Using tube amp with electrostatic speakers.

@bdp24 From my conversations with Roger, it’s based on frequency response. Most curvilinears at the time were not very flat without significant EQ.

Roger's stuff is flatter, with much better dynamic range. Earlier stuff did not have very well matched woofers though, that's improved.

Now if some one could convince him to make a 2 part ESL panel for better horizontal dispersion he might own the speaker world. :)

Best,

Erik

Being a long-time Quad ESL (original 57's) owner, a small sweet spot is old news to me!

Very few amps can drive the CLS (esp. of that time), which is why they -IIz came out pretty quickly.  ML's with dynamic bass are not that difficult to drive with some tube or hybrid amps - which is the topic.

Off topic - I've never heard any tube amp that could drive some tough full range panels such as Scintilla's, or the CLS.  The CLS IIz can be driven, but not by any reasonable priced tube, and I've never heard a tube amp that doesn't make drums sound like a rotten tomatos getting hit with a mallet when trying.  I owned mine for 15 years, and with 3 dealer/friends vying for my business I heard just about all of them.

No matter what amps I try, I always end with back with my Nelson Pass products - which besides the Aleph Series can drive any panel or hybrid and avoid the SS hardness tube heads so dislike.

So bagwell, are you saying you haven't found a tube amp that works for you with full range electrostats or with any electrostats (including hybrids)?

Bag, The ORIGINAL ML CLS was a match made in heaven for a tube amplifier; it was a nominal 16-ohm load.  After I auditioned a pair in a store, I bought them immediately and loved them in my home system, although they were a bit bass shy.  I related this same story somewhere else earlier in this thread.  Very shortly after the CLS debut, ML could not leave well enough alone; they rapidly replaced the original with the "CLS II".  This is the speaker to which you refer when you speak of difficult to drive. Foolishly, I replaced my CLSs with CLS IIs without knowing much about the difference between them. Turns out, the II had a hellacious impedance dip at mid-frequencies, as you say, I think down to 2 ohms at something like 1-2 kHz. This was bad for any amplifier, and it sounded awful with my then Futterman OTL tube amplifiers.  ML got the message very quickly and replaced the II with the IIz, which was merely a bandaid on the problem they introduced when they went from the original CLS to the CLS II.  To my ears, the IIz bore no comparison to the original CLS in greatness. At that point in time (when the II was replaced by the IIz), I called the factory and asked them what was up.  They told me quite frankly that they did not care much that I could not drive the CLS II or even the IIz with my OTL tube amp; they were playing to the SS amplifier owners.  If you like the IIz with a tube amp, look around for a pair of original CLSs; they are Quad 57-like in their midrange transparency, only with more oomph.  Way better than any version of the CLS that came after them.

All flat-panel ESLs (and magneplanars too) will have issues with beaming, increasingly at treble frequencies.  I am not sure that the ML curve or the SL pseudo curve completely cures this problem.  If you love ESLs, you live with it.  I also don't think that the curvilinear design of the ML speakers is a "real" issue in causing audible distortion.  It's a theoretically real issue that a competing manufacturer, like Sanders, can use in advertising.  The original CLS was one of the lowest distortion speakers I have ever heard in my life.

I heard the Sanders amplifier (not his speakers) extensively driving my friend's large Acoustat speakers.  He and I were very underwhelmed, despite all the bloviating about voltage.  He sold the amplifier within a few months and replaced it with a Berning ZH270, a pair of them, in fact.