I think ignoring the fact that the woofers INSIDE the Harbeths actually woof renders objections to putting them on subs ridiculous.
Speakers on top of subwoofer
Is mounting a speaker on top of a sub a bad idea? Specifically, a Harbeth 40.x mounted with isolators on each corner so the cabinet can flex/breath on top of a Rythmyk E15 I have a limited amount of floor space and the Rythmyk is a little taller than a Tonteger which is a good thing since the Tons are a little short to place the tweeter around my ear height.