||The following are the three usual methods of
connecting subwoofers to your system.
Method 1: passive filters,
A dual-voice-coil (DVC) driver is normally used in this
method. Filters are used to block the low bass from the
main speakers and higher frequencies from the subwoofer. All drivers are driven by the
same amplifier, so there is no control over the output level of the subwoofer relative to
the rest of the system. Also, it may be expensive to construct filters that work at the
required low frequencies (<120 Hz). Note that a passive bandpass subwoofer usually
requires filter as well, but one well outside of its passband.
Method 2: passive filters, active subwoofer
Here the subwoofer is driven by its own amplifier and you can adjust the output level of
the subwoofer to match the rest of your system. As before, the passive filters may be
expensive to construct.
Method 3: active filters, active subwoofer
Here, the passive filters are now replaced by active filters for even greater flexibility.
This is the preferred method, as now you can easily fine-tune the system to achieve the
best results. If your amplifier has pre-out/main-in jacks, then use a subwoofer amplifier
with a line-level x-over with a high-pass line-level output. You can then connect your
amplifier's pre-out jacks to the line-in jacks on the subwoofer amplifier, then connect
the high-pass line-out jacks from the subwoofer amplifier into the main-in jacks on the
amp. This will take care of the filtering requirement for your main speakers.
Home Theater: Typically, your home theater receiver will
provide all the active filtering that you will need (usually referred to as "bass
management" in the receiver's manual). However, it is still a good idea to use a
subwoofer amplifier that comes with its own line-level x-over, for the additional
flexibility this provides.