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

@erik_squires   

+1 the link you gave states this about Quad:

"The second downside is that they are a difficult load for the amplifier to drive. They are highly reactive loads (primarily capacitive). Their impedance drops as the frequency increases. This makes the Quad ESL a bad choice for single ended tube (SET) amplifiers."

@almarg    

+1 that is what I stated I even clarified that damping equates to  "(output impedance)" 

" They need about 15 Watts of the best amplification you can get your hands on."

" The Quads will play up to about 100 dB, which is much louder than I play music even when playing loudly. "

" The second downside is that they are a difficult load for the amplifier to drive. They are highly reactive loads (primarily capacitive). Their impedance drops as the frequency increases. This makes the Quad ESL a bad choice for single ended tube (SET) amplifiers. "

I think I can figure out why this guy isn't an authority, desperate or not.

All ESL panels I know of follow this descending impedance curve, which is a problem for a lot of amplifiers since most amplifier’s have rising impedance at the upper end of the frequency spectrum, resulting in an overall significant net loss of output.

This is in addition to current limiting, which thanks to music being bass heavy, is less of a concern.

Tube amplifiers rarely have the low output impedance (anywhere) that solid state amps do so they start at a disadvantage.

However this is all basic electrical / and voltage dividing theorems. The final choices about matching any given amp to any given speaker has to include the speaker’s acoustic output and room.

Given the impedance curves of the amps and speakers you can predict reliably that amp X’s electrical output will drop 6 dB at 20 kHz with a given speaker, but I can’t tell you if you’ll like it. :)

Best,


E

So this brings me full circle. I've seen speakers that are hard to drive at the top end, at the bottom and all across the spectrum.

The ESL speakers come by their low impedance and difficulties as do the full-range planar-magnetics (Apogee) via legitimate reasons. That is, the speaker technology itself poses challenges which the designers accept in exchange for other benefits. ESL's are essentially giant capacitors, no way to get around that.  The sacrifice is made to submit the amplifiers to brutal loads in exchange for having a large single driver driven across it's surface (how well ESL's actually do this is arguable, but not for here).

I think that with the worst of these panels, a lot of OK amps are going to perform quite a bit differently, which with "nice" speakers could perform nearly identically.

And  as I mentioned, some speakers are deliberately hard to drive in the bass, or use smaller-dual woofers which put a strain on amplifiers.  When I look at the impedance curves and read about reviewers talking about how "discerning" this speaker is, how easily it could tell the difference between a Boulder XYZ amp and their Onkyo receiver, well, duh. It was made that way.

But this discernment does not make either the amplifier or the speaker more musical. It's just more demanding.

Best,


E