What's the heaviest speaker you've ever owned? What's the tallest?

Classic Audio T-3.4 Field-Coil powered 24" W x 30"D × 48"T, weighing in at 350 lbs. Best sounding, most dynamic loudspeaker I have ever owned by far. It makes me believe that size does matter in some respects. Monkey coffins just won’t do what these do. I can play these at a lower volume with very satisfying fidelity. And with that, yeah these speakers are like 98db 16Ω with a fairly friendly impedance curve, so they will perform delightfully on just a few watts, but put like a hundred watts to them and there is a sense of better overall control and impact. The razors edge you now face is as amps tend to get bigger and more complicated they tend to not be as tonally pure and airy in their presentation. So with these I have found a sweet spot of running Atma-Sphere MA-1 Mk.3.3 OTLs which produce 140w @8Ω. Single gain stage triodes, and it works quite well.

My Jbl 4435’s. 225# each

6.5’ tall / 3’ wide /about 700 lbs each. (4 sections) 

Acoustat 1+1s, 7'10" tall

B&W Matrix 800, 240lbs each

ESS AMT 6, around 175 lbs each.