OK, you have bought some beautiful woofers, build a great box
out of hand-cut burled oak, and had the whole thing dipped in
gold, and wrapped in rich Corinthian leather by Ricardo Montebalm
himself. Now it has to go into the car. This also can make a big
difference to sound quality and sound pressure level.
This is all going to depend on the type of car you drive, and
the type of system you are building. If you have just finished
building a dozen dual reflex band-pass enclosures and are going
to slide them into the back of your Cube van, then you are likely
going to make out just fine without my help. But, if you built
a sealed enclosure with a pair of Focal Utopia 10-inch
subs, and you want them to blend nicely with your MB Quart or Dynaudio front
end, and you drive a nice big BMW, Mercedes, Lexus or Infiniti,
then you will want to be aware of how the placement will affect
your sound quality.
Certain cars have inherent problems with bass. I have had the
luck to come across three of them. 1989 Mazda MX-6's,
Ford's Thunderbird last generation before the return of the little two-seater, and
some older generations of Honda Accords. These cars, due to their
dimensions, seem to simply swallow bass from about the 40-70 Hz
range. Right where all the fun is.
The solution to these problems seems to be in firing the woofer in different directions (towards the rear seats, straight up, or towards
the rear of the car. But this doesn't work every time. The subsequent alternative
is to effectively alter the length of the vehicle by firing the
subs through the rear deck, or rear seat, and seal off the trunk
from the rest of the car. Your low frequency output will be
decreased as compared to someone who can use their trunk, but you will have
bass, and it should sound good.
Never be afraid to experiment. The S.A.S. Bazooka tubes can be
a great way to get bass into your car. You can make enormous differences
in low frequency output by simply adjusting the placement of these
units. They're worth playing with for quite a while before bolting
down.