Piezo Testing Rig (video)

[RubiconProSound]

I started on another pair of melded arrays this weekend so I thought I would actually get some video this time of the rig I use to test all the piezos before they get glue'd up... I think I mentioned using it in another post a few months back but never got around to posting it.

This is a quick and dirty set-up and it takes all of about a 1/2 hour to throw together. It doesn't need to be pretty it just needs to work. The PVC was floating around the garage and it fit over the back of the tweeter nicely. I just drilled a few holes in the pipe and ran two pieces of 14 gauge through the sides so the wires would line up with the tabs on the back of the piezo. Some left over 1/2 inch made for a nice mic stand for the RTA.

If you don't have True RTA or a similar program you can still use the base plate portion to run sweeps and pink noise. The sweeps will tell more about the tweeter than the pink noise if your doing it by ear. You'll hear the frequencies drop out during the course of the sweep. The sweep and pink noise come from the Binks test CD. (Google it)

http://s252.photobucket.com/albums/hh9/ ... estrig.flv

[horst]

oh very nice, for someone who uses a lot of piezo's this is going to be a massive time saving, Leland will love you for this.
you should also wire up another known piezo with a switch so you can check for polarity.

[RubiconProSound]

The polarity check is next on the list...
I'm going to create a track with Audacity that flips the polarity only on the "test tweet" channel at 10 second intervals, (in phase, out of phase, in phase) the reference tweet channel will remain in phase. My amplifier is stereo so I'll just create one track with all of the tests on it. I just need to confirm the reference tweet is in fact the correct polarity before I mount it.

[gdougherty]

Nice setup. If I made more melded arrays it might be worth the time.

[horst]

The polarity check is next on the list...
I'm going to create a track with Audacity that flips the polarity at 10 second intervals and add it to the test track list. (in phase, out of phase, in phase) My amplifier is stereo so I'll just create one track with all of the tests on it. I just need to confirm the reference tweet is in fact the correct polarity before I mount it.

I think it's going to be easier and quicker to use a three position switch, 'off-one way-the other way', to confirm it is the polarity that is the problem or not some other funk

[LelandCrooks]

Leland will love you for this..

I kept thinking I needed to come up with something like this, and just never did it. Nice, simple, easy.

[pwfirst]

Now that is just cool. Phil

[RubiconProSound]

As a side note I've also discovered hot glue works well for Piezo repair. I wasn't having much luck with the super glue for re-attaching the cone to the piezo element so I tried a very small dab of hot glue. Worked very well. I didn't notice any adverse affects with the frequency response when compared to good units either. (at least no more difference then what can be found between the units normally )

If you do use the super glue method I'm guessing the gel type would work better. I had a high defect rate with this batch (25%) but gluing the cone back on brought all but one back to good working order again.

[AntonZ]

This jig is so simple yet so effective. I intend to make one with a second array fixed and a switch, to test for polarity as well. Thanks again, Rubicon.

I've spent quite some time looking through the forum for this one, as I see a few melded arrays in my near future so will have some piezo's to test. I wouldn't mind if this thread got stickyfied, or linked to from one of the sticky posts. A few pictures would be nice, too (I keep some pictures of particularly nice jigs for my reference, I have now made a couple of screenshots of the video for myself).

[AntonZ]

I made my own "Rubicon piezo test jig" today.

Getting some parts together.


Piezo loaded on the finished jig, connected to the Earphone out of a transistor radio tuned between stations.


The starship controls. Beam me up, Scotty

[Tom Smit]

So Anton, your "known good one" is held in the uprights, and your "test subject" is in the cup?

Thanks.

[AntonZ]

That's correct, Tom.
I've got to work a bit on the thick copper wires, it takes some wiggling to make both lugs from the piezo make a good contact. Not as smooth as I had expected. Then again this is good enough as it is for sorting out the 30 tweeters that I'm looking at doing in the near future.

The phase switch works nicely. It's not total silence when out of phase, but the difference is very noticable. I do not have RTA software, could set up a mic stand above the jig and connect to the DEQ for RTA if needed. I just look for similar response by ear for now.