Grounding cable gauge size

Thank you Ozzy for trying this stuff and reporting your results, I think it was you that put me onto the Puritan power filiters which continue to wow me.

Just read an Analog Corner article from Nov 2021 on electrical wiring that I thought might interest:

Please help me to understand, I'm curious to try this speaker grounding tweak since my speaker cables go directly into a floor hole and are suspended in the rafters of my basement.

So I can run a wire from the black '--' speaker terminal to either the copper water pipes below (the panel box ground runs directly to an outside copper ground rod) or since it would be easy to drive a grounding rod underneath the speakers this is prefered? I can also easily do this at the amp '-' and compare the two spots and the two grounding strategies..

Thanks much.