View Full Version : Using piezo tweeters wisely: a "how to"


Paul C
08-23-2006, 08:45 PM
The only piezo tweeters worthy of high fidelity or pro audio use are the Motorola/CTS units, and of those, only the Powerline Series are suited for pro audio. The ones made by other companies are junk. I have seen them selling for as low as 75c each to dealers. If you pay more than $2 for one made by anyone but CTS, you are being ripped off.

Sometimes it is said that piezo tweeters are "harsh" or "bright". First, if they aren't a real Motorola/CTS unit, they are junk. But with the Motorola/CTS units I have come to see (and others agree) that they have higher sensitivity than the published 92-93 db/wt SPL ratings. They seem to be 3-5 db higher.

I have used the KSN1165a, rated at SPL = 92 db @ 1w @ 1m, with woofers in the 96-97 db range and they seem to have excellent balance. Using the KSN1165a with a 92 db SPL woofer, the tweeter does sound very bright. By reducing the tweeters output by 4 db it matches the woofer very well and makes for an excellent speaker. (more on this later)

Ignore everything you have read about resistors and piezos. Most all are quoting each other and MISQUOTING the manufacturer. Some will tell you to place a resistor in series with the piezo tweeter, some say parallel. And both are wrong.

Years ago with some of the Motorola line, not all, just some, and I have the paper from them about this, Motorola recommended a 20-50 ohm resistor in series with SOME of the tweeters. This gave protection to the amp from high freq (100khz or so) oscillations as well as some protection to some of their tweeters. They did not recommend using resistors for any of the Powerline series, which include the KSN1142a, KSN1165a, KSN1188a, and a few other in the series.

(The Motorola piezo speaker division was purchased by CTS some years ago)

The CTS/Motorola Powerlines were the very high quality ones for pro use, and contained built in protection circuits, quite sophisticated. This protection circuit uses a resistor and thermal breaker paralleled with a tiny light bulb. At about 100 watts the thermal breaker heats up, opens and now the power goes through the light bulb. As the bulb heats up it increases resistance. What this does is give "soft clipping", that is, a sort of compression of the highs. This is very mild and almost inaudible, and certainly not noticable. They burn out about 400 watts. These are once again available through Martin Sound.

http://www.martinsoundpro.com/item.asp?id=340

Anyway, don't use a resistor with the Powerline Series piezos for power protection purposes; it is simply not needed. If you do put a resistor in series (and even Martin Sound says for Lpad use a 20-30 ohm resistor) I say, go ahead, but it will NOT make a difference in sound. Do you know why? Because a piezo tweeter has an impedance of 1000 ohms or greater. If you put a 20 or 50 ohm resistor in series with a 1000 ohm speaker, well, it is a miniscule change in power to the speaker. Duh!

So, how DO you pad down a piezo?

The CTS/Motorola paper says you can put a small CAPACITOR in series with the piezo to reduce the level, and that can work. But if you put an 8 ohm resistor across the terminals (follow this whole discussion now...) now it looks like an 8 ohm load. The piezo will not know the difference, it works off voltage only, drawing almost no power.

http://i15.photobucket.com/albums/a384/PaulCoats/PiezoResistor.jpg

Now, put an L-pad to this 8-ohm load. Make sure you use an 8 ohm L-pad. (or if you use a 16 ohm L-pad, use a 16 ohm resistor) An L-pad is actually two rheostats, one in series with load, one in parallel, and the taper of each is such that the load presented back to the crossover is constant. Now this piezo, plus 8 ohm resistor, plus 8 ohm L-pad looks like 8 ohms to the crossover.

http://i15.photobucket.com/albums/a384/PaulCoats/PiezoResistorLpad.jpg

What crossover? Well, now that it is 8 ohms, it needs a crossover to keep from putting unnecessary load on the amp below the frequency produced by the piezo tweeter, power that would be wasted in the L-pad and resistor. A simple cap calculated for an 8 ohm load (or 16 ohm load if 16 ohm L-pad and resistor are used) is all that is needed. For example, for the KSN1165a or KSN1142a, which roll in at 1800 hz, if these were to be crossed in at 2000 hz it works out to 9.9 uf, which is a non standard value. But 10 uf is standard and plenty close enough. If you wanted to use all of the 1800 hz-20 khz available from that piezo tweeter use 11 uf (10 uf + 1 uf in parallel). If you wanted to cross this at 3000 hz use 6.6 uf (5.6 uf + 1 uf in parallel). Etc. Just remember, you can't go lower than the piezo tweeter is capable of going, but you can go higher. Calculate the capacitor using an 8 ohm impedance.

http://i15.photobucket.com/albums/a384/PaulCoats/PiezoResistorLpadCap.jpg

So now with this setup you can not only control the level, but control the crossover point, too.

You may also use a "fixed L-Pad" like this:

http://i15.photobucket.com/albums/a384/PaulCoats/PiezoFixedLpad.jpg

-3 db R1 = 2 ohms, R2 = 6 ohms
-4 db R1 = 3 ohms, R2 = 5 ohms
-6 db R1 = 4 ohms, R2 = 4 ohms

These are approximate, as in, "close enough for jazz".

One caution--Do not try to use a steeper crossover, 12 db/oct, or higher. This is not needed for tweeter protection, and the piezo can react with the inductor in these and produce chirps on occasion.

Celt
08-23-2006, 09:23 PM
Good info Paul. Thanks!

ozmoid
08-23-2006, 10:07 PM
Thanks, Paul! Excellent info, as always! :music:

crackerkorean
08-23-2006, 10:23 PM
I will be putting this exact info to use soon hopefully. I cant wait.

Thanks again paul

GordonW
08-24-2006, 04:24 PM
There's more than one situation here...

Many people using piezos, are using the KSN1005 type... the "fluted bullet" type, like the ones in the Dahlquist DQ10, basically. These CAN cause amp mis-behaviour... they go to as low as ONE OHM at extremely high frequencies (ie, 100KHz region), and can cause amp oscillation. Especially with vintage amps (which have less high frequency stability), it's a VERY GOOD idea to use a series resistor. I've personally heard MANY cases, where a harsh "gritty" sound was ELIMINATED, by the insertion of even 4 ohms in series... this damped and alleviated the "resonant circuit" created by the capacitive load on the amp output. If using a KSN1005-type piezo with the above circuit diagram, I'd place a 4 ohm resistor (the value isn't critical, anything from 4 to 10 ohms would be quite reasonable) just before the driver... after the resistor to ground...

Also, with Powerine type piezos... many people wind up using the 1" throat screw-on piezo drivers, with various horn flares. In these cases, the Powerline drivers oftentimes wind up having TOO MUCH output in their lower registers, due to the "horn gain" (horns have a tendency to cause a "tilted down" response as frequency increases, due to their pattern narrowing at low frequencies down to the horn cutoff, since more of the sound is projected on axis and less off-axis). The way to correct this, is to use a low-electrical-Q quasi-third-order highpass crossover... a cap, then a resistor to ground, then another cap, then the L-pad/resistor/piezo driver. This can be tuned to give a pronounced "tilt-up" to the drive of the peizo, which cancels out its falling response. As for cap values... I would say, start at the value that gives the frequency desired for a simple first-order crossover, for both caps... and then tune to taste. It is OK to use different values for the first and second caps, if that works out best...

Regards,
Gordon.

Paul C
08-24-2006, 09:06 PM
Yes, GordonW is correct about using a resistor in series with the KSN1005 (and its near twin, the rear mount version, KSN1001).

You will find the 1005's mostly in older PA gear.

http://www.martinsoundpro.com/upload/item/0116.jpg

Paul C
08-24-2006, 09:08 PM
Hey, Gordon, have you used the KSN1165a?

http://www.martinsoundpro.com/upload/item/1407-1.JPG

This is a PowerLine model that produces 1800 hz - 30 khz. It is rated SPL = 92 db, but is actually more like 96 db. Has the horn built onto it, and has excellent sound.

GordonW
08-25-2006, 12:55 PM
I went back and looked up one that I had done, for a Powerline on a typical 4x10 horn. I stole part of Paul's graphic, but changed the diagram layout to what I was talking about. :D

This was for a PA app, from a 10" woofer, so I went with a higher crossover point... IIRC, it was around 4000 Hz. You can scale the caps larger, to have lower crossover points. Changing the cap relative values so that the first one is larger and the second is smaller, will make more of a "gradual" rolloff... while making them "more the same" will result in a flat top-end, with a more pronounced "break-point" near the crossover point (ie, a sharper "knee" to the curve). This can be useful in tuning the horn/driver combo... if there's too much upper treble/lower mids, then make the second cap smaller, while leaving the first one the same (or maybe SLIGHTLY larger)...

http://www.audiokarma.org/forums/attachment.php?attachmentid=24176&d=1156528493

macaltec
08-25-2006, 12:59 PM
Thanks Gordon. Clear as mud now :D .

GordonW
08-25-2006, 01:05 PM
Hey, Gordon, have you used the KSN1165a?

http://www.martinsoundpro.com/upload/item/1407-1.JPG

This is a PowerLine model that produces 1800 hz - 30 khz. It is rated SPL = 92 db, but is actually more like 96 db. Has the horn built onto it, and has excellent sound.

Actually, I did use one of those recently, to make a monitor cabinet, with a 15" Heppner woofer. Let the woofer run "open" on top, and used a resistor pad plus a 2.2 uf cap (IIRC, a 3 ohm resistor in series, and a 10 ohm in parallel with the piezo). Probably around 6KHz. Just to "extend" the top of the 15" (which sounded good by itself, just no treble).

For its app (PA monitor), it was VERY nice! Probably better than it needed to be!

Regards,
Gordon.

Paul C
08-25-2006, 05:56 PM
Right now for my main speakers I have some some Speakerlabs (10" woofer, W1008b) with the KSN1165a's rigged up with L-pads as per one of my drawings.

Originally these were 3-ways crossing at 800 hz and 8000 hz, but the Polydax mids are no longer available. I reworked the crossover to roll the woofer off at 1800 hz, where the KSN1165a's roll in. With -4db cut on the L-pads, they sound great.

GordonW
08-26-2006, 02:40 PM
Originally these were 3-ways crossing at 800 hz and 8000 hz, but the Polydax mids are no longer available. I reworked the crossover to roll the woofer off at 1800 hz, where the KSN1165a's roll in. With -4db cut on the L-pads, they sound great.

Get 'em while you can (since they're discontinued)... but the Vifa M10MD39-08 is a very good replacement for the Audax 12P25FSM (and given the Speakerlab parts, I assume that's what was in there?). Efficiency is very similar, as is impedence and frequency range...

Regards,
Gordon.

Paul C
08-26-2006, 05:45 PM
No, I have long forgotten the Audax/Polydax number on the mid, the Speakerlab number was M408b. The mids I had were similar to, but not the same as the 12P25FSM. It was discontinued back about 1990 or so. I got the last two that Madisound had. Then the surrounds on one of those went south and I replaced the mid AND tweeter on each with one KSN1165a each.

The woofer and tweeter on the Speakerlabs were SPL = 92 db, that Vifa is only 88 db. No problem, the baffle has been modified and I am satisfied with the sound now. These speakers will soon be replaced with some Pi Speakers 4pi Theatre's, using Eminence Delta-15's and PSD2002/H290 horns. Mo' bigger is mo' better! I just need to wait for the rainy season to stop so I can get outside and cut some wood.

crackerkorean
08-27-2006, 10:15 PM
Well they are hooked up and running on a Fisher TA-600 tube receiver. I have to say im impressed. This system is slowly coming together. The highs are detailed and coupled with the carlson cabs it sounds great.

I listened to a variety of things tonight and all was good.

Paul C
08-27-2006, 10:30 PM
Crackerkorean is referring to some drivers and horn lens I sent him a few days ago.

He has some Carlson cabs with Coral woofers. The tweeters were gone. His testing indicated the woofers were getting up to about 2000 hz. He and I exchanged a few emails, one of which I edited slightly into the first post on this thread.

One of the better piezo drivers is a screw in unit that produces from 1800 hz - 30 khz, and the published specs say SPL = 92 db, but they are really more like 95-96 db. I thought these might work well with his Carlson cabs simply wired parallel, since the woofer rolled off very close to where these drivers come on.

See the KSN1142a here (scroll down):

http://www.martinsoundpro.com/item.asp?id=340

http://www.martinsoundpro.com/upload/item/0962.jpg

This is the same driver section as in the KSN1165a.

I happened to have some of these on the shelf waiting for a floor monitor project.

For horn lens I had some of these to send him, too:

Parts Express 270-092

http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=270-092

http://www.partsexpress.com/images/270-092m.jpg

So, he has been playing with these, and can possibly tweek them by using the crossover and L-pad circuits above. He could also try other horn lens.

MarkAnderson
08-27-2006, 11:06 PM
So, will these frankenspeakers :D be available for audition at the mini-Fest in Atlanta? I'm curious to know just how good a piezo can be made to sound. :scratch2:

crackerkorean
08-28-2006, 07:57 AM
Im debating this mark.
I got some new speakers since out last little meet at the beginning of this year and thye are amazing and smaller.

The corals also would be one load pretty much by them selves. I just not sure as to which ones I want to bring.

crackerkorean
08-28-2006, 04:02 PM
Actually I think i might take them to the fest. The thoght of transporting my triangles in my car scares me a bit.

GordonW
08-28-2006, 04:20 PM
The woofer and tweeter on the Speakerlabs were SPL = 92 db, that Vifa is only 88 db. No problem, the baffle has been modified and I am satisfied with the sound now. These speakers will soon be replaced with some Pi Speakers 4pi Theatre's, using Eminence Delta-15's and PSD2002/H290 horns. Mo' bigger is mo' better! I just need to wait for the rainy season to stop so I can get outside and cut some wood.

It may say 88 dB on the Vifa spec sheet... but the M10 is within 1 dB of the 8 ohm 12P25. I've measured them back to back...

Regards,
Gordon.

Paul C
08-28-2006, 05:20 PM
Gordon, all of the original xover components are gone, the baffle has been changed. They sound good like they are. But those spkrs will soon be retired or given away. I start construction soon on the 4pi Theatre's. All of the components are in the shop, I just have to pick up some ply. But thanks for the info on the Vifa mid. Too bad I didn' know about that 5 years ago.

Paul C
08-30-2006, 10:57 PM
OK, Cracker is now testing some bigger horn lens, this 11.5" x 11.5" model by Dayton from Parts Express. The small 6" x 8" horn lens above are a little bright sounding to him. Well, they are made for PA speakers. So, he's testing these right now:

http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=270-300

http://www.partsexpress.com/images/270-300m.jpg

crackerkorean
08-31-2006, 11:45 PM
Ok here are some pics.
And I have to say they sound amazing!!!!!
Nice rich mids and highs that are not too bright
http://img.photobucket.com/albums/v609/crackerkorean/Audio/IMG_3980.jpg
http://img.photobucket.com/albums/v609/crackerkorean/Audio/IMG_3981.jpg
http://img.photobucket.com/albums/v609/crackerkorean/Audio/IMG_3982.jpg

macaltec
09-01-2006, 08:58 AM
I like the support in that last pic. Nice Atari 2600 game there. Which one is it?

Paul C
09-01-2006, 10:06 AM
This was a "best case" use of that piezo with his woofer. The Carlson rolled off right where the piezo tweeter rolled in, and the SPL's are apparently close enough for a good blend. No other components were used, just the piezo driver wired parallel to the woofer. Couldn't get any simpler. :banana:

Macaltec... do you think he should experiment to see which game cartridge has the best sonic attributes? :scratch2:

You can see in one photo, on the floor in front of the left speaker is one of the smaller horns I had first sent him. You can see the difference in size from that to the largers horn on top of the speaker.

macaltec
09-01-2006, 01:10 PM
I'll bet some of the more simplistic games would sound better from a purist standpoint :D . Just my opinion, yours may vary.

crackerkorean
09-01-2006, 05:19 PM
I guess I need to find several copies of PONG LOL

On the other side I have two because the one pictured is a little taller than the other.

macaltec
09-25-2006, 10:16 PM
I have joined the ranks of a piezo enthusiast. A brief of background on the project. An Altec Santana II cabinet, Dayton Classic 12" woofer, reworked port, and a new crossover, 12db/octave on the LF with a zobel network and a simple 6db/octave on the HF and an L-pad for level matching (Paul is that right?). I have installed a CTS KSN 1165 mid/tweeter and the crosover is @ 1800hz. I went on recommendation from Paul for the tweeter and am fantastically pleased with the results. Very smooth and detailed. Great imaging and depth as well. I am so pleased with this overall combination (especially the KSN 1165) that I plan to duplicate it in my Altec stonehenge cabinets. This has got to be one of the best sounding set of speakers in my house and I've got alot of speakers but that is for another thread. For the cost versus performance the KSN 1165 has got to be the best bang for the buck for your HF needs. Simply amazing.

Paul C
09-25-2006, 10:32 PM
Macaltec described it well. He didn't just tear up some Santana's to install these components. He had some perfectly good Santana cabinets with no drivers and wanted to put them into operation now without spending a lot of money, with the idea to later install original type drivers. He really did his homework and found those Dayton Classic woofers for the Santana cabinets. Nice choice! RUBBER surrounds, not foam, and the numbers worked well for his cabinets. All he needed was an inexpensive tweeter that would work in a two way configuration with his woofers.

I have attached the schematic I sent him.

http://audiokarma.org/forums/attachment.php?attachmentid=29103&stc=1

This schematic is similar to the one I use in my living room now with a Speakerlab W1008b (10" woofer) in a 2 cft cabinet. This same schematic could be used with other 6-8 ohm woofers by changing only the capacitor in the zobel network (computed from the woofer's Re and Le).

Macaltec said he did have to dial down the L-pad to match the woofer, even though a look at the SPL's say they should match without. I had to do the same with my Speakerlab woofers. These woofers are rated at 92 db SPL, as are the Daytons. Either the KSN1165a's produce more than 92 db at 2.83v, or these woofers do not produce 92 db at one watt (PE's graph shows 87-88 db). Anyway, it has been my experience that using an L-pad will allow you to get a good tonal balance with these piezo tweeters.

What was neat about using these for Macaltec's boxes, these tweeters fit the tweeter holes in his cabinets. If he wants, later on he can restore these cabinets with original woofers and tweeters. Or he may not want to. :D

These tweeters coming down smoothly to 1800 hz allows them to be used with many 10", 12", and even some 15" woofers in a two-way configuration with good results. The KSN1165a has the same driver as the KSN1142a in CrackerKorean's horns, only the 1165a has its own small horn lens built on. Like the KSN1142a driver, the 1165 is rated for 100w, with protection up to 400w level. The built in protection circuit gives a "soft compression" effect at high levels and its effect is practically inaudible.

KSN1165a

http://www.martinsoundpro.com/upload/item/1407-1.JPG

I have built smaller PA speakers and floor monitors with KSN1165a's that perform very well in these high power applications. They will certainly hold up in a home listening environment. More likely you'll smoke a woofer before you smoke these tweeters!

Mac, since you no longer need those A7's... you have my address. :D

DaWoofer
10-18-2006, 04:00 PM
Paul- I thought you might find this interesting in which way 8 of these tweeters were wired together. Switchcraft is the maker of the speaker box. Thats what I was told so I guess they are the ones who wired it.I haven't hooked them up to any source as of yet to see if they work or not. That is my next goal with them. I will let you know when I do. These are what apperears to be very similar to the KSN1001A.

DaWoofer
10-18-2006, 04:20 PM
I opened up the second matching box and its wired different! Look and see. The first box reads 83 kOhms this boxs reads 170 kOhms. As you can see they used different componants wiring the two. Do you know why that would be. A church had them and claimed they work and were in use. Wouldn't the different Ohms be difficult on the amp. Im gonna need to get them both the same aren't I. Any suggestions?

Paul C
10-20-2006, 11:30 AM
No, the different ohms had no effect. As far as the amp driving these was concerned, there was no load at all. The impedance was so high there was just no load on the amp.

I have NO idea how the manufacturer computed that impedance, but it is meaningless.

These are hooked up parallel, with a resistor in series with each tweeter.

There are three "groups" of CTS/Motorola piezo drivers:

The KSN1165a, KSN1142a, and one more, a 2x6 horn that I don't remember the number, all have the built in "Powerline" protection circuit mentioned earlier. These had a low end rolloff of 1800 hz.

Also in this "Powerline" series was the KSN1188a, which replaced the older KSN1086 (which lacked the Powerline protection circuit). This is a very large driver that goes down to 800 hz. It is very smooth, with some minor dips and humps that are far less than many well thought of drivers. For making a 2-way with a large woofer, 12" or 15", this is ideal.

In the second group are the various other 1800 hz drivers, KSN1025a (2" x 6" horn), and others, had an internal 22 ohm resistor, but no other protection.

The third group is comprised of various drivers with a low end rolloff of 4000 hz. This group includes the KSN1005a (which are what you have) and the similar KSN1001a (same but rear mount), KSN1016 (2" x 5" horn), KSN1038, KSN1041 all had the same 4000 hz driver. These had no internal components, just the driver mechanism.

BTW, while the 1005 was, and still is very common, the 1001 is pretty rare. So much easier to front mount.

Piezo drivers act like a very small lossy capacitor. In the audio range they have an impedance of about 1000 ohms. Up around 40 khz they drop as low as 4 ohms. And as frequency goes even higher, the impedance continues to drop. This extremely low impedance can cause some amplifiers to oscillate. Or if the amp picks up RF, it can cook the tweeter... I have seen this myself. It is really fun at a gig to see smoke coming out of the PA tweeters.

To prevent this, the 1800 hz drivers and the Powerline series have an internal resistor in series with the driver. This resistor is for protection of the amplifier, not the tweeter.

The various 4000 hz drivers can use a series resistor to protect the amp, just as you see on your tweeter arrays. Each tweeter has its own resistor. CTS recommended 20 ohms to 50 ohms. I have done listening tests, shorting around the series resistor, and you just cannot tell, either in level or tone quality. It makes absolutely no difference in the audio range. Putting 50 ohms in series with 1000 ohms is insignificant.

Again, this resistor is not for protection of the tweeter, and will not pad the tweeter at all, regardless of what you read in some catalogs. Whoever wrote those catalogs did not read, or completely misunderstood CTS's own paper on the subject.

If you want to use a 1005 or other 4khz driver with crossover and L-pad, put the resistor between the 8 ohm parallel resistor and the piezo tweeter.

http://audiokarma.org/forums/attachment.php?attachmentid=28285

DaWoofer
10-23-2006, 06:51 PM
Wow Paul, I want to thank you again. They really added some sparkle to the Heresys. The Heresys sound dull and flat without this array. I have a 2230b powering them running off of the Art 311. Sometimes ya just don't know what your missing until you have it and take it away. The 15 in. W-Bins on bottom running off the Art 311, the Heresys running by themselves and the array on top. The signal is being split off the 2275 wich runs the Heresys. It might sound confusing or not, but it sure "sounds" good to the ear. Much, much better than just a set a Heresys. I use to think the Heresys were great speakers by themselves. Now I know there can be much inprovement to be had on many speakers. Specially since these lacked so much now that I realize it.

Paul C
10-23-2006, 08:00 PM
Isn't the ART 311 a great little unit? I have one I use with my PA gear. The thing I like about it is the 1/4" inputs/outputs, making it easy to convert to RCA via adapters.

And it sure solves a lot of crossover problems.

dc270
11-12-2006, 04:41 PM
Found this old file, maybe it'll help too! Sorry for the size, dont know how to reduce it!


http://webpages.charter.net/dc270/Speaker%20Sales/OCR.BMP

Paul C
11-22-2006, 06:51 PM
Excellent!

Troy
01-24-2007, 07:39 AM
Sense i took up deejaying i'v had 3 set's of speakers. Out of the three, one set had a 1 1/2 screw Pizeo driver (which screwed onto the horn). It was the worst sounding horn i'v ever had, no matter how i adjusted my EQ'S it was harsh and nasty sound. I would avoid pizeo for all cost now. I did how ever spend the 75 EACH on new 1 1/2 compression drivers for those speakers, and the sound was great after that.

Celt
01-24-2007, 08:55 AM
Sense i took up deejaying i'v had 3 set's of speakers. Out of the three, one set had a 1 1/2 screw Pizeo driver (which screwed onto the horn). It was the worst sounding horn i'v ever had, no matter how i adjusted my EQ'S it was harsh and nasty sound. I would avoid pizeo for all cost now. I did how ever spend the 75 EACH on new 1 1/2 compression drivers for those speakers, and the sound was great after that.
Sorry, you can't judge the piezo design as a whole on your one encounter. You could have said the same for dynamic compression drivers, since many of them will etch glass.

bowtie427ss
01-24-2007, 09:06 AM
Sorry, you can't judge the piezo design as a whole on your one encounter. You could have said the same for dynamic compression drivers, since many of them will etch glass.Very well put!

A piezo element simply doesn't have the physical and mechanical properties to be an effective substitute for a compression driver.

It's all about application, and as the title of the thread suggests, "using piezos wisely"

just my .02

macaltec
01-24-2007, 09:07 AM
Sense i took up deejaying i'v had 3 set's of speakers. Out of the three, one set had a 1 1/2 screw Pizeo driver (which screwed onto the horn). It was the worst sounding horn i'v ever had, no matter how i adjusted my EQ'S it was harsh and nasty sound. I would avoid pizeo for all cost now. I did how ever spend the 75 EACH on new 1 1/2 compression drivers for those speakers, and the sound was great after that.

You most likely encountered a setup with inadequate crossovers in place. That is what this thread is about. How to use them properly and with good results.

Paul C
01-24-2007, 06:51 PM
Or, as likely, you had an encounter with cheap imitations made by someone other than CTS/Motorola. I warned about this early in the thread.

pmsummer
06-27-2007, 12:41 PM
Great thread. Makes me feel better about my newly acquired Piezo-equipped Frazier Mk V-IIs!

http://img452.imageshack.us/img452/2165/p62400015rs7.jpg
Front

http://img523.imageshack.us/img523/4154/p62400033zl8.jpg
Back (of tweeter)

SPL db
06-27-2007, 01:00 PM
How are you liking the sound of those Fraziers PM?

Scott

pmsummer
06-27-2007, 01:06 PM
How are you liking the sound of those Fraziers PM?

Scott

I still haven't put these "in system" yet, so I can't say. I'll have the terminals replaced by this weekend (one is broken), and I'll be A/B testing them against my AR-3a speakers, and maybe against my stacked Advents (which may have to find a new home soon).

I can say that 70% of my listening right now is through my Monte Carlos. Those things are just sweet.

Paul C
07-10-2007, 12:07 AM
Real CTS piezo tweeters are back in production:

http://www.piezosource.com/index.htm

"PiezoSource is proud to announce the acquisition of the CTS Piezoelectric Speaker product line, formerly announced as discontinued by CTS."

Here is a product list and data sheets for various CTS tweeters and horn drivers:

http://www.piezosource.com/general/Piezo_Products_list.htm

The KSN1142a horn driver is not listed. I have emailed them to find out if this will be available in the near future. They do list the KSN1165a and KSN1141a (same driver, differently shaped horn), as well as the large KSN1188a.

Another source is http://www.itcelectronics.com/store.php?cPath=1174_1288

Thanks to CuppaJoe for the above links.

And I have been buying genuine CTS piezos from Martin Sound Products.

http://www.martinsoundpro.com/item.asp?id=340

fdrennen
09-18-2007, 08:44 AM
Paul/Gordon:

I found an old PA/Speaker on a junk pile that had three piezo tweeters in the top the cabinet was ratty so I removed the tweeters and found that they were Motorolas. How do I identify the model # the only thing on them were Motorola and 206 stamped on the back.
:music:

Paul C
10-11-2007, 09:43 PM
Paul/Gordon:

I found an old PA/Speaker on a junk pile that had three piezo tweeters in the top the cabinet was ratty so I removed the tweeters and found that they were Motorolas. How do I identify the model # the only thing on them were Motorola and 206 stamped on the back.
:music:

Do your tweeters look like this?

http://www.martinsoundpro.com/upload/item/0116.jpg

KSN1005a's.

2pist
12-19-2007, 10:58 PM
I still haven't put these "in system" yet, so I can't say. I'll have the terminals replaced by this weekend (one is broken), and I'll be A/B testing them against my AR-3a speakers, and maybe against my stacked Advents (which may have to find a new home soon).

I can say that 70% of my listening right now is through my Monte Carlos. Those things are just sweet.

I suppose you have made the comparo by now? As a fellow Frazierholic I am interested in the results...

pmsummer
12-20-2007, 05:11 AM
I suppose you have made the comparo by now? As a fellow Frazierholic I am interested in the results...

The AR-3a and the Frazier Mark V are VERY close in sound and balance, with the Frazier being far more efficient, and therefore seemingly more dynamic.

I won't part with either.

fdrennen
12-20-2007, 05:37 AM
Do your tweeters look like this?

http://www.martinsoundpro.com/upload/item/0116.jpg

KSN1005a's.

No the "horns" are white and they screw on from the back. Just saw your reply.

Paul C
12-20-2007, 06:05 PM
Does the inside look the same? the fluting in the horn?

They made a rear mount version of the 1005, the KSN1001a.

http://www.martinsoundpro.com/upload/item/0115.jpg

And they made them in various colors and chromed, too.

Grainger49
12-20-2007, 06:41 PM
Yes, GordonW is correct about using a resistor in series with the KSN1005 (and its near twin, the rear mount version, KSN1001).

You will find the 1005's mostly in older PA gear.

http://www.martinsoundpro.com/upload/item/0116.jpg

I think I bought 4 of these a year or so ago. Do all that resemble this one apply?

fdrennen
12-21-2007, 05:49 AM
Does the inside look the same? the fluting in the horn?

They made a rear mount version of the 1005, the KSN1001a.

http://www.martinsoundpro.com/upload/item/0115.jpg

And they made them in various colors and chromed, too.

Yes they do look the same.

MartinV56
01-01-2008, 09:07 PM
Thanks Paul, excellent article, at the moment I am experimenting with piezo tweeters in a Altec 870B system (woofer 420y which he added a tweeter EV t-35) as the EV is not very good at high frequencies put a piezo tweeter with 2.2 MF for high frequencies, I go experiencing with the piezo tweeters, call my attention your excellent article, again thanks

MartinV56
01-04-2008, 07:49 AM
Experimenting with the tweeter piezo electric with 8 ohm resistor and 2MF capacitor, thanks Paul

zekk
01-17-2008, 08:03 PM
Hi Paul ... Is it wise to add a piezo tweeter to my Altec 604-E ?
If so, how do you wire it up ?
Thanks.
Zekk

Grainger49
01-18-2008, 11:48 AM
Well CRAP! I got the tweeter box out and it is a "super tweeter" just not the one you are posting about.

Do you have any info on this rocket tweeter???? (I can get better pictures to add)

Thanks,

2pist
01-18-2008, 08:14 PM
I doubt thats a true piezo with that hugh magnet hanging off the back.

Grainger49
01-18-2008, 09:19 PM
I think you are right, too much magnet for piezo.

bluewizard
01-23-2008, 11:58 AM
Some further thoughts on using Piezo Tweeters -

Using the KSN-1141A as an example, which is a 2x6 piezo horn.

Here is a link to the data sheet on this tweeter -

http://piezosource.com/general/datasheets/Piezo_1141_datasheet.pdf

First look at the Frequency Response Graph then scroll down to the Impedance Chart. Notice on the Freq Response graph, the peaks at about 8khz and 14khz.

This Tweeter appears as a 0.3uF load to the amp.

It's relative impedance according to the impedance chart at 2khz is about 210 ohms and at 20khz it is about 40 ohms. Though using 0.3uF and calculating the reactance, ignoring phase angle, gives us 256 ohm at 2khz, 26.5 ohms at 20khz, and a calculated 2.65 ohms at 200khz.

I would likely use a L-Pad to attenuate the Tweeter and stabilize the apparently load. But an L-Pad depends on having some resistance in parallel with it (R1 on the attached drawing). So, personally, I would likely use a 16 ohm L-Pad with a 15 to 20 ohm resistor(R1) in parallel (though a precisely 16 ohm resistor would be ideal). In this case, 16 ohms would be the value I would use to calculate the capacitor for my crossover.

However, many people suggest using a resistor in series (R2) with the Piezo to act as a frequency dependent attenuator, and to protect the circuit impedance from dropping too low at high harmonic frequencies. But you can see from the impedance chart for the KSN-1141A, that what we assume the impedance is can be very different from the actual apparent impedance. Consequently, you can only wisely chose a series resistor(R2), if you know or can calculate the impedance of the Piezo at various frequencies.

Now back to the Frequency Response chart and again, notice the peaks in the upper half of the chart. Some people think these peaks make the piezo sound a little harsh. By adding a series resistor, you can soften the high without reducing them too much.

For example, if we use a 5 ohm or 10 ohm resistor in series with this piezo, we have the following attenuation at various frequencies -

At 2khz, 5 ohm = 1.9%, 10 ohm = 3.6%

At 20khz, 5 ohm = 16%, 10 ohm = 27%

At 200khz, 5 ohm = 67%, 10 ohm = 79%

Note, that I based this on calculated impedances, rather than the impedance chart. Using the values from the chart, the attenuation at 20khz is going to be closer to 11% for the 5 ohm and 20% for the 10 ohm.

So, by adding a 5 ohm resistor we have created a gradual roll-off slope that goes from 1.9% at 2khz to 16% at 20khz. That should server to soften the high without wiping them out completely.

For this particular Piezo Tweeter, the perceived impedance seems to level off above 20khz, but adding a 5 or 10 ohm resistor can make sure that the impedance never drops below the value of the Resistor.

But to accurately pick a resistor for R2, you need to know the relative impedance of the actual tweeter you are using.

Steve/bluewizard

Paul C
01-23-2008, 02:44 PM
Some further thoughts on using Piezo Tweeters -

Using the KSN-1141A as an example, which is a 2x6 piezo horn.

(snip)

Steve/bluewizard

:thmbsp:

tallmike
01-29-2008, 06:30 PM
Well CRAP! I got the tweeter box out and it is a "super tweeter" just not the one you are posting about.

Do you have any info on this rocket tweeter???? (I can get better pictures to add)

Thanks,

It's not actually a compression driver - it's a mylar diaphragmed tweeter, really common design - kinda thing you can buy from Radio Shack.

In my opinion would sound nicer than a Piezo though. Often used as 'super tweeters' as they can't handle much in the lower mids.

Mike

Grainger49
01-29-2008, 07:54 PM
It's not actually a compression driver - it's a mylar diaphragmed tweeter, really common design - kinda thing you can buy from Radio Shack.

In my opinion would sound nicer than a Piezo though. Often used as 'super tweeters' as they can't handle much in the lower mids.

Mike

Ok that makes sense. I bought them to "open up the high end" of an open baffle stack of 4" "full range" Pioneer speakers I bought from Parts Express (8 per side).

It has not been implemented yet. But one per side in a shoe box sounded "pleasant."

photoman2
02-09-2008, 07:51 PM
GordonW,
Any chance you can pop over to this post and see if you have a idea on how to get a little more power to my soft dome? I would like a increase of about 25%..I have some crossover pictures posted. My thought was to replace the 12 ohm resistor to a 8 or 6 ohm.. Your thoughts please. Thanks! George
http://www.audiokarma.org/forums/showthread.php?t=146379

PioneerGuy75
03-27-2008, 09:24 PM
Excellent Information here!!! :banana::banana:

Thanks to all who contributed!

colterphoto
07-04-2008, 09:35 PM
Thanks for the great info here, esp Paul. I am a Klipsch collector and have some of their 1970's PA stacks the MCM-1900. The very high cabinet is called the MTM and houses 5 piezo tweeters in a vertical stack, arrayed in a curved formation. These are the rectangular models and measure 2 5/8 x 5 3/4 overall to the outside of the mounting flange. Are these from Motorola/CTS? I need a a few replacements- are the Parts Express models the real deal or inexpensive imitations? Thanks

colterphoto
07-10-2008, 01:05 PM
Paul? Anybody?

2pist
07-10-2008, 03:45 PM
Parts express peizo's are made by goldwood. which are imitations. I have no idea how close they are to the originals.

macaltec
07-10-2008, 05:03 PM
Paul? Anybody?

Last I remember Paul was getting the "real deal" from Madison/Madisound....something like that. I've been known to be wrong though, just ask my wife.

colterphoto
07-22-2008, 06:51 AM
I'll check Madison- thanks

jackfish
07-22-2008, 02:08 PM
Paul? Anybody?
capanjr on ebay has real Motorola KSN1005 piezos for $10/pair.

The CTS KSN1005 which is manufactured to the same specifications as the Motorola can be found various places for $15-22 each.

PiezoSource is the current manufacturer of the Motorola/CTS piezo line.
Piezo Source
250 Gish Road
San Jose, CA 95112
408-487-1700; 408-487-1707 FAX
usea@usea.com EMAIL
http://www.piezosource.com WEB

Celt
08-08-2008, 02:45 PM
Had a pair of PA cabs brought to me today for repair. They were dropped and it damaged one of the piezo drivers, breaking it's phase plug and lug post. Anyway, for those who have never seen the internals of one of these, here ya go. Note the paper cone with the piezo element attached, the waveguide and backchamber, that are sealed when bolted together. There's a 10uF cap and an inductor that surrounds the waveguide. You usually see small lamps in these for clip protection, but these (for whatever reason) don't have that. I also included a side view of the undamaged driver. Going to replace both with CTS Powerlines.

rocketj
10-27-2008, 08:12 PM
The information in this thread has given me the confidence to add some tweeters to my guitar cabinets, through which I run a Roland VG-99 and GR-33.

My question is this:

If I use the L-pad / crossover circuit (as illustratred by Paul C) and I wire it in parallel with a single 8-ohm speaker, will the load on the amp drop to 4-ohms or does adding the tweeter in this fashion have no effect on the load?

cheers.

gychang
10-30-2008, 10:17 AM
Paul C: I have the PE piezo tweeter and like to mate it with the B20 Pioneer (8" fullrange) http://www.parts-express.com/pe/showdetl.cfm?Partnumber=290-045 with a spare L-pad. (am considering putting the piezo on the backside of the speaker cabinet).

Will the combo work?, thanks,

gychang

Fred Sanford
10-30-2008, 12:12 PM
The information in this thread has given me the confidence to add some tweeters to my guitar cabinets, through which I run a Roland VG-99 and GR-33.

My question is this:

If I use the L-pad / crossover circuit (as illustratred by Paul C) and I wire it in parallel with a single 8-ohm speaker, will the load on the amp drop to 4-ohms or does adding the tweeter in this fashion have no effect on the load?

cheers.

Is this for acoustic guitar, or electric? I've used piezos successfully with acoustic amps, but always hated the sound of them with electric, even when properly installed. You might want to rig it up as a temp/test setup before putting too much work in it (or modding the cabinets).

YMMV-

je

rocketj
10-31-2008, 06:39 AM
I'm adding tweeters primarily for acoustic sounds and guitar synth, but will be playing electric through it, as well. The cabs will be powered by a clean, solid state amp. The VG-99 provides amp modelling and has output settings for line/phones, which makes it sound very good through a full-range system. I'm hoping that using an L-pad will enable me to dial-in just enough high-end to give a good balance for everything.

My cabs are Rocktron S112's (single 12" in ported trapezoid)...I have 4. Planning to add tweeters to only two of them and if the sound is too harsh for the electric sounds, I can put them on a separate amp and route my signals accordingly.

I'm just a little confused about how to wire the tweeters. I think I'll start by just using an L-pad with a series resistor in front of it (I was told this is the recommendation from the Motorola specs for the 1165's...to protect the L-pad). Hopefully, that will sound good...if not, I'll have to start experimenting with a crossover.

If I add a crossover, do I have to be concerned about the load on the amp? For example: the woofer (8-ohm) will be wide-open with a top-end freq. response of about 5K. If I crossover the tweeter at, say, 4K, in parallel with the woofer, will it put any extra load on the amp? What if the crossover point is lower for the tweeter (still full-range on woofer)?

marantzfan
02-14-2009, 12:24 PM
Good one to bookmark.:yes:

greenboy
04-20-2009, 12:15 PM
I haven't but skimmed a couple posts in this thread, but I believe the following link - also seen at Parts Express - is considered about as definitive as any by at least one pro designer (Bill Fitzmaurice) who has used piezo arrays in some of his designs:

Piezo Tweeter Application Note (http://www.pulsardevelopments.com/products/detail/piezoan.html)

Dub Special
05-13-2009, 08:51 AM
Can anyone help? piezo again u probly thnking!
how many piezo tweeters KSN1001A
can i hook up per channel on a power amp? safely!
just got hold of a cab with 14 in it and there wired in parallell.and had a resister on every tweeter.can i use all 14 on one channel?
so watt the differenece in series ie output? sound? ohms? do thay need resisters? ect ect
localy pa man at shop said u can wire as many as u like! cus no impedance but surly not?
hope someone can help
many thnks!!

dobias
07-31-2009, 04:54 PM
Paul C,
You have me convinced to go with piezo tweeters. I have a question about the horns though. How do you feel about waveguides, especially 12" waveguides for over 5kHz?
My present OB started out with a 12" full range on top augmented with a 12" woofer& a 15" sub. I found that it's better with just the fullrange & the sub.
It occured to me that I could use a 12" waveguide.
Frank

dc270
07-31-2009, 05:20 PM
Paul C convinced me as well to use a mid piexo driver on a EV build a while back. It was very impressive to say the least! I now consider Piezo in a new light- the good ones that is, not the knock off that are around every corner. The driver was very neutral sounding- not at all "hony" ot brittle soundng.
DC

dobias
07-31-2009, 06:00 PM
......to fill in the top 12" cutout. I've talked myself into believing the waveguide philosophy.
Frank

cmechmann
08-28-2009, 09:08 PM
I've been using 1005s in several different speakers.
recently however I bought a set of Eminence Beta 15As.
I have to say this with these and a set of 6 inch mids and caps at 2.6uf for the tweeters and 36uf at the mids these are about the most effecient I have use in a long time the 15As are rated at 97db the mids at 95.
the crossovers have adjustable attenuation.
4ohmn 10ohm and 20ohm thru a switch to the tweeters.
the crossover shows -3db 0 +3db positions.
I find it best right in the middle.
the mids come in a little light but this seems to match well for a slight gap between the motorolas and the Eminences. recorded guitars sound excellent.
Bass is clear,strong and not muddy even in a ported box. (tired of the weight of non ported)snares and the rest of the drums are right on the money.
I think I've found what I want in a ported box.

Also I have another speaker set, strictly home use, that has strange Motorola 621s.
they set flat about 5/8 inch thick, no need for a hole except for the leads.
they are piezos. they are in a dual set up, side by side in one package.
a 3 1/2 x 5 inch rectangle (I'll have to try to get a pic)
noticed they are not as sensitive as the 1005s but have a wider sweet spot.
the 1005s seem to have about 90 degree sweep, where as the 621 has about a 130 degree

Woofman
11-20-2009, 01:48 PM
I am going to use a KSN1005 piezo as a super-tweeter, crossing in somewhere in the 8khz range. I will be using an 8 ohm L-pad, and the R1 will be 8 ohms. If I am understanding this correctly, I will also need to use R2 to keep my amp stable. What value should R2 be? And will it affect the crossover components below it? I've attached a schematic for reference.

P.S. I borrowed this drawing from an earlier post, I hope you don't mind.

Woofman
11-20-2009, 01:51 PM
Sorry, I forgot to attach the drawing for my question, so here it is.

scoob
03-26-2010, 02:22 PM
Hi to all, great thread loads of usefull info however i could really use some advice and someone to check my mathematics for a crossover i have planned, could someone help? please resond!!! i dont want to bother going into the details in case this is a dead thread! many thanks in anticipation of some much needed help! (im a novice)

Woofman
03-26-2010, 02:50 PM
I hope someone will help you with it, although I didn't get an answer to my last post. This has been a great thread.

gearfreak
07-23-2010, 10:08 AM
Very informative thread. Thanks to the contributors.

Perhaps someone can comment on the lineage/model of Motorola piezo's in the attached pic.

Details noted:
-Pin connectors instead of solder tabs. Interesting.
-No screws hold the driver halves together, metal spring clips used.


Markings noted/transcribed:

-Blue dot terminal marking
-From back of horn mounting flange, near mounting hole, markings in this arrangement:

15E60617B01
3

- Stamped on back of the each driver near pins: 'B09'

- * There is an additional string of characters (smallest found on the units), on the front face of the 'driver' portion, but so small that I'll need to try again with a loupe, or disassemble one to be able to read them. (the horn obscures the line of sight for the most part).

Doc Rock
12-01-2010, 03:37 PM
I've been considering adding piezos to my open baffle rig that I'm putting together. It will have an 8" Tang Band 1808 full-range driver. I could mount the piezo facing up at the top of the baffle, or in a cutout above the full-ranger (possibly in a waveguide). Since its a full range, I'd like to have the piezo start adding in at above about 8 KHz. I'd also like to keep the total impedence at 8 ohms (which is what the full-ranger is), so it would be nice to be able to pad the piezo down and roll it off without adding a "crossover". Any suggestions for me?

VolvoHeretic
10-01-2011, 12:07 AM
Ok, I've read this thread a couple of times, and although I wired my 8 late '70's Radio Shack piezos per Altec A7 backwards as in parallel/series, but even still, they sounded great singing outside with 150 watts, I don't think that I need a super tweeter that puts out down to 3500 hz. Any suggestions for a crossover point and maybe a wireing diagram to match my A7's? 8000, 10000 Hz? I just found out I'm deaf above 12000 Hz:( but I am thinking a Death Star arrangment like this by stealing and molesting my kid's 12" Earth globe.:)

http://i143.photobucket.com/albums/r123/VolvoHeretic/Stereo%20Stuff/globetweeters.jpg

Delta287
10-17-2012, 11:24 PM
I went back and looked up one that I had done, for a Powerline on a typical 4x10 horn. I stole part of Paul's graphic, but changed the diagram layout to what I was talking about. :D

This was for a PA app, from a 10" woofer, so I went with a higher crossover point... IIRC, it was around 4000 Hz. You can scale the caps larger, to have lower crossover points. Changing the cap relative values so that the first one is larger and the second is smaller, will make more of a "gradual" rolloff... while making them "more the same" will result in a flat top-end, with a more pronounced "break-point" near the crossover point (ie, a sharper "knee" to the curve). This can be useful in tuning the horn/driver combo... if there's too much upper treble/lower mids, then make the second cap smaller, while leaving the first one the same (or maybe SLIGHTLY larger)...

Hi Gordon, after read this thread I wanted to check it on a new HI FI proyect
Where the Piezo will be, more as a super tweeter, from 15KHz and up.
The high band pass will be a 6dB / octave.
Ive tried your sugestion of the drawing, but it seems not to be working, But today I realized why ( I think ) my Vaccum tube low frequency generator have a very high impedance output.
Crossing a 16 ohms resistor brings everything down.
Im gonna try tomorrow using an audio amp between the generator and the tweeter.
Going back to the reason of this contact, what capacitor values do you suggest to start testing your design, having in mind , the 2 resistors involved will be 16 OHMs. ( I had it from time ago ) if it works as you state, Im gonna buy new components.
Thank you for your time and best regards.
David

barkerd
04-04-2014, 07:16 PM
for what its worth I am resurrecting this thread from the deep . Goes like this : saw some homemade model 14-ish clones for sale . Really good price / trying to put a tube console pull together with something for a friend. The horn is actually a magnavox powerline (which dropped me here) .... whoever made this had strange ideas or no knowledge whatsoever ....... he used a 12" cast basket Pro woofer ...nothing unusual .... and this horn ..... now I get that this model piezo horn goes down to "800hz" (more like 1000) and does not require a crossover .... but the only component in the cabinet is a 6.4mh iron core (1.2 ohm dc res.) inductor ...... woofer is 7.8 ohms dc ....that puts it around 200 hz for the woofer doesn't it ? doesn't sound good , horn needs to be pulled down and I'm hoping with help here I can get a handle on it's crossover needs.

dc270
04-04-2014, 10:21 PM
you might try posting this problem over in AK's "Speaker" forum!


oooops already there...damn it's late for me.....
DC

dc270
04-04-2014, 10:30 PM
Can you tell us what model tweeter & woofer being used here? Hopefully the woofer can cross over higher! I would be tempted to make this a 3 way set up if possible- just add a decent mid might work.
DC