Then they say things like "it will sound closed in" Brilliant deductive reasoning.Or, they’ve listened and came to that conclusion. OP, try it yourself. Turn it up. Play a track you know well with the cover down, off, and down again.
Turntable lid up or off?
My Pro-Ject Classic turntable came with a dust cover. I usually spin vinyl with the cover completely removed and never closed. Does it matter if the cover is just up or fully removed? The ultimate test is just listening, but I cannot detect a difference between either mode (up or completely off).