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Ziggy 24th November 2008 01:52 AM

PIEZO NXT type panel
Have been mucking around with a couple of old Motorola piezo elements(dismantled from their casings) - piezo actuator disk and small cone only.

Stuck the small black cones with thin strips pf packing tape to the back of a thin corrugated cardboard panel: 18 inches x 12 inches approximately. Used a small matching transformer from some old Le Son piezo tweeters.

Wow! was I surprised!:eek: on their own in free air sound was reasonable loud but not very ''full sounding''. When stuck to the panel, the sound became louder and deeper. Still needs a woofer to fill in the gap, but I was amazed at the dipole like panel sound that reminded me of the NXT panels I have played around with.

These panels however, produce MUCH MORE high frequencies with lightening speed - and that's just crappy old cardboard:bigeyes: Is this some form of distributed mode thingy happening or what?
Perhaps worth some further investigation as piezo elements are not expensive and relatively east to find in various types and forms??

Will try some much larger thin poly. foam sheet to see what happens.;)

Ziggy 25th November 2008 02:06 AM

The two piezos are now mounted on a 3mm thick piece of MDF (medium density fibre board : dry wall in U.S ?) 3.5 feet X 2.5 feet. Sound has gotten much louder and deeper again. The high frequencies are still very much audible but I suspect that this is due to the rear radiation of the piezos.
From the front you can tell that the whole board is resonating as one large panel with louder sections where the piezos are mounted from behind.
There does not seem to be the typical ''piezo sound'' that we all know. Perhaps because the transducers are not horn loaded and encased in plastic?
I think there is some potential to this NXT type of implementation providing you have the impedence matching transformer which increases volume dramatically.

Anyone care to comment ??

Ziggy 1st December 2008 05:49 AM

Changed to ''CORE FLUTE'' (corrugated plastic laminate) of around 5mm, 3 foot X 2 foot.
Man, now we're talkin.........two piezo tweeters create this much sound?.........and go this low? You can just feel the entire panel vibrate on voice and guitar/drums.
For those who have frowned upon the idea of NXT panels(including myself), I'm beginning to see where the advantages are : obviously this is only an upper mid(??)/tweeter range, but percussion, piano, guitar sounds AWESOME:hot:

Ziggy 2nd December 2008 05:40 AM

231 views and NO COMMENTS?????...........looks like no one is taking this seriously.

Oh well, at home I have a working DISTRIBUTED MODE ACTUATOR PANEL of monsterous proportions producing sounds that I would not think were possible from a couple of transformer coupled , stripped down piezo drivers.

I have some NXT moving coil exciters on their way and will try to incorporate both methods(piexo + NXT) of panel excitation to compensate for the high frequencies loss of the NXT driver.

The prototype panel will be a large one - 6 foot x 2 foot with two NXT drivers per side plus a piezo on the front or rear depending on what the performance is like.

I have access to many different panels and have researched the NXT principles of sound reproduction for a few months now.

I know others have tried to implement these exciters without success, but I have a few aces up my sleeve on this one.

We'll see what happens..........if anyone cares that is

Damosan 3rd December 2008 10:42 AM

Send me a PM. I am in Perth too, and would like to see this.


theAnonymous1 3rd December 2008 03:20 PM

I've played around with moving coil exciters. After the initial excitement of experimentation wore off I came to the conclusion it's nothing more than a noise making novelty.

It's interesting you find Corflute to sound good as this was the worst sounding panel material I tried; second worse being foam core. Surprisingly the best thing I tried was some good old stiff corrugated cardboard.

coloradosound 3rd December 2008 04:06 PM

Do you have any pics for each of the above to show what
you were doing as these evolved? That way it may be easier
to see what you did and anybody with the old piezos can
also experiment. I had several of those that I took apart
and played with about 25 years ago, but I think I eventually
blew all of them!

Ziggy 4th December 2008 05:38 AM

At last some replies !!!:D

I'll try again to post some pictures. May need to compress the images as my last attempt failed.

I think that the coreflute sounds best so far because It is so large compared to everything else I've tried.
I agree that corrugated cardboard seemed to be much louder in a small piece. Wonder how it will go in a giant size?

Damosan, let me get a large size piece of board First and I'll get you to come around and here this princile in operation.

Damosan 4th December 2008 06:03 AM

Look forward to it.


Ed Holland 4th December 2008 06:26 PM

Interesting stuff Ziggy,

Do you have any means of making measurements? I must admit to having immediately dismissed NXT and anything resembling it directly to the "dustbin" without a moment's consideration! However, I find the planar & alternative technologies section of this forum to be the most interesting of all. People really are "thinking outside the box" if you'll pardon the pun.

Keep up the investigations!



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