I have one memphis pr 15 and it started to sound distorted yesterday for no apparent reason, When it hits a low note like a sound Young Jeezy - Hypnotize, it makes a weird noise can't even describe it. I checked to see if it blew but everything looks good, did a free-air bass and it did the same thing after 4-5 seconds into the song. Is it bottoming out? wired up wrong? or gain too high?