Can one use assymetric wire gauge for speaker cable construction?

Yes... but why?

You can bundle together into a single conductor multiple differeng gauges into  a single larger effective gauge.  You can also use 2 different effective gauges for + and - to some degree.

You must ensure each conductor has a safe minimum gauge for the current carrying, and this depends on the length as well as the power and speaker impedance.  You could often use 16 gauge for small HT type speakers, but I'd recommend 14 as a minimum. So long as your two conductors are at least 14 gauge you should be OK.

@audio_phool - The speaker cables I and many others have built use 2 x 16 gauge solid UP-OCC copper wire (or 2 x 14 gauge) for the signal and 1 x 10 gauge Silver plated stranded Mil-Spec wire for the Neutral wire and they sound excellent

Here’s a link for DIYer’s on how to make them

http://image99.net/blog/

And here’s what other Audiogon members think of them

https://forum.audiogon.com/discussions/duelund-conversion-to-diy-helix-geometry-cabling

If you have and questions just post them on the thread above

Regards - Steve

I think this will be helpful regarding bi-wiring, the reason for different guages

I chose to believe in small diameter individual strands, so I make my own speaker wires using cat 8: 8 22awg = 13 awg, each strand insulated; each pair foil wrapped, those 4 pairs insulated, ofc copper. two different colored legs, thus red = 8 positive, black = 8 negative = 13 awg. double your length of each color for a pair, add some slack, cut in half, cut the factory ends off, pure copper spades ...

Shielding can sure kill the sound of a speaker IC. I'm prone to mini solid core individually insulated with teflon and then a weave 8-24 strands, I like ribbons too. Actually one of my favorites is the combination of the two, The weave is OCC with Teflon and the ribbon is OCC/silver clad with teflon.. I also add a stinger of 99.99% tungsten in an air tube of silicone on the + side only..

Who cares I'll try almost anything... :-)

I use solid core 14 gauge UP-OCC copper in Teflon. It's perfect for me. You might try it as a control against which to judge yours.