Adding Subwoofers in the Mix

Most subwoofers have floor-based enclosures with active speaker systems (that is, with built-in amplifiers) for driving the low bass frequency ranges. Your biggest decision when choosing subwoofers for your audio system comes in bass management. That is, how do you want the bass signals in your system to be handled? You have a couple of options:

  • The subwoofer can complement your full-range front speakers, providing for an even fuller bass signal.
  • The subwoofer can handle all the bass, giving your front speakers the ability to focus on the mid- and high-range frequencies.

Most home theater experts will advise you to move all bass to the subwoofer. This results in more power and attention to the mid- and high-frequency drivers and less strain on the amplifier and speaker systems. This setup also gives you a more dynamic range, because the bass can go lower than most full-range speaker woofers can themselves (hence the term, subwoofer).

If you have a modern A/V receiver, you use a standard line level audio interconnect cable to connect your subwoofer to the receiver. If you're using an older receiver as a stopgap until you purchase that nice new Dolby Digital A/V receiver, look for a subwoofer that also accepts speaker level connections. These connections enable you to run the speaker wires from your receiver to the subwoofer, and then on to your front right and left speakers. The wires aren't nearly as good as the cable, but they work.

Many subwoofers come with an Auto On/Off function that turns the active subwoofer's amplifier on and off with the presence of a signal. So the amplifier turns itself on when you're playing music or a movie soundtrack and then off again a few minutes after you're done.

The subwoofer is usually powered by its own amplifier. As such, there is a volume control and a phase adjustment switch. You adjust the volume when fine-tuning your system and pretty much leave it at that setting. Your phase adjustment switch is sometimes a +/–180 degree switch and sometimes a continuously variable switch from 0 to +/–180 degrees (preferable). This comes into play when trying to fine-tune your system in relation to your front left and right speakers. You adjust this so that the sound coming from each is relatively in alignment, despite the fact that the subwoofer and front speakers may be located at different distances from the listeners. By adjusting the phase, you can move the timing of the sound coming from the subwoofer.

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