The Mark Levinson subwoofer in my 07 LS 460 sounds like it is blown. The dealer quoted me $700 for the speaker and $225 labor. I'm pretty sure I can fix the blown speaker with a hot glue gun but I'm unsure how to access it. Is the cover behind the middle headrest removable? If so, how do you do it? If not, how do you access the speaker at all? Any info would be helpful.