The volume is set to 75% and yes I called jl audio about it. It was them that got me to beleive that the signal amplitude is too high. But they ask me question that I can't answer like the crossover point of the oem amp. I don't know what else to do.

Does your X5 have DSP?

Did it have a subwoofer that you replaced?

There is no DSP and I did not replace anything. Looking at the connectors, I think it is Harman Kardon.

OK, we've reached the limit of what I can figure out though a forum... I think you need to go visit a pro shop. 30 seconds of seeing firsthand will beat hours of typing...

Thank you very much for trying.

It sounds like you are getting way too much input into your amp.
Most amps should never get more that 8volts (RMS) into the RCA inputs.
By sending 22 or more volts you may have damaged the input section of your amplifier -----however JL Audio amps are built pretty well so you might be ok.

I would suggest installing a hi-low converter between the outputs from the factory subwoofer and the input on your amp.
Other than that go to a shop and have them check it out.
Sounds like an easy fix.