Leaning Tower of Piezo

[Perplexed1ne]

I have not owned a piezo driver since the early 80's and my distinguished looking Dahlquist DQ-10's.

I am leaning in the direction of acquiring 5 of them now. I want to be sure to hear the glass breaking and siren screeching of Television shows and movies in a home theater system using somewhat limited "full range" drivers, the Aurasound NS4-255-8A 4", that like my ears, do not appear to do much above 15kHz. My kids however have less withering audio histories and fresher ear drums. I have learned on this forum that even dogs notice this driver's deficit and think that given the price of a piezo and the typical resistor/attenuator implementation, it is a good solution (especially if they are back firing).

These days is there anything that distinguishes any particular piezo, or given the construction and usage they all perform the same?

Recommendations, resistor values, and other sage advice is welcome.

Bruce

 

[Racket Scientist]

I've been debating adding a piezo as a supertweeter to my fullrange speaker. In my online perusal, the consensus seems to be that the cheap piezos (like Goldwood) have a pretty high failure rate and maybe don't sound so good. If I do go forward I plan to get some from www.piezosource.com - more expensive but probably worth it. There is also a thread (can't remember if its here or on AudioKarma) that discusses using crossover components to improve the sonic results using piezos.

 

[Godzilla]

The round one, the lemon squeezer one and the 2"x5" one at PE all sound about the same to me. I am crossing them over around 20k so just about any tweeter would probably sound about the same. Perhaps on paper with measured performance extra circuits and wiring may be better but for such a limited bandwidth i believe keeping it simple is better... imho.

The experience i've had i'd recommend trying two different things:

Rear firing - 20ohm resistor across and a 1uf or a 1.5uf cap (the 1.5uf cap will have more treble)

Front firing - 8ohm resistor across and a .33uf or .47uf cap (the .47uf cap will have more treble)

The resistor protects the amp but also changes the overall volume. 20ohm sounds louder than 8ohm.

I played with L-pads but found the above usually works well for me. Some may add a coil for a 12db slope (rather than 6) but for piezos i like them just fine as described above... and in the spirit of CHEAP... using less sometimes amounts to more.

I used piezos with drivers that were around 90 - 93db per watt (pioneer b20, various fostex, the Betsy and various Tangbands (around 86 - 87db). If the Aura is in this range i think you will have a good match that adds some air and even some realism to the overall sound. Now i am curious how the Dalquist was wired... does anyone know?

Zilla

 

[Perplexed1ne]

Funny you should ask. I was reminiscing and curious myself. When I bought them in 1981 they were second hand and just shy of ten years old. I set about re-capping and re-wiring the speakers and taking the big metal screen out from under the cloth. But, apropos to this thread the piezo were made by Motorola which I have just learned is making this driver again.

 

[Perplexed1ne]

Oh, and I found the "everything you wanted to know" thread on AudioKarma:

Using piezo tweeters wisely: a "how to" - AudioKarma.org Home Audio Stereo Discussion Forums

 

[planet10]

Another cheap tweeter worth looking at is the little Audax at ApexJr...

Since postage can often be more than the tweeters, i got a bag of these so if people needed them, they could piggy back on the postage of any order.

dave

 

[planet10]

Oh, and I found the "everything you wanted to know" thread on AudioKarma:

This to. Piezo Tweeter Crossovers | J Risch

dave

 

[Redge]

Hi all,
it's funny to see this thread because I wanted to post one with questions about piezzos !

Here is some questions about piezzo.

I had to say that I'm not good in english, and it is hard for me to understand all the things there's on audiokarma.

I build a 2 way with a piezo KSN1165a Motororla and a spa 25pa from monacor in a 56 L for the cabin and in bass reflex. First, they were mounted in parallel with only a 3,3µf on the piezo. I wanted to try without crossover.

But the high middle range doesn't sounds good. I guess that the piezzo and the monacor frequencies were playing together and makes some bad resonances.

I have to admit that I'm a noob .

The only solution I found to have a good sound is to connect an equaliser and almost cut between 2500 hz and 3500 hz.

I would like to optimize this configuration but I don't know really how.

Is someone can help me and show me what I have to do to cut the piezo or the monacor (maybe 12 db or 18 db crossover) ?

I don't have a lot of money and so, this project is very important to me.

(I think this 2 way speakers can give a very good sounds, I love this piezo motororla, they sounds smouth and never kill my ears, and the monacor is perfect for the price)

Again, sorry for my bad english, I'm just a french frog

 

[Radugazon]

Hello...

Once, i did this just for testing: see the pics

from the cheapest chinese piezo, I removed all the plastic stuff, just keeping the paper cone and the piezo disc, and put in a piece of wood.

Well, it's pretty horrific, not better that with the plastic make up horn , and phase plug, never seen such high Q dips and peaks.

Anyway, with a DCX, it's possible to keep it flat (the yellow curve is from something else) and the sound was enjoyable, especially considering the price. For sure something nice can be done with some piezo and some special tricks (Phy-HP Km 30).

 

[chrisb]

Funny you should ask. I was reminiscing and curious myself. When I bought them in 1981 they were second hand and just shy of ten years old. I set about re-capping and re-wiring the speakers and taking the big metal screen out from under the cloth. But, apropos to this thread the piezo were made by Motorola which I have just learned is making this driver again.

Bruce , thanks for the trip down memory lane.

In the first couple of years that the DQ10 were one of the hot items on audio scene, a buddy and I each had a pair, and just for fun decided to mirror image them. We did leave the wiring harness and mesh grille intact.

This required complete mechanical disassembling and reversing the four drivers mounted on individual baffles, and rewiring of 5-way XO, which were dipped in paraffin wax and the wiring was solid core. Both of those ideas seemed strange at the time, when big-*** gauge stranded wire was just becoming "the ticket", but in retrospect ....

FWIW, I owned the DQ10 & matching sub (passive XO) shortly after living with Quad 33/303/ ESL57 combo for a couple of years, and for my money Jon's attempt at homage to Peter Walker's design was an unqualified success. I could never get the same degree of involvement with the Quads as with the Dahlquists - but even 35yrs ago, "domestic" factors precluded keeping the "radiators" in the house.

 

[Redge]

I tried to tweak many times cheap piezo made in China, I never find them good.

Only Motororla piezo are good, but it is difficult to find them in France.

 

[sreten]

Hi, There is also a good "wiki" on piezo's on this site, though I'd go with p10's suggestion, rgds, sreten.

Speaker Stuff

 

[GM]

Oh, and I found the "everything you wanted to know" thread on AudioKarma:

Good to know, saves me from a lot of copy/pasting from all mine and others old posts on the subject, so it boils down to paying for quality or the 'shrieking meanies' best suited for car alarms, pest control or similar that require a LOT of damping and/or a very high XO point, ergo it's hard for them to have too much efficiency.

In short then, like the car repair ad says, 'you can pay me now or pay me later', so depending on the app either buy quality or try to save some $$$ by trading more time to get it 'musical' with a larger quantity of cheap parts.

Since you just want a bit of top end 'air', a cheap unit (or two) XO'd up around 30-40 kHz 1st order with some electrical damping to quell the worst of it will probably suffice.

For wide BW apps though, using a single cheap piezo (or two) normally equates to mostly listening to the quality of the XO if you don't use an array of them to raise efficiency enough to use CD horn EQ to flatten it (up to ~ +12 dB depending on how close to its cut-off you want to use it, same as a horn), so to my way of thinking this is a 'penny wise, pound foolish' approach for the casual DIYer.

For the more adventurous, making a piezo horn (or even cheap cone tweeter after Bozak) version of a large vintage multi-cell horn can be an entertaining experience.

GM

 

[Cal Weldon]

The round one, the lemon squeezer one and the 2"x5" one at PE all sound about the same to me. Zilla

Isn't that interesting. I recently did an informal listening test and found them all have a different sound with the lemon squeezer being the least painful. I used to think it was the 3X7 deep horn but not anymore. These are all Motorolas.

 

[GM]

Another cheap tweeter worth looking at is the little Audax at ApexJr...

Hmm, these look like the tweeters in the original Infinity Kappa series car audio drivers that I've had in a couple of vehicles. If so, definitely a step up from most piezos. Hindsight being 20-20, I wish I'd taken advantage of HIFI Buys dumping of these drivers (at least locally) since as I posted many years ago, the various two ways make well above average studio/mini-monitors, though of course need a 'sub' system for best full range performance.

GM

 

[amp_guy]

I don't want to muddy up someone else's thread here but I have some motorola KSN 1005 that I want to cross over at around 17k to add a little air to some fullrangers . Any reccomendations ? this is just for a center channel for my HT rig. These were liberated from a very beat up pair of Frazier monte carlo's

 

[Godzilla]

>>> I recently did an informal listening test and found them all have a different sound with the lemon squeezer being the least painful. I used to think it was the 3X7 deep horn but not anymore.

Thanks for that Cal! I never compared them back to back but felt the overall result was similar enough that they can be interchangeable (perhaps with minor cap value changes). Having used that 3x7 recently i was not really a fan, preferring the smaller ones. Personally, as they approach 6khz i can hear their signature sound and feel the need to push the crossover upwards.

Amp-guy, i recommend starting with 8ohm across and a .47uf cap for your project and play with cap values up or down depending on what you think works best with the driver you have. The B20 works well this way using the lemon squeezer version imo.

 

[amp_guy]

>>> I recently did an informal listening test and found them all have a different sound with the lemon squeezer being the least painful. I used to think it was the 3X7 deep horn but not anymore.

Thanks for that Cal! I never compared them back to back but felt the overall result was similar enough that they can be interchangeable (perhaps with minor cap value changes). Having used that 3x7 recently i was not really a fan, preferring the smaller ones. Personally, as they approach 6khz i can hear their signature sound and feel the need to push the crossover upwards.

Amp-guy, i recommend starting with 8ohm across and a .47uf cap for your project and play with cap values up or down depending on what you think works best with the driver you have. The B20 works well this way using the lemon squeezer version imo.

Thanks ,47uf was actually the value I had in mind but the 8 ohm would be needed given the high impedance of the piezo. I think what I have is what you all are calling the "lemon squeezer" the other drivers are the 4.5 inch fullranges that parts express was blowing out a few years ago, yeah I bought a load of those things too