These are simply the way the receiver, with a proper Sub-woofer output, gets the signal to the speaker. This is just a different method than having standard speaker wires connect to it, which can't carry the load/signal that the sub-woofer needs. When you have a receiver with the proper "sub" output, you will notice that the "output" has these type of connections, not just speaker wires. As far as brand, my 2-cents is to stay away from speaker companies that also make TVs, receivers, etc. Try to stay with a manufacturer that specializes in speakers. Axiom, Energy, Infinity are a few. You may find that the sub-woofer is the most expensive speaker you buy...but a good sub is worth the money.
I recently was given a sherwood 5.1 reciever. It doesn't have a jack for a bass input, However, I know that it used to have a sub that had audio jacks on the back of the sub. I was wondering what this is called, when a subwoofer has audio input jacks on the back? And if anyone could suggest a some what good sub with that function.

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