piezo with reversed polarity

[brodave2]

I just went through testing a batch of piezos before building a pair of melded arrays for a pair of omnitop 12s. Almost half of the piezos had reversed polarity. Is this common, or do I need to find a different supplier. I got this batch from BLT sound. This build and the last one, I had so many piezos with reversed polarity that I built some of the arrays with the reversed ones, just remembered to wire them reversed. If someone built an array without testing, they'd have a mess.

[LelandCrooks]

I tried a couple of hundred after your original post and didn't find any. I don't know where he gets his. I get mine direct from Goldwood. I have another batch coming in, I'll try it on them.

[brodave2]

I tried a couple of hundred after your original post and didn't find any. I don't know where he gets his. I get mine direct from Goldwood. I have another batch coming in, I'll try it on them.

I pick one out as my standard, then I put each one side by side , one at a time, with the standard. I run a test tone, 3khz through the standard. I then add the test tone to the one next to it. It's night and day, if one is reversed polarity, the volume stays the same and you can hear the sound divert. Take the same piezo and connect the leads reversed, it gets a lot louder. I try each one that I find reversed both ways, to confirm my results. There's no mistaking, almost half of them are reversed.

[LelandCrooks]

Yea, I put a polarity switch on my test rig so I could do the same thing.

[SeisTres]

Out of 54 I order from leland, I got none with reverse polarity (or maybe 1 but I decided to discard it anyway), to with "bad" ones, about 4-6 with low output and then the majority pretty even, and about 30% with high output.

[brodave2]

looks like I need to order from leland next time