Perforated, unless you like loud all the time. I drove both and the ACM method does drone a bit, so the claim of zero drone is not accurate.
2011 Sapphire Black/Black E70 X5 M "Torquegasm"
2010 Jerez Black/Black E90 M3 DCT -Gone-
2009 Montego Blue/Grey E90 335i -Gone-