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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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.
.