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RPG Abffusor

There is a need for a surface treatment that controls strong first order reflections over a wide range of frequencies and angles of incidence which also offers near field scattering to provide a natural ambience.

The Abffusor® solves these problems by using two absorption mechanisms in addition to diffusion. Absorption extends to lower frequencies than flat porous absorbers due to the QRD® pressure gradient mechanism. Near field QRD® diffusion provides additional sound control.

The Abffusor® is the industry’s first absorption phase grating. It is an extension of RPG®’s research on the reflection phase grating (RPG) which provides sound diffusion from a series of divided reflective wells of equal width and different depths. The depths of both the reflective wells of the RPG and the absorptive wells of the Abffusor® are based on mathematical number theory sequences. The Abffusor®’s absorption efficiency extends below that of a traditional flat porous absorber because it utilizes two absorption mechanisms.

The first is the traditional dissipation of sound energy into heat by frictional losses in the pores of a porous absorber. The second is the viscous losses due to high particle velocity flows across the well dividers induced by the pressure differences in adjacent wells. This pressure gradient mechanism results in additional low frequency absorption. The absorption phase grating topology also offers efficient glancing angle reflection control and near field diffusion to create a natural sounding, attractive room treatment.

The graph illustrates the absorption efficiency of the Abffusor® for an A mounting directly on a wall and an E mounting with a rear cavity depth of 16 inches. Note the excellent low frequency absorption the Abffusor® offers when attached directly to a wall and the improvement that is possible when a rear air cavity can be employed.

The Abffusor® can be mounted on a wall, in a T-bar ceiling grid, or left free standing. Type E Flush Mounting provides improved absorption. Hardwood feet are available for free standing installation.


  • Similar appearance to a QRD® 734 Diffusor
  • Complimentary performance to a QRD® 734 Diffusor
  • Frictional dissipation and pressure gradient absorption mechanisms
  • Number theory surface topology
  • Modular and versatile
  • Attractive design element


  • Can be used in conjunction with the QRD® 734 Diffusor to provide an integrated visual design
  • Broad bandwidth abffusive performance compliments the broad bandwidth diffusive performance of the QRD® 734 Diffusor
  • Frictional dissipation and pressure gradient absorption mechanisms offer extended broad bandwidth random incidence absorption for uniform attenuation
  • Irregular number theory surface topology effectively absorbs and diffuses glancing incidence reflections more effectively than a flat porous absober providing natural sounding reflection control
  • Modular construction makes wall, drop ceiling, or floor mounting simple and attractive
  • Wide variety of custom fabric finishes makes the Abffusor® a decorative design element as well as a powerful acoustic tool

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