So I decided to post this outside my build log to see if anyone might have any ideas to help me solve this issue.  Equipment:  SLS 8inch Midbass Drivers running 60hz - around 200 i think. Mounted in the doors w/ a pretty solid treatment of SDS  MLV, CCF, and CLD. Shitty GM doors aside, its a pretty solid installation.  kicker 250.2 bridge to each side Description of problem: Midbass from left side is quieter by rough 1/2 to the ear w/ an 80Hz sine wave tone (measures around 8dB lower IIRC). I don't remember there being a huge difference between left and right previously, though I didn't really touch the stereo for over a year. My understanding of interaural time difference suggests that I could have overlooked this issue after setting my TA correctly.  Stuff I've Tried: The only thing I've done recently with respect to the installation of the drivers was rebuilding the left door baffle after the MDF was exposed to water. I used 3/4 in cutting boards to build the replacement to the exact same shape. Maybe I didn't build a robust replacement but it seems to be fine when I feel for vibration and so forth (feel solid when speakers are playing).  More CLD in the left door. I had a resonance issue in the door at 75hz so I went after it. Did not improve output.  swapped drivers around to rule out issues with amps, speakers, difference between doors, etc.  measured speaker voltage to rule out amps Ideas acoustic mode maybe I can build a small enclosure that I can move around the foot well to test this out?  I suck at building speaker baffles out of cutting boards (I didn't find a great glue so I used machine screws) fuck IB door speaker, build door enclosure or IB kickpanels Take some nearfield measurement of the midbass to see what they're doing. Probably do these doors open and use a sweep I'll take some measurement later and post them.