I'm always horrified when I see musicians using instrument cables to connect amplifiers to speaker cabinets.

Instrument cable is not meant to be used as a speaker cable.  The fine inner conductor is not designed to take the high voltage and current that amplifiers generate.  It's designed to carry the very low-level signal from your instrument to your amplifier with the minimum of noise and interference.  By using it as speaker cable you run the risk of causing major and expensive damage to your rig every time you crank it up.  Much better to invest in a fit-for-purpose speaker cable that is individually hand-made to order. 

This Rock-Wire cable assembly is individually hand-made using Klotz Twinaxial 2.5 sq.mm. speaker cable which has 50 x 0.25mm strands in each conductor.  Klotz cables are rated as some of the best on the market, they have a very low resistance, are extremely flexible and will bring out the best from your guitar amp and speaker. 

You really don't have to pay Hi-Fi boutique prices for good performance.

This cable is suitable for guitar amps and cabinets fitted with 1/4-inch jack sockets and comprises Rean (a Neutrik brand) 1/4-inch Heavy-duty Jacks and 1.5-metre of Klotz Twinaxial 2.5 sq.mm. cable.

See my eBay shop for

Bass Amplifier speaker cables

Instrument to wireless beltpack cables