PIEZO NXT type panel - Page 58 - diyAudio
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Old 27th August 2012, 09:17 AM   #571
CLS is offline CLS  Taiwan
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Exciter: cheapo from PE is good enough for both experiments and mid or even long term using (depends on how you use them, of course)

Panel: feel free to experiement for yourself. Think light and stiff first, then do whatever you want/can for stiffening and damping. Go big.

It'd be an easy start, then you'll get confused, frustrated, excited again... Eventually, it's really hard to get perfectly right (like everything else).

Fun? no doubt!
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Old 28th August 2012, 02:45 AM   #572
pol_bct is offline pol_bct  Reunion
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hello all !
I have made some promising tests with a set of fresh DML on very big panels,
2 x 2.1m x 1.25m, (not enough place to keep with my usual tri-stereo setting.)

when using more than one driver on a panel, comes the question of "where should I set them?",not too close, not too far, not too even, not too random...

for single driver setting my best choice was at 1/3-2/3, in order to get a 1/4 wave in one direction and an 1/2 wave in the opposite side.

keeping in mind that we want to spread resonances of the panel, I set the 4 DML in a 1/2 , 2/3 , 3/5 , 5/7 sequence in both directions vert. & horiz. at 1/2H-5/7V, 3/5H-2/3V, 2/3H-3/5V, 5/7H-1/2V...

POL
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Old 28th August 2012, 04:40 AM   #573
CLS is offline CLS  Taiwan
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Hi POL,

Glad to meet you here

The 1/3-2/3 positions you mentioned are based on a flat rectangular panel, right? (or at least roughly a rectangular shape)

If the shape gets more complex, the vibrating modes are getting complex, too. At least for higher frequencies with shorter wavelengths. And if there are some reinforcing ribs / frames ... etc., things change further. Do you agree?

I'm planning on a curvy surface panel with a 'spine', and maybe some additional tricks on the drivers...

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Old 28th August 2012, 07:53 AM   #574
pol_bct is offline pol_bct  Reunion
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Hi CLS
Yesssss, assuming the panel is about rectangular, mine are with upper corners rounded.

POL
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Old 6th September 2012, 07:28 AM   #575
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Quote:
Originally Posted by stera66 View Post
Sorry I overlooked that the topic is about piezo exciters.
I'm more interested in Bertagni type of panels.
I had built Beratgni type panel couple of years ago with limited success.
I used Styrofoam panel and a driver unit with the diaphragm+ voice coil assembly stuck into the panel..It was really exciting for a first build..but I want to try a refined build once again
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Old 6th September 2012, 08:40 AM   #576
CLS is offline CLS  Taiwan
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Hi there,

My recent work:

A piece of 3mm thick foamcore board, 180 cm by 90 cm overall, with a curvy spine on its back.


The rear side:
Click the image to open in full size.


The 'spine' for 5 drivers:
Click the image to open in full size.
(the rear surface is brushed with diluted PVA glue, that stiffens the paper significantly)


With drivers installed:
Click the image to open in full size.


With frames for hanging:
Click the image to open in full size.
(top/bottom wood bars are sticked with the panel by 2 layers of double side adhesive tapes - the type with thick soft foam)


The front view:
Click the image to open in full size.


It's there on floor during the works, now it's hung above the TV. This DML board plays the central channel in a linear matrix 3-channel system. You might see in the pic for other part of the system - dipole array midrange and slot loaded OB bass units.
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Old 10th September 2012, 09:19 AM   #577
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I know the whole point of most people's NXT experiments have been to build truly full range and usable panels but has anyone tried a 2 way?

Apart from ceiling panels for background music, There are only a handful of successful commercially available large panels that pass as proper hifi. The rest of the time you see NXT panels commercially available is with smallish panels and a subwoofer(TDK, Mission, Wharfedale Pioneer etc)

I was thinking a smaller panel(say 300mm x 750mm ish) mounted in a 350mm x 1200mm high 'frame' with either smallish woofers in each(think martin-logan style) or just that panel on its own running 100hz and up with a subwoofer or 2? I think a 350 x 1200 black cloth and veneer panel(black cloth hiding eps foam exciter panel) with 2-4 exiters each in a 5.1 system would look very nice and should sound good with some experimentation.

Running active would gain some headroom for the exciters too?

This allows smaller panels and some WAF(few people including myself can have 2400 x 1200 panels in the loungeroom haha!)

I know it is not the 'point' of these excercises, but I'm figuring if these major manufacturs with mega R&D capability have found this to be the 'best' implementation of the technology, maybe its worth a look?
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Old 10th September 2012, 09:41 AM   #578
CLS is offline CLS  Taiwan
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I make it a wide range unit in an active 2way all the time.
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Old 10th September 2012, 12:03 PM   #579
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How has it worked out for you? I figure it would be along the lines of a F.A.S.T. type system. I've ordered some basic exciters to play with anyway :-) I'm currently building a 36 driver a side line array too :-)
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Old 10th September 2012, 01:00 PM   #580
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Has anyone tried putting an exciter inside of a periodic structure? (sphere, cylinder, squashed version of them) This would eliminate boundary effects. I haven't read enough about excitors to have an idea of whether you can actually excite such a structure, though.
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