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4th December 2012, 02:39 PM  #11 
diyAudio Member
Join Date: Mar 2004
Location: Budapest, Hungary

These are static capacitances, but how do you take into account the radiation resistance of the air mass load, when the diphragm is moving?

4th December 2012, 03:08 PM  #12  
diyAudio Member

Quote:
I have no idea what the value is exactly. I think it should be insignificant to overall behavior of the circuit. If a real world panel is measured IMO there should be some difference in impedance vs frequency when bias is connected or not, from that you could in theory calculate back load resistance. BTW this also suggests that frequency response will change somewhat depending on bias voltage. I might be completely wrong as well. Regards, Lukas. 

5th December 2012, 09:23 AM  #13 
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Join Date: Mar 2004
Location: Budapest, Hungary

Right, since the efficiency is about 0.1%, the radiation loss (that't what we hear) could be neglected.

5th December 2012, 11:30 AM  #14  
diyAudio Member

Quote:
It is not the same. The radiating area of ELS element is large, so coupling between the film and air is good and losses are minimal. The problem is with amplifiers which have to dissipate almost all the power. Class D behave much better here as it can pump energy back into power supply. Regards, Lukas. Last edited by Bazukaz; 5th December 2012 at 11:38 AM. 

6th December 2012, 11:29 PM  #15 
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Join Date: May 2011

The ESL57 speaker has a real impedance component, that is the amount of power going into it.
It might have a sensivity of 87dB per Watt at 1m distance. 
7th December 2012, 10:42 AM  #16 
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Join Date: Mar 2004
Location: Budapest, Hungary

87 dB? I suppose it is not more than 82 dB...

7th December 2012, 11:40 AM  #17 
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7th December 2012, 02:31 PM  #18 
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Join Date: Mar 2004
Location: Budapest, Hungary

Lukas, I read in the original leaflet (http://www.quadesl.com/graphics/quad...cs/quaddia.gif) that the maximum output is 93 dB at 6' distance in its full range, which is 50 c/s to 10 Kc/s.
Now originally it was paired with the Quad II valve amplifier rated at 15 W. We can assume that 15 W resulted in 93 dB SPL (synergy between Quad components). 1 W gives about 12 dB less output, that is 81 dB. I don't know if dipoles follow the same law, but point sources give 3 dB increase with halving the measuring distance. So from 6' to 3' it gets 84 dB/1W/1m... Please correct me if my calculations are wrong. 
7th December 2012, 04:50 PM  #19  
diyAudio Member

Quote:
As far as I know, point sources drop by 6 and not 3 dB when distance is doubled. Larger planar surfaces drop at about 3 dB. Indeed, it looks like specification is for max. output: a) 93 dB@2m for 50 Hz.. 10 kHz b) 100 dB@2m for 70 Hz.. 7 kHz We can calculate in a different way as well. Max. input voltage for esl 57 as specified by quad is ~33 Vpk before arcing. Thats around 23.4 Vrms. Expressed in dB and compared to 2.83V that is : delta = 20* log(23.4 / 2.83) = 18.35 dB. So for figure b) we arrive at sensitivity of 10018.35 ~= 81.65 dB @ 2m At 1 meter it should be around 85 dB. However if measured at two meters this equals to a dynamic driver of around 8788 dB because drop rate is more like 3 dB doubling the distance compared to 6dB for point sources. Regards, Lukas. 

27th December 2012, 10:28 PM  #20 
diyAudio Member
Join Date: May 2011

When I feed 4.4Vrms into the ESL57 @1kHz I get about 85dB at 1m.
So depends on the impedance curve, what is the voltage for 1W? 
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