How do I swap audio output of the left and right speakers?

You could get a cable that splits into two channels and one that merges them again. Then just swap the channels inbetween. For example this kind and this kind, if I read correctly... cables and audio isn't my thing :p Anyways, something along those lines should work maybe work?

"I experienced this same problem with a set of Logitech speakers whose cable wasn't long enough to be placed the right way round on my (long) desk - they seem to assume that the PC will always be underneath the monitor, or on the right hand side.

My sound chipset doesn't have any support for swapping channels, so I had to make an adapter plug/socket combo. Find someone who can use a soldering iron, and get a 3.5mm plug and socket, and several inches of stereo audio cable - should be done in less than 5 minutes."

"If this is a simple 2.1 stereo speaker setup (just a L + R + subwoofer) with a 3.5mm jack that plugs into your computer, then you can find a 6ft headphone extension cable that simply extends the reach of any 3.5mm plug.

I used to use one with my TV to extend the reach of my headphones from the TV's 3.5mm headphone out.

I just used that same cable to extend the reach of my speaker setup that had the same constraints as yours — the right speaker has the plug but it would not reach my PC's jack. Hope this helps."
"If this is a simple 2.1 stereo speaker setup (just a L + R + subwoofer) with a 3.5mm jack that plugs into your computer, then you can find a 6ft headphone extension cable that simply extends the reach of any 3.5mm plug.

I used to use one with my TV to extend the reach of my headphones from the TV's 3.5mm headphone out.

I just used that same cable to extend the reach of my speaker setup that had the same constraints as yours — the right speaker has the plug but it would not reach my PC's jack. Hope this helps."

"There is currently a software solution that's easier to implement. Voicemeeter Banana (it's currently free)

Reference link
Set windows default output to Voicemeeter VAIO, this brings the sound into voicemeeter (it lands in the blue section in the reference link).
In the Voicemeeter VAIO section of Banana make sure A1 is lit (this means it's sending the sound to A1 output, it's usually lit by default)
Set A1 output to your speakers/headphones (green section in reference link)
In the A1 section, click Mono a couple times and you'll get the swap icon"

"As posted by Avatar further up Equalizer APO is quick and easy and a completely software based solution, no fiddling with wires or breaking out the soldering iron or digging around in all your applications / games hoping they have the option to swap channels (most do not). One application, does it all, quick and easy to configure and you can forget about it afterwards.
Here is a link to test left and right channels.
I would just like to clarify on Avatar's post, there are two applications, ""Configurator.exe"" to select the device you want to edit so it can install drivers.
Then ""Editor.exe"" to import the config file to swap speakers."