Using tube amp with electrostatic speakers.

@tomcy6

I think your skepticism, in general, is well placed. I've seen speakers who have crossovers DELIBERATELY designed to be hard to drive.  That's not the case with electrostatics however.

Plug: Has anyone seen my LM-1 monitor kits? Easy to drive, completely neutral, and free designs. :)

There's just no way to avoid the impedance dropping at the top when you are making an ESL. The entire panel is basically a capacitor, as opposed to a dynamic speaker which is an inductor + resistor. That's one of the main reasons Roger Sanders got into offering amps specifically designed to be excellent with ESL speakers.

I have however read about some radical designs where ESL's are driven from tube amps WITHOUT a transformer. Those who hear them say they are breathtaking. The amps are carefully designed around the ESL's though.

Not all panel speakers are the same though. The old Apogee's did have a ridiculously low impedance but it was relatively flat.

Best,


Erik

^^ to further build on that, many transistor amps can't continue to increase power into low impedance loads like 0.5 ohms. Further, the speaker cable itself becomes a significant factor when dealing with impedances like this!!

This works in ML's favor to help tame high frequencies, because the impedance curve of any ESL is not also an efficiency curve. What I mean by this is that if you put a watt into the speaker at its four ohm impedance level for a given output you should not be seeing 8 watts into the 0.5 ohm impedance level to get that same output level.

It is this 10:1 impedance ratio which is why tube amps are usually favored on ESLs as they tend to be less bright and there is a better ability to play bass. The brightness in this case is a simple frequency response error caused by a solid state amplifier's tendency to act like a voltage source (which is another way of saying that it tries to put out the same voltage regardless of what the load impedance is). By setting the impedance as low as they have, ML has limited the ability of most amps to be too bright, but I suspect various users will find that a lot depends on the amp and the speaker cables.

Erik, Roger Modjeski is indeed currently offering his own self-designed and built ESL speakers with his tube amps connected to them without output transformers. Anyone in the San Francisco Bay Area wishing to hear them can do so at Roger's new facility.

@bdp24

That's fantastic! For several reasons.  First, proves I don't make stuff up, which most readers think I do.  Next I am actually in the Bay Area so I'd love to.

Best,


Erik

I used a pair of Ralph's 60 watt mono blocks to drive my Acoustat Four's for a few years. Under powered for sure ... but oh my God, that mid-range!! To die for! 

The Atmosphere amps were on loan from a friend and I ended up using an ARC Classic 60 to drive those speakers. Still under powered with better bass. The speakers are long gone, and the Classic 60 is my spare amp ... just in case. :-)