Sheilded cable used as speaker cable

[Jammin'John]

Would someone please tell me a few reasons NOT to use sheilded instrument cable to hook a high power bass amp to a speaker cab.
A person at a jam session wanted me to do just that.
I refused & he made some stupid comments about me being wrong & that it was OK to do it !

Thanks,
JJ

 

[Mudcat]

Because the instrument cable is most likely 28 AWG. If you tried to run the several hundred watts through it, it would light up the stage - literally.