I am thinking about stuffing all the holes that I can find behind the panels in the interior and trunk of my car to reinforce and improve sound quality. Thoughts?
poly-fill is used to increase the apparent volume seen by a speaker. in sound quality this has the effect of smoothing out the response. however, it also lowers the efficiency of speakers. meaning, put some in a sub box and the sub may sound smoother, get lower, but it won't get as loud. sounds to me you need sound deadening more than poly-fill.