Ken,
I have heard the 20.7’s on only two occasions. Therefore, please take what I say about the two speakers in that context.
The biggest difference to my ears was the ability of the 30.7’s to portray accurate bass. The old bugaboo about planars not being that dynamic was always in evidence to my ears...until I heard the new 30.7. This is another area where I feel the new speaker leaves all of the other Maggie’s ( and for that matter all other planar speakers that I have heard) in the dust!
Add to this a larger stage and slightly better high frequency purity...and you have the general differences between the 20.7 and the 30.7. OTOH, this could all be off-set by the fact that the 20.7’s probably will work in far more settings and in slightly smaller rooms.
Basically in thirty five years of being in this hobby, I can say that I have only heard maybe a handful of speakers that sound better than the 30.7’s! None of those speakers were priced at,or below, the price of the 30.7’s. Many were priced at multiples of their price!
In my opinion...if one is looking for that last speaker...one that is full range and will deliver the ability to amaze, and if one has the room size (crucial), then this new 30.7 should be on everyone’s short list. It’s going to take some set up skill, the right gear upstream ( including preferably quad amping or at least bi-amping) a great source and the ability to add room acoustic treatment behind the speakers; but get this done....and you are at the end game. They are that great
