ALTEC 846B Trouble/week sound?

blzatrl123

Member
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 .
 
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
 
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
 
blzatrl123 said:
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.

blzatrl123 said:
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.

blzatrl123 said:
Who is GPA? I need this person.
Dgwojo linked you there, above....
 
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
 
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
 
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,
 
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.
 
blzatrl123 said:
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

Altec_846B_NoGrills.jpg


Altec_846B_Components.jpg


Altec_N800_8K-1.jpg


Altec_846B_848A.jpg
 
I See the Puzzle of the N800-F Remains Unresolved @ Lansing Heritage...

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.
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.
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.
N800F_Plot1.jpg

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 ;)
 
Steve O said:
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? ;) ]
 
Steve O said:
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
 
Steve O said:
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.... ;)
 

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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
 
: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.
 
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.
 
macaltec said:
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.
 

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bowtie427ss said:
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?
 
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