Hi Pani,
The Tannoy dual-concentric really is not time aligned. The compression driver diaphragm is about 6 inches behind the woofer's acoustic center. However, Tannoys are phase coherent at the crossover point, thanks to the following slick hack: that 6 inches is equivalent to 180 degrees of phase at the crossover point frequency of 1.1kHz -- hence the tweeter's wiring polarity is simply reversed to yield phase coherence at that point.
A while back Tannoy gave in to market demands and introduced a compensation network to electrically time align the dual-concentric driver. However, apparently the cure was far worse than the disease...it was very short lived and never surfaced again.
I also read somewhere (I forget where; not much value without a citation, unfortunately) there was a study that concluded there was audible improvement for a speaker to be either time aligned or phase coherent, but that having both of them together didn't seem to further the improvement.
Anyways, looking at 6inches divided by 340 meters/sec (the speed of sound) is going to vastly exceed the time mis-alignment effect of any cable discrepancies divided by 200 million meters/sec (about two thirds the speed of light, i.e. signal propagation in cables)...by several orders of magnitude.
That said, I wouldn't turn down a chance to try identical cable top & bottom, but I'm not going to make any purchases to do so. The mixed run sounds better than single run of either, and that's good enough for me.
