My speakers sound amazing!

[Axel]

Interesting.

I mean they weren't loose so to speak, just not tight. I could turn the bolts with practically no force so just carefully finger tightenened them further. They're only a 2.5mm allen bolt so I'm guessing not designed for huge force.

No idea whether PMC don't tighten much, or they'd loosened over time with the previous owner (who said they had very few hours as a demo pair).

Either way they sound much more like the pair I demoed.

The question now is - how tight should they be?! I don't want to overtighten.  For now they sound great so am leaving them. Have asked PMC but no reply so far.

I checked the bolts on my ProAcs recently and found that they were not fully tightened. I got the right sized Allen key out and proceeded to tighten them, tightening one, then the one opposite and so on.
I cranked them down as much as I could, bearing in mind that they were fairly small bolts into soft wood.  I couldn't detect any change in the sound, but it's pretty obvious that if the driver can move, then your  SQ will suffer.