Over-treated rooms are a real problem. Pack too much absorption into a space and it starts to feel unpleasant: dead, uncomfortable, slightly disorienting. A recording made in an over-damped room often sounds thin and lifeless on playback. Diffusion gives you a way to manage reflections without absorbing them.
A diffuser scatters incoming sound waves in multiple directions rather than absorbing their energy. The result: reflections still reach your ears, but they arrive from many angles and at slightly different times — which the brain interprets as spacious and natural, rather than the harsh single-bounce reflections from a bare wall. Flutter echo disappears. The room remains alive.
What's the difference between diffusers and absorption panels?
Absorption panels take energy out of the room. They reduce the level of reflections. Too many of them, and the room starts to feel uncomfortably quiet and dry — particularly at higher frequencies.
Diffusers redistribute energy rather than removing it. The reflections are still there, but they are scattered so widely that they blend into a pleasant ambience rather than bouncing back as a distinct echo. Most well-treated rooms use both: absorption at early reflection points, diffusion at the rear wall or ceiling.
As a general principle: use absorption where you need to reduce reverb time or kill specific echoes; use diffusion where you want to preserve the sense of space and energy in the room while still addressing flutter and discrete reflections.
Types of diffuser
QRD (Quadratic Residue Diffuser) — the classic form. A panel of wells of varying depths, calculated using number theory to scatter sound evenly across a wide angle. Highly effective and visually distinctive.
PRD (Primitive Root Diffuser) — a variant of QRD with different mathematical well sequences. Similar performance, different aesthetic.
Skyline diffuser — a 2D array of columns at different heights, diffusing both horizontally and vertically. More effective than single-plane diffusers where side-to-side and front-to-back scattering are both required.
Typical use cases
- Home and professional recording studios — rear wall diffusion behind the listening position preserves room energy while eliminating the "slap" from a flat back wall
- Listening rooms and hi-fi spaces — diffusion maintains the recording's spatial information and prevents the room from feeling like a padded cell
- Practice rooms — a balance of absorption and diffusion creates a comfortable acoustic without the oppressive quality of a heavily absorbed space
- Broadcast and podcast studios — rear wall diffusion adds a natural room feel to recordings that would otherwise sound uncomfortably dead
Technical notes
Diffuser performance depends heavily on the frequency range being targeted, which is determined by the well depths and spacing. We can advise on diffuser type, placement, and quantity based on your room dimensions and treatment goals. All diffusers are tested to BS EN ISO 11654; scattering coefficient data is available on request.