Well I don't think so. The fader has always been in the middle pre and post install. The bass is flat at 0 and the treble is between mid and all the way up. The surround sound mode WAS the best and loudest sound, stock. Surround now is almost useless somehow (compared to stereo). I had to switch to stereo to get some mid and highs back. Its not terrible but it is noticeable hence me using 20 vs the 15 that I mainly had it at before. I will get used to it but I was just wondering if a plug or connector was inadvertently unplugged...ie a simple fix.That is strange as the sub should not affect the rest. Did your installer check all the levels and fader to make sure nothing changed.