MRehorst said:No, it's not one of the Quad 57s. Not an ESL63 either. Could be one of the newer models (I haven't seen their guts), or someone else's speaker altogether.
peterr said:I remember seeing this picture before somewhere...
As far as I remember it is a diy project using the panels of two Quad esl57 speakers per side.
specialx said:Hi on the topic of ESL's I have a few questions if anyone would care to help.
Firstly, with high/low resistance diaphragms 'gilid' mentioned 100Kohm resistance. Now I have been following this page regardin ESL's, http://www.amasci.com/esloud/eslhwto.html, and they say also 100Kohms, but make note that the resistance is measured using two pennies placed on the film a few inches apart, and then using a digi-multimeter. Would commercial speakers be around that or do they measure resistance differentl? Also is it bad to have too much resistance, say, 400Kohms or 1Mohm even? Or would you just have to bump up the bias suppies power? If that is the case, why not just use a high condutive material for the diaphragm and use a low power bias supply? (I am no electronics/physics genius so please excuse my questions if they aren't logical)
The bias charge on the diaphram has very little to do with the resistance. If you take a standard resistor and apply some voltage to one end, leaving the other end open, in a negligible time the other end will be at the same voltage. This is true for a 5 Ohm resistor and a 50 MegOhm resistor (if they go that high.) The high resistance of the diaphram coating, as has already been pointed out, is to prevent the charge from moving around a lot while the speaker is operating.
From a physics point of view, if you consider the stators alone, there is no electric field between them when the speaker is not playing. They are both at some high voltage relative to ground, but there is no net voltage between them, so the potential (Voltage) between them must be zero, and the electric field, which is the gradient of the potential (measures the rate of change in space) is perforce zero also. This also means that with no audio signal, the only thing holding the diaphram in place is the tension from the sides. Without that tension, the diaphram would be free to move anywhere between the stators. I'm ignoring edge effects in this model, but that's a very good approximation, because almost all of the active stuff of the speaker is in the bulk, and not on the edges.
The reason that there is a resistive coating on the diaphram is that it has to carry some charge, or the speaker wouldn't work. Think of this resistance as being a poor conductor. Now, the film itself is an insulator, so you couldn't really store much charge in a uniform way on it. Personally, I don't think that the resistive film needs to be very even. Any conductor, even a resistive one, will have any electric charge that is on it evenly distributed around a uniform surface. Corners will get charge concentration because of boundary effects, but a flat resistive sheet will have an almost completely uniform charge density on it, even if there are inhomogenities in the resistance. This is all for static situations; I haven't pondered the deeper ramifications of the speaker while it is playing.