The bass on my Accord is really muddy and indistinct. I'm thinking of replacing rear deck speakers and subwoofer, but I am also wondering if this will have any effect, i.e. would I be wasting my money on new speakers?
After doing some research on muddy bass, I discovered this is mainly due to the ANC (Active Sound Cancelation) cancelling out the bass from the speakers. Apparently the good engineers at Honda aren't able to figure out how not to cancel out the bass from the sound system. And there is no provision to turn ANC off.
I found several recommendations suggesting that disabling the rear ANC microphone will bring back the bass response by cutting the wire for that microphone. However, I thought there may be other alternatives, so I tried placing something over the mic to lessen its sensitivity. I discovered that the most effective method was a self-adhesive 3/4 inch felt pad taped over the microphone grill. I initially tried a 3/8 inch pad. It helped, but the larger size works best.
What I like about this solution is that I get better bass without completely disabling the ANC. The mic still picks up the road noise conducted to it via the car's frame. It's also really cheap.