Tabl10s, I did not notice a drop in volume. I had Bybee filters on everything when I bought the PASI. As I experimented with the system I found that it sounded more open with the Bybees removed. Just my personal opinion, I would definitely experiment if I had the PASI in addition to other inline filtration. Truth be told I was never overly impressed with the Bybees (deluxe balanced and deluxe speaker). They were very expensive and to my ears in my system their audio effect was minimal at best. The PASIs effect was much more noticable. The sale of the Bybees more than paid for the PASI.