Instruction: Given a question and the related document, and generate the answer to the question based on the information provided in the document.

Input:
Question: I see 4 speaker inputs on the back. Do other speakers feed thru this?
Document: I just bought this item at Amazon after months and months of research and what can I say this subwoofer has enough power to fill the entire living room.I bought this to add to my Home Theater and with my  Pioneer VSX 819 , Klipsch center speaker and 4 Harman Kardon Speakers(Front and Surround), the sound was phenomenal specially in movies and music! !
I purchased this subwoofer to complete my home theatre system and am very pleased with it. Keep in mind that this is not "top of the line". I paid somewhere in the neighborhood of $1000 for the entire system including Yamaha a/v receiver, 4 Yamaha surround sound inceiling speakers, a Yamaha center speaker, and this subwoofer.The bass is full and with the internal power supply it can be boosted to suit your taste.Overall, for the money, this is a great choice.
Also, the speaker grill can't be taken off, Yamaha doesn't want you to see the actual woofer like those worthless 3 piece desktop c.d. radios at Kmart! A clear sign of, cheap!Well, what was I to do besides plug and play? I teamed this sub up with a classic pair of Bose series III 301's , a worth while set of speakers if you didn't pay the retail price. I have to say I am honestly surprised by the clean bass that the Yamaha sub system creates.
I purchased this subwoofer to augment some rather small bookshelf speakers. I reviewed the owner's manual online before buying and decided that this sub would match up well because the built in low-pass crossover would match the roll off of the small speakers. The sub arrived and was well packed in the manufacturer's carton. The sub is not heavy so you can expect the same experience (no shipping damage).I connected the sub via the speaker level inputs and played around with placement and level with a variety of music types.
The Onkyo is also more powerful and has legs attached vs the Yahama which sits on rubber pads, the kind you stick on. The only thing the Onkyo does not have are that the Yamaha has are the speaker wire inputs.UPDATE: I definitely now recommend the Onykyo over this model since they are now about the same price.
There is some adjustment needed if you are using it for your TV and sound system. There are also separate speaker wire outputs on the back for surround systems, but I have found them unnecessary. Denon also makes a great subwoofer, but is somewhat more costly (its worth it).
My first subwoofer, and it's great! I got a Yahmaha HTR-6040 home theater receiver to replace an old Sony that finallly started shorting out on surround speakers, and decided after hearing the great sound from the new receiver I'd add a low priced subwoofer to see how it sounded- nice for the price! A satisfied customer.
This subwoofer is a great sub for any surrouind sound. Though my reciever had a subwoofer pre-out, the directions said to use the speaker terminals if your subwoofer terminal in the back of your receiver has only a pre-out for subwoofer, you need low pass terminal. anyways I had to run speaker wire, but this sub "Booms" and now we jump when watching scary movies when the bass hits! Great sub for the price and highly recommeend. five stars..
My 10 year old model of this subwoofer finally broke, so I bought a new one. The qualityon this one was as good if not better than the old one, probably because of the newpower amplifier technology. The unit is part of a my home theatre system that includesa Yamaha receiver and 2 large infinity floor standing speakers. All of the controls arein the back, which isn't the most convenient, but the sound is great and it doesn't takeup as much room.
Amps. Remember the neighbor downstairs hitting their ceiling with the broom handle & yelling , __Yup__ , that's the sound now! Check your Mfg. owners manual.Like  "ZENAGIN's " review said " spend some time dialing in", Thanks Zenagin,TX.Space is about 16 ft. X 30 ft. one is working fine w/o sattilites, may go for two , then add 4 satt. speakers to 2 Subs.Fine, that will be just___ fine.
Answer: There are two ways to connect this sub woofer to your amplifier.  If your amplifier has a sub woofer output this is the preferred method to connect the sub woofer to the amplifier (this connection would be and RCA style connection).If your amplifier does not have a sub woofer output then you can wire the front left and right speaker channels through the sub and it will then process the speaker level output to build the sub track. With this type of wiring the front left and right speaker wires would need to be run from the amplifier to the sub woofer and then from the subwoofer to the front and left right speaker.  Again you would only want to use this type of connection if your amplifier does not have a sub woofer output.