Combine stereo to mono

[Jonfess]

Short
I want to combine the center and sub chanells from my PC to mono then to a stereo plug for my center speaker with its powerful sub

Long
I have my
Front. Big reciever
Side PC speakers
And rear. Chair speakers
And it sounds alright but I want to add my soundbar with its powerful wireless sub but if I do that only one side would work so I was hoping to convert

Left. Cen Left cen/sub
From PC. Mono. To soundbar
Right sub. Right cen/sub

That way I have equal audio and since it's the center I don't care about losing stereo quality

Other
The speakers are close enough to sound like the center

I really don't want to buy anything

Also I have some components and a couple of aux cables that I could splice for it

 

[americanaudiophile]

You would need to mix the center and subwoofer outputs of the PC. It would not be mono but a full range dual center channel output.
You could built this and wire it to output the center sub mix to both inputs of the soundbar.
http://www.instructables.com/id/Altoids-Tin-18-Stereo-Mixer/