One test mule lamp shade received two sloppy coats of Minwax water-based polycrylic via spray can. Once the second coat was dry I put it into service with an untreated lampshade at the opposite speaker.
I used a new CD I hadn't heard yet for the audition, Spanish Harlem Orchestra's "United We Stand". I chose Latin jazz because it is heavy with percussion.
I listened to what I thought would be key areas of the various tracks, high frequency percussive notes such as cymbals and high-hats, rim taps on drums, cowbell, and the like which is found in this style music. I repeated sections of the tracks at three different volume levels, which I shall call "social" , "private listening" , and "show off" .
The result was both enlightening and welcome. The soundstage was changed very little, the various instuments affected only very slightly speaker-centric. All mid-highs, mids, and lows remained the same with or without the B-T diffusers.
The more notable difference, was with the aformentioned instruments. There is a definite improvement in the definition and resolution of the percussive elements. Strike and fade of the cymbals / high-hats were crystal clear and where there were many of these simultaniously played they were all very individually distinct, as to without the diffusers they were almost as just one wall of sound. Rim taps, cowbells, etc. also had the improved resolution with the diffusers, again noted by their clarity with strike and fade and individual definition.
Definitely a keeper here, and I'll be treating another two shades using the same polycrylic but brushed on instead of sprayed. The distance behind the speaker seems to be right for the moment, but I shall see where different positions affect things.