Question from a Audio Masterclass visitor…
“In my rehearsal room, I have found that by stacking all my speaker cabs (which are unconnected, some loaded and some empty) along the wall opposite the main PA stack, the overall sound has improved dramatically. Why is this?”
What your unconnected speaker cabinets are doing is breaking up the sound waves. Adding irregular surfaces to the room is increasing the number of reflections.
This makes the sound field in the room more complex, which is more interesting to the ear.
If the room is left uncluttered with just bare walls, floor, ceiling and main PA, there will be just a few strong reflections from the walls, floor and ceiling.
For some reason, the ear and brain do not like strong reflections that are few in number. We prefer more reflections that are weaker.
By breaking up the sound wave, the few strong reflections are converted to many weaker reflections.
This is known as 'diffusion'. Professional studios frequently use purpose-made diffusors to break up the sound.
However, as you have found, it is possible to apply diffusion from objects that just happen to be around, often at no cost.
Diffusion is a technique that is strongly recommended, both for recording studio and rehearsal room.