Longest Advisable Speaker Cable Runs?

I run 20ft cables from my 10watt Sophia Baby. Mine are simple Vampire wire 12ga continuous cast copper hook-up wire.

Variables that are relevant to your question include speaker impedance (the higher the better); the variation of speaker impedance as a function of frequency; the type of cable; the criticality of woofer damping to the particular speaker; the output impedance of the amplifier; and possibly amplifier bandwidth and how much feedback the amplifier uses (the long cable conceivably could act as an antenna and introduce rfi into the feedback loop, if there is one).

So as a minimum let us know the make and model of the speakers and amplifier.

Regards,
-- Al

Thanks guys for the replies. I've heard the baby packs a good punch-it's a tube amp and mine is class AB solid. The amp is an Altmann BYOB and speakers are modified Klipschorns with Volti Horns and Beyma drivers. Being Khorns, the far speaker is way off in the opposite corner-about 30 ft from the desired amp position.

Speaker impedance is 8 ohm
frequency is 400hz to 6khz
The type of cable is undecided - any recommendations for long runs? I've had NacA5 but that's the only cable I know of meant to be used for long runs. No idea of critical damping.

The Altmann BYOB is a pretty esoteric peice so I couldn't find much of the info you listed Almarg. I'm not sure of the impedance but it's powered by car battery so there's a lot of power in reserve. Not sure of bandwidth or feedback.
I hope that helps and I appreciate your effort here.
Dave

Keep your amp between your speakers and purchase longer interconnects.

Hello. I manufacture cables and 30 ft. is not to long. It's dependent on the type cable used.
I'm not promoting my cables by any means. Just making reference that 30 ft. can be done.
I've made 75 ft bi-wires for a costomer that was very happy with the results.
Do your home work and find the right cable and you can do 30 ft. with no problem.
Hope this helps.