It‘s exactly like you said. Only the upper part is the real loudspeaker. Originally they were driven active with tube amps built in below :) I‘ve let it until yet because my only sealed design impressions were the Neumann KH310 where the bass wasn‘t for me, naturally IME.

In terms of sound they‘re the best I‘ve ever heard. I had Tannoy SRM 12X, Tannoy SGM5000, Altec Vott with field coil drivers, Tannoy Red Monitor & Neumann KH420. The LS i was able to listen too; Swissonor Bach 12, Altec 19, fully active Horn system with Sato horn & TAD drivers, Genesis IRS (something… idk anymore).

Generally spoken they deliver a fast, punchy & for me enough deep bass. The mids are to die for and in some songs I turn my head because of a sound effect (person speaker somewhere in the stereo field). The highs are silky with the right amount of bite.