I think I stated it in an earlier thread somewher that it is VERY IMPORTANT to NOT let the sound waves from the back of the sub find the sound waves from the front of the sub within the passenger compartment. IF POSSIBLE.
(7th order enclosures are perfect for this)
I.E. it helps if ya have a sealed sub enclosure OR you gotta send the back wave outside the car for OPTIMUM base. The front wave cancels out the back wave when they hit each other. This also goes for MIDS and MID base speakers.
This cancels out the volume of sound (DB) and quality of the sound wave in a BIG way.
Tweeter are sealed on the back (with rare exception) Therefore it is not an issue.
There are isobarik, 5th and 7th order enclosures, tubes and all kinds of ways to get around this. Some work OK... Others suck. Just depends on the car.
Just because a system sounds Killer in a Honda.. Same system might absolutely suck in a Chevy or a VW. Depends on how ya do it. And ya gotta experiment a bunch on each system to make it right.
Cause cutting holes in the firewall is kind of a problem. The biggest problem with subs in the firewall (in a sealed enclosure) is that the voice coils in the woofer get hot after a time from engine heat. And the crisp bass simply goes away. Sounds like a speaker that you placed in a mud bath... (Unleess you can keep em kewl)
Remember that all of this is only nesasary if you really need/like excellent sound. If ya just want decent sound.... Do whatever works.
I built a 914 system some years ago for an regional IASCA event. Took home 2nd place in fact. (yup, got beat by a Buick GNX)
It took me bout a 100 man hours to get it right on the install. And bout 20 hours with a stereo RTA and my ears and much speaker positioning tweaking to tune it right.. Thats what the client wanted and that is what he got.
I think I charged him bout 10 G for that system. It can be done very well. if ya have the time and knowledge. (and a crap load of duckets)
It just kinda depends how good ya want it to sound. If you are really good at fabricating and don't have fear of cutting a bit of metal. And you can handle basic fiberglass enclosure making and molding. You can build a killer system for a G or so in cash and boat load of labor....
Then ya gotta figure out how to keep the 60 cycle hum from the alternator out of the system, which is indicative of spurious signal and grounding issues in a teener and many other cars.
That can a be a real PITA. The fix for that takes good equipment. Clean grounds, caps and coils on the hot leads to everything and the best RCA cables money can buy. Unless your using DIN cables or optical fiber.
Then the crossovers become very consequential, As this will setup your drivers (speakers) to conform to your interior in a way that the sound becomes alive and tight.
Hell i could write a book... OOOps.. I did....
If ya need a few suggestions. I will help. Just mail me... And I will see what I can do....
I only know high end stuff. Thats all i did. That is my only experience.
Gunna sleep now...LaterZzzzzzzzz
Just my .02 worth......
And by the way.. I LOVE THIS FORUM... Bets folks I ever met.....
Twystd1