Bobbydd, re comments on ’stuff between speakers’, even though Jim Smith sez so it ain’t necessarily so. For example if you listen to your speakers toed in so that the axis crosses in front of your listening position there is a fair amount of signal which has the wall behind the speakers acting as a 1st reflection point. Treating that wall with diffusion materiel or even stuff like equipment, bookcases, recordings etc can produce a much cleaner signal. What I think about Jim’s advise is that it is more important when dealing with sound waves hitting sensitive equipment, such as phono cartridges, and causing distortions. I’ve even seen ’knowlegable’ audophiles place TT’s in corners. Go figure.
An interesting experiment you can conduct to see how this works is to make a panel of materiel which absorbs high(er) frequencies and place it next to the inside surface of the speaker. You might be surprised at the benefit it can bring. Looks ugly though. :-)