For subwoofers equipped with a speaker-level input and a speaker-level output, simply connect the receiver speaker outputs to the speaker-level input on the subwoofer and the speaker-level output of the subwoofer to your speakers.
Speaker-level inputs let you hook up your powered sub by using the speaker connections from your receiver or amp, eliminating the need to run a separate RCA patch cable.
If your sub amp has only high level inputs, you will need to connect the subwoofer in parallel with your main speakers. If your sub is near the mains, simply connect another pair of cables from the main speakers to the sub amp. If closer to the amplifier, you may connect another pair from the amp to the sub.
How to Connect the Low-Level Input on a Subwoofer. The low-level input on your subwoofer will usually require a single RCA cable to connect to your AV receiver. Although you can buy dedicated subwoofer cables, you dont have to buy one of these if you dont want to. Any RCA interconnect will work.
Dual input allows the subwoofer an extra sensitivity adjustment. Normally, it would be enough to use a mono LFE subwoofer signal from its processor. By using both inputs with the same mono signal doubles the subwoofer sensitivity. This means that there is now only half the signal strength to drive it to full output.
Can you use any speaker as a subwoofer?
A normal speaker is not capable of producing low-frequency sound emission and hence, cannot be used as a subwoofer. Given the subwoofers unique purpose, a normal speaker cannot replace it. You can use a woofer to achieve low bass tones, but even this does not compare to a sub.
Can I connect left and right output to one speaker?
Wiring of two channels on one speaker is possible but in many ways, it can damage your amplifier. You may be trying to run both the left and right channels on one speaker only. It can be done but method may vary from setup to setup of the amplifier.