In terms of things placed in the room deliberately which affect the sound, or have an effect, I have included the rug. Easily the biggest outlay, but The Wife got it, so
.
Other than that, no room measurement apart from my ears.
All corners have something in them that breakup/disturb and ? absorb the sound. All walls have hanging fabric on them, in one fashion and another.
Large-ish voluminous paper ceiling lampshade.
We have floorboards with a 3’ void underneath, so not ideal.
All speakers and equipment are supposedly de-coupled from whatever they sit on, rather than sorbothane-style
attached to whatever they sit on. Including the speakers, which sit on a sandwich of granite, felt and cork (sounds a bit odd, works very well.) That experiment cost about £50, and is one of the most profound differences I have achieved.
The room has shelves of records, c.d’s and boxes of records all over the place.
I do not have a coffee table, I like a clear path in that triangle twixt the speakers and my ears, so the floor is clear.
(edit: also the floor is clear so that I don’t trip over, another reason not to have a coffee table, as I would walk into it.)
I don’t use anything other than records and c.d’s, so don’t have call for the dsp thingy.