I thank my lucky stars every day.
I had these made by my custom furniture builder,

He had been saving a small flitch of Rosewood Veneer for many years (acquired before it became illegal to import).
Furniture grade MDF, front panel gasketed and back-screwed; removable rear panel gasketed, 16 big bronze screws, interior lined, zero bracing, on 3 dual wheel casters.
I fully expected some vibration, wondered if I would be having some bracing added in the future.
They tilt back, thus top is sloped, nothing moves, put your hand anywhere, you feel nothing That ElectroVoice 15W Woofer with monster magnet weighs 37 lbs

It made me less in awe of all the special material, methods, and bracing I have witnessed and marveled at over the years.