Dave Liquorice wrote:

And if you have to run longish speaker cables it may well be better to
do it at 100v line rather than ordinary LoZ stuff. Apart from losses
in the cable the amp might object to the much more reactive load.

Not sure I follow that, Dave. The capacitance of a given length of
cable of a given construction doesn't, to a good approximation, depend
on its size. It depends more on the ratio of conductor diameter and
spacing. So if you compare, say, 0.75 mm^2 cable for 100 V line use
with, say, 4 mm^2 in a low-Z system the total shunt capacitance will be
about the same (for a given run length). However the shunt reactance of
the cable is going to have far more effect on the higher-impedance 100 V
line system, since the reactive current will be a much larger fraction
of the LS load current. If you're worried about the amplifier
'ringing' or bursting into oscillation then the low-Z system is the
safer bet.

In reality though, with a half-decent amplifier it's only the series
resistance of the speaker wiring that matters, and there of course the
100 V line system wins hands down if it's a long way from A to B.

--
Andy