PIEZO NXT type panel

[Ziggy]

Ed, good idea!.

Just a quick note(had a 30 minute listen) of the performance of the SOUND PADS................... surprising bass, good midrange, not bad highs, not bad, but not brilliant : very similar to what you would expect from an average full range driver - dual cone type.

The plastic corrugated coreflute I'm using can definately be improved on in the form of corrugated cardboard as suggested by theAnonymous1.

Have an idea in making a SHELLAC VARNISH(even ROSIN based varnish) to coat the cardboard. Will try on some small samples first to see what the result is.
Looking to harden the surfaces without causing warping.

[Ziggy]

Well I must confess that I am impressed with the sound of these little gadgets. They are not junk or cheap noise makers in my opinion.

I was prepared for a weak and thin sound but the reverse is apparent. Man, can these things vibrate a large panel or what!!!?

That, is where a few facts come to light :

1. If the panel edges or panel itself touch anything, and that includes thin wires, you will hear it, believe me. That's probably why the Audio Express magazine article recommended that the panels be suspended from the ceiling in mid air for best sound.

2. The corners of the panel are the most likely spots to buzz or resonate. Is this why the PODIUM speakers have(quote) ''ROUNDED EDGES BECAUSE THEY JUST SOUNDED BETTER THAT WAY'' ?

3. If the panels are to be mounted on a frame they will ABSOLUTELY require some form of rubber edge support/damping as suggested by Ed. Plus, pieces of blutak or something similar can be positioned in various places by experimentation as they can easily be removed or shifted as required. This may help in damping out any problems in regards to resonance.

4. As mention by theAnonymous1 and I agree, coreflute panel is not ideal and there are other alternatives to try.

After researching all the marketing hype regarding this technology which is a variant on the NXT principle, does it take rocket science for this to work? I think not.


On a positive note, the panels have that unmistakable ''coherency'' , ''crossoverless'' sound and musicality that comes with a full range driver.
In this case however, there is a huge room filling sound eminating in my study that is eery. Something that I have not experienced before.
Horns sort of do this, but in a different way - more up front, smack you in the face way which is not like the real thing from my experience.

Regarding the high frequencies, I can't truly say and conclude or agree that they are inadequate. On the contrary, some recordings sound superb in the high frequency department.

As most of us have been accustomed to forward firing high frequency ''death beams''(LOL) , these diffuse highs are at first strange sounding until further listening reveals that everything is still there only presented to the listener in a completely different way.Room acoustics/damping will play a huge part in the highs no doubt.

I own a large 2 way Azzura horn system and can already notice where it is lacking compared to the actual sound of live music in an acoustic environment which I am quite familiar with.

I guess NXT eciters on panels really are music /room/position dependant. Then there is the compatibilty and characteristic of the equipment, cables running them coming in to the equation.

If there are any knowledgeable NXT experts out there, I would love to hear your advice (or anyone else's for that matter).

I think this project can be licked and provide us with another great panel speaker that's easy to build and very cost effective

[el`Ol]

Some time ago I found bending piezo actuators in the web, but I have forgotten their name and where to source. Any help?
They were not cheap, but as they have much more excursion maybe they can do the low frequencies as well.

[gamgee]

Originally posted by Ziggy
.......to get the required output from piezos you MUST HAVE TRANSFORMERS!.

What kind of transformers?

[Ed Holland]

Hey Ziggy - here's another wacky idea for you:

A lightweight stiff mounted panel could have an exciter, plus a voice coil, in the style of a magnetic planar, interacting with a series of NdFeB magnets to augment bass.

What do you reckon?

Ed

[Ziggy]

el'Ol, I had saved a link to my P.C of such a site before my hard drive crash
The site was in English but was a Chinese company?

Anyway....has anyone got a link they can share?

Ed, yes, that's very interesting and would work. However, from What I'm hearing from a 3 foot X 2 foot polyprop. coreflute panel, I don't think it's needed.
There seems to be plenty of bass but the real test will be in my main listening room with TWO much larger panels and aditional exciters.

I'm expecting more bass and a good probability of more highs according to the technical papers regarding NXT panel dimensions and use of multiple exciters per panel.

I have just got hold of a 5.5 foot X 2.5 foot 2/8'' thick corrugated cardboard sheet to experiment with. In the next day or so, I will be experimenting with this as well as ''foam pvc''(expanded pvc) or ''Sintra'' board.

As I will be visiting my local sign making shop tomorrow, There may be other materials of interest, who knows?
As long as the panel material meets what we know as the basic requirements : light, rigid and not too thick, we will be on the right path I believe.

Then there's the fun of various and possible coatings??

[Ziggy]

The cardboard DOES NOT sound any good. It actually attenuates the high frequencies. Bass is better due to to a larger panel size no doubt,but that's about it. By the way the cardboard is actually thinner than I first thought.

Changing back and forth from polypropylene coreflute and corrugated cardboard, the difference is quite obvious. I have a set of drivers on each panel and switch from speaker A & B through my amplifier.

So, next step is to get hold of some large coreflute panels and stick all four exciters on one of the panels to see how it performs.

Not even going to bother with foamcore as I believe the secret is in the open cell corrugated interface that has the greatest effect on sound reproduction and the transfer of high frequencies.

It's a great pity that these exciters have been dismissed as toys or just noise makers. I am getting some fantastic sound here and I feel confident that the sound will only get better with some decent size panels correctly mounted in some frames.

[el`Ol]

I found one American and two German manufacturers of piezo actuators:
http://www.amercanpiezo.com
http://www.argillon.com
http://www.physikinstrumente.com
and one American shop:
http://www.piezo.com

6 g 20x60 mm Fs 60Hz seems to be common.

But is Fs below the operating range, as with dynamic drivers?

[Ziggy]

Interesting links el'Ol. Some of those piezos may be useful.Thanks for that.

Lat night I mounted all of the 4 drivers I have on the corflute sheet. The sound output increased noticeably of course, but, here's the thing.........the aditional two drivers were mounted to the far left and right of the panel.

As I was once again able to switch from one pair to the other quite easily and quickly, the sound quality was not as good as the more centrally mounted drivers.

It all makes sense now when you realise that the PODIUM speakers mount their drivers down the centre line of the panel width. Also noticeable from the photos on 6 moons , and as mentioned before, no one driver is positioned at the EXACT CENTRE of the panel - important?....yes, I think so.

[tiki]

Hi,

I found ... German manufacturers of piezo actuators: http://www.physikinstrumente.com

It's funny, many years ago I was involved in the development of the first piezo motors drivers for PI Ceramic, their manufacturer. If interested see Ansteuerelektronik und Leistungsendstufen für neuartige Piezomotoren hoher Leistungsdichte PI Ceramic 1996.
Regards, Timo