After firing up my crown ce100 last night I found that I may be a victim of the "sub output too low to drive my pro amp" club. I didn't have the BFD hooked up yet. I was able to get to referrence level with the gain maxed out and the sub level half way but I have a feeling once I cure the room peek at 40Hz it may change the referrence level. Anyway, I read that the BFD can be used with both -10dbv and +4dbu, so will it help drive the voltage level to the amp? BTW, The old 100W receiver/amp I was using previously at half volume drove the tempest much louder than the 450W crown does at full gain. I guess I'm lucky to have a small room, I don't think I could get to referrence if the room was larger. I also checked the specs for my sub output on my Yamaha receiver and it said: 4V @ 1.2Kohms Don't know how it would relate to the input level on the amp though.