I have a Harmon Kardon 310 and a Cambridge Soundworks BassCube 15. The Basscube is brand new, so there shouldn't be anything wrong with it. I hooked it up the other day and no sound came out. I have be messing with it and now have some sound, but the booming bass that I should. I have to turn the amp on the woofer up very high to get the sound that I have. I have checked the gains on the reciever and they seem to be O.K. Does anyone have any ideas what could be wrong. Can the subwoofer post on the reciever be broke, but still let some sound out?

How do you have it hooked to the receiver? just the sub out line?

It is hooked up by a monster cable, through the subwoofer port on the back of the reciever

To be clear you are turning the amp gain on the subwoofer up "very high" to get the sound that you want? And then the receiver is set at around nominal?

If so bring the receiver sub gain up and back off the sub amp gain. Between these two controls work so that neither is at max. You may just have efficient speakers which is no problem.

Also, make sure that the speakers in your setup is set to "small" in the receiver settings. Disable the crossover on the sub and set the crossover setting in the receiver to 60-100 htz.