums/k98/dgwojo/Altec_N800_8K-1.jpg

http://i86.photobucket.com/albums/k98/dgwojo/Altec_846B_848A.jpg

Steve O
03-31-2007, 08:57 PM
That linked thread on the Lansing Heritage board is so long as to be almost un-followable. Too bad it couldn't be broken up into logical chapters for ease of comprehension. Anyways...

I see that the puzzle of the potted Altec N800-F is still not totally solved. I've had a few of those apart and reverse engineered the circuit and measured both the components and nominal response. My experience comes mostly from refurbing a pair of Altec Carmels. These use 2x12' 16ohm LF drivers wired in parallel @ 8 ohm with a 16ohm 511/806. Also, worked on a pair of Valencias. Based on this work, my observations:

The N800-F schematic posted on the LH board and reproduced below is not quite correct.
http://home.att.net/~steve.o.neill/N800F.jpg
The basic circuit is correct but the level control is shown as an "L" pad. Based on my experience and deciphering the comments from the LH board thread, the control is actually a simple 25ohm, linear taper pot used in a somewhat unconventional manner to partially simulate the constant input impedance input characteristics of a true L pad. The actual circuit is as shown below. It's a relatively common Altec xover topology from the late 50s/early 60s. This image comes from How to Build Speaker Enclosures by Badmaieff and Davis. The usual arrangement was for the control to be wired up as an attenuator so the "hot" lead going to the HF driver was connected to the CCW side of the pot. Thus max HF level occurs non-intuitively at full CCW rotation.
http://home.att.net/~steve.o.neill/N800F6.jpg
Notice how the the HF driver is connected to the pot. One of the drawbacks of this arrangement is that the input impedance is not constant. At max level with a 16ohm load the hi-pass portion of the xover sees 11.8ohms, 15.2ohms, at mid rotation and 13.4ohms at max atten. More about this a little farther down.

My measurements essentially confirm the component values in the first image above. I got ~3.1mH for the inductors with 0.4 ohm DCR. The lo-pass cap is consistently specd at 10.0 or 10.5uF. The hi-pass section is not consistent. I've discovered at least two versions. One uses 10.0 or 10.5uF which is sorta conventional and results in a nominal xover F ~750Hz assuming an 11.8ohm load. The other version uses a 4uF cap in the hi-pass section. This results in a xover around 1200Hz again @ 11.8 ohm. It also produces a calculated dip in response of > 3dB centered on 1200Hz. From date codes on the caps (1962 and 1963), the 4uF hi-pass iteration is the later one. Seems that Altec might have recognized the need to tame the mid range a bit and combined with the relatively higher eff of the HF driver, maybe a bit of simulated HF boost.

One other issue with the N800-F xover is that it presents a variable load on the hi-pass portion of the xover depending on attenuation, which in turn alters the xover point as well as the HF level. This effect is quite noticeable to my ears on both the Carmels and the Valencias. I simulated the electrical response of the xovers in the following two images. These assume 8ohm lo-pass load and 16 ohm hi-pass load and don’t include acoustic response. The show what happens in theory at max ccw , mid and max cw rotation of the attenuator.
http://home.att.net/~steve.o.neill/N800F_Plot1.jpg
http://home.att.net/~steve.o.neill/N800F_Plot2.jpg

Everything above applies to the earlier, potted versions of the N800-F. I have no idea what's going on with the later, unpotted versions. +The may indeed be using true L-pads for level control.

Considering how the N800-F was applied to the Carmel and Valencia and who knows what other models and impedances, I have to wonder if Altec was really paying attention the to the details back in the day. Or maybe it’s subtle genius. Regardless, I'm probably going to redo the Carmel xovers as 2nd order LR @1000Hz using actual impedances and not nominal, Will probably add some form of HF "equalization" too although not like the std Altec bridged "T" config.

Got any leads on where to obtain correct foam for LE14A, the “early” version with the reverse roll, lansaloy surround. None of four possible sources so far have been able to provide anything close. I’m leaning towards brake fluid. No lectures please ;)

Zilch
03-31-2007, 09:28 PM
Got any leads on where to obtain correct foam for LE14A, the “early” version with the reverse roll, lansaloy surround. None of four possible sources so far have been able to provide anything close. I’m leaning towards brake fluid. No lectures please ;)Don't know where my reconer gets 'em, and I doubt he'll tell me, but I'll try to get the answer. Best approach is a full recone, of course, as the spiders are usually tired and aged on the old ones, as well. Kits go on and off backorder routinely, but the wait is often months. They're only available through Harman Consumer, not JBL Pro, alas. I've done one pair with H-1 kits also -- nobody seems to know if they're "compatible," and I haven't measured them yet.

I will be indexing and reorganizing that thread to make the information more accessible. It's a collaborative effort, and playing out in real time. Latest posts show the behavior of factory N-800-F in comparison to one I built using a conventional 16-Ohm L-Pad today. The curves clearly show the consequences of the varying impedance in the acoustic response, including the HF boost at MIN attenuation. I can certainly see it happening on the RTA, and hear it as well, using a JBL LE85 driver, which becomes decidedly "crisp." It's not so apparent with the 806As I'm working with, which are not playing real well in the region of 10 kHz and above.

Yes, the mids clearly benefit from that small amount of compensation. They're too "forward" without it. Seems like the Altec engineers knew what they were doing, even if it was accomplished empirically.

I'm getting confirmation on the 25-Ohm pot vs. L-Pad question. Seemed odd to me that the legs are symmetrical, and the wiper doesn't run off the resistive element. Doesn't feel like it's wirewound, even. :dunno:

Thank you for the insight.... :thmbsp:

[You don't happen to have similar for the 8-Ohm 846B, do ya? ;) ]

jackgiff
03-31-2007, 11:11 PM
The basic circuit is correct but the level control is shown as an "L" pad. Based on my experience and deciphering the comments from the LH board thread, the control is actually a simple 25ohm, linear taper pot used in a somewhat unconventional manner to partially simulate the constant input impedance input characteristics of a true L pad.


Hi Steve,

You are correct, the part shown as an Lpad is simply a potentiometer. When I measured it, it was in circuit, and the readings varied depending on wiper rotation. I just didn't believe Altec would use a pot instead of an Lpad. But they apparently did. Taking the device out of the circuit shows it is not an Lpad. I have egg on my face.

We could use your input on the LH site.

Thanks, Jack Gifford

Zilch
04-01-2007, 03:30 AM
One of the drawbacks of this arrangement is that the input impedance is not constant. At max level with a 16ohm load the hi-pass portion of the xover sees 11.8ohms, 15.2ohms, at mid rotation and 13.4ohms at max atten.Using a 16-Ohm L-Pad instead, in the Altec configuration with wiper as input, I calculate the reflected impedances using nominals as follows:

0% attenuation, full CCW = 11.07 Ohms
25% rotation = 14.03 Ohms
50% rotation = 15.35 Ohms
75% rotation = 15.40 Ohms
95% rotation = 14.44 Ohms
(Disconnect at 100%)

If I'm correct, the L-Pad is somewhat better in this respect. I should measure it to see what's actually up, I suppose.

In any case, here's the measured acoustic response using the stock N-800-F with BMS 4550 and a parallel trap filter for compensation on the 811B horn. Jack's going to do the listening in Valencias as penance.... ;)

blzatrl123
04-01-2007, 08:36 AM
I do not mean to be stupid but does this mean that I need to upgrade my crossovers to something new.The way I understand it I blew my horn because of bad crossovers.Right? And i need to repair this. I wish i unserstood all of this. Iam learning every day

macaltec
04-01-2007, 09:21 AM
:lurk:

Zilch, in all of your testing of the 806 (and other Altec drivers) have you used this crossover or a close facsimaly? Still holding on to bit of hope.

bowtie427ss
04-01-2007, 09:37 AM
The way I understand it I blew my horn because of bad crossovers.Right?I don't see how that can be anything other than speculation until the crossover components have been tested to verify value.

Altec diaphrams USUALLY fail in one of 3 ways:

1. the lead in conductors (thin copper ribbon) fatigue and break, this is normal and will eventually happen to all of them over enough time and physical motion.

2. the aluminum surround fatigues and fractures, it'll sound like a horn full of BB's

3. the diaphrams thermal power limit has been exceeded (Pe), this can happen for many reasons, could be a failed cap in the Xover, could be excessive clipping from a SS amp, could just simply be from too much input.

EDIT: I should also mention that drifting capacitor values can also contribute to, or expedite reasons 1 and 2.

There are some other things that can happen, the most common being a dropped driver which can cause the pole to shift and misallignment of the coil in the gap, it rubs and shorts. Curious fingers sometimes damage them, mounting screws get sucked to the gap by the magnet.

Zilch
04-01-2007, 12:55 PM
Zilch, in all of your testing of the 806 (and other Altec drivers) have you used this crossover or a close facsimaly? Still holding on to bit of hope.The initial work was done using the raw drivers on 811B and 511A horns. Last week, I received factory crossovers from two members, and yesterday, I built one from scratch to verify the schematic. Here's the "best" 806A sample I have run on a factory N-800-F crossover and 811B horn, which, from what I've measured thus far, may well be representative of what Valencia owners are listening to. The black curve at the top is the raw driver and horn, so you can easily see what the crossover is doing.

Answer: Yes, the MF compensation Altec engineers built into the crossover improves the performance somewhat, but there's still nobody home in VHF, where it's down 10 - 15 dB, depending upon the attenuation setting. Compare to the result with new BMS, second. A pair of GPA-refurbished Altec Model 19 drivers will be here this week for evauation; everybody's kinda holding out for that right now. We're available to measure any Altec drivers anyone's willing to send and cover shipping for expanding the database.

Zilch
04-01-2007, 01:30 PM
I don't see how that can be anything other than speculation until the crossover components have been tested to verify value..Blzatrl123's Valencias are 846B. Do you have the schematic and component values for that 8-Ohm version?

Anyone?

bowtie427ss
04-01-2007, 02:22 PM
AFIK, 846B uses N800-8K, at least mine do. They were recapped prior to my owning them so take the cap values with that in mind.

Appears to be a standard 2nd order network, both inductors are the same part number, i assume equal value. the hi pass cap is 8.2, i "think" it should be 8 even. The woofer shunt cap is much larger, 20mfd, but i think it should be closer to 28mfd. I was once told the reason for the dissimilar values is that the large value of the shunt cap was supposed to act as compensation/matching for the impedence characteristics of the 416 and 421 woofers.

EDIT: inductors measure 1.716 and 1.756 mH

Indeed the factory networks intended for 515 woofers all seem to use the same value shunt and hi pass caps.

I'm also with the understanding that there are no "factory" schematics by model number as a given network could be used in more than one model and can have differing component values according to the impedence and number of drivers.

For instance the 846A uses an N800-F network with 16 ohm components for both LF and HF, i have 9844A's that also use N800-f, yet they have a 16ohm HF and 8 ohm LF load, and yes a freekin potentiometer instead of an L-pad. Until i get brave enough to scratch build new networks for them, biamp is the answer for me.

Zilch
04-01-2007, 04:19 PM
AFIK, 846B uses N800-8K, at least mine do. They were recapped prior to my owning them so take the cap values with that in mind.Thank you for that info. The values you quote translate to an 8-Ohm equivalent of N-800-F.

Closest I've gotten so far is this, which may not relate in any way:

http://www.altecpro.com/pdfs/vintage/SpeakerAndMics/crossOverNetworks/N809-8A%20Crossover%20Network%20Schematic.pdf

Pics of actual 846B crossovers seem to show the caps as symmetrical. (Well, maybe not, now that I look more closely; smaller one's in the HF.) No values printed on them. :dunno:

[They DO have a REAL L-Pad, tho, and it's connected conventionally.... :thmbsp: ]

bowtie427ss
04-01-2007, 06:40 PM
Zilch, i just checked my Heath AS-121 crossovers, i recapped those but kept the originals. Original layout used a 10mfd and 11mfd parallel accross the woofer circuit, and 8mfd in series to the HF.

The AS 121 uses 8ohm 806 and 8 ohm 416.

Must be Solen doesn't make an 8mfd cap as i used 8.2 in the Heath's, But i'd dare say 21mfd is the correct value for the shunt cap, it's been a while so the memory is a little foggy there.

And yes, my 846B networks have nice big chunky ceramic L-pads. The Heaths had much cheasier pads and i replaced those with Violets from MCM.

One thing of interest i'd add, when i took the plunge of attempting to get a look into the N800-F "pandora's box" tar potted mess, there was a fixed resistor in line with something. I never went further with them once i discovered the tar. These networks are in 9844A's and i'm wondering if there are resistors in the other N800-F networks that you've encountered, or if they're exclusive to the 9844???

dgwojo
04-01-2007, 07:06 PM
Pics of actual 846B crossovers seem to show the caps as symmetrical. (Well, maybe not, now that I look more closely; smaller one's in the HF.) No values printed on them. :dunno:

[They DO have a REAL L-Pad, tho, and it's connected conventionally.... :thmbsp: ]

The values should be on those caps, maybe even imbedded in the cap model #, I might just have to dig through my old parts to see if I still have mine to get the exact values!! Dave.

dgwojo
04-01-2007, 07:07 PM
We're available to measure any Altec drivers anyone's willing to send and cover shipping for expanding the database.

I wish you lived in Michigan!!! I have loads of things for you to test!! :tears:

Tom Brennan
04-01-2007, 07:09 PM
It appears that the BMS driver attains it's extended response by means of a resonant spike. I don't know if that's proper behavior or not, generally I prefer smoother to rougher but one never knows what works until one actually listens.

macaltec
04-01-2007, 07:09 PM
I have been told that you can remove the tar by dipping the XO in boiling water. Anyone tried it? Warnings against it?

Zilch
04-01-2007, 07:15 PM
One thing of interest i'd add, when i took the plunge of attempting to get a look into the N800-F "pandora's box" tar potted mess, there was a fixed resistor in line with something. I never went further with them once i discovered the tar. These networks are in 9844A's and i'm wondering if there are resistors in the other N800-F networks that you've encountered, or if they're exclusive to the 9844???See Steve O's post at #12:

http://audiokarma.org/forums/showpost.php?p=1102415&postcount=12

It's an unconventional way simulate an L-Pad with restricted (8 - 10 dB) adjustment range using just a potentiometer. Wiring an L-Pad the same way operates similarly, if you're willing to live with the consequences of the inherent impedance variations of either approach.

[21 uF it is, then.... :thmbsp: ]

Zilch
04-01-2007, 07:28 PM
It appears that the BMS driver attains it's extended response by means of a resonant spike. I don't know if that's proper behavior or not, generally I prefer smoother to rougher but one never knows what works until one actually listens.I have knocked down the spike at 19 kHz with active EQ and don't hear a difference. It's present in virtually all of the BMS re-entrant ring radiators. I need to contact them for details. That spike is not the entirety of the HF extension, of course.

It's not as if I can actually hear up there, but if it's parasitic resonance, it would not be desireable. BMS drivers are well-regarded in the industry, though, so I don't think that's what's happening.

Yes, listening is the bottom line, and thus far, it's only me with this project, though others have recommended this driver as a "fix" for Altecs in the past. There's also the fact that the diaphragms are polyester, which has a different sonic character than conventional metallics....

Zilch
04-01-2007, 07:34 PM
I have been told that you can remove the tar by dipping the XO in boiling water. Anyone tried it? Warnings against it?I've done it with the JBL crossovers; it's alleged to be bee's wax, but I can tell you it's pretty nasty. Spousal units would not typically approve of such activity in their kitchens.

In those early JBLs, the capacitors are also wax-sealed, so it's only useful for the purpose of recovering the tapped inductors in there, or to empty the metal box for reuse with new components....

Steve O
04-01-2007, 08:17 PM
big snip...


[You don't happen to have similar for the 8-Ohm 846B, do ya? ;) ]


I don't have any info on the 846B but it looks like you've gotten what you need below. My guess would be to just scale it to 8ohm and that appears to be the case.

Steve O
04-01-2007, 08:37 PM
I have been told that you can remove the tar by dipping the XO in boiling water. Anyone tried it? Warnings against it?

Boiling water migh work but seems kind of messy. I got my N800-Fs apart by drilling out the two spot welds that hold the cover plate to the can flanges. I then used a heat gun on low to warm up the exterior of the can. The can interior is lined with what looks like heavy "fish paper" so once the tar material is softened the whole works can be carefully pried out of the can. Use heat resistant leather gloves because the can will be ~180 F at this point. Once everything is out of the can, the heat gun can be used to further soften the tar but a lower temp will be possible. I found that the tar could be cleanly peeled off the components w/o need to actually melt it.

I rebuilt mine using metalized PP caps at the stock values but re-used everything else. I repotted using purified beeswax. Probably won't be using beeswax again what with the onslaught of hive collapse syndrome sweeping the world.

Redboy
04-01-2007, 09:42 PM
Man, if you were new to this forum and you started with this thread... :no:

Who'd have guessed that speaker discussions would include talk of boiling beeswax on the stovetop! (BTW: I can tell you definitively that such an activity would not go unpunished in my house!)Yes, listening is the bottom line, and thus far, it's only me with this project, though others have recommended this driver as a "fix" for Altecs in the past. There's also the fact that the diaphragms are polyester, which has a different sonic character than conventional metallics....Bottom line, Zilch... are you liking the way those drivers sound?

Zilch
04-02-2007, 12:28 AM
Bottom line, Zilch... are you liking the way those drivers sound?Most assuredly. The 8-Ohm version is playin' in the background on hombrew N800-8K networks from this thread in the other room (ZilchLab) right now on 811B. I do that so I can play them loud and listen for anomalies without endangering my hearing.

I use the BMS drivers in other systems here, as well:

http://audiokarma.org/forums/showthread.php?p=1100685#post1100685

Even sweeter on your 511s, most likely.

[I'll get to that soon.... ;) ]

bowtie427ss
04-02-2007, 08:02 AM
Probably won't be using beeswax again what with the onslaught of hive collapse syndrome sweeping the world.This is a scary scenario, i had no idea it was so widespread, this needs more attention than it's getting, i don't think most people understand the threat this is to our crops and food supply as a whole.

Apologies for the OT...................

Zilch
04-02-2007, 01:37 PM
Well, I'm getting nowhere with Google looking for the Heath AS-121 manual for verification of the component specs.

Anybody have that?

Who knew they made all of these:

Heathkit (C) AS-2U Speaker System
Heathkit (C) AS-10 Speaker System
Heathkit (C) AS-15 Speaker System
Heathkit (C) AS-16 Speaker System
Heathkit (C) AS-17 Speaker System
Heathkit (C) AS-18 Speaker System
Heathkit (C) AS-21 Speaker System
Heathkit (C) AS-37 Speaker System
Heathkit (C) AS-38 Speaker System
Heathkit (C) AS-48 Speaker System
Heathkit (C) AS-101 Speaker System
Heathkit (C) AS-102 Speaker System
Heathkit (C) AS-103 Speaker System
Heathkit (C) AS-103A Speaker System
Heathkit (C) AS-104 Speaker System
Heathkit (C) AS-105 Speaker System
Heathkit (C) AS-106 Speaker System
Heathkit (C) AS-1039 Speaker System
Heathkit (C) AS-1042 Speaker System
Heathkit (C) AS-1140 Speaker System
Heathkit (C) AS-1320 Subwoofer spk
Heathkit (C) AS-1321 2-Way Speaker
Heathkit (C) AS-1332 Speaker System
Heathkit (C) AS-1344 2-Way Speaker
Heathkit (C) AS-1348 Speaker System
Heathkit (C) AS-1352 2-Way Speaker
Heathkit (C) AS-1363 3-Way Speaker
Heathkit (C) AS-1373 Speaker System
Heathkit (C) ASA-1320-1 Passive X-over
Heathkit (C) ASX-1383 3-Way Spkr MTD

geaugafletcher
04-02-2007, 02:16 PM
Are you sure it's Heathkit AS-121? My Heathkit/Valencias are AS-101.

Unfortunately, I don't have a manual either.

Zilch
04-02-2007, 02:53 PM
My Heathkit/Valencias are AS-101.Thanks for that, which led me to the Altec Forum:

http://www.hostboard.com/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=3729&t=2597

N800-8K values: 1.75 mH, 8 uF, 21 uF.

800 Hz LF, 1350 Hz HF.

N-800-F values: 3.5 mH, 4 uF, 10.5 uF

[They were melting crossovers over there, too, apparently.... :p: ]

Steve O
04-02-2007, 11:32 PM
Thanks for that, which led me to the Altec Forum:

snip...

N-800-F values: 3.75 mH, 4 uF, 10 uF

[They were melting crossovers over there, too, apparently.... :p: ]

I think this pretty much clears up the mystery of the N800-F design. I plugged those values into my N800-F model and the calculated response just about exactly matches the measured electrical response. However, it sure isn't an 800Hz xover by any conventional definition with the load the Carmel drivers present to it. I can also see why Altec changed the hi-pass cap from 10uF to 4uF in later versions. Too bad they didn't also change the model # to something like N800-G.

Zilch
04-03-2007, 12:25 AM
It's interesting to read the speculation regarding the network asymmetry; in spite of it being the HF that was altered, the focus is vectored on the LF.

Fact seems to be that anyone running that driver combination active biamped at 800Hz without compensation has mighty forward midrange happening.... :yes:

Another approach here:

http://audioheritage.org/vbulletin/showthread.php?p=160635#post160635

bowtie427ss
04-03-2007, 08:54 AM
Apologies Zilch, the mind fog, dim lighting, and a fleck of debris combined for a genuine "faux pau", they are indeed AS-101, sorry for creating unnecessary confusion.

As a side note i'd mention that when biamping or building new networks, i do not cross below 1200hz for ANYTHING on an 811. Depending on room size and acoustics i'm very happy running the 806/811 with no eq, but then again my ears aren't exactly "youthful" anymore.

Again, i guarantee everyone's mileage will vary at least slightly................

Ocupatto
04-04-2007, 12:43 PM
Interesting discussion.

I am the culprit who started and owns the 846B's with EV T-35 tweeters. They sound great to me - but when Zilch informs me of another tweeter to use that is better, I will do that. For now, it works just fine.

Thanks.

-Storm.

:thmbsp:

macaltec
04-04-2007, 01:57 PM
Amen Storm. I've heard alot of people talk down about the EV T35 but no one really offers an alternative. My issue is that the horns should cover the HF without the aid of an "add on" as claimed/advertised/mentioned and so on. Especially for the price they command. I like Altec but it seems they are just one big midrange lacking in both HF and sometimes LF.

Ocupatto
04-04-2007, 02:17 PM
Mac -

Do you think I should remove the EV's?

Yeah, everyone is down playing them - but you are right, no one is giving a solution or finding a better tweeter.

Thanks.

-Storm

Amen Storm. I've heard alot of people talk down about the EV T35 but no one really offers an alternative. My issue is that the horns should cover the HF without the aid of an "add on" as claimed/advertised/mentioned and so on. Especially for the price they command. I like Altec but it seems they are just one big midrange lacking in both HF and sometimes LF.

bowtie427ss
04-04-2007, 02:48 PM
I've heard alot of people talk down about the EV T35 but no one really offers an alternative. The EV T-350 is a vast improvement over the T-35, it can be found in the old style alnico version with a horn flare very similar to the T-35. The newer ones with ferrite motors and cheek type horns are the best IMO, the Peavey HT94 is also a close facsimile.

Personally, i like these for the price of admission, it's a Selenium ST-320, a clone of the JBL 2405 slot tweeter. This is the older all aluminum housing version, still pop up now and then on that auction site, i haven't heard the newer all plastic version.
http://i107.photobucket.com/albums/m283/bowtie427ss/st320.jpg

Zilch
04-04-2007, 05:38 PM
We measured various tweeters and settled on APT-80. Liked Bob Crites's (BECtoo) CT125, but opted for the smaller footprint of the original Eminence horn.

With any of them mounted outside the horn there's massive combing and time-alignment issues; the tweeter has to be crossed below 6 kHz due to limited bandwidth of 806A drivers we have measured.

Mounted in the horn, there's shadowing and still the time-alignment problem to deal with.

The answer to all of that is a driver that actually plays VHF, and we're moving to comparative listening evaluation of these two approaches, now.

Personally, I think Macaltec's got it right, and am working on Model 19 now. 811 and 511 both support VHF if the driver delivers; thus far, vintage Altecs don't....

Zilch
04-04-2007, 05:56 PM
The EV T-350 is a vast improvement over the T-35, it can be found in the old style alnico version with a horn flare very similar to the T-35.T-35's hardly even a tweeter by contemporary standards, and the one report we have of T-350 measurement indicates uneven response and a precipitous drop at 14 kHz.

http://audiokarma.org/forums/attachment.php?attachmentid=42326&d=1173412878

Someone wants to send me a couple of the radial cheek version, I'd be pleased to measure them. I can't get the sample similar Ramsa horn I have to mount on stock threaded-throat drivers to test, alas. Metric or something, in any case, it don't fit, and it's not mine to bust trying.

Converting a two-way in to a successful three-way is not a mere matter of slapping on a tweeter, unfortunately....

Tom Brennan
04-04-2007, 08:40 PM
I think the T-350 is being confused here with the ST-350. The T-350 used a huge Alnico magnet on a diffraction horn similar to the horn of the T-35.

The ST-350 used the same ferrite motor as later T-35s but with a constant directivity "buttcheek" horn. The ST-350 should be used with CD horn compensation for extended response.

Zilch
04-04-2007, 09:47 PM
http://archives.telex.com/archives/EV/Horns/EDS/T35A%20EDS.pdf

http://archives.telex.com/archives/EV/Horns/EDS/ST350B%20EDS.pdf

dgwojo
04-04-2007, 11:06 PM
I have the ST-350A's, they have fairly huge round magnets, they seem to be more efficienct than T35's but less efficient than my T350's, Dave.

http://home.earthlink.net/~dwojo/sitebuildercontent/sitebuilderpictures/altec_a7_akfest2005_511b_902-8b_8x6.jpg

Zilch
04-05-2007, 02:33 AM
I have the ST-350A's, they have fairly huge round magnets, they seem to be more efficienct than T35's but less efficient than my T350's, Running them with the requisite compensation's gonna give up efficiency. Are you doing that?

CD horn's also "distributing" the energy as opposed to concentrating it. I'm finding it's tough to mate them with high-efficiency woofers unless the driver has really high sensitivity to start with....

Ocupatto
04-05-2007, 03:00 AM
So, scrap the T-35's and replace them with, what?

Thanks.

-Storm

:scratch2:

Zilch
04-05-2007, 04:03 AM
So, scrap the T-35's and replace them with, what?We'll know in another week or so, Storm. A/B listening tests are just about underway.

I THINK we can get you an invitation, maybe, and you can decide for yourself among the several alternatives.... :thmbsp:

dgwojo
04-05-2007, 06:04 AM
Running them with the requisite compensation's gonna give up efficiency. Are you doing that?

CD horn's also "distributing" the energy as opposed to concentrating it. I'm finding it's tough to mate them with high-efficiency woofers unless the driver has really high sensitivity to start with....
I'm running mine with a 3.3 or 4.7mfd cap in parallel with the horn driver, the Lpad is driving both, the efficiency is almost a perfect match to my ears, I don't have anything to do measurements with so I can't confirm output levels. I'm not into specs, just good sound, Altecs never struck me as a speaker with great specs, afterall, they were meant for large spaces like a theatre and to top it off, they're normally behind the screen. I'd love to tweak my systems with an analyzer some day just to see if there's much difference to my ears, thing is, I'm already happy with their sound. Dave. :yes:

http://www.lansingheritage.org/images/altec/catalogs/1971-home/page02.jpg

bowtie427ss
04-05-2007, 11:57 AM
I'm not into specs, just good sound, Altecs never struck me as a speaker with great specs, afterall, they were meant for large spaces like a theatre and to top it off, they're normally behind the screen. I'd love to tweak my systems with an analyzer some day just to see if there's much difference to my ears, thing is, I'm already happy with their soundAhhhhhhh the voice of reason is music to my ears.

I think it's important to remember the "human factor" in this, keeping in mind that we all hear differently with the result being: just because a speaker is "analytically perfect", doesn't necessarily mean it's sonically perfect in the ear of every listener.

We all have individual preferences with regard to sound and source.

In my experience i've found the best sound comes from speakers that don't inspire me to add inline eq or other "effects" to color the source signal.

For me, i've come to prefer the sound i get from my '60's technology born, HF subdued, jagged responding Altecs.

Just my totally non-inflammatory .02................ based entirely on opinion and prference.

Richard C.
04-05-2007, 02:13 PM
We measured various tweeters and settled on APT-80. Liked Bob Crites's (BECtoo) CT125, but opted for the smaller footprint of the original Eminence horn.


Zilch, I guess I missed it, but when did you test these other tweeters, and what were the results? Was it by ear or tested with response curves? I know the marketing hype for all tweeters is always 20 kHz, but I guess not.

Richard C.

Zilch
04-05-2007, 02:54 PM
I'd love to tweak my systems with an analyzer some day just to see if there's much difference to my ears, thing is, I'm already happy with their sound.All the more reason, of course. What's good? What's better? Why? How can you help others get there? The entry fee is $300 or less.... :yes:

For me, i've come to prefer the sound i get from my '60's technology born, HF subdued, jagged responding Altecs.
Well, here's where we part ways, of course.

Kinda looks to me like that Altec guy is actually holding a measurement microphone those many years ago; I ask myself what those four VOTTs were reproducing. :p:

As Tom points out, if you look at the ST350 data sheet, unless you're using the requisite compensation network, it's a midrange driver peaking at 3 kHz and down 10 dB at 10 kHz, i.e., not even a tweeter.

Properly applied with compensation, it looks to go out to ~14 kHz successfully, plenty good, perhaps, but not up to contemporary fidelity standards.

I don't much trust specs myself, especially old ones like those, compiled when the best available measurement technology wasn't even up to the capabilities of what we can do at home ourselves today. I'd certainly be measuring that driver/horn myself before using it in any system, and trying out the several compensation schemes suggested there for comparison.

Look, this is pretty simple, really: Unless a system is capable of accurately reproducing the full audio spectrum, it is adulterating the program material the pros have provided for all of us to enjoy. That coloration precludes our hearing the music as they intended. We make it worse misapplying speakers in our own spaces.

Is it possible to have a system that plays the full spectrum accurately and still sounds like poop? Sure. I've measured plenty of those, and built quite a few myself, in fact. The challenge is to figure out why, and fix it.

I've apparently got some AKers rethinking the subjectivism vs. objectivism issues, and if this results in more open discussion of them in public forum, that's good, in my view, and if it also results in more audio hobbyists making the effort to figure out what it's all about, so much the better, even.

Personally, I don't give a flying whit what other people listen to. But I DO care that those who might be interested (recognizing also that there are plenty who AREN'T,) have available to them the resources necessary to competently maximize potential enjoyment of their gear and the hobby itself.

If "The care is not there," as someone recently responded to me here, well, that's fine, too. Just put me on "Ignore." I am not offended, and I certainly do not intend that anyone else should be, either.... :thmbsp:

Zilch
04-05-2007, 03:15 PM
Zilch, I guess I missed it, but when did you test these other tweeters, and what were the results? Was it by ear or tested with response curves? I know the marketing hype for all tweeters is always 20 kHz, but I guess not.T-35 GETS to 20 kHz, but down ~24 dB, is all. :)

We did the JBL ring radiator comparisons nearly two years ago, and some dome tweeters at the same time, as I recall:

http://audioheritage.org/vbulletin/showthread.php?t=6368

I did preliminary measurements on EV, Crites, and Eminence last month. "Preliminary" was enough to kick out the T-35, as is obvious from the curves I've posted above. No surprise, really, they seem to populate "junk tweeter" boxes most everywhere; I just needed to verify.

I still have some piezos, planars, and others to do yet. For my own part, it's clear that adding a tweeter to an 811-based system is not a simple task, and perhaps not the optimum approach, either, now knowing that the horn itself will support VHF without beaming excessively.

Have I done polar response studies on 811 and 511 to verify that? Nope. That's an expert "Tilt the horn and watch the RTA" finding.... ;)

bowtie427ss
04-05-2007, 04:03 PM
Zilch, i absolutely applaud what you're doing, and follow with great interest, please don't take offense at my comments or opinions.

My point in brief since i don't want to derail a great thread is simply that even tho the classic Altecs may fall well short of ruler flat response and high frequency extension, many of us are unlikely to modify or change them.......... much.

However, thanks in very large part to the information you've provided, many of us will be able to avoid "cloning" the negative attributes of those classic designs.

I'm also a DIYer to an extent, and i respect/admire/envy what you're doing, and will most assuredly use your findings and recommendations in future projects.

Zilch
04-05-2007, 06:07 PM
My point in brief since i don't want to derail a great thread is simply that even tho the classic Altecs may fall well short of ruler flat response and high frequency extension, many of us are unlikely to modify or change them.......... much.Well, for ~$250 the pair, you can be the first AKer to try this in their existing sytem, and then tell the forum at large whether the Zilchster's got his head up his ass or not.... :thmbsp:

[I don't sell none of this stuff, folks.... :no: ]

bowtie427ss
04-05-2007, 07:03 PM
That's most impressive............... so much so that i'm going to scratch up the admission fee and see the show!

Best response graph i've seen until now is of the PSD2002 on the 811 w/Pi Speakers 1K6 XO (see attached), but the 1600hz bottom end limitation just won't do.

45812

Zilch
04-05-2007, 07:16 PM
That's most impressive............... so much so that i'm going to scratch up the admission fee and see the show!COOL! :banana:

Both BMS and 811B are usable down to 800 Hz, but 1.2 kHz just sounds better. Use 511B to take it to 800 Hz authoritatively.

BMS is clearly the winner above 14 kHz, not that I can hear much of anything up there.

[Not with my ears, anyhow.... ;) ]

Notes:

1) Those are metric threads to mount the driver. My hardware store had metric studs in various lengths, so that's what I used. I don't think the size is what's stated on the data sheet, tho.

2) Do NOT solder to the terminals; use the correct-size Fastons. They are not mechanically supported other than by the plastic back cap, and if you get the terminals very hot, they will pull out.

bowtie427ss
04-05-2007, 08:15 PM
1) Those are metric bolts to mount the driver.Just reading about that........ i'm a semi-retired machinist so i have metric hardware on hand.

and if you get the terminals very hot, they will pull out.Voice of a bad experience?

Polyester diaphram eh?

After nearly 60 years of aluminum it stands to reason an improvement would be found.

Have you had a BMS 4550 apart?

My assumption is they're pretty familiar aside from the diaphram.

Can i make their diaphrams fit my altec drivers?

I was going to PM my questions so as not to go OT, but then decided others may share in the curiosity.

Zilch
04-05-2007, 08:36 PM
I have had them apart, yes. Some details are here. The conical phase plug is part of the diaphragm assembly:

http://www.assistanceaudio.com/02_bms.html

If you go to the BMS website, there's a link to their patent showing more of the mechanical details:

http://www.bmspro.info/

You cannot retrofit these diaphragms into existing Altec drivers. Their different technology, "Re-entrant," is very old, actually. The diaphragm plays to the rear of the driver, where the sound is radially summed and fires back out the front from the center. As a machinist, you'll find the design of it intriguing, very likely, and clever. You can see the radial soundpaths through the transparent diaphragm in the pic there.

Yes, I've melted the terminal mounting on ONE BMS driver in the past.... :p:

The Mylar diaphragm is inherently damped, so the output is smoother than the familiar metalics. To me, they sound more natural. First time I played them flat, I recall thinking there was something "missing." After a bit of critical listening, I concluded that what was missing was the trash of parasitic resonances.

I cannot listen to undamped titanium anymore. Aluminum is still tolerable, but it's better damped, also. My very best-sounding drivers here are damped titanium and beryllium, but their cost is prohibitive for these sorts of retro-DIY pursuits. The BMS Mylars are right up near the top, tho....

Steve O
04-05-2007, 08:39 PM
Well, for ~$250 the pair, you can be the first AKer to try this in their existing sytem, and then tell the forum at large whether the Zilchster's got his head up his ass or not.... :thmbsp:

[I don't sell none of this stuff, folks.... :no: ]

Based on the plot legend, I assume that plot below was achieved using 811 horn/BMS4550 driver thru M19 xover (N1201A-8A) and that a parallel notch filter (0.75uF||0.8mH||6ohm) is in series with hi-pass output and HF driver. Did I get that right? By my quick calcs, the notch is resonant at ~7kHz. If so, what anomaly is being corected by this. In previous plots of 811/4550 response I didn't see anything around 7Khz that needed correction. Insights appreciated.

bowtie427ss
04-05-2007, 08:52 PM
The diaphragm plays to the rear of the driver, where the sound is radially summed and fires back out the front from the center. You'll find the mechanics of it intriguing, very likely, and clever. You can see the radial soundpath through the transparent diaphragm in the pic there.


Lots of interesting reading there, particularly interesting are the large format coaxial drivers............ many thanks:thmbsp:

It'll be a week or so but i'll be ordering up a pair of 4550's, very anxious to hear them in a couple different applications:D

Zilch
04-05-2007, 09:31 PM
Did I get that right? By my quick calcs, the notch is resonant at ~7kHz. If so, what anomaly is being corected by this.It's a series notch filter across the driver to knock down the 6 dB, 19 kHz peak the BMS drivers seem to all have. I developed it empirically, and have yet to put it into Spice to confirm the values. Is it close to correct?

http://audioheritage.org/vbulletin/showthread.php?p=160865#post160865

Zilch
04-05-2007, 09:44 PM
Lots of interesting reading there, particularly interesting are the large format coaxial drivers............ many thanks:thmbsp:Well, part of the price is that you post your findings here.

[We'll want plenty good PICS, of course, of what you do with them.... :huge: ]

Steve O
04-05-2007, 11:46 PM
It's a series notch filter across the driver to knock down the 6 dB, 19 kHz peak the BMS drivers seem to all have. I developed it empirically, and have yet to put it into Spice to confirm the values. Is it close to correct?

http://audioheritage.org/vbulletin/showthread.php?p=160865#post160865

After checking out the link you provided I think I now understand what you're doing. You're using a series resonant filter parallelled across the BMS driver, not a parallel resonant filter in series with the driver. This is after passing thru the hipass portion of the N1201-A, right?

As far as being correct, the math would point to 1.581uF + 0.395mH + 8ohm as values that resonate ~20Khz. This is consistent with what you posted on the LH site a day or two ago:

"Xover3P says 1.581 uF, 0.0395 mH, 8 Ohms. Tried that several days ago with another crossover and it didn't work. That's when I checked with active EQ; cranking the 20 kHz band down 6 dB made it flat, so I know it's do-able with the right values".
The values you're using now work out to a notch centered on ~7KHz. I wouldn't have ended up with this particular set of values as a starting point myself but I sure can't argue with the results you got either. Bears further investigation.

Zilch
04-06-2007, 12:49 AM
After checking out the link you provided I think I now understand what you're doing. You're using a series resonant filter parallelled across the BMS driver, not a parallel resonant filter in series with the driver. This is after passing thru the hipass portion of the N1201-A, right?Yes, that's correct, but I believe both of us have slipped a decimal, 0.0395 mH, originally, no? And the final value was 0.08 mH, not 0.8; my legend is wrong on that value, sorry. Does that calc out any better?

In any case, I started with the calculated values, using 1.6 uF, 0.04 mH, and 8 Ohms, and tweaked from there. As you say, there's something going on I don't yet understand. I'll measure the driver parameters up there, and also see what Spice has to say. It'll be the weekend before I can get to that, tho. I ended up with about half the capacitance, twice the inductance, and 3/4 the resistance, but it's certainly working.

Edit: Forgot that I already had the circuits in Spice from originally doing the sims last October. Voltage drive for what I've got now appears below, and seems to be familiar and correct, or at least, as intended....

bowtie427ss
04-06-2007, 08:51 AM
Well, part of the price is that you post your findings here.

I will happily oblige.................

It'll be a while before i build my N1201 clones, for the time being I'll be running active and i'd like to simulate the compensation circuit thru the use of PEQ in my digital crossover, can you tell me the parameters of the compensation circuit?

I understand i need to cut 6db at ~19khz, what kind of slope, or how wide or narrow should that filter be?

Sorry for the inane questions.................... best to get them outta the way now.

dgwojo
04-06-2007, 10:56 AM
I understand i need to cut 6db at ~19khz, what kind of slope, or how wide or narrow should that filter be?

Question, should anyone be concerned about this peak at 19khz, I don't know about you but I can't hear crap at much above 15khz, I guess our pets will appreciate this?? :scratch2:

Zilch
04-06-2007, 11:48 AM
I'll be running active and i'd like to simulate the compensation circuit thru the use of PEQ in my digital crossover, can you tell me the parameters of the compensation circuit?The voltage drive curve is attached to post #70. That'll get you close. Ignore everything above 20 kHz; that's just me and Steve determining what's going on.

Post your parameters when you get something close, so we can all tweak with them. I haven't tried contouring with EQ on this one. Concensus seems to be it's best to do the compensation passively, even when actively biamped.

Two notch filters will render the driver listenable; it is well-behaved in this respect. AutoEQ can get you there in about five minutes flat....

Question, should anyone be concerned about this peak at 19khz, I don't know about you but I can't hear crap at much above 15khz, I guess our pets will appreciate this?? :scratch2:There are theories as to how we perceive frequencies above what we can actually hear. Without even getting into that thesis, I made the decision to pursue it after looking at the distortion curves. The second harmonic tracks that peak, telling me that it's an artifact deserving some attention.

I can't hear whether it's there or not, but I'm an objectivist when it comes to the fundamentals; the curves don't lie.

Also, the fair sex hears higher than us knuckle-draggers. They count in this.... ;)

dgwojo
04-06-2007, 12:46 PM
There are theories as to how we perceive frequencies above what we can actually hear. Without even getting into that thesis, I made the decision to pursue it after looking at the distortion curves. The second harmonic tracks that peak, telling me that it's an artifact deserving some attention.

I can't hear whether it's there or not, but I'm an objectivist when it comes to the fundamentals; the curves don't lie.

Also, the fair sex hears higher than us knuckle-draggers. They count in this.... ;)
I hear you, no pun intended, I've heard the symbiotik diaphragm 808's and although they claim to hit 16khz they really seem to lack the crispness of the aluminum phragm 802's that go a little higher. Yes, many woman have hearing like cats!! :music:

dgwojo
04-06-2007, 12:55 PM
Zilch, I wish I lived closer to you, it'd be really neat to pit the 802-8G alnico against the 902-8B ferrite magnet drivers, as much as I miss the shielding of the 802 the 902 still sounds best to my ears, maybe the 18,000 gauss of the 902 vs the 15,250 gauss of the 802 makes the difference??

http://www.lansingheritage.org/images/altec/specs/components/902-8b-16b/page2.jpg

http://www.lansingheritage.org/images/altec/specs/components/802d-804a/page2.jpg


http://www.lansingheritage.org/images/altec/specs/components/808-8b/page2.jpg

Steve O
04-06-2007, 01:00 PM
Yes, that's correct, but I believe both of us have slipped a decimal, 0.0395 mH, originally, no? And the final value was 0.08 mH, not 0.8; my legend is wrong on that value, sorry. Does that calc out any better?
snip....

Yes, the 0.08mH value makes all the difference. Resonant freq is now calcs out to ~20KHz, just as your response plot and spice sim show. Your tweaked values produce a sharper "peak" than the values originally suggested by "Xover3P" and this makes sense too considering the relative sharpness of the 19KHz peak in the BMS4550 response.

FWIW, I used 0.0395mH in orig calc but can't type ;) so that's where 0.395mH comes from. We need better man/machine interface.

Zilch
04-06-2007, 01:29 PM
Your tweaked values produce a sharper "peak" than the values originally suggested by "Xover3P" and this makes sense too considering the relative sharpness of the 19KHz peak in the BMS4550 response.Thanks, Steve.

Well, it's all good, then. :thmbsp:

Whenever I diddle in Spice, it gives me other ideas, but I'm done with this particular aspect for now. The results are good, so I'm not gonna mess with it. There's more benefit to be achieved "modernizing" the overall crossover design....

Zilch
04-06-2007, 01:52 PM
Zilch, I wish I lived closer to you, it'd be really neat to pit the 802-8G alnico against the 902-8B ferrite magnet drivers, as much as I miss the shielding of the 802 the 902 still sounds best to my ears, maybe the 18,000 gauss of the 902 vs the 15,250 gauss of the 802 makes the difference??If you want to send them out here, I'll be pleased to measure them for you.

I've tested 802, 804, and 806, the 802-8Gs being newly refurbished by GPA. You've seen the results. I can make any of them play full-range with compensation, but that's not an option for most users. There's also issues as to how hard one can "push" the VHF without the sonic quality deteriorating. It'd take a far more sophisticated crossover to have them approach what is easily achievable with modern drivers, and, in my view, much more effort than they warrant....

Richard C.
04-06-2007, 09:03 PM
Zilch, Your testing has made me like my Altec 811's even more, now! A little damping and they won't ring.

Do you know which diaphragms were in the 802-8G that you tested? The original's are supposed to be #23744 which are light, fragile, and supposed to sound better. They are also very delicate. I have these in my Model 19 802-8G's and I had to repair the voice coil leads.

There is a normal one now (#34647), that is about the only one you can buy new from GPA. I also have a 902 light diaphragm #35480 which I use in my model 14's.

I don't use the black loading cap either, as I use a steep crossover slope (2 or 3-pole) and limit them to 1.2 kHz. I use felt in the aluminum cover.

The 902 drivers also come either, open thru the voice coil gap region to a small inner chamber, or with a blanking plate under the gap that shunts off this small chamber.

Lots of possibilities with Altec drivers.

Richard C.

Zilch
04-06-2007, 09:52 PM
Zilch, Your testing has made me like my Altec 811's even more, now! A little damping and they won't ring.I am certainly enjoying them, and the 511s, also. They are top tier. :thmbsp:

[And there's no shortage of horns for comparison around here....]


Do you know which diaphragms were in the 802-8G that you tested?The diaphragms are new "standard" ones installed by GPA. I also have a vintage "light" one, which I'm going to try in an older (non-tangerine) 802 motor.

Problem is, the "light" is NLA, of course, even if it behaves perfectly.

With all of the variants, the Altec approach is thus far a bag of snakes. I sure wish someone would send me some Altec drivers that measured well so I'd have an answer that I can recommend.... :dunno:

Lots of possibilities with Altec drivers.Right.

Richard C.
04-06-2007, 11:02 PM
With all of the variants, the Altec approach is thus far a bag of snakes. I sure wish someone would send me some Altec drivers that measured well so I'd have an answer that I can recommend....

I wish I could send you a couple of 902's, but I am 3000 miles away and the shipping costs back and forth. :sigh: They also have large unshielded magnets, so I would want them packed tight, in the center of a large box, so as not to bother sensitive equipment during shipping.

I need to get my TrueRTA and calibrated mic going...

My interest in all of your testing, is the "lack of testing" I have seen so far in the Altec world. Mostly there are guys posting what they like! Always what sounds good to their ears AND by using some "special" amp. I would rather see some "real" response charts, first. It narrows things down.

This kinda reminds me of your testing of the JBL 076 tweeter. It didn't seem to be anything special, except for the shape, and the price.:yikes:

Richard C.

Zilch
04-06-2007, 11:33 PM
My interest in all of your testing, is the "lack of testing" I have seen so far in the Altec world. Mostly there are guys posting what they like! Always what sounds good to their ears AND by using some "special" amp. I would rather see some "real" response charts, first. It narrows things down.I was quite taken aback by the dearth of quantitative information relating to Altec performance. No problem, we can now generate it ourselves, for better or worse.

[I'm finding plenty of both.... :yes: ]

I need to get my TrueRTA and calibrated mic going...It'd be great if more audio hobbyists got set up to do it. Measuring and figuring this stuff out certainly adds another dimension of fun to it all.... :thmbsp:

Zilch
04-08-2007, 12:23 AM
http://audioheritage.org/vbulletin/showthread.php?p=161337#post161337

Steve O
04-08-2007, 10:42 AM
Let's see if I've got the two-way version of this correct (because this is what interests me at the moment).

1. 8 ohm version of Altec 846 (Valencia)
2. BMS 4550 driver replacing Altec 806
3. Altec N1201-8A or home brew equivalent repl N800(?) stock xover
4. Zilchlab series resonant trap placed across 4550 terminals (0.75uF + 0.08mH + 6 ohm) to tame 19-20KHz peak

If #3 is correct, is the N1201-8A implemented as on schematic complete with level controls and strange lowpass takeoff point?

This pan-forum, stream-of-consciousness, cross-linked thread has not been real easy to follow esp wrt conclusions and recommendations. Hope I got the two-way part correct because I think I'm going to try a variation of it on my Carmels. If I got it wrong, correction appreciated.

Thanks for the insights so far.

macaltec
04-08-2007, 10:53 AM
I think it's time. I'm ordering my BMS (4550) drivers and compensation parts this week. I will be using them with my A7's.

Zilch
04-08-2007, 01:17 PM
This pan-forum, stream-of-consciousness, cross-linked thread has not been real easy to follow esp wrt conclusions and recommendations. Hope I got the two-way part correct because I think I'm going to try a variation of it on my Carmels. If I got it wrong, correction appreciated.Please understand that this is a group project, work in progress, and you are a participant. :thmbsp:

1) The 846A (16-Ohm) HF is basically done, using BMS 4550-16 plus a simple parallel notch filter for compensation, and that is presently undergoing "proof-of-concept" listening evaluation. The 19 kHz spike is only minimally addressed in that implementation, and we have not worked on optimizing the LF/HF transition using the stock crossover.

2) For 846B (8-Ohm), I've done preliminary work on the HF using N800-8K crossover clone and BMS 4550-8, applying the same approach. The purpose with both 846A and B is to provide a quick and simple "fix" for the HF problem of Valencia and similar Altec two-ways. Merely swapping the BMS 4550-x driver in place of the 806A alone confers substantial performance improvement. Whether users will "like" the character of the sound of the Mylar diaphragm itself is indeterminate.

3) I evaluated the potential of a pair of GPA-refurbished 802-8G with new standard (not "light," which is unavailable new,) as alternative to BMS 4550. The answer is "No, not without the N1201-8A crossover," and the results even with that were marginal. However, using that crossover (stock) with the BMS 4550 driver, I was easily able to produce an excellent FR result. The added series notch filter developed literally just days ago addresses the 19 kHz BMS driver spike.

For now, I'm keeping the controls, but separating the HF section from the LF so it can operate "stand-alone." Spice tells me that's fine; nobody seems to have a logical explanation as to why Altec interconnected it in the first place. This allows independent evaluation and development of filters appropriate for various LF drivers and boxes. It appears that the compensation portion may also be parsed out for use with active filters, but I have not thoroughly evaluated that option as yet.

So, while not specifically developed for 846 Valencia upgrades, the combination of BMS 4550-8 and N1201-8A HF (LF too, perhaps,) provides an opportunity for DIY with other systems. It works quite well with either 811B or 511 horns.

And finally, to toss in another option, the neodymium-magnet BMS 4552 version of this driver provides additionally improved HF detail via higher flux in the gap. However, the minimum recommended crossover frequency is 1 kHz as opposed to 800 Hz; if you're working at 1.2 kHz, spend the additional money to get those.... :yes:

Robh3606
04-08-2007, 01:47 PM
Whether users will "like" the character of the sound of the Mylar diaphragm itself is indeterminate.

You might want to have a fall back position with an improved HF network for those who don't like them. Can't hurt.

we have not worked on optimizing the LF/HF transition using the stock crossover.

You may not be able too without changes there as well. That transition through the midrange will be more important than being down 10Db at 20Khz. Won't be easy to measure well either figure you will need to get down at least an octave and an half below.


Rob:beer:

Zilch
04-08-2007, 02:08 PM
That transition through the midrange will be more important than being down 10Db at 20Khz. Won't be easy to measure well either figure you will need to get down at least an octave and an half below.Not my job.

[Steve O's gonna do that part.... :huge: ]

Steve O
04-08-2007, 02:40 PM
Please understand that this is a group project, work in progress, and you are a participant. :thmbsp:

1) The 846A (16-Ohm) HF is basically done, using BMS 4550-16 plus a simple parallel notch filter for compensation, and that is presently undergoing "proof-of-concept" listening evaluation. The 19 kHz spike is only minimally addressed in that implementation, and we have not worked on optimizing the LF/HF transition using the stock crossover.

2) For 846B (8-Ohm), I've done preliminary work on the HF using N800-8K crossover clone and BMS 4550-8, applying the same approach. The purpose with both 846A and B is to provide a quick and simple "fix" for the HF problem of Valencia and similar Altec two-ways. Merely swapping the BMS 4550-x driver in place of the 806A alone confers substantial performance improvement. Whether users will "like" the character of the sound of the Mylar diaphragm itself is indeterminate.

big snip...

I guess I'm in dense mode today...I still don't quite understand what's being evaluated in #1 or being prepared for #2. I can't figure out what xover is being used (stock N800-F with 10uF or 4uF HP caps???), or what the compensation network is (19KHz peak tamer or padding down midrange). Can you provide a diagram? Even a crude one would clear things up for me.

Sorry if I'm missing the obvious but today it isn't (obvious).

Thanks

Zilch
04-08-2007, 02:54 PM
Sorry if I'm missing the obvious but today it isn't (obvious).Not obvious, never posted:

Parallel trap filter: 4 uF, 1 mH, 28 Ohms. Also, 0.08 mH in the other leg knocks down the spike ~2 dB.

Richard C.
04-08-2007, 10:45 PM
SO much so, that I ordered a pair of APT-80's from Parts Express! I think they will work well with my 902 Altec drivers - I just wonder where to mount them. Won't they cause a "shadow" in the mid-range, if placed "in" the bell of the 811? I plan to build a tall (~50"), pair of 9 cu. ft. cabinets for my 416-8B's, and my 902/811B horns.

I know, I didn't order the BMS drivers, but I will add the APT-80 tweeters, if I need more highs.

The price is very good though, for what the BMS drivers do. The 19 kHz peak wouldn't bother me, cause it's narrow enough, and can be dealt with. Maybe next time.

Richard C.

Zilch
04-08-2007, 11:08 PM
Won't they cause a "shadow" in the mid-range, if placed "in" the bell of the 811?Yes, but time and phase alignment were more significant issues when I tried it. Within the bell seemed to be the best location.

Try that, and also the BMS solution. That's what the present comparative listening tests are about, but you might make the determination yourself and report it here as well.... :thmbsp:

Ocupatto
04-10-2007, 11:45 AM
Anyone from this board coming to the A/B/C listening party over at Jacks House in Prescott, Arizona?

I will be bringing my 846B's with EV T-35 tweeters for testing...

Lets get some more people and make this a party to remember!

;)

-Storm

Zilch
04-19-2007, 12:44 AM
Add-on compensation for BMS 4550 driver is everything to the right of the HF L-pad:

Paul C
04-19-2007, 01:01 AM
That's most impressive............... so much so that i'm going to scratch up the admission fee and see the show!

Best response graph i've seen until now is of the PSD2002 on the 811 w/Pi Speakers 1K6 XO (see attached), but the 1600hz bottom end limitation just won't do.

45812


The 1600 hz rolloff is the crossover working as designed. You can build a similar crossover, same compensation, as low as 1200 hz with that driver and horn combo.

Zilch
04-19-2007, 04:37 PM
I don't get it.

How can they claim that driver has usable frequency response out to 20 kHz in light of their own published curves for it?

http://www.eminence.com/proaudio_drivers_detail.asp?web_detail_link=PSD200 2

jackgiff
04-19-2007, 05:23 PM
I don't get it.

How can they claim that driver has usable frequency response out to 20 kHz in light of their own published curves for it?



The average buyer never looks at the specs. He just goes :banana:

But it does respond just a little at 20 KHz. Down 25 db or so ain't totally bad, is it? It worked for Altec for years. :yes:

bowtie427ss
04-19-2007, 05:24 PM
I don't get it.

How can they claim that driver has usable frequency response out to 20 kHz in light of their own published curves for it?

http://www.eminence.com/proaudio_dri...link=PSD200 2

Very interesting Zilch! i just looked at their graphs and it sure looks to me like they don't roll off so much as take a steep dive above 14k or so.

I would just note that eminence really didn't provide enough information with those graphs to really be sure.

I wonder if the HF roll off is the result of limitations of their test equipment or procedures, it sure is steep and consistent.

Zilch
04-19-2007, 06:35 PM
Down 25 db or so ain't totally bad, is it?

:lmao:

Very interesting Zilch! I wonder if the HF roll off is the result of limitations of their test equipment or procedures, it sure is steep and consistent.Those curves are obviously taken on some unspecified horn, not a plane wave tube, as there's no mass breakpoint in evidence. It looks like an exponential doing the compensation by progressively narrowing the beamwidth with increasing frequency, or an indeterminate network included.

Compare to the Pi Speakers curve for that driver. Same deal -- 811B horn? How much compensation was required to get it flat like that? UHF augmentation would be required to make a system using it play full range.

Clearly, 20 kHz could be "boosted" the requisite additional 14 dB, but it'd likely be a fruitless endeavor. On the optimum constant-directivity horn/waveguide, one MIGHT be able to make a viable two-way, but the 1200 Hz "recommendation" on the low end is a serious limitation. They're saying 1600 Hz, actually, with a 12 dB/octave highpass.

Perhaps all that is so that users don't blow them up in SR applications, but it's still a titanium diaphragm, and may not be suitable for home listening in any case. :dunno:

Zilch
04-19-2007, 07:10 PM
The average buyer never looks at the specs. He just goes :banana:

It worked for Altec for years. :yes:Well, the subject of this thread is Valencias, and there's probably few more experienced with these than yourself, after 40 years of listening to them.

I don't know who I'd be more pissed at -- the marketeers playin' fast and loose with the specs, or the "Ignore the numbers, trust your EARS, it's the MUSIC, stupid" subjectivists perpetuating the myth:

http://www.harman.com/wp/pdf/AudioScience.pdf

jackgiff
04-19-2007, 11:39 PM
I don't know who I'd be more pissed at -- the marketeers playin' fast and loose with the specs, or the "Ignore the numbers, trust your EARS, it's the MUSIC, stupid" subjectivists perpetuating the myth:

http://www.harman.com/wp/pdf/AudioScience.pdf

After 40 years of listening to Valencias. and trusting the marketing pitch of how great they are, I am pissed at myself for falling for all the BS. Now after some research and measuring, we know that they aren't really all that great. But they were designed to follow the X curve, which doesn't cut it for home stereo, but is useful in large theaters. I have had friends over who listened to my Vals, and thought they were really great. So maybe the "trust your ears" thing can be good. But knowing how much better they can be is simply amazing. Either by adding decent tweeters and some crossover/compensation to add the missing HF, or by replacing the HF drivers with ones which have the HF capabilities simply opens new horizons when listening to them. They almost become "MONITORS". That is, they don't miss any big pieces of the audio spectrum. They can be eye opening, especially for one used to Altec Voice of the Theater performance. And Zilch has done a magnificent job for any Altec owner who wants to improve the performance of his Valencias, or any of the related series of speakers using the same components. I am now a happy camper with the pair with added Emminence APT-80 tweeters, and the pair with replacement BMS drivers. They are both so far superior to stock Valencias that I cannot imagine how I listened to them in stock condition for 40 years. Shame on me. My third pair of Valencias will be fixed with BMS drivers as soon as the comparison of 5 pairs of "tweeked" Vals is completed this weekend. They truly are that good.

Jack Gifford

Redboy
04-20-2007, 07:34 AM
:banana:

Ordered my BMS drivers on Tuesday!

Ocupatto
04-20-2007, 11:45 AM
Bringing my Altecs to Jacks on Saturday and will let you guys know the results...

I can't wait..

Maybe Jack can give a little help to my x-overs or something.

;)

-Storm

avguytx
04-20-2007, 12:03 PM
I ended up selling the Valencias I had. I know I was doing them an unjustice in the small room I had them in and I didn't want to put them in the living room which is 23 X 20. I know the new owner is enjoying them, though. For me and the area that I do my listening, I like my other speakers better of which I'll make no mention of since I'm not here to bust up a thread. But I do agree with everything said in these posts about the response being almost non-existent about 14kHz. I went so far as to borrow an Audio Control SA-3050a 31 band analyzer and it showed the same results. It was a steep roll off from about 12kHz on up.

Great speakers for lots of people...just wasn't my cup 'o tea.

Richard C.
04-20-2007, 06:54 PM
I found this article to be very similar to the Infinity white papers that I have read in the past few years. I think there are several good points addressed here. It seems they should be designed by measuring, and then listened to and compared. I like the point made about trained listeners. I guess speakers aren't designed for every listener. Some people have pre-conceived requirements, some are happy with anything, and some are not happy with anything - always searching!

I especially liked the point made about the "dead" recording studios using forward facing (usually horn loaded) monitors to base their recordings on.

I won't run out and buy new "Harmon" speakers, but I do see how speakers have evolved thru the years to be more "accurate". Yes, even accurate enough for Rock-n-Roll! As if "any" junk speaker can reproduce Rock music.

Richard C.

Zilch
04-20-2007, 07:13 PM
I had to read the "Good enough for Rock and Roll" part several times, and I'm still not sure I have it right. It seems the more complex the music, the greater the smoothness required. I'd think it'd mask the anomalies, but no, it apparently renders them more and more audible as the content approaches wideband noise.

That's what we routinely use for test and measurement, and I can certainly hear small differences....

jackgiff
04-20-2007, 07:34 PM
I am almost ready for the Valencia comparison tomorrow, and have moved all my Vals into the living room. Ocupatto is bringing his Vals, and S1A is bringing the tweeters he hooked to a friends Vals. We should be able to compare five iterations of Vals, going from stock through Klipsh tweets, Emminence tweets, EV T-35 tweets, and BMS drivers. Which one is best? Stay tuned!!

dgwojo
04-20-2007, 10:12 PM
Now that's my kind of picture!!! Excellent!! Dave. :yes: :music:

Steve O
04-20-2007, 11:16 PM
After 40 years of listening to Valencias. and trusting the marketing pitch of how great they are, I am pissed at myself for falling for all the BS. Now after some research and measuring, we know that they aren't really all that great. But they were designed to follow the X curve, which doesn't cut it for home stereo, but is useful in large theaters. I have had friends over who listened to my Vals, and thought they were really great. So maybe the "trust your ears" thing can be good. But knowing how much better they can be is simply amazing...

snip...

Jack Gifford

Don't you think you’re being a little hard on yourself when you say you're pissed for falling for all the BS. You ended up with what you had by listening and isn't that what's really important? The situation couldn't have been too bad if it took 40 yrs to realize something better might have come along. Speaker sound is such a personal thing I sometimes wonder how there can be any consensus as to what sounds good and what doesn't.

I've been following this thread (and lurking on the LH board) because I've got a pair of Valencias and a pair of Carmels and both exhibit the “flaws” being discussed (shouty, colored midrange and no real VHF). OTOH they have some characteristics I find really attractive such as high efficiency and a dynamic sound. I also like the basic concept of a two-way design. IOW, I really want to like these speakers but it hasn’t been easy.

Over the years I've coped with the worst part of the flaws by pairing the speakers with vintage equipment that have "loudness" controls or thru judicious use of tone controls but I consider this really a band-aid. Ideally, I’d like to see the speakers perform more neutrally on their own so I could have more latitude in the paired electronics. I had never considered changing HF drivers or making xover mods as a viable solution but now I see that this could indeed be the best solution. Also, I never realized how haphazard Altec was when it came to xovers. It really bothers me that the N800-F came in at least two undifferentiated versions AND that Altec specified the N800-F for use with systems containing 16 ohm LF and HF drivers AND for use with systems containing 8 ohm LF and 16 ohm HF drivers. Sloppy or cavalier and certainly not a means of showcasing high quality drivers. Same goes for Altec cabinets to a lesser extent (one box, many drivers spec’d for it w/o sig change)

Zilch has done a good job diagnosing the root causes of the flaws and has provided some interesting suggestions for fixing them. However, I think this journey is still a ways from being completed.

As I allude to above, I find the two-way concept much more attractive than the three-way, add-on tweeter approach. So… As a direct of Zilch’s work, I decided to acquire a pair of 8 ohm BMS 4550s that I plan to use with the Carmels. Due to lack of free time, I haven’t had much of a chance to play with the BMS drivers yet but I can offer these preliminary listening observations based on a 511 horn and compared to Altec 808-8B also on a 511:
1. The 4550 driver is definitely more efficient than the 808-8B. No meas yet but I’d guestimate 6-8dB mid band.
2. The 4550 goes higher than the 808 but the difference is not as pronounced as I was expecting.
3. The 4550 does not go as low as the 808. The specs state that the low end of the 4550 is 500Hz with rec xover of 800Hz. Based on my listening, I believe the 4550 would do a lot better @ >=1KHz.
4. Driven full range at low power (~50mW) the 808 sounds much fuller, relaxed and effortless than the 4550. The 4550 sounds “pinched” and maybe strained. I realize that full range operation is not a designed-for condition for either driver but I find it revealing. I wonder if the unstrained full-range sound is somehow related to the tendency of devotees to the Altec sound aesthetic to overlook the obvious measured flaws.

The next step will be to make the driver comparison using more-or-less optimized xovers. For reasons I note above, the stock N800-F won’t cut it, even with compensation network(s). Since the Carmel LF section is nominally 8 ohms, a starting point might be Zilch’s “N800-8K Modified”. However, since I’m going to be going for 1KHz, modifications will be required. First thought would be to simply scale Zilch’s design from 800Hz to 1KHz. As I think about it, that may be too simplistic an approach. The HF cutoff will be getting awfully close to the midrange notch filter and I expect to see non-intuitive interaction betw the two filters to occur. I would also like to use a 2nd order L-R network which the N800-8K really isn’t. Lastly, I assume Zilch’s design is optimized for the non-conventional Altec practice of making the HP cap 1/2 the value of the LP cap even though inductors are equal. I think my personal journey is just beginning. Guess I’m going to have to start making my own acoustic measurements. Or maybe I’m thinking about this too much.

As a closing comment, It sure would be cool if we all were physically closer to each other. I know my learning curve would be steeper. I’d also like to have been able to participate in the “Valencia auditions” about 12 hours from now but physical distance prevents it. The internet may have eliminated the distance between us in some respects but when it come to things like speakers, I guess you’ve just gotta be there. Good luck on Saturday. Looking forward to listening session results.

Zilch
04-21-2007, 01:16 AM
Thank you, Steve, for joining the effort at this new and higher level. Your participation has already been helpful in our getting as far along as we have, and speaking for everyone involved, we welcome you to this open source "collaboration."

I've completed four iterations thus far, and each time I get a bit better at it. In all of those cases, I worked with and around an existing crossover, without the option of optimizing the basic filters. Fortunately, the BMS drivers require little compensation and I was able to accomplish it with simple low-Q parallel notches. You are already well familiar with my series notch approach to the 19 kHz spike. In the latest 8-Ohm version, I zeroed in on it more precisely.

I developed these designs empirically with the assistance of Spice. If you don't have some version of that, PM me and I'll get you set up with it. The combination of Spice telling me what to try versus actual measurement results allowed me hone in on a working design within a couple of hours in each case.

The last 8-Ohm version came together easily once I discovered that 20 Ohms across the driver tamed its inductive reactance and made everything behave more predictably. I don't know if that's the optimum value, or if a Zobel might be a better choice. Impedance measurements will define the situation, and I'll try to get those posted for the 4550 and 4552 drivers on both 811 and 511 horns this weekend.

I certainly agree that two-way is the better approach, particularly since finding that these Altec horns support VHF reasonably well. While there remains a time-alignment issue, I consider that to be second or third order behind getting good frequency response coherently implemented in these various sytems.

Working with the 811B horn, I was not at all dismayed to discover that the stock Altec crossovers were actually doing the highpass at 1200 Hz or above, as I did not much like the onset of horn coloration I hear using the BMS 4550 down at 800 Hz. 511B seems fine down there, and the version I did for Redboy sounds reasonably good to me, though I can't certify that I have a particularly discering ear. I may go back and tweak that one a bit once I know better what's going on with the driver impedance. The priority in all of these cases has been to get the systems up and running reasonably well with potential fine-tuning later.

Jack developed the 1200 Hz crossovers he's using independent of the Altec designs, and simply added on the compensation filter I designed for the 16-Ohm N-800-F. I'll be discussing how we might optimize that with him as he moves toward completing his third system pair, which I believe will incorporate the premium neodymium 4552. I'll get that documented here, as well.

You are correct that I paid little attention to interaction between the highpass and the low end of the parallel notch. If you run the numbers, you may find the notches actually start lower than the highpass in some of these instances. I didn't see anything anomalous in either the sims or the measurements that I felt was necessary to correct.

I hope some of this accelerates your learning curve; we're ourselves anxious to learn how you approach the problem and what results you may achieve. We certainly all agree these vintage Altec systems are worth the effort.... :thmbsp:

theophile
04-21-2007, 01:25 AM
There are probably thousands of drivers out there,which posess a flatter frequency response than the 806a,but don't sound as good.:no:

Can we please stop equating flat frequency response in a driver with the concept of overall quality.There is not a direct correlation between the two concepts.
I've no problem with the attempt to attain flat frequency response,but there's any number of drivers which could be tacked onto a 806,to lift the HF,which wouldn't be better for the execise.

I just had to say that.:smoke:

Zilch
04-21-2007, 02:09 AM
Can we please stop equating flat frequency response in a driver with the concept of overall quality.There is not a direct correlation between the two concepts.In my view there is, thus clearly highlighting where we fundamentally differ in design philosophy and objectives. Without uniform full-spectrum frequency response, the system has an inherent coloration undesireable to many, and it's best to mitigate that with minimal intervention. As Steve just stated, "Ideally, I’d like to see the speakers perform more neutrally on their own...."

True, the BMS driver may not be the optimum choice, and ultimately, some may not find its sonic character to their liking by comparison. I have begged for someone to send me an available Altec driver/diaphragm combination I could demonstrate is up to the task, or to provide credible documentation that such a combination exists. It certainly hasn't happened with any of the five driver pairs I have measured to date.

I also recognize that to some, what we're doing here is an adulteration of perfectly fine vintage Altec systems, and offensive. I'm sorry, but the consensus among many knowledgeable owners at this point is that they simply do not perform up to contemporary standards, alas, and thus arises a motivation to update them.

By the same token, however, nothing we're doing here should in any way be seen as mandating or even suggesting that anyone must themselves be dissatisfied with the performance or pleasure of the stock vintage systems....

theophile
04-21-2007, 03:35 AM
Like I asked Zilch,can you add any flat frequency response driver and improve on the 806?

Zilch
04-21-2007, 04:08 AM
Like I asked Zilch,can you add any flat frequency response driver and improve on the 806?Jury's still out on our first attempts; check back tomorrow.

There is no "flat frequency response driver," of course, unless you're talking about adding a tweeter, which has its own set of difficulties and compromises.

For driver substitutions, by virtue of the inherent nature of compression drivers, some compensation will necessarily be required. I chose the BMS driver presently under evaluation because the requisite amount of compensation is minimal, which, in combination with that driver's higher sensitivity, allows it balance with the stock woofer and crossover while playing "flat."

The "improve on the 806" portion of your question is obviously loaded. I have previously provided extensive documentation of the "problem." Here's 806A on 811B run by SS vs. vintage tube amp, alone, and using Valencia crossover, as I posted in another thread here earlier today. Without EQ, an active system would be characterized by the upper curves, run full range. Overlay highpass as appropriate:

http://audiokarma.org/forums/attachment.php?attachmentid=47454&d=1177116095

theophile
04-21-2007, 04:46 AM
Yes, and determined by reason.
What makes you determine that flat frequency response determines better.
On a qualitative/quantitative level what "data versus wank",do you have to prove that the BMS IS BETTER than the 806?

Zilch
04-21-2007, 05:07 AM
What makes you determine that flat frequency response determines better?

I can't get you to read it, apparently, but I will cite again here for your convenience:

http://www.harman.com/wp/pdf/AudioScience.pdf

On a qualitative/quantitative level what "data versus wank",do you have to prove that the BMS IS BETTER than the 806?That's the loaded part, of course, restated, and there is nothing to prove, rather, I am merely assisting some friends in apparently achieving more satisfying performance from their Valencias. You are certainly welcome to similarly take advantage of the information and experience we are sharing here.

[Or not, as you please....]

theophile
04-21-2007, 05:45 AM
Indeed Zilch,
You have made many assertions implicitly on this thread which imply that we need to be informed about the falling frequency response of the 806a.Thank you for informing us of the fact.
This fact has been known for 40 years.

The frequency responce measurement is a measurement of relationship of one part of the audible band to the whole of the audible band
the "loaded part".The reference being 1kHz,Correct?
OK, then would you care to divulge by the(By your own admission)criteria," data less wank",just how you've EMPIRICALLY determined that the frequency response measurement proves superior fidelity?
Proves superior fidelity.
"Data less wank"
Show us all how the relationship between a 1KHz signal to another within the audible spectrum in a random configuration in any combination of room/system interaction relates to what the heck you are talking about as some kind of absolute.
You'd be more honest if you admitted that there is more to this than driver addition or substitution,crossover configuration,or box design.But having viewed the current biased propaganda on this thread,I will challenge you,have you tried many other drivers? And if not,why put forward one particular brand without (let's say)any number of other "flat frequency reponse"dirvers and fuel therefore a listening panel comparison?
I hereby challenge you to empirically (not anecdotally)prove your assertions that flat frequency response=QUALITY.

Zilch
04-21-2007, 11:29 AM
I hereby challenge you to empirically (not anecdotally)prove your assertions that flat frequency response=QUALITY.Done, by others.

Read the paper.I know that the 811b/806a isn't comparable but I find the defintion,dynamic nuance and veracity of the Altec horn top-end responce [sic.] to be very able and satisfying.Others don't, apparently, is all, and we're making some attempts beyond vacuous rhetoric to correct that.

No one has suggested you should not enjoy your system for what it is....:thmbsp:

geaugafletcher
04-21-2007, 11:45 AM
No one has suggested you should not enjoy your system for what it is....:thmbsp:

I heard the HF rolloff immediately when I fired up my Valencia's for the first time. Still, they're the most enjoyable and 'life like' speakers I have - and I enjoy them quite a bit!

Zilch
04-21-2007, 04:57 PM
I heard the HF rolloff immediately when I fired up my Valencia's for the first time. Still, they're the most enjoyable and 'life like' speakers I have - and I enjoy them quite a bit!The obvious question, then, is if you mightn't enjoy them even more if they played full range flat, other factors being equal?

We should be seeing reports from the initial listening tests here in a couple of hours, maybe.... :yes:

macaltec
04-21-2007, 06:19 PM
Theophile, I want to take a shot as to "why" the BMS driver and "why not" other drivers. I do not have them, nor have I heard them. I have no test equipment and am struggling to understand all of this new information. To me it appeers that the Altec drivers are lacking in HF extension above 10K. Some, in the past, have added a tweeter to help with this even though they may not have seen the need (according to a chart) or even been informed of the deficiency. Some have heard them and "subjectively" decided that something was missing or not to their liking. The choice of replacements/upgrades should be made the same way a manufacturer decides to use a specific driver, because it posseses certain attributes that are thought to be of value to the design and help attain the desired results. The BMS drivers offer measured performance specs and seem to be a good starting point for such an endeavor. The test data is just a reference from which to build from. :thmbsp: YMMV

Zilch
04-21-2007, 07:25 PM
The choice of replacements/upgrades should be made the same way a manufacturer decides to use a specific driver, because it posseses certain attributes that are thought to be of value to the design and help attain the desired results. The BMS drivers offer measured performance specs and seem to be a good starting point for such an endeavor. The test data is just a reference from which to build from. :thmbsp: YMMVYes, exactly.

I chose the driver based upon my best judgement of how the Valencia's issues might be resolved within the specific design constraints of the project, such as keeping the stock crossovers, no mods to the horn mounting, reasonable cost, sensitivity compatible with the stock woofers, the requisite compensation, etc., all from analyzing the specifications. I was also already familiar with the driver "family" and how it might sound, comparatively.

[Speakerlust would doubtless have used a different approach.... :p: ]

Robh3606
04-22-2007, 12:00 AM
Hello Zilch

I have a question for you. Of all the combinations you have available which sounds best to you?? I am going to guess at least one is a set-up using the JBL 2435 Vertec driver using a Beryllium diaphragm. There's a reason for that and it's not flat response out to 20K. I can set-up a 2426 on a 2344 horn and a 2435 on the PTH1010 waveguide with almost identical frequency and polar response and yet the 2435 is the hands down winner. It's not always obvious from measurements which driver will sound better and even then we may not agree which one that is. That's just the way things are.

Rob:D

Zilch
04-22-2007, 12:20 AM
I have a question for you. Of all the combinations you have available which sounds best to you?? I am going to guess at least one is a set-up using the JBL 2435 Vertec driver using a Beryllium diaphragm.Hi, Rob!

You'd guess correctly. The Be diaphragm purportedly operates pistonically out to 18 kHz in 2435HPL, and the difference is audible. "Pushing" an undamped titanium diaphragm as in 2426H, the VHF is generated from operating the diaphragm in breakup mode. At lower frequencies, we'd be calling it "distortion."

Aluminum diaphragms with their inherent damping handle it perceptibly better, and the Mylar ones, as well, though I have not seen laser interferomety of either of these in operation. Mylar's used in supertweeters operating at 30 kHz and beyond.

Of all of the drivers I've evaluated here, the large-format 4" aquaplas-damped titanium-diaphragm JBL 2452H-SL is the best sounding. I don't have any Be TADs to compare, but I'd bet they'd be close. I should have some aquaplas'd Be 2435s here to try soon.

There's no denying diaphragm material and driver design play a significant role in this, which cannot be ignored. Push any driver beyond it's limits trying to force out VHF out and it'll sound like crap. Yup, guaranteed. :yes:

Zilch
04-22-2007, 12:28 AM
Results are in. Bottom line, Valencias (and similar Altecs, most likely,) may be significantly improved via any of the several options evaluated:

http://audioheritage.org/vbulletin/showthread.php?p=164400#post164400

[The quest continues.... :thmbsp: ]

Robh3606
04-22-2007, 09:28 AM
There's no denying diaphragm material and driver design play a significant role in this, which cannot be ignored. Push any driver beyond it's limits trying to force out VHF out and it'll sound like crap. Yup, guaranteed.

Hello Zilch

You can't push a driver beyond it's limits trying to force VHF out of it. That's not how compensation works. You attenuate the midband response. If the VHF is not there you can't put it there no matter what you do. If the VHF is rolled off too much no amount of attenuation will give you a usable response. The distortion levels are not going to change using attenuation to level out the response.

You can however significantly increase the distortion levels by trying to run these drivers too low or using a horn to its cutoff frequency. The lower you go the greater the diaphragm displacement and this increases distortion. If you use a horn to cutoff the diaphragm can unload and you will get more displacement.

"Pushing" an undamped titanium diaphragm as in 2426H, the VHF is generated from operating the diaphragm in breakup mode. At lower frequencies, we'd be calling it "distortion."


How do you think they get the 2452 to have usable response out to 20K?? Damped or undamped it's the controlled resonances that are built into the diaphragms that get you the last octave. The aquaplas damps and lowers the spurious and unwanted modes. If anything the 4" diaphragm on the 2452 will have more issues with these modes than the smaller 1" drivers simply because the diaphragms used in the 1" drivers are much smaller in comparison. With the 2426 they are break-up free to almost 15K. The first mode in a 4" driver will be significantly lower and more into the audible band. If you want to remain pistonic stick to the beryllium drivers.

Rob:D

Zilch
04-22-2007, 01:33 PM
Hi, Rob.

I always get into trouble using "push" or "boost" in descriptions of how it's accomplished. There's no power added directly in the VHF, typically, rather the midband is attenuated, as you point out.

However, if the VHF is down 20 dB, and I attenuate the rest of the frequencies to balance with that, then 20 dB more power must be applied to restore the overall SPL up to the original level, with the VHF receiving the fullest measure of that increased power. Whatever the distortion component of the VHF out there is increases accordingly.

In 4430, JBL stopped at ~14 dB at 16 kHz. "Push" 2426H harder/higher than that, and it sounds nastier, is what I'm saying.

Altec Model 19, it's more like 9 - 10 dB, i.e., not as aggressive.

BMS 4550 requires just 7 dB, and less at VHF.

I don't know what's happening with 2452H-SL. There's no specs or technical information available, and the PWT FR response curves are "not for distribution." As you say, the VHF is coming from somewhere and the FR curve is certainly different. I'm told the phase plug is a revised design and a different material.... :dunno:

Robh3606
04-22-2007, 03:57 PM
Hello Zilch

However, if the VHF is down 20 dB, and I attenuate the rest of the frequencies to balance with that, then 20 dB more power must be applied to restore the overall SPL up to the original level, with the VHF receiving the fullest measure of that increased power. Whatever the distortion component of the VHF out is increases accordingly.

Actually it doesn't. You have to remember what your doing. There is no extra power applied when you are normalized for flat response. You don't change the sensitivity of the driver and horn, which in a 4430 as an example is 107db one watt. You attenuate the midband response. If you take a 2344 with a 2426 normalized for 93db for one watt, like in a 4430 to match the woofer, the actual power applied to the compression driver at say 2k for that 93db on axis is actually 13db down, to make it easy, or 50 milliwatts due to the attenuation from the network.

The power input at 16Khz is 1 watt for the 93db reference because there is no padding there. Look at the attached Voltage drive courtesy of Giskard for the 4430. You can see that the compression driver is attenuated at the crossover point. You have to subtract the attenuation from the power going in. That's what the compression driver really see's. You are not adding power to make up the original sensitivity. The distortion now is still that same as it was before you added the compensation circuit.

If you run 20 watts into a 4430 your going to get 106db @ 1 meter that's damn loud. I don't think many of us listen that loud. That gets you back into the area of the original sensitivity of the horn so at 106Db the driver see's 20 watts worst case only at the top of it's bandwidth well within it's power rating. How much music and actual power content is in the 10-20k bandwidth??

Rob:D

Zilch
04-22-2007, 05:58 PM
Alas, sensitivity is not measured at 16 kHz.

2426H on 2344(A) is 107 dB (uncompensated, presumably,) representing the average between 1 kHz and 4 kHz:

http://www.jblpro.com/pages/pub/components/2426.pdf

To accomplish the requisite compensation for "flat" according to the posted network voltage drives, that gets attenuated 14 dB to 93 dB.

At 16 kHz, there is no compensation, so, in effect, the HF has been "boosted" 14 dB for any given output level, dB being relative as used here, not absolute.

Distortion is not specified for the driver alone, but it IS shown for that driver on the 2344A horn:

http://www.jblpro.com/pub/obsolete/2344A.pdf

It looks fine there, but both the distortion and the frequency response are shown only for the uncompensated condition. It's obvious from that curve why 16 kHz was chosen for the HF limit. It'd take an additional 14 dB to play it flat to 20 kHz.

Finally, in the 4430 specs, we see the distortion in the compensated operation of that driver and horn, clearly illustrating the consequence of the compensation in Fig. 15:

http://www.jblpro.com/pub/obsolete/443035.pdf

4430 sounds fine, of course. My thesis is merely that pushing the response flat out to 20 kHz would be problematic. The usable limit is defined by the horn/driver response curve....

Robh3606
04-22-2007, 07:53 PM
Alas, sensitivity is not measured at 16 kHz.

Yes it is, its 93db at 1 watt :banana:

At 16 kHz, there is no compensation, so, in effect, the HF has been "boosted" 14 dB for any given output level, dB being relative as used here, not absolute.

What's important is the absolute. The absolute tells you how to accomplish what you need to do.

Finally, in the 4430 specs, we see the distortion in the compensated operation of that driver and horn, clearly illustrating the consequence of the compensation in Fig. 15:

Yes we do and it's relevant to any compression driver using a CD horn.

4430 sounds fine, of course. My thesis is merely that pushing the response flat out to 20 kHz would be problematic.

If it sounds fine why would you want too?? If it's not broke don't fix it.

Rob:thmbsp:

Zilch
04-22-2007, 08:06 PM
Yes it is, its 93db at 1 watt :banana:That's plenty loud enough for me.

[Maybe I run 'em on a tube thing.... :thmbsp:]

Zilch
04-23-2007, 02:40 AM
I'm not seeing any low resonance peaks; "Blips," maybe.

The utility of 20 || Ohms is apparent.

Factory curves:

http://www.bmspro.info/photos/bmspro_info/bms-4550.pdf

http://www.bmspro.info/photos/bmspro_info/bms-4552nd.pdf

bowtie427ss
04-23-2007, 07:08 AM
Here's 802-8G on Clio..................... Your mileage may vary

Not my analysis, nor my drivers, you can currently find them on that auction site.

http://i107.photobucket.com/albums/m283/bowtie427ss/802-8Gonclio.jpg

macaltec
04-23-2007, 12:06 PM
Here's 802-8G on Clio..................... Your mileage may vary

Not my analysis, nor my drivers, you can currently find them on that auction site.

http://i107.photobucket.com/albums/m283/bowtie427ss/802-8Gonclio.jpg

That's actually not half bad looking.

Zilch
04-23-2007, 12:16 PM
COOL, Bowtie. Thank you!

Looks kinda familiar, no?

From Italy, he says that's the response on a 1 kHz Tractrix horn.

And here's his impedance plots, with a clear resonance peak at 500 Hz:

Zilch
04-23-2007, 12:25 PM
That's actually not half bad looking.Compare to Gary's GPA-refurbished pair, which measure a bit better than those, actually. The VHF response is also better on 811B horns than those particular Tractrix:

http://audioheritage.org/vbulletin/showthread.php?p=160605#post160605

Italian seller's citing the measurements as evidence they're "matched."

Not all that well matched, actually.

[I'm certainly pleased you guys are getting this.... :thmbsp: ]

cabinover
04-23-2007, 12:54 PM
Now what would happen with 2 average cone speakers against each other? Would they also show the differences of 3-5dB like these 802s in the plot above?

I really don't know but that would explain a few things to me in my own little world. Like why one of my drivers just sound louder than the other, same with speakers. Maybe my hearing ear to ear isn't quite as bad as I thought.

Zilch
04-23-2007, 01:58 PM
Cones do better:

http://audioheritage.org/vbulletin/showthread.php?p=120126#post120126

Compression drivers require tolerances to be tightly controlled; the smallest deviations show up in the response:

http://audioheritage.org/vbulletin/showthread.php?t=6050

http://audioheritage.org/vbulletin/showthread.php?t=6368

There are exceptions. Some vintage designs are more forgiving. JBL LE85 comes to mind:

http://audioheritage.org/vbulletin/showthread.php?p=159517#post159517

http://audioheritage.org/vbulletin/showthread.php?p=135642#post135642

Contemporary manufacturing methodology does a better job building quality compression drivers:

http://audioheritage.org/vbulletin/showthread.php?p=147389#post147389

Scroll on down to see a dozen more.

BMS (a newer design) can get them so close you have to blow up the plots to differentiate them:

http://audioheritage.org/vbulletin/showthread.php?p=159367#post159367

Compare to the vintage Altec 806A pair on that same plot (red, orange).

:scratch2:

jackgiff
04-23-2007, 06:50 PM
http://audioheritage.org/vbulletin/showthread.php?p=159367#post159367

Compare to the vintage Altec 806A pair on that same plot (red, orange).

:scratch2:

Those 806A plots look awfully familiar. Are you exposing my 806A's, Zilch???

Wow, how can I ever live this down? :lmao:

Jack Gifford

Zilch
04-23-2007, 07:02 PM
Those 806A plots look awfully familiar. Are you exposing my 806A's, Zilch???I've got a pile of them here, Jack, and as a matter of discretion, I don't name names.

You'll have to cross-reference the numbers, 'cause I forget which are whose, now.... :p:

Zilch
04-24-2007, 02:31 PM
A glitch in the listening tests:

http://audioheritage.org/vbulletin/showthread.php?p=164709#post164709

Compensation filter for BMS 4550 was not properly connected. :no:

Zilch
04-27-2007, 01:43 PM
For the 8-Ohm Valencia and similar, using BMS 4550-8 or 4552nd-8 HF driver. Expanded vertical (dB) scale, last:

Ocupatto
05-02-2007, 11:43 PM
Zilch,

Would it helped if I found a pair of 8 ohm EV-T35's, or should I get a new pair of tweeters altogether?

Thanks!

Keep up the good work!

I however wank more and work less...

;)

-Storm

Zilch
05-03-2007, 12:08 AM
Hi, Storm.

8-Ohm T-35s would not improve your system, I don't believe. Yours seem to be connected as 8-Ohm equivalents presently.

If anything, I'd put Crites tweeters in, instead, if they'll fit, and, in the end, you decide you still want tweeters. They're deeper than your T-35s, probably, at 3.5" behind the horn mounting flange.

I have an 8-Ohm pair of those.

Jack's just got set up to do measurements, and is figuring this stuff out, now.

I suspect he'll know a lot more in a week or two.

I'll send the 16-Ohm T35s back to him in a couple of days so he can evaluate them among the other alternatives. :thmbsp:

[Still a bit more testing I need to complete here, first....]

Zilch
05-06-2007, 09:35 PM
Before, left two.

After, right two.

http://audioheritage.org/vbulletin/showthread.php?p=167133#post167133

Seems we're all but done with it now.... :thmbsp: