Wayne Parham Messages: 18756 Registered: January 2001
Illuminati (33rd Degree)
The only way a speaker can be made to tolerate facing upwards or downwards is to make it have a suspension that takes much more force to overcome than the force due to gravity on the cone.
The trouble is, that is exactly the opposite of what a subwoofer generally is. Subwoofers usually have heavy cones and soft suspensions. Those qualities give low resonant frequencies and generally lend themselves to low-frequency characteristics.
However, another thing that lends itself to low-frequency characteristics is having a large cabinet. Conveniently, a car trunk is a pretty large cabinet, especially for a relatively small woofer. So a woofer can be used that has a more rigid suspension and still hit the low notes.
Car speakers have other hazards that they must endure - not the least of which is sunlight. The sun will bleach the cones and disintegrate rubber surrounds. They are exposed to temperature extremes, often from well below freezing to over 150° Fahrenheit, sitting parked in the sun. Humidity ranges from 0 to 100%. So they're frozen, cooked, dried and soaked.