The rear speakers in my car are essentially running free-air into my trunk. They are also up against metal. I am wondering if this will be decreasing my sound quality from these speakers due to magnetic interference with the metal and the fact they are not even close to sealed. if yes, how much space should I give em? 5.25" mb quart reference componenets.

free air is not that big of a deal but bass is reduced, also your car is not a big magnet and will not affect your speakers. also depending on the car there is like already a big plastic port the size of the speaker, if you could close that up that would be helpful.

If you are running subs or plan on it, you will run into problems. Your speaker cones receaving pressure built up by the subs and moving ridiculasly. I have never owned a car with a trunk so personaly have never ran into the problem....but I have seen it on multiple occasions.

your speakers can get some interferance from the metal that the magnets are up against, since that metal will warp the magnetic field slightly, I'm using this principle to change the sound of my tweeters, and it actually helps in my application. that said, it's not a huge difference.

If you add a sub, it'll probly wreck your speakers, which is a good place to start a good SQ system... ditch the rear speakers and get a really nice set of componants, like the DLS iridiums, you'll never miss rear speakers.

Im new to the SQ scene and I want to know where can I find info and where can i buy dls iridium if I find thate they re good for me

PM tom or Mark from Kankar Marketing, or PM the guys from Perfect Tones, they sell DLS, the guys from Kankar are the canadian distributors and will take care of you well, and they may be able to point you to someone in your area who sells DLS

I'm currently running 4 8''s free air up on my rear deck of my vw jetta and all is fine yet I have mounted them all to a nice 3/4 inch mdf board.
Good luck man.
Yes as everyone has stated if you install any subs then you need to isolate your other speakers to ensure that there is no cancellation nor damage to your speakers...

L.

__________________
Old school guy.
Kicking it with:
stock door and dash speakers (don't laugh)
Kenwood KDC-7009 phantom face
1 12'' JBL P1220II sub
ESX 475.1 amp
Earthquake P2030


Less is more people.
It's easy to add a ton of equipment yet it's most difficult to make a great sounding system with less.