Speakers that work with Atma-sphere M60 amps.

Generally speaking, OTLs are going to be happier with higher impedance speakers and speakers with smooth impedance curves (no big dips, not a lot of complex phase shift in the crossover). Impedance is perhaps more important than high sensitivity. This is due to the typically higher output impedance of the OTLs. In the Atma-Sphere line, the increased number of tubes in the MA-1 makes it less subject to impedance challenges and the MA-2s are virtually immune. The M-60s use about 1db of negative feedback to lower the output impedance to make them compatible with more speakers of lower impedance, but users with highly OTL-compatible speakers often defeat this negative feedback for even better sonics from the M-60.

Your B&W CDM7SE speakers have a nominal impedance of 8ohms (4ohm minimum) and sensitivity of 90db. The sensitivity and nominal impedance are in a good range, but the 4ohm minimum is probably challenging your M-60s a bit, depending on where that minimum falls and how complex the crossover design is otherwise (phase shift, etc.). If you like the sound you're getting, one thing you might experiment with to increase your speaker impedance is a Paul Speltz "Zero" autoformer speaker impedance multiplier.

With all this being said, manufacturers who make speakers that are highly OTL-compatible and a good for the M-60s (and this may just be selected models within the manufacturers line) include:

Merlin (both the TSM and VSM, but the VSM will benefit from more power)
Reference 3A (the MM de Capo is a very nice match)
Coincident
Harbeth
ProAc
Spendor

There are certainly others, but this is a starting point.
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Great input and info,Rushton.---Would horns be included too?

I think Rushton made an excellent suggestion with the Merlins...

Very happy Merlin VSM-MM owner.
Chris

Speakers I've heard work well with the Atma-Sphere M60 include models from Classic Audio Reproductions, Omega, Quad (the 57's), Avantgarde, and the new GedLee "Summa". Disclaimer - I peddle some of these. While there are others that I'm sure would work well, these are the ones I've heard and especially enjoyed with M60's.

Duke

ironically,it is my experience that elctrostatics have the transparency, speed, and detail necessary to reveal just how good otls' are. 'stats tend to be ineficient and have wicked impendace curves. once you hear that combination, youll be addicted. try it with a quad or a m/l aerius. you'll never go back.

Von Schweikerts work well also.

Avguygeorge, certainly various horns will fall into that category of OTL M-60 compatible. Note Duke's recommendation of the Avantgarde. Also, Cain & Cain, Zingali and others. It will usually come down to the design of the crossover.
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THanks for all the info. I have heard that coincident and Merlins are good matches. ANyone have experience with Silverline speakers? Their impedance also matches.

Add Lowthers to the list. Members of the Chicago Horn Club heard a pair of Lowther PM2As driven by a pair of Atma-Sphere MA-1s a few weeks ago to great effect, perhaps overkill since M-60s and probably an S-30 would have been adequate. Jon Ver Halen of Lowther America was there as well. It can't speak for him but one could ask his opinion.

The ZERO autoformers enable other speakers to be used successfully with the amps.

Brian

As a corollary to Gregadd's post, I found that my Raven R3.1 ribbon drivers truly revealed their dynamics and speed with M60s. Their 3ohm nominal impedance doesn't labor the the M60s given their 99 dB efficiency. I have the luxury of actively biamping, keeping the M60s from having to drive paired 12 inch midbasses at 4 ohms. Matched to the right loudspeakers, otls are quite remarkable.

Brian, interesting you bring up the Lowthers.

A friend and I got together this weekend for some fun. I brought two pairs of Lowthers (PM6C and PM6A), and he brought the cabinets (Lowther design big ports). With an 18 wpc, 300B amp, we discovered some of the MOST involving sound either of us has come across. We didn't even get to try the PM6As, but he wrote to me that he's spent the past two days listening exceptionally late into the night in absolute joy. Even his wife couldn't get over how terrific they sound.

In the end, we'll each have a pair of ported Lowther speakers, and I intend to see if my heavily modded M60 MKIIIs make a nice marriage with them.

Jb0194 -- what are you partnering the 3.1s with? You mentioned a 12" midbass... could you give more info? Cheers