I've made an intensive research on cables for tannoys and found a significantly impressive number of different views about cables to connect the Tannoys to the ampli.
However, I believe that given such a diversity of opinions the most reliable source was the Tannoy website, where we can read only tips about the gauge vs. length. Here it is:
"Recommended loudspeaker cableStaff, posted this on May 23, 2012, 15:52
Unfortunately we cannot recommend any specific brand of cable to use with any of our loudspeakers and always recommend consulting your local hi-fi dealer for more advice.
Always use the best quality of cable available within your budget. High quality audio signals passing from the amplifier to the loudspeaker are unusual in their demands on the cable. Wide dynamic range and frequency bandwidth information has to coesist with the ability to transmit peak currents of at least 10amps, without incurring any loss or signal impairment. This explains why the sound quality of the information reproduced by the loudspeakers is so dependant on the physical properties of the cables connecting them to the amplifier.
Technically, we recommend two-core cable with cross section area not less than 1.5mm (14 gauge) for cable runs of up to 3 meters. For longer lengths we would suggest that you use cable with a minimum cross sectional area of 2.5mm (12 gauge). We do not recommend the use of braided (Litz) or small diameter coaxial cables as these have a high capacitance that may affect the stability of certain amplifiers."
http://support.tannoy.com/entries/21479097-Recommended-loudspeaker-cableBest regards