I had an installer put my subwoofer amplifier in the little space underneath this panel based on specONE's post. I've got great bass but it seems like I'm missing mid-bass and wanted to check out the crossover settings on the sub amp to see if that's possibly the cause.

Anyways, II'm trying to open this panel and it's stuck where the hook clip is (noted by the arrow). Can anyone tell me what I need to do to get this off? Just prying around that area doesn't seem to be working. Thanks.

 

There is a 10mm bolt holding that panel down you have arrow pointing at

you need to pry center cover off with a small flat head screwdriver and then it will expose the 10mm bolt