How to build guitar cabinets?

Jim Marshall first went into business in the early 1960s with a small shop in Hanwell, London, selling drums, cymbals and drum-related accessories. Marshall Ltd later expanded and started selling guitars and amplifiers, the most notable of which at the time were the Fender amplifiers imported from America. These were very popular with guitarists and bass players, but also very expensive, and Jim Marshall thought he could produce an equivalent product for less money. He enlisted the help of Ken Bran, and between them they decided they most liked the sound of the 4x10 Fender Bassman. Not wishing to fix something clearly not broken, they set about making copies of this amplifier. The first few production units were almost exactly the same as the Bassman, with US-origin transformers and military surplus 5881 power valves. The first difference was the cabinet used, as Marshall decided to build separate amplifiers and speaker cabinets, and as they were originally intended as bass amplifiers, Marshall chose to use four 12 inch Celestion speakers in a closed back cabinet, instead of the Bassman's four 10 inch Jensen speakers in an open back cabinet. This new amplifier was named the JTM45 after Jim and his son Terry, and 45 as in theory it produced 45W of power.