Answer to your second question: with speakers on long wall in 12 ft wide room, your back ends up against the wall. Basically impossible to get any control on behind your head reflections that way. Diffusers won't work that close behind you. Ideally need 8 ft or more behind you to get the best sound. Just my experience. I would stick with the short wall.
Setup Speakers Along Long Wall?
Just moved into new house and was gifted by my wife a 121/2’x23’ room with 7’-101/2’ sloping ceilings. I’ve been putting together a system, which so far consists of Technics 1200G/Hana ML, Sutherland 20/20 LPS, Audioquest interconnect/speaker cables, i7Roon Core NUC, iFi Zen Streamer and Shunata power cables and conditioner.
Unfortunately, every turntable position other than against the wall 7’ in front of speakers results in horrible cartridge bass/room interaction. Against the wall either requires 15’ speaker cables, or a balanced phono preamp and 12’ balanced interconnects.
So, here is my two part question. Better long interconnects, or speaker cables?
Second question. What downside is there to placing my listening position against the long wall? Currently, 7’ from short wall.