Yeh, I think the only difference between the M80v3 and v4 are the crossover and tweeters. And of course the diecast around the woofer drivers but that doesn't change anything.
And the only thing different reallywith the redished tweeter is the heatsink for higher volumn, which doesn't matter to me and the area above 12K which I probably can't hear.
So, I think Ian meant between the v3 and v4 I shouldn't notice any difference. Specially if I am using a sub.
Where I will notice a difference should be in the HP, and only if I am no sub for music and at higher volumns.
