I have long been a fan of quite simple enclosure designs. I have
used acoustic suspension (sealed) and bass reflex (ported) enclosures
in my vehicles for years. All have performed certain tasks very
well, while lacking in certain areas at the same time.
Sound reproduction is based on the laws of physics. If
you take into consideration, and account for all the laws, to
the best of your abilities, you should end up with a great sounding
audio system. Sound is basically a wave traveling through the
air. The length of the wave (or frequency) is what causes most
of the problems for subwoofer systems in a vehicle. High frequencies have very short
wavelengths, while low frequencies are just the opposite. The
wavelengths of a deep bass note can be 20, 30 or 40 feet. It is
difficult to transmit this wave through the air in any form. (This
is why radio stations modulate the information (music) onto a
high frequency carrier to transmit it.) There is one advantage
of trying to recreate low bass in a car. A small area like the
interior cabin of a vehicle exhibits what's known as a transfer
function. What does this do for you? It is an inherent gain associated
with this small space. And it's what allows a pair of 8-inch woofers
to have low frequency output below 25 Hz in a car.
What did you want your system to do? In my case, accuracy is important,
but so is having some fun. So I am likely to use a ported enclosure,
subwoofers with moderate physical power handling, and supply them with lots of
power.
JL Audio
specifies a combined physical and thermal power handling rating for all their drivers.
In their case, this number represents the amount of power, that, in a properly designed enclosure,
will, for 8 hours, not cause any damage to the speaker. They also
specify a normal, and long-life power level in their Enclosure
design book (see you local JL Audio dealer). The other way of
rating power handling is the one that produces the big flashy
numbers. Lots of companies list outrageous power handling numbers on
their drivers. Numbers between 1,000 and 2,000 Watts are not uncommon. BUT, this number is
commonly
the amount of heat that the drivers voice coil and magnet assembly
can dissipate before causing damage. It does not necessarily describe
power that can be absorbed with the driver in any type of enclosure.
It also does not provide a length of time at which this level
can be maintained. I am not saying that there is anything wrong with
this number, but the true useable power handling number must then
be calculated from the specific enclosure design you wish to utilize. A drivers
suspension will allow it to only move so far before some component (the spider,
surround, tinsel leads or voice coil former) is damaged.