I'm helping a friend make changes to his audio-video system, principally
moving a main AV equipment rack to a different location. This involves
rerouting a good deal of speaker wiring, almost all of it running in the
loft under insulation and in some areas chipboard flooring.

The "correct" way would be to uncover the existing cables and relocate them.
Given the necessary disruption and severely limited headroom, a far more
attractive idea is to connect new cables to the accessible ends of the
current ones and run them across the top of the loft floors and areas of
exposed insulation then down through to ceiling to a new AV hub.

The maximum extension would be in the region of sixteen feet, resulting in a
cable run some thirty feet from amplifier to loudspeaker; would that make
any material difference to the sound or the loading on the amp? This is a
decent mid-price hifi setup but nothing really ultra-high-end.

We can of course experiment with extending the cables on just a pair of
speakers in order to assess the sound, but it would be useful to know in
advance if a run of such a length is pushing things a bit.

Many thanks.