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Power handling capability of original Quad esl 57s

After many years of hearing about how wonderful the original Quad esl 57s are, I finally found a near mint late serial number pair. I'm in audio heaven! I used to own the 63s and the 989s, and these are much better ( in the sweet spot).

Now my question: what is the power handling capability of the 57s? There seems to be some confusion here. According to the original manual, it is safe to use any amplifier as long as it does not produce more than 33 volts at any impedance. This is an interesting specification because it does not differ from the 63s.

Ok, let's do some math. At 8 ohms, 33 volts into 8 ohms gives us
33^2/8 = 136 watts! At higher imoedances, power must drop, so at 30 ohms, the speaker can only take up to 30 watts.
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tuttles OP
1 posts
 
Thanks for all the input, folks! I do have a pair of 405-2s, with the voltage limiter installed. This reduces the output of the 405-2 to 50 watts into 8 ohms (20 volts maximum). For the price of a used 405-2 (around $250), the sound is amazingly good.

But, the 405-2s don't reveal the full glory of the Quad's legendary midrange. The best amp I've tried so far is the Macintosh MC275. A truly spectacular marriage of two audio legends. The Quad II is widely recommended, but it has such high distortion at even moderate volumes, I can't seriously consider using it.

I'm seriously considering installing the protection circuitry, but I'm worried about their audible effect on the sound.
ct0517's avatar
ct0517
2,041 posts
 
The 405 works well. The sound I heard taking it easy with a Music Reference RM9 was amazing. One knowledgeable member has commented on the protection circuit in my review of them.
hornguys
180 posts
 
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Regarding its sound, don't forget that the 405 inverts signal polarity.

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clio09
3,353 posts
 
IIRC Roger Modjeski designed and voiced the 35 watt RM-10 for use with his ESL-57's.
dracule1
1,085 posts
 
Here is a recommended and not recommended amp list for the 57.

http://www.quadesl.org/Amplifiers/AmpList/amplist.html
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