A&Q about 350Z
Q:
Some of us have spent a lot of money upgrading the ok stereo. Any upgrade should include sound deadening material because ambient noise in the cockpit will reduce or eliminate the ability to hear them, especially in the upper octaves.
I've had some vinyl based sheets of accoustic damping material I bought from Parts Express last year. I was waiting for a sunny day when I had some time because the material needs a lot of heat to make it pliable.
I removed the door behind the drivers seat (where the bass goes) and the floor of the lockable glove compartment behind the passenger seat. Both areas have a little piece of plastic backed cotton material inside for sound deadening. Took that out.
Made some rough measurements, cut the material and set it on the roof of my BY Perf to soften. Fitting it to the rear wheel wells was the only special cut. The rest were basically rectangles. Rolled it up, stuffed it in, pulled the paper off the sticky side and pushed and poked it to fit the area. Two sheets 27 X 40 was enough to do a decent job. The stuff will conform fairly easily when it is hot and it's ok if they overlap.Put back the factory pads.
I'm very happy with the results. Where I previously had the radio set at 12 I can now put it at 10 and hear more detail and depth in the sound from the rear speakers. A lot of the muffler noise is gone. Cost was about $60.
A:
I did that and more, filled bottom of support beam with foam, dynamat in trunk, didn't make any difference for me.