Hi Tom
Most car subwoofers are designed to take advantage of so called "
cabin gain" in order to produce much bass. The small volume of the car's cabin space greatly increases the bass from speakers and subwoofers. You get much the same effect from small rooms but don't get nearly as much free bass. So the subwoofer has to work much harder to play loud bass in a larger space. In a normal room the results are likely to be very disappointing.
Running any subwoofer on a full range speaker signal is likely to disappoint too. You can't use the Sub-out (or LFE) connection because this is a low level signal of a fraction of a volt and needs an active (amplified) subwoofer to make any noise at all.
If you connect the subwoofer in parallel with a speaker on a speaker channel the car subwoofer will play all the notes from high to low. This will probably sound very bad.
You will also run the risk of burning out that channel on a stereo amp or AVR because of the very low impedance load placed on the amplifier by the two units working together. (speaker + subwoofer) Usually placing two units in parallel halves the impedance seen by the amplifier. Some car audio drive units have 2 Ohm voice coils which results in a very nasty load indeed on any amplifier not specially designed for it. That means you can't use most AVRs, stereo amps and pro power amps.
Many car audio subwoofer speakers (drive units) have a very low spec compared with home audio and HT drive units. They suffer from lots of chrome and bright colours to attract the innocent buyer. They might work fine in car but not in a home system.
In summary: Probably not a good idea at all.
