My brief impression about pfe232 vs 4.Ai :
pfe 232 sound thinner and smoother treble than the 4.Ai , pfe232 has an ambient vent which make pfe232 sound a bit more airy than the 4.Ai , especially instrument genre . however , the 4.Ai has much better mid range than the pfe 232 , much more natural than pfe232 , pfe232 sound dryer and somewhat sibilance with female vocal . The 4.Ai also has provide more forgiven sound than pfe232 . Bass on the the 4.Ai is more balance and faster than the 232 , the 232 has a more mid bass than the 4.Ai . i prefer the 4.Ai over the pfe 232 for overall presentation
It doesn't have vents. They're there for looks and does nothing to the sound.