Deformation of Piezos

Anything not covered elsewhere.
Post Reply
Message
Author
jemo1234567890
Posts: 43
Joined: Wed Jun 19, 2019 2:51 am
Location: Germany

Deformation of Piezos

#1 Post by jemo1234567890 »

Hello all,

last week my order of parts-express with my goldwood piezos for four DR200 arrived from US.

I tested them with pink noise first and noticed that some are a hint more sensitive than others.
Two piezos out of 100 are very quiet or didn't work.
The rest is working for the initial test.

Because of the different sensitivity I measured the capacity of every piezo.
Of the 88 pieces I get a range between 147 nF and 177 nF. The average capacity was 159 nF.

Because I don't want destroy the tweeters while cutting and painting the pastic horns, I opened all the piezo-tweeters.

Did you ever opend your piezos?

Out of 88 pieces, 41 have a deformed paper membrane. Some a little some extremely heavy (like you can see in the pictures).
deformed_piezos_out-of-88_1.jpg
deformed_piezos_out-of-88_2.jpg
Do you know if I would hear the deformed paper membran later in the melded array?

Do you know a solution to fix these deformations?

I think the little deformation I can maybe carefully fix with my hands.
For the really bad ones I think the cables are to short and the piezo elements aren't centered. For these piezos I could try to desolder the metal connection and solder longer cables to the piezo elements.
I'm a electrical engineer so the soldering job wouldn't be a problem for me if the procedure could be the solution.

Thank you very much for your help and answers.

Best regards
Josh

User avatar
Chris_Allen
Posts: 3355
Joined: Wed Jul 11, 2007 2:43 pm
Location: Huddersfield, UK

Re: Deformation of Piezos

#2 Post by Chris_Allen »

I've been through plenty of piezos and opened enough too when spray painting arrays. I can honestly say I've never seen any like that. Given the small vibrations of the piezo and distance to the plug which sits into the cone, those deformations must have an effect on output.
Built:
6xDR200, 2xT39, 2xT48, 2xJack110, 1xOmni10.5, 1xAutotuba, 1xT18, 1xSLA Pro, 1xW8, 1xW10

User avatar
Seth
Posts: 2731
Joined: Thu Sep 10, 2009 8:06 pm
Location: Sacramento, California, USA
Contact:

Re: Deformation of Piezos

#3 Post by Seth »

From the Goldwood website:

"Goldwood offers a Lifetime Warranty against manufacturers defects on most the products we sell. You can buy with confidence knowing that our decades of experience in the industry will provide you with high quality products. We independently test all the products we sell and stand behind them 100%. You can view the warranty details below."

https://www.goldwood.com/warranty/
Build in process - 2 WH6, one Alpha 6a loaded, one PRV Audio 6MB250-NDY loaded

Two 2x6 shorty SLA Pro's
One T39, 16", 3012LF loaded
Tall AutoTuba, 20" wide, 2x 8" MCM 55-2421
TruckTuba, 8½" wide, 2x 8" MCM 55-2421

jemo1234567890
Posts: 43
Joined: Wed Jun 19, 2019 2:51 am
Location: Germany

Re: Deformation of Piezos

#4 Post by jemo1234567890 »

I wrote to the sales team of parts-express and waiting for feedback.

But maybe I should check the warranty options of goldwood, too.

Thank you Seth.


Best regards
Josh

himhimself
Posts: 599
Joined: Fri Nov 13, 2015 9:34 pm
Location: Vancouver BC & Bloomington IN

Re: Deformation of Piezos

#5 Post by himhimself »

Parts Express has awesome customer service. I had a few piezos in my order that were DOA and they credited my account. I over ordered anticipating there might be a few bad ones (allowed me to hit a price break point too), so in the end I had just enough good ones for my arrays.
2xT30 (20", 3012LF)
2xT30 (21", 3012LF)
4xOtop J-array (Beta12, melded/straight piezos)
Truck Tuba (MCM)
Next up: 2xJack12 or family of table tubas

User avatar
Charles Jenkinson
Posts: 1125
Joined: Sat Aug 06, 2011 3:25 pm
Location: Manchester, UK

Re: Deformation of Piezos

#6 Post by Charles Jenkinson »

Small sensitivity differences in piezos balances out in an array. When I'm checking phase with the reverse polarity rig and SPL meter i write down the loudness of each one. The deformation you uncovered may or may not be viewed as a manufacturing defect by the manufacturer. The diaphragm / surround is possibly not highly structurally loaded under working conditions, so durability may not be affected if not clamped properly between the housings. Given the lowish value and aggregation when working, if they're working when one tests them, stick 'em in an array would be my philosophy. One needs to satisfy ones self however. The manufacturer may have changed something or they may be chucking them out with less quality control due to all the BF purchasers, who knows.
2xJ12L (3012HO) switchable/melded
2xT30

Words&graphics - Audio&Acoustics - Hardware&DSP; 3 different paradigms.

jemo1234567890
Posts: 43
Joined: Wed Jun 19, 2019 2:51 am
Location: Germany

Re: Deformation of Piezos

#7 Post by jemo1234567890 »

Yes, I think that something in the manufacturing process went wrong, too.

I wrote to goldwood and they will talking to an engineer.
Goldwood told me that for my problem I have to find a solution with parts-express because I didn't order from goldwood.

I think that the small deformation wouldn't be a problem in an array because with a gentle tweezer fixing they schould be as normal.
But I'm concerned about the bigger deformated piezo tweeters which have not centered piezo elements because of too short cables.

But thank you all for your answers.

Post Reply