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Old 23rd December 2006, 12:27 AM   #11
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Default RTR Panels Wanted

Quote:
Originally posted by stokessd
Why cross so high? You'll be mostly listening to the woofers, not the hard to build expensive, and good performing, ESL portion.

Sheldon
Because they will be be (in my case) mated to 100 db plus sensitive line arrays and I don't really want to use some power sucking lifeless HF drivers (like in my Acoustats).

I have used the little RTR panels in arrays with large horns with success in the past. Nine of the RTRs in a vertical array biamped will do the job. I'm a horn guy by nature....

Anyone have any?

I sold mine -

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Old 23rd December 2006, 07:58 PM   #12
Calvin is offline Calvin  Germany
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Hi,

the problem was, is and will be that You won´t be able to reach an efficiency of 100dB/2.83V/at whatever distance with a classical flat ESL!
One interesting idea -and the only one I could think of at the moment- could be to fold the diaphragm in a way similar to the AMTs. This could lead to a greater diaphragm size with same panel width or to a smaller width with the same membrane area. The stator would not be a single pair but it would be a array of small rectangular and massive rods with always changing polarity and the membrane would be zigzagged between those rods.
Click the image to open in full size.
For a good HF-response the depth of the driver would probabely have to be less than 5mm. To build such a thing would of course be a pain in the .......
As an theoretical advantage, besides that the smaller width supplies for a better dispersion characteristic, I see that there´s no stator in front or behind the diaphragm through which the sound has to propagate. The acoustical openness is therefore much higher than with a flat panel ESL. The stators on the other hand could and actually they must(!) be massive, which gives the highest field strength and most homogenous field distribution! Which is an advantage for small values of d/s.
Further do I assume that the membrane wouldn´t need very much mechanical tension since of the small dimensions of the stator rods. Maybe no mechanical tension in vertical direction would be needed anyway!??!
To keep stray capacitances (losses) at a reasonable value the diaphragm coating should only be right opposite the stator rods which leaves us with the nice problem to solve how to do this and how to connect this multitude of strips to a bias supply?

..and so on...and so on

jauu
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Old 24th December 2006, 03:01 AM   #13
Few is offline Few  United States
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Calvin,
Great minds think alike! I have a quickly assembled prototype of a folded ESL sitting next to me as I write this. I put it together last summer, but assembled it in a rush and introduced a short circuit somewhere and haven't had a chance to go back and do it right. I used copper clad fiberglass boards (an unusually thick version of the boards usually used for making printed circuit boards) for the stators. I etched away the copper where it would have just increased stray capacitance, and used 1/16" thick 3M foam douoble-stick tape for spacers.

I'm not quite sure what the relationship between depth and high frequency response will be. I made my stators much deeper than you suggested (several cm instead of 5 mm) in order to get some feel for the way the drivers behave. It's not clear to me that they must be as shallow as 5 mm to achieve good high frequency response, but I'd be very interested in hearing about your reasoning. I know the Heil drivers were quite shallow, but they also had magnetic field constraints to contend with.

By the way, Peter Walker of Quad fame included a device of this type in one of his ESL patents, so we're a few decades too late if we want to claim to be pioneers. I'd love to get one up and working nonetheless!

Few
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Old 24th December 2006, 02:29 PM   #14
Calvin is offline Calvin  Germany
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Hi,

my assumption for a small depth of the driver is, that the depth of the cavity that is formed by the membrane and the stators might lead to phase probs with higher freqencies. Too the membrane won´t work in a pistonic way and probabely not even in an a curved way, but the pressure building up in the cavity will rather send kind of a shockwave running over the membrane. This would introduce distortion as well as a reduction in efficiency. The membrane is getting ´stiffer´ the smaller the depth becomes.

jauu
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Old 17th January 2007, 04:25 PM   #15
WrineX is offline WrineX  Netherlands
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ever heard of the solosound panels , there 10cm w - 15 cm high.
4 of them make a nice 90 db already. they where used from 350 hz, so maybe you can decrease the 1,8 mm stator disctance to 1,5 or maybe even 1 and get a real nice SPL, only possible if you gona cross them over higer up in like 750 or whatever, just trial and error. also could use metalized mylar also huge SPL boost, but nasty load resistance.
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Old 19th January 2007, 12:50 PM   #16
Calvin is offline Calvin  Germany
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Hi,

with such a small panel (width, btw. which Panel anyway?) You hardly get the claimed efficiency below ~800Hz. Using the panel just above so high frequencies a reduction in d/s will be useful and necessary and will rise efficiency clearly.
The choice of diaphragm material is of low importance regarding efficiency, as well as the question of the conductivity values. But high conductivity has severe disadvantages with regard to other design aspects of a panel. Those disadvantages ragard safety aspects (arcing) and linearity, but definitely not SPL or load resistance! You´ve got something seriously wrong.

jauu
Calvin
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Old 19th January 2007, 01:20 PM   #17
WrineX is offline WrineX  Netherlands
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its pretty clear theres is a connection between conductivity and SPL, the other coating does not play that loud. i look and listen to 2 right now , the same panels only differents in the coating. and the one with alu does sound louder.


and for the crossover frequenty of those panels. search solostatic
they only use 4 of those panels and they claim 90Db

and they sound great so i dont think they have a gab between 350 - 800
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Old 20th January 2007, 09:42 AM   #18
Calvin is offline Calvin  Germany
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Hi,

if there´s a clear difference in SPL noticeable than thats a sign for a defect or a wrong coating material! As long as the coating doesn´t reach a too high resistivity, the choice of material doesn´t influence the SPL noticeably (btw. just one invisible fingerprint can spoil the hole thing!). So rather have a look for leakages in the softer panel or bad connection to the membrane!

I suggest rather than me searching around on a slowly loading website, You provide for a precise address!

What someone claims and what reality says, that can be quite differen matters.
First of all the SPL statements are incomplete since the data is not precise. No measuiring voltage and no impedance plot is given, as the supply with precise measurements over all is terribly low.

And again, panels of such small width will suffer from phase cancellation (depending on the baffle size) below ~1kHz. As any passive correction for this effect cuts on efficiency it´s quite unbelievable that they reach an effective SPL of 90dB@2.83V(8Ohms)/1m from 350Hz on. Measuring an unequalized panel at ~1-2kHz (where SPL is highest), recalculating for a lower impedance and voila we have the desired high number, while in effect @350Hz -10dB would be probable.

My critics is not about the resultant sound quality but solely about the belief in claimed specs that seem unrealistic and can´t be proofed because of missing information

jauu
Calvin
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