Hi,
Try an persevere with them they do work well--those you pictured are the Studio Traps
they have slightly different characteristics from the Domestic variety-I suggest you email
Ty at ASC -they are very helpful.
Ty Moyer / ASC
ty.m@acousticsciences.com
Re the covering I have seen Muslin large stretch sock material that would stretch over the existing possibly.
The top of the traps if you notice, has a rubber ribbed ring that pushes into a circular groove-this can be removed and the "sock" held in place top and bottom.
Good luck
Des