Jl Audio E1200 Car Audio Amplifier "back ground music seems high" Questions

...back on, a heart beat sound immediately started coming from the subs, but no music bass was being made. It is a constant beat, even when the head unit is changing between inputs, or the volume is ...

back on like normal. Did I connect some thing wrong? Cant seem to figure this out, some people telling me this is normal but it dosen't feel normal to me. Any help I can get would be greatly welcomed