A subwoofer amp works off the same electricity as the accessories in the vehicle, which means it operates on 12 volt power. The output wires from the stereo, whether they be regular speaker wire or patch cables, are directed to the input side of the amplifier. Whatever sound the stereo is putting out is fed into the amplifier before it can get to a speaker, and in this case, the specific speaker is a subwoofer. So, what makes a subwoofer amplifier different from a regular one?
The amplifier takes the signal coming into it from the stereo and literally amplifies it within the circuitry of the amplifier. In this manner, the wattage on the output side of the amp is much greater than the wattage that comes into it. While all amplifiers are capable of increasing the signal strength, subwoofer amps are made specifically for bass. Therefore, they are produced with components that limit or filter out the upper frequencies, so that only the low sounds come through the amp. This process eliminates putting the midrange and high range frequencies through the subwoofer, which is a low range speaker. The result is clean, crisp bass that isn't muddled with other sounds.
The output on the amplifier has provisions to hook speaker wires or patch cables directly from it to a subwoofer. This eliminates the chances of the low range signal passing through other speakers in the system, such as midrange speakers or tweeters, which reproduce the upper-end of the sound spectrum. Some amplifiers have built in "crossovers," which allow the user to decide which portion or portions of the stereo output sound is sent to the speakers. With the flick of a switch, some amplifiers can go from full range to midrange or subwoofer only mode. Be advised, however, that amplifiers that produce only the low range sounds will probably have quality that's superior to the adjustable units.
Amplifiers, by nature, produce heat. Be sure to mount any amplifiers in the vehicle in a location where they will get good airflow, or attach a cooling fan to the unit, or both. Amplifiers have a shut-off safety built into them, and when they get too hot, they will lose power until the temperature is once again in an operable range. You can increase the life of your amplifier greatly by ensuring that it remains as cool as possible. Also, unless you have the proper tools and good working knowledge of car electrics, it is recommended that a professional install any amplifier for you.
