ways to increase spl.

hi, currently my 2 alpine type r subs are sealed at 1.25 ft^3 and i am getting a custom box made by a audio place locally for them since i don't have the time and the toos to make one. so i was wondering how big of a difference would going from the sealed boxes to a 1.71 ft63 tuned to 34hz make to make it louder and also would putting dynaplate (http://www.dynamat.com/products_car_audio_dynaplate.html) make it louder and also would fiberglassing my trunk increase spl.

Check out secondskinaudio.com. For the price of the dynaplate you could over more of the car with a better product for the same price. AS for the fiberglass, second skin will work for that to. Fiberglass is a good thing for making odd shapes but it doesnt work very well as a sound deadener considering it flexes. AS for a fiberglass enclosure that will work good so you can make the enclosure form better to the sheet metal and get more volume. And the ported enclosure will be a huge difference over the sealed one hands down.

for sound deadning i was going to use spectrum sludge for the trunk lid and i dunno yet for the floor part but i heard if you use fiberglass resin in the inside of the sub box it does something to it so i thought maybe if i liners my trunk with it it might do something.

Resin -ing the inside of an MDF box suposedly makes it stiffer and gets a couple db's. I used RAAM mat on my car. $130 for 60sqft. Going from sealed boxes to a tuned ported one should be a nice boost.

putting resin in the sub box makes it MUCH smoother, so there is less turbulence - but this only works for a slot ported box. It works in the same way that polishing the ports in an engine does.