Actually, with a fairly resolving system you are likely to hear some difference when switching to otherwise *identical* cables one of 12 ga and one of 8 ga.
Two factors, the 8 ga will have more self inductance.
The 8 ga in a "zip cord" configuration (for example) will also have more capacitance (probably) due to the larger
diameter giving more surface area for the charge.
In other words it will have measureably different parameters. Which will sound better is another issue entirely, one that has almost nothing to do with anything that can be predicted or measured.
But, you'd probably find that there's a bigger difference between a "shotgun" wiring (even on a non bi-wired speaker) approach and standard or even paralleled wired (for the same actual speaker wires).
If you happen to have an extra set of the 12 ga wires, you can play with this and see what the differences are. Two 12 ga wires are going to get pretty close in circular mils to a single 8 ga conductor...
_-_-bear
Two factors, the 8 ga will have more self inductance.
The 8 ga in a "zip cord" configuration (for example) will also have more capacitance (probably) due to the larger
diameter giving more surface area for the charge.
In other words it will have measureably different parameters. Which will sound better is another issue entirely, one that has almost nothing to do with anything that can be predicted or measured.
But, you'd probably find that there's a bigger difference between a "shotgun" wiring (even on a non bi-wired speaker) approach and standard or even paralleled wired (for the same actual speaker wires).
If you happen to have an extra set of the 12 ga wires, you can play with this and see what the differences are. Two 12 ga wires are going to get pretty close in circular mils to a single 8 ga conductor...
_-_-bear