Richard Clark $10,000 Amplifier Challenge - Why Couldn't Anyone Pass this Test??

This is a reason why I strive to make my speakers easy to drive. Easy to drive means they will sound great across a variety of amplifiers and electronics.

+1

Not surprised by your finding as Quad ESL can be an extremely tough load. Differences in amplifier damping (output impedance) would be quite audible. This only proves one of the major design issues with Quad.

This passage is false.

The 'original Quad' (as bdp24 put it) is an easy load to drive. Differences in damping between amps is one of the few things that **isn't** audible on the speaker, owing to the fact that in the bass range the impedance is rather high. This reduces the difference heard between an amp with say 10:1 damping factor as opposed to one with 100:1.

OTLs are traditionally thought to not be able to drive 'tough loads' but OTLs can drive the Quads with ease. The real issue here is that the Quad is pretty transparent and does not need a lot of power, so its that 'first watt' that becomes so vitally important. Many traditional solid state designs are not so good at that first watt. Put one on a 'scope sometime and look at how they behave. Usually they have much higher distortion in the first watt than they do at higher powers until they approach clipping.

To actual musicians, the "feel" of the instrument is what counts, and Strads (not all of course) seem to have a feel and tone that people who play them really like, thus they might play better using them. Nobody disputes that fact really, and since there are a limited amount of zillion dollar Old Master built instruments out there, most good musicians can’t get near one…so, of course, they use other things and sound fine. Note that among Strads and other old and great violins the utility is often tweaked (i.e. repairs are made) that would be blasphemy among "vintage" guitar players (something I actually know something about as I am personally vintage). I saw a 50s Stratocaster advertised at Mandolin Brothers that didn’t actually work because to make it work you’d have to replace an original part (an original tone or volume pot or something), and that would make it less valuable!…love that…also, since Brazillian rosewood isn’t legal now (new stuff anyway), Martin Guitars is taking guitars from the 60s and 70s (a less than "special" era) apart for their rosewood, and making new and expensive high end guitars out of the backs and sides…clever bastards. The good news is there are thousands of great instrument makers doing fabulous work these days, so great instruments are available.

@atmasphere

Wrote this false and misleading statement (<-----  a paraphrase of how atma has posted):

The ’original Quad’ (as bdp24 put it) is an easy load to drive. Differences in damping between amps is one of the few things that **isn’t** audible on the speaker, owing to the fact that in the bass range the impedance is rather high. This reduces the difference heard between an amp with say 10:1 damping factor as opposed to one with 100:1.

Rather than argue with someone desperate to be an authority, I submit this link:

http://www.quadesl.com/quad_main.html

Best,

E

IMO it is a somewhat misleading oversimplification to categorize the ESL57 as being either an easy load or a difficult load.

It is a difficult load in the sense that its impedance descends to low values in the upper treble region, due to the capacitive nature of the impedance. Although even in that region its impedance is not nearly as low as the sub-1 ohm impedances of some other electrostatics, such as many of the Martin-Logan designs.

However, that difficulty is of course mitigated by the fact that most music contains relatively little energy in the top octave, where the impedance is particularly low.

It is an easy load in the sense that damping factor is a non-issue **with respect to bass control,** as Atmasphere indicated, because of its high impedance in the lower parts of the spectrum.

However, it will be a load that is **revealing** of amplifier differences, not only because of its transparency and musical resolution, but because differences in damping factor among different tube amps, and also between tube amps and solid state amps, will have tonal consequences.

Damping factor is inversely proportional to an amplifier's effective output impedance.  (I add the word "effective" to indicate that I am referring to output impedance taking into account the effects of whatever feedback may be present). The interaction of the amp's effective output impedance and the speaker's wide variations of impedance over the frequency range will certainly have tonal consequences, especially among different tube amps, and between tube amps and solid state amps. Less so among different solid state amps, since their effective output impedance is near zero in most cases.

In any event, the bottom line with respect to the tube-friendliness or lack thereof of the ESL57 is perhaps indicated by the fact that it was designed before solid state amps existed.

Regards,
-- Al