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-   -   woofer array for ESL? (http://www.diyaudio.com/forums/planars-exotics/32296-woofer-array-esl.html)

Few 15th April 2004 04:43 PM

woofer array for ESL?
 
I'm considering using a linear array of woofers in combination with a tall and relatively narrow electrostatic midrange/tweeter panel. I'm looking for woofer suggestions. Here are the constraints, as I see them:

1) I'd like to cross over between the ESL and dynamic drivers at a frequency that's low enough so that the wavelengths in the overlap region are long compared to the ESL/dynamic driver spacing.

2) I'd like to cross over high enough so that I can get away with a narrow ESL panel (12"?) and moderate stator/diaphragm gap (I'll probably use 1/16", based on previous experience). I'm thinking something around 500 Hz would satisfy these requirements.

3) I'd like to be able to consider using shallow slope crossovers, so the woofer must be well behaved for at least a couple of octaves above the crossover point.

4) I'm imagining 9 woofers per channel so that series/parallel wiring maintains the nominal impedance of a single woofer, and so that I can have a full height linear array (>5'). The cost of 18 woofers implies that Scan Speak drivers etc. are going to be out of my range. I can probably afford drivers costing not more than $25 each.

5) I have two NHT 12" woofers in sealed boxes so the woofer array need not handle very low frequencies. However, if it turns out I don't need the 12" woofers, so much the better.

6) I'm hoping that a significant fraction of the cost of expensive drivers goes into making them linear even when playing loudly. With 9 drivers per side, each driver's excursion will be proportionately reduced and linearity should be less of a problem. Does anyone know of low cost woofers whose small signal behavior rivals that of more costly drivers, even if they handle large signals less well? Or, if you see a flaw in my logic, can you explain?

7) I'd prefer drivers without major response glitches that would have to be ironed out with the crossover (such as severe cone break-up below 2000 Hz or so).

8) My first inclination is to go with ~6.5 inch drivers but could be swayed if others see advantages to larger or smaller drivers.

Thanks in advance for any thoughts you care to share.

Stephen D 15th April 2004 05:29 PM

Tangband W69-1042..?
http://www.tb-speaker.com/detail/1208_03/w69-1042.asp

Just under $27 here - http://www.nuera-acoustic.ca/products.html

Judge by the data sheet of that 1st link I posted though, not the one they show at Nuera as it's an old out dated & seriously in error data sheet.

goudey 15th April 2004 05:39 PM

The Peerless 850488 or 850439 may be of interest. The vifa P13WH-00-08 is also relevant.

The above drivers are reasonably priced, though not really cheap. They all have smooth rolloff at the high end. I have experience with the 850439 and the vifa, and have considered them all for an application similar to your own.

The 6.5 inch 850439 would probably allow a low order crossover at about 250 hz and provide good bass performance if a subwoofer is used. The smaller drivers are also adequate with bass, even of an open baffle is used, and would be better for a higher crossover frequency such as the 500hz you are considering.

If you are not already considering an open baffle approach, I would recommend at least an experiment. They don't measure well without a considerable amount of design refinement, but they sure sound good after you do. Mixing open baffle midbass with electrostatics can work very well.


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