Just in case it's not widely understood....
The idea behind bi-wiring is to prevent interaction between bass and treble (assuming a 2 way speaker) signals to the respective drive units due to the resistance of a single run of cable shared by both. By Ohms Law V=IxR. I is current, V Voltage and R resistance. Hence when a current is delivered to the speaker a voltage is developed between the amp and speaker ends of the cable due to its resistance. Now if a kick drum gives a big current to drive the bass unit then a voltage in sympathy with the waveform of the kick drum will be developed across the speaker cable and this will modulate the envelope of other frequencies such as a cymbal feeding the tweeter... and vice versa.
The back EMF of the drive units sending a current back to the amplifier will experience the same effect due to the same cable resistance.
This effect is added to by the same process in the internal speaker cable and shared tracks on the crossover PCB.
In a bi-wire speaker the crossover is electrically separated into the bass and treble sections with no connection between them. + & - on each drive unit goes to + & - on its own part of the crossover which then goes to its own + & - terminals on the rear of the speaker and thence via its own cable back to the amp and so they only connect together where they meet at the back of the amp. QED there can be no interaction between the bass and treble sections
due to the resistance of a shared single run of speaker cable. Bold there for a reason
It should be apparent from this that 4 Ohm speakers will suffer worse than an 8 Ohm one from a single cable run and that speakers with a nasty dip to say 2 Ohm's in the bass will make it much worse around this dip.
So that's the theory...
In practice
amplifiers are not perfect voltage sources, which is another way of saying they have internal resistance and can't provide infinite current to a perfect short circuit... another way of expressing this is that they don't have infinitely high damping factor. Now (to keep things simple) it can be said that this internal resistance of the amplifier is exactly the same as a the resistance of a single run of cable electrically speaking. So although we may have provided separate cable runs to the speaker by bi-wiring it is, electrically, as if they then share a single unseen run of cable inside the amplifier, which just moves the problem back to the amplifier end and partially negates the effectiveness of the bi-wiring.
It should be clear from the above that the higher the damping factor of the amplifier the more potential advantage to the bi-wiring.
It should also be clear that the thicker and shorter you make a single run of cable then the less its resistance and so the less the "interference" between bass and treble at the speaker end...
....and that an amplifier with a low damping factor is going to cause so much of this "interference/interaction" due to the "long imaginary single length of shared cable inside it" that there will be little or no advantage to bi-wiring OR, and for the same reason, to using a single cable run of mega thick cable.
It can be seen from all this that the greatest potential improvement from bi-wiring will be when using an amplifier of high damping factor.... which means a high feedback solid state amplifier... and that little if any advantage will be apparent with low feedback low damping factor amplifiers such as most valve amplifiers... and indeed some of the best sounding low feedback SS amps.
FWIW I'll point out that Naim amps have an actual physical 0.22 Ohm resistor at the output anyway which is equivalent to a shared run of lets say 10 meters or more of 79 strand speaker cable inside the amplifier between the PCB and the speaker terminals... so not a good candidate for potential improvement from bi-wiring!