Ralph, is the need for the very short speaker cable unique to the
planar/OTL combination or long cable inherently causes low frequency
roll-off? I didn't think the cable length should be that
detrimental given a 1.75 ohm output impedance on the MA-2.
The issue is that tube amps generally speaking have a higher output impedance than solid state. When you add a long speaker cable, the cable is a series resistance added to that of the output impedance of the amp. It may not seem like much, but fairly small resistances like that can have a big effect when the impedance of the speaker is already pretty low.
(This is one big disadvantage of 4 ohm speakers- the cable becomes really critical! You also have to make sure your connections are good and tight.)
So the simple solution is to keep the speaker cable short. I really don't think it makes a difference what tube amp is used (as long as it make a satisfying amount of power)- the speaker cable should be as short as it possibly can to make the connection. I think a foot is about as long as you want. I've heard this make a profound difference in the bass impact on several different Tympanis, MG3s, 20.1 and 20.7.
We use 10Gauge copper OFC speaker cable, using both conductors joined together at both ends by a single heavy speaker lug. So we have to build up four such jumpers but it really pays off.
A Big high current solid state amplifier would have much better grip, control On the Panels.
I don't find this to be the case. What seems to be happening is that the lower output impedance of higher powered solid state amps allows more leeway with the series resistance of the speaker cable. We've been running fairly high output impedance amps on Maggies for decades and they seem to 'control' the panel just fine with plenty of bass impact. So I regard this as a common myth, caused by a misunderstanding of how critical the speaker cables become when you run 4 ohms and use tubes. Put another way, if you compare a tube and solid state amp on the Maggies and you also have longer speaker cables, its likely the solid state amp will have more impact. But if you use really short cables the differences between the amps will be less profound.
