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Using tube amp with electrostatic speakers.

Moons ago I started similar discussions and thought I had been given enough good advice not to approach the subject again. Here goes anyway. I've used Martin Logan electrostats for well over 30 years with quite a few different amps but have recently switched to a tube amp and dynamic speakers with which I am very satisfied.  It consists of the Cary Rocket 88R amp and Serie Reference 3 speakers. 

My brother was visiting last week and was so impressed with the sound that he decided that he might want to try a tube amp also (probably the same one as mine).  However, he is using a pair of SL3's that I gave him years ago and I'm concerned primarily about the current requirements of the Martin Logans as well as other concerns that I'm not thinking of.  I don't want him spending money on something that may not bring him improved sound so would appreciate more advice to pass on to him.  He currently uses a Rogue Audio SS amp with his SL3 speakers and, to me, it sounds very good. 
jimbreit
stewart0722
184 posts
 
Planars whether it be magnetic or electrostatic sound their best when fed prodigious solid state juice.....

I have Magnepan 3.7s and I use Bryston 28BSST2's

I do couple it with a full tube pre (Convergent SL1 Renaissance)

I don't think I give anything up to a full tube rig in terms of overall
musicality, but I gain a lot in terms of headroom.....
bdp24's avatar
bdp24
9,400 posts
 

Good info Lew. Yup, 14k is inaudible to me too now, thanks to over fifty years of performing and attending live shows, some with excruciatingly loud SPL. I had molded ear plugs made when I was in my 30’s, but the damage had been done. Youngins’, don’t put it off, use protection!

Stewart, ESL's and Magnetic-Planar loudspeakers present quite different loads to an amp, ESL's a very reactive one, M-P's a resistive. In addition, ESL's benefit from a voltage source type amp, M-P's a current source design. That's why Roger Sanders makes an amp for each type loudspeaker. Right Lew? 

stewart0722
184 posts
 
Everything you say bdp is absolutely correct.......
but none of it negates the fact that ESLs and Magnetics
require a lot of wattage to really sing....

That's why Sanders amps are typically 900w into 4 ohms

Can't get there with tubes, at least not w/ reasonable size/cost
restraints......although I've heard musical results with stats
and tubes, they just haven't had much authority at reasonable
to higher spls
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cleeds
5,640 posts
 
stewart0722
Planars whether it be magnetic or electrostatic sound their best when fed prodigious solid state juice.....
That really depends on the specific speakers. You're certainly mistaken if we're talking about Infinity Betas, for example.  
atmasphere's avatar
atmasphere
11,567 posts
 
Those effects will become increasingly pronounced as speaker impedance in that octave decreases relative to amplifier output impedance, everything else being equal.
Al, as I mentioned earlier, the impedance curve of any ESL is not a graph of its efficiency (unlike a typical box speaker; this is due to the fact that the impedance curve is based on a capacitor). The fact of the matter is the efficiency curve looks a bit different and often ignores the impedance curve. This is why an amplifier that acts as a voltage source will tend to sound bright on an ESL and might not make so much bass.

none of it negates the fact that ESLs and Magnetics
require a lot of wattage to really sing....
This statement is really questionable. If it were completely true a 15-watt amp would not do so well on Quad ESL57s (but they do- Quad used to make a 15-watt tube amp that was made for the ESL-57). Or a 60-watt amp on Quad ESL63s and Accoustats (we've sold lots of our M-60s to such owners). I've seen 70-watt amps play Sound Labs quite nicely. We sell a good number of our MA-1s (140 watts) to Sound Lab owners.  We also have a number of customers running M-60s on Magnaplanars (although they use a set of ZEROs to allow the M-60 to deal with the impedance).

The reason the Sanders needs such a powerful amp is that the speaker is inefficient. This is a conundrum with ESL designers- how to place the diaphragm... closely spaced so its easier to drive (might not handle excursion well)? Widely spaced to handle excursion (will be really inefficient)?

A speaker that **requires** a 900 watt amp to drive it is next door to criminal (and FWIW the Sanders does not seem to need that sort of power). The last thing you want to do with **any** amplifier is make it work hard (such increases audible distortions that make the presentation harsher and less detailed; exactly the opposite of what you want on an ESL). If you've set up your system properly, your amps won't be working hard most of the time.

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