Interesting subject. I'm from the "everything makes a difference"
camp...be that good or bad; but I do wonder about this. In particular,
over the years I have seen certain preamps with acrylic tops installed
to show the pretty innards. A Klyne pre comes to mind; and I've wondered
if that incidentally has any audible effect on the way that it sounds.
Of course it does. The reason is vibration control. The minute you start running a music signal through anything the whole thing starts vibrating. Its not only speakers, turntables- everything. This is why its so wrong to think of vibration control as isolation. Its not about isolation. Even somehow perfectly isolated you still have the problem of vibration generated internally within the component itself.
There are all different ways of controlling vibration. One is with mass. Adding dive weights literally results in a more tightly controlled presentation with greater bottom end foundation. You could call it weightier. If you wanted to be clever. Or accurate. Opening the component up by removing the top will, uh, open up the sound. Just like the OP heard.
This is not by the way conjecture. I've actually tried all this stuff. Heck you can see the blue dive weights on top of the Oppo player in my system.
https://systems.audiogon.com/systems/8367 They're there not because they're perfect, but because they're good enough. Its digital. Who cares? Never gonna sound good anyway. Good enough's good enough.
Long before the dive weights were on the Oppo they were on the Aronov.
https://www.theanalogdept.com/c_miller.htmNotice the top and sides of the Aronov are removed. I listened to it both ways, it sounded better this way. Notice they are not on the Melody.
That's because its about vibration control. Like tuning a violin, no one can tell you what to do by remote control. Of course it will sound different with an acrylic top compared to metal. Or wood- or none. Which is better? You just have to try it, listen, adjust, listen, compare, and listen and tweak and listen some more. There is no substitute.