Originally Posted by
RMC
Putting a piece of stockings, or any other fabric covering the vent inside or outside, is generally not a good idea acoustically. This makes a somewhat resistive vent to air flow in/out the port. And resistive vents tend to make the box act as partly vented and partly sealed (a mix of the two). Therefore reducing some of the vent's "magic" action on LF driver which lowers driver excursion and distortion.
The only place i would put some "see through" lightly stretched fabric, assuming there's no other such protection, is on a driver's back vent, only to prevent fiberglass fibers from migrating into the woofer gap for example. With very little spray paint or hairspray on the fiberglass then a driver back vent cover would probably not be required.
Free vent air flow is important for proper box operation and should remain King.