Bi-wire v's single with jumper leads.

Kijanki: I had misread your earlier post - you did indeed remark ( and correctly I might add) that the cable - amp Z was less than the HF circuit Z.

Musicnoise - This is just hypothesis and changes are so miniscule that it's
difficult to make sense of it. My speakers show slightly more air in the sound
when bi-wired but now I'm not so sure if I made right decision buying shotgun
cable. It costs practically twice and I could get better cable for the same money.

Another strange thing that somebody mentioned is leaving one of the jumper
brackets in-place (one on the ground side). For some reason it made sound
with my previous amp slightly more coherent/focused. It worked only when
jumper was on the ground side and since I have right now class D full Mosfet
bridge driving my speakers there is no ground side and I haven't tried it again.
From engineering point of view it doesn't make sense at all.

I'm reading a bunch of stuff in these posts that doesn't make sense. The reason bi-wiring works is due to the finite but definite level of resistance a wire has. If you send a current to the tweeter and woofer and the crossover splits it and then the signal returns via the "ground" speaker wire. That return post from the crossover will develop a voltage. Because the current is flowing through the wire that has a resistance. Bi-wiring improves the sound because the tweeter return path is on it's own wire and therefore the voltage at the crossover is due only to the tweeter current and you will not get intermodulation with the current flowing through the bass wire (the voltages sum when using one wire for both). The net result is that the larger currents that flow through the bass network do not affect the amplitude of the tweeter signal.

You dug up a 4 year old thread to reopen the can of worms it already was?

Jkorten, since you opened the can of worms, here is something else for you to read that talks about more than just the intermodulation issue.

Bi-wire, not only an advantage

If you like bi-wire, great, I'm happy for you. In reference to the OP, I prefer single wire with jumpers of the same wire.