Questions about piezo testing.....

[Bruce Weldy]

Seems to be the consensus here that piezo testing is a must. I'm guessing I should have bought extras....but 48 will be a good start.

- will the headphone output of an IPod be enough to test with? Figured I'd just download white noise from audacity. If not, should I just drag out the old Peavey PA head and use that?

- other than making sure there is a volume increase when running two parallel, are there any other things to look for?

[AntonZ]

The noise should sound pretty much identical on all. Once in a while you get one that sounds quite different. That means something is wrong. Sometimes it can be fixed. Open it up, see if the cone is attached to the element, no extra glue drops on the cone, no openings blocked in the horn throat, things like that.

[LelandCrooks]

Sweeps for spurious noise. 3k to 15k.

[Bruce Weldy]

Sweeps for spurious noise. 3k to 15k.

I don't do windows and I don't sweep.....so, explain this to me.

Can I download a file that does this? Or, does it require a device?

Thanks..

Still would like to know if the IPod puts out enough juice from the headphone out to test with...

[Bill Fitzmaurice]

Or, does it require a device?

.

A radio, tuned between stations.

[doncolga]

This is very timely for me since I'll be doing this too...I should be getting about 30 tomorrow afternoon...bringing me to a grand total of about 42 on hand for my two 12 element melded arrays planned for the OT12's.

So...if the cone has detached, it can just be glued back on?..that'd be handy.

[Bill Fitzmaurice]

it can just be glued back on?..that'd be handy.

Yes. There's a small vibrating element that's glued to the back of the cone. Most failures are when it comes unglued. To fix it put the cone in place on the horn body, put drop of hot melt glue on the apex of the rear of the cone, then quickly put the rear housing in place. Give it a minute to set, test it.

[Frederic Gelinas]

So...if the cone has detached, it can just be glued back on?..that'd be handy.

I did it with Krazy Glue and it worked.

[Bruce Weldy]

Or, does it require a device?

.

A radio, tuned between stations.

So, would the headphone output of a boom box be sufficient. Or, do you need to pop it open and get to the speaker leads?

[Rune Bivrin]

Headphone output would probably be OK, but not very loud.

Test it and report back, there's a good boy.

[LelandCrooks]

http://www.natch.co.uk/downloads/SigJenny/SigJenny.html

Headphone jack alone will work. Through a little amplifier is better.

[Bruce Weldy]

http://www.natch.co.uk/downloads/SigJenny/SigJenny.html

Headphone jack alone will work. Through a little amplifier is better.

Nice download. Already built audacity files with it to load to the IPhone and use in the garage. I'll let everybody know if the headphone output is enough juice.....as soon as I can come up with a cable for it.

[Bruce Weldy]

Ok, I 'm having a problem here. I build a tester. Simple design, running off the headphone output of my IPhone. The concept seems to work fine - not real loud, but works.

Here's the problem. I have one piezo hardwired as my basline. When I then add another piezo, the sound gets louder, but when I turn it around and reverse the polarity, it sound pretty much the same. I was expecting to hear a marked difference.

After testing several this way, I decided to try a 4k test tone through them. With proper polarity, volume goes down - when reversed, it's get way louder. So, my test piezo may be the one with a problem right? I swapped out when using the white noise and it made no difference.

Is it normal for there to be no discernable change when reversing polarity? Should a test tone work the same as noise when adding an extra piezo? In other words, it should get louder?

Not sure I'm doing something right here.

[Bruce Weldy]

Here's the tester..

[Rune Bivrin]

At 4kHz the wavelength is about 8.5cm = 3 3/8". You need to bring them really close. The long edges should be parallel and touching.