Too much uncorrelated rear-wall diffusion scrambles center imaging

Evidence

I sat at the center of the console and listened; something was wrong, the center image was strangely unclear. Looking around I saw that the entire back wall was covered with beautiful and expensive wooden diffusers, vertically arranged to spread the sound horizontally. I asked for monophonic pink noise to be played, and from the stereo seat there was simply no center image—the sound spread across much of the space between the loudspeakers. Others heard it too; it was not subtle. There was concern, as this was obviously not good. The movers were still on the premises, so we found some moving blankets and hung two of them in front of the diffusers. The center image snapped into place where it belonged. The problem: too much uncorrelated sound arriving from behind the listener, scrambling the information in the direct sound from the loudspeakers. Lesson: there can be too much of a good thing. The ETC probably looked impressive, though. Somebody may have measured but they did not listen. — Toole, Floyd E, Sound reproduction- the acoustics and…, 1397

Categorization

• SEED: An essay on why good acoustic measurements can mask bad listening — ‘they measured but they did not listen’ as a critique of objective-only engineering.
• SHARE: Send to anyone building a studio control room: a concrete anecdote proving diffusers everywhere is a hazard.