Sub woofer is connected to the back of the pc via usb and speakers lights are on but no sound apart from built in pc speaker system

Did you connect power to the sub-woofer? Most subs have their own amplifier. Just check if there is also an on / off switch on the sub.

as far as i know these speakers contain the and everything else in the subwoofer. The good news is that the system itself works, as the speakers produce sounds. If you feel like taking the system apart yourself , you may check for some wires that got de-attached from the subwoofer, if not, i would advise you to take the system to check it by technical support.

Alright i had a chance to look over things, this is how you are going to hook up the sub. first we'll be connecting the surround sound unit to the sub woofer.
surround sound unit sub woofer
left front: positive (+) <-----to------------->(+) left speaker level in
negative ( - )<- - -to- - - - - - ->( - ) left speaker level in

right front: positive (+) <-----to------------->(+) right speaker level in
negative ( - )<- - -to- - - - - - >( - ) right speaker level in

now that the surround sound unit is connected to the sub woofer you will need to connect the front surround sound speakers to the sub woofer.
sub woofer front surround sound speaker
left speaker level out (+)<-----to--------> (+) left front speaker
left speaker level out( - ) <- - - to- - - - ->( - ) left front speaker

right speaker level out (+)<-----to--------> (+) right front speaker
right speaker level out( - ) <- - - to- - - ->( - ) right front speaker

Alright now that the wires are all over the place and plugged in
turn everything on and see how it sounds. let me know if everything is working as it should. if you need help with anything else or if something does not seem right please feel free to contact me via e-mail or phone
Mark Woodring

Hi,
Your sub-woofer apparently does not have an amplifier built into it. This type requires you to use your front left and front right speaker output to got through it to your regular speakers. It is called a passive sub-woofer for that reason.
To set it up, Connect your front speakers to the "output" of the sub. It should say "to speakers" on it.
Then connect the Speaker Outputs for the left front and right front on your Denon AVR-391 directly to the Sub. It should say on the back of the Sub "to amplifier".
Here is some theory you should know, if you don't already know it, that will help you get a satisfactory result in setting up this system.
There is a condition on setting up all speakers and subs that not everyone know. It's call "phase alignment". Phase alignment (A Good Thing) refers to all of the speakers in a system moving in the same direction (in and out) at the same instant in time. This gives you much clearer sound and better response from your sub-woofer.
Phase Cancellation (a bad thing) is when some of the speakers are moving out and other moving in during the very same instant in time. It causes problems in sound.
IN A SUB-WOOFER, IT CAN CANCEL OUT THE LOW NOTES.
Here is how to handle it:
On the back of the receiver the speaker terminal outputs are colored Red and Black. Black is considered negative and Red is considered positive. On the back of the Sub woofer and on the speakers the same colors apply. MAKE SURE THAT ALL OF THE CONNECTIONS GO BLACK TO BLACK AND RED TO RED WHEN CONNECTING UP THE SPEAKER WIRES.
The system will work either way. But you will have severe bass loss if the woofer wiring is out of phase because of phase cancellation.
Hope this helps,
Best Regards,
Mark


"Phase Cancellation"

You need to use an amplified sub. The Yamaha receiver is only sending "Pre-Amp Signal" not amplified audio like the rest of your speakers. If your sub has a crossover built in, connect it's speaker level (wires) to the "B" side of the receiver which will send audio to your sub and it will cross it over internally. Not the best sounding, but it works. Amplified subs range in price from 200 and up. Hope this helps

sounds like they are picking up interference. make sure they are grounded well.

The Boston Micromedia speaker set comes with two speakers (right and left),a subwoofer, and a complete set of cables to connect everything up.

1.) Position the speakers. The two small speakers typically are spaced equal distance apart on a desk/table top to the benefit of the listener. The sub-woofer typically rests under the surface, on the floor for example.

.) Connect the cable sets to the back of the two small speakers along with the speaker feet.
Note: the small speaker with the volume control knob will have three cables coming from it. This will be the "right" speaker. The other speaker will have a single cable and will be the "left" speaker.

2.) The cable ends will be color coded to match the jackson the sub-woofer. Match up the color coded cables to the respective colors on the subwoofer as follows:

(a) White cable end (left speaker) to white jack on sub-woofer.
(b) Red cable end (right speaker) to red jack
(c) Purple cable end (input) to the purple jack
(d) Green cable end (computer out) to the computer's microphone output jack.

Note: if any of the cables are too short to reach their jacks for whatever reason, an extender cable with a female and male end can be purchased relatively inexpensively to make up the difference in distance.

3.) Power up the system (plug in power cables to the sub-woofer and wall), play some music, and adjust the sub-woofer sound (control knob) to suit listening pleasure.

A nice little set of speakers, I had mine for some years now and continue to enjoy them. Good luck!

The problem is most likely the amplifier circuit. It is probably over-heating and the speaker relay is turning off. it is not likely that it can be diagnosed properly on an online forum, since it takes some troubleshooting to be certain of it. Does this system have the amplifier built into the sub-woofer? If I had the model number I could probably give you much better advice, not all home theater systems have the exact same problems. Each different model of every brand have there own unique problems specific to that model number. There are some universal problems, but this is not one of those easy to figure out universal type of problems. I work at an authorized Samsung service center and have experience with repairing these type of systems, so if I were to get the model number I could offer you a better solution. But it is likely that it will need to be serviced to determain the exact problem. A couple of the Samsung home theater systems that have the amplifier in the sub-woofer must have the entire sub-woofer replaced because they do not offer the parts and service data needed to do a component level repair.

One way to determain if the sub-woofer has the amplifier built into it is if all the speaker wires for the sattelite speakers all connect to the sub-woofer.

Sometimes a bad speaker can cause the amp to get hot and shut down, you can check these very easy yourself.

First, while the system is turned off, disconnect one speaker. Any speaker is OK to start with. After one speaker is disconnected, turn on the system and play it at medium volume. If the system stays playing and doesn't turn off the speakers as it did before, the speaker that is disconnected is probably bad. Take it to a service center and get it checked to be certain. Most service centers will do this for free as a courtesy to their customers, it only takes a minute to check.

If the system turns off as it did with all speakers connected, you then need to reconnect that speaker and disconnect one of the other speakers and go thru the proccess again. Make sure to do all of the speaker connecting and disconnecting while the system is turned off.

If you end up disconnecting all the speakers one at a time and the system still shuts off, it could be that the sub-woofer speaker is bad or the amplifier is bad.

If you can give me the model number of your system, it would help.

Dave

You need to take apart tthe sub woofer and check the connection to bass speaker for continuity. It sounds like an internal broken connection to speaker on sub woofer unit.

Most likely the sub has the crossover in it, most likely the 2 input cables from whatever device you want to play through the system will plug into the sub then the 2 speaker cables will come out of the sub and go to the speakers, just be sure to have everything connected into and out of the sub and make sure the power cords for the speakers and sub are plugged in, I am assuming this is a self powered system wich means the amplifiers are built into the speakers and sub.