Sound only from the right speaker

There is a setting that changes the output format of the audio. It is my suspicion that the left channel of your audio is being routed to your subwoofer. Windows may not be autodetecting your speaker configuration properly and might be sending a stereo signal to your speakers incorrectly.

Try right-clicking the sound device and clicking Configure Speakers, instead of double-clicking to get to Properties.

A configuration wizard should appear, starting at the "Speaker Setup" step. It should let you change the output format of the sound. Choose the one corresponding to your setup. For instance, this is what I see when I do it on my laptop:

Also, make sure that you are hooking up your cables properly behind your computer! I have a 5.1 audio system hooked up to my computer at home, myself. My motherboard supports up to 7.1 surround, and so not all of the audio output ports are hooked up. Make sure the color-coding on the speaker cables and your back panel connectors match. In my case, the orange and pink-labeled inputs are very similar and, if you aren't careful, can be easily mixed up.

Have you tried disabling the mobo soundcard from BIOS and running strictly off of your PCIe one?

Are you getting full range sound from your subwoofer instead of only low frequencies? Can you hear voice and system sounds, or is it playing correctly?

Since your getting stereo from the 3.5mm jacks, sound is being processed correctly into analog, which is actually one degree further than using the SPDIF which is full digital.

Have you tried changing your SPDIF output mode?

Does your speaker setup have different options for surround output modes? Dolby, Quadraphonic, etc....

What model of edifier speakers are you using?

Root cause : The cable for the LHS speaker is broken. It might have broken at either of the ends.

Try connecting your speaker to another audio output - ipod etc. If it does not work, then this diagnosis is right.

It's almost definitely the jack on the back of your computer that the speakers are plugged into or the motherboard itself (either drivers/hardware/bios). I have a 5.1 system that has had similar problems and I narrowed it down to the motherboard jacks. You can certainly try jiggling them but your ultimate solution is probably to get a nice sound card.

Depending on where/how the volume knob extension is hooked up, it is probably consistent with what I am saying. ie, if the volume knob comes from the right speaker which works, the knob's jack would need to be able to receive full stereo through it and that's why you get full stereo with your headphones.

For any playback device, you can go into the sound properties and configure it to be a range of things but it is often limited by what it's detected capability is.

Also, given that your stereo 2.1 set up probably has 1 main audio plug that goes into the back of the computer, switching how the individual speakers are hooked up changes nothing about how the motherboard is transmitting the audio signal. ie, still will only send to the same speaker it has its connection with.

Wiggling the rear jack and pulling it out a little bit will help troubleshoot this while playing a stereo music file.

It could, alternatively, be the connection point on the back of your 2.1 sound system from your computer where your sound system receives the signal transmitted from the motherboard.

It is still likely the S/PDIF port on your motherboard or how the motherboard handles the S/PDIF interface in general (ie, a sound card using S/PDIF would still need to go through the motherboard). The audio jack on the front of your PC is interfaced differently so it is not relevant.

The only thing to try in that case is to try it out on a different motherboard. (I had a motherboard from asus where the audio chip crapped out and wouldn't play standard 3.5mm audio correctly - I was effectively getting mono all the time instead of stereo).

Also, try your sound card on another motherboard to rule that out.

If it is not the actual connection jack on the motherboard, it may have to do with your OS but that's not as likely as it being the motherboard at this point.

It would be good to try a free Linux platform like Ubuntu nevertheless.

All audio getting processed goes through the motherboard regardless of where/how its connected. It is the key juncture and if you rule out everything else around it, the motherboard itself must be what is wrong.

You may have some luck tweaking bios settings or updating the motherboard bios but if that doesn't work, I'd just go grab a drop in motherboard from a different manufacturer that fits your current spec.

I had the same problem (Windows 7 x64) sound on the right speaker only. Here is the solution:

I changed speaker properties from 16 bit-48000 Hz to 24 bit-48000 Hz. SOLVED.

After searching for a solution for a long long time, now I can not believe it was such an easy one...