Ralph of Atmasphere would say that for tube amps difference between 1 meter and 2.5 meters speaker cables may very well be audible and could in fact be significant
Atma-Sphere utilizes OTL and zero feedback designs and, as such, its output imp. (5-15 ohms) has been relatively higher than the tube counterparts without. It is understandable that Ralph will want cable as short as possible to reduce total impedance before the load. Nevertheless, given the speaker cable impedance (0.005 ohm/ft) is two orders of impedance less than the most of tube amp., the difference caused by a bit longer cable is in general negligible.