testing piezos

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Christian · #1 Post by **Christian** » Mon Nov 12, 2007 5:40 pm

Someone care to lay out their testing methodology for peizos?

Do you just hook 'em up to see if they work or actually measure the response or what? Will a damaged or faulty piezo be obvious to the naked ear or do I need yet another piece of equipment.

thanks.

DAVID_L_PERRY · #2 Post by **DAVID_L_PERRY** » Tue Nov 13, 2007 4:29 am

All I do with mine is test them with a cd player (Just connect the CD Audio out straight onto the piezo element) and listen to see if they sound the same.....to be honest all I am really doing with this is testing that the piezo is actually working. Like any HF element, they always sound like crap on there own...

Dave

gdougherty · #3 Post by **gdougherty** » Tue Nov 13, 2007 6:14 pm

The obviously bad ones will sound obviously bad. My last set of 50 I had 3 that had very noticeable distortion and one that sounded like someone had stuffed cotton down inside. Even after disassembly and checking the usual posted suspects they were relegated to the trash. I'm starting to think DP's method of listening to music is the way to go rather than radio white noise. Both may be in order. I used white noise to test consistency of frequency response (it's amazing how much that varies) but it's hard for me to hear anything other than very obvious distortion with noise. When I cranked it up, the HF got painful and unpleasant sounding with the noise. I'd like to test them with a fairly strong signal using music next time around to see how they sound.

#4 Post by **Bill Fitzmaurice** » Tue Nov 13, 2007 6:32 pm

gdougherty wrote:The obviously bad ones will sound obviously bad. My last set of 50 I had 3 that had very noticeable distortion and one that sounded like someone had stuffed cotton down inside. Even after disassembly and checking the usual posted suspects they were relegated to the trash. I'm starting to think DP's method of listening to music is the way to go rather than radio white noise. Both may be in order. I used white noise to test consistency of frequency response (it's amazing how much that varies) but it's hard for me to hear anything other than very obvious distortion with noise. When I cranked it up, the HF got painful and unpleasant sounding with the noise. I'd like to test them with a fairly strong signal using music next time around to see how they sound.

The advantage with noise is hearing whether they're in phase played side by each. If so they get louder, if not softer. I use one as a control, two sets of wires, one set goes to the amp, the other to the second tweeter being compared.

gdougherty · #5 Post by **gdougherty** » Tue Nov 13, 2007 6:37 pm

Bill Fitzmaurice wrote:
gdougherty wrote:The obviously bad ones will sound obviously bad. My last set of 50 I had 3 that had very noticeable distortion and one that sounded like someone had stuffed cotton down inside. Even after disassembly and checking the usual posted suspects they were relegated to the trash. I'm starting to think DP's method of listening to music is the way to go rather than radio white noise. Both may be in order. I used white noise to test consistency of frequency response (it's amazing how much that varies) but it's hard for me to hear anything other than very obvious distortion with noise. When I cranked it up, the HF got painful and unpleasant sounding with the noise. I'd like to test them with a fairly strong signal using music next time around to see how they sound.
The advantage with noise is hearing whether they're in phase played side by each. If so they get louder, if not softer. I use one as a control, two sets of wires, one set goes to the amp, the other to the second tweeter being compared.

So you won't get the same result with music, or it's just not as noticeable? I'm pondering doing a two pass test, one with noise to get my semi-consistent set in terms of response and the second with music to listen for distortion. Just have to find the right music to loop.

DAVID_L_PERRY · #6 Post by **DAVID_L_PERRY** » Wed Nov 14, 2007 3:36 am

Bill Fitzmaurice wrote: The advantage with noise is hearing whether they're in phase played side by each. If so they get louder, if not softer. I use one as a control, two sets of wires, one set goes to the amp, the other to the second tweeter being compared.

....are you saying that sometimes they are wired out of phase in the factory...or are you talking about once they have been wired up as part of an array and this is check on your own wiring ?

Dave

#7 Post by **Bill Fitzmaurice** » Wed Nov 14, 2007 9:00 am

DAVID_L_PERRY wrote:
Bill Fitzmaurice wrote: The advantage with noise is hearing whether they're in phase played side by each. If so they get louder, if not softer. I use one as a control, two sets of wires, one set goes to the amp, the other to the second tweeter being compared.
....are you saying that sometimes they are wired out of phase in the factory...or are you talking about once they have been wired up as part of an array and this is check on your own wiring ?

Dave

Rumor has it that some have come through from the factory out of phase. Never found one myself, but I figure if I'm testing for function it's just as easy to test polarity at the same time.

gdougherty · #8 Post by **gdougherty** » Wed Nov 14, 2007 11:18 am

Bill Fitzmaurice wrote:
DAVID_L_PERRY wrote:
Bill Fitzmaurice wrote: The advantage with noise is hearing whether they're in phase played side by each. If so they get louder, if not softer. I use one as a control, two sets of wires, one set goes to the amp, the other to the second tweeter being compared.
....are you saying that sometimes they are wired out of phase in the factory...or are you talking about once they have been wired up as part of an array and this is check on your own wiring ?

Dave
Rumor has it that some have come through from the factory out of phase. Never found one myself, but I figure if I'm testing for function it's just as easy to test polarity at the same time.

+1, though out of the ~130 I've worked with in the past few months I have found zero phase problems. I do wish the manufactured results were more consistent though. I've carved excess material out of the phase plugs in maybe 20% of them and even then the elements seem to be pretty inconsistent in terms of sound. I'd be happy to pay at least $2-3 each to know they're all the same even if I did still get an occasional unuseable one. Then again, by the time I figure in the extra I'm ordering (5 for every 4 I need) I'm almost at $2 each anyway.

Christian · #9 Post by **Christian** » Wed Nov 14, 2007 1:34 pm

I would gladly pay an extra dollar per tweet for a little consistency.

Sounds like a simple music test is all I need. I had no idea the response varied so much. Wish I had tested all my other arrays....ah well.

thanks.

AntonZ · #10 Post by **AntonZ** » Wed Nov 14, 2007 4:10 pm

I found different sources had different levels of consistency. The cheapest were cheap indeed: < €1 each, low and inconsistent output levels, plenty manufacturing faults. Apparently no quality control at all. They were ok for practice cutting. I put some in an e-bass cab, would not recommend to use them in any other application and even for that use cherry pick the best ones. For some €3 each I also got a batch of 30 excellent piezo's. No defects, loud and consistent output. With the losses due to inconsistent levels and manufacturing faults, the cheap piezo's cost almost as much as the other model, and the latter was noticably louder and more consistent.

I know what I will be ordering next time.

gdougherty · #11 Post by **gdougherty** » Wed Nov 14, 2007 4:33 pm

AntonZ wrote:I found different sources had different levels of consistency. The cheapest were cheap indeed: < €1 each, low and inconsistent output levels, plenty manufacturing faults. Apparently no quality control at all. They were ok for practice cutting. I put some in an e-bass cab, would not recommend to use them in any other application and even for that use cherry pick the best ones. For some €3 each I also got a batch of 30 excellent piezo's. No defects, loud and consistent output. With the losses due to inconsistent levels and manufacturing faults, the cheap piezo's cost almost as much as the other model, and the latter was noticably louder and more consistent.

I know what I will be ordering next time.

Wish we had someplace like that to order from here. My experince with the $1.30 GT-1016's sound more like your cheap source than your more expensive source. The only other type I've found are the CTS tweeters and the prices I've seen on those are substantially more expensive than the GT's, like 10x more expensive.

AntonZ · #12 Post by **AntonZ** » Wed Nov 14, 2007 4:49 pm

I can take some detail pics of the two different models that I got, if that would make it any easier for you to distinguish between offers. There may very well be more than those two models out there though.

gdougherty · #13 Post by **gdougherty** » Wed Nov 14, 2007 4:54 pm

AntonZ wrote:I can take some detail pics of the two different models that I got, if that would make it any easier for you to distinguish between offers. There may very well be more than those two models out there though.

The Farnell CPC and GT piezos apparently look pretty identical. If it didn't cost an arm and a leg to ship them I'd probably pick up a few to compare.

Wed Nov 14, 2007 5:47 pm

gdougherty wrote: The Farnell CPC and GT piezos apparently look pretty identical. If it didn't cost an arm and a leg to ship them I'd probably pick up a few to compare.

There are some details on the frames that are different. Curiously, the better looking frames with added trim details are not the better models.

gdougherty · #15 Post by **gdougherty** » Thu Nov 15, 2007 10:56 am

Bill Fitzmaurice wrote:
gdougherty wrote: The Farnell CPC and GT piezos apparently look pretty identical. If it didn't cost an arm and a leg to ship them I'd probably pick up a few to compare.
There are some details on the frames that are different. Curiously, the better looking frames with added trim details are not the better models.

Maybe the GT's have more money put into the frame when they should be investing it in the elements?