testing piezo

[hufftoast]

Is there a way to test piezos before you glue them all together

[Bill Fitzmaurice]

Hook them up to a radio/receiver tuned in between stations, which is white noise.

[AdamZuf]

A non scientific way of doing it:


Get a few more piezos because it might be that some won't be usable.
Get a nice mic, preferably omni, place on stand.

Make something to put each piezo on (in turns), and place it in front of the mic about 1m away.

Get a recording software that has a frequency analyzer.

Tag each of the piezos with a number/letter.

Record each piezo with the same level of radio noise and mic gain setting. Make sure you mounted each exactly like the previous one to have results you can rely on later. Name the files after the piezos.

Compare the analyzer analysis of them all and pick the ones that resembles each other the most.
This will ensure that you'll have a close response from the tweeters in all cabs.
You can also "class" them after you see the results. I ended up with class A,B,C,D , about 65% were A and the rest were B,C,D. I only used the A and B classes at the end.

I had a problem with my Pyles when I built my DR250 and after doing the above procedure the cabs sounded the same.
It's not so easy to evaluate by ear because the response is varies too much when you move around the tweet. That's also why it's important to mount each piezo exactly like the previous one, in front of the mic.

Hope this helps
Adam

[DJ Big Ronn]

Wow, that sounds like a lot of trouble, but I guess you get them to match that way. I test mine by hooking them to a radio and if they come on I use um'.

[AdamZuf]

Don't pass on the mic test. I did and later had to take all of the piezos from my 4 DR250 and to rematch them. On some Piezos you can hear the annomalies, on the others you don't. They might differ in level and impedance (IIRC), not just frequency response, so it might sound ok but overall a few bad ones and you ruined your cab.

It seems like trouble but it's a nice afternoon activity, I enjoyed it.
Hey, these are piezos, you could expect the responsibility of serving as quality control

[Sydney]

I recently found 2 piezos leftover from a junked speaker given me. They are copies of KSN1016 2x5. They are stamped "THUMP" made in USA. They sound equal in volume w some variation in an impedance sweep. But I don't know if these are typical readings & since I don't have a large number to compare a Grade A to a lesser grade, I'm not sure sort-out using impedance curve data has any merit.
If the 65% grade A rate is typical. It would appear that ordering lots of extras might be wise.

[AdamZuf]

Well, I remember someone told me that the Pyles once had a better quality control, maybe it's specific to those, I don't know.
But with the price of Piezos, I think I'll still order a bunch of spares when I make other projects, even if these won't be Pyles.