I have seen several car installs where the speaker boxes are filled with polyfill to increase the over all sound quality. I have even seen this done for a few show cars.

 

I think sound deadening will help with acoustics. I could be wrong though.

 

What about dynamat superlite? Seems a light weight version

 

I put a stero in our golf cart. I used 6" marine round speakers. I made some some speaker cans out of 6" PVC ( coupling cut in half, pipe cap,) basically looks like a speaker with a coffee covering the cone. I put some poly fill (pillow stuffing material purchased from walmart). I filled about 1/3 of the can with the fill. It makes a huge difference gives the sound a lot of depth. I was told that the dampening of the fill causes the speaker to react like it's in a larger box by absorbing sound pressure. I have 6x9's mounted in a dragonfly fairing. Removing the outter fairing takes me 5 mins tops. Rain predicted this weekend. I am going to take a tuuperware container, add some poly fill and tape it to the inner fairing, can't hurt.

 

I was chatting with a couple audio guys, said that dynomat is over kill for our application as dynomat is used to dampen sheet metal vibration and it's heavy and expensive. They also thought that any foam material used would really for noise dampening in cages, as there is no insulation in the the doors etc. and that the speakers and person are inside, s that the foam is keeping road and external noise out of the listening area.

I inquired about speaker baffles, thought about it for a few but when I looked into them it seems as though they would actually kill midbass response. Our fairing is already an enclosed box, with rider outside of it. Does any of this stuff really help.

I am putting J & M 7.25 speakers in my EGC next week and am trying to figure out if any of this stuff is actually beneficial in our application? Wouldn't just the speaker upgrade suffice?