Primacoustic Razorblade N17 QRD Diffuser

Primacoustic Razorblade QRD Diffuser


The Primacoustic Razorblade is a true quadratic residue diffuser (QRD) that provides high quality acoustic diffusion from about 400 Hz to 5.5 kHz.

Built from birch wood laminate and MDF (medium density fiberboard), the Razorblade boasts low frequency diffusion which is not achievable with lightweight plastic diffusers. To disperse low frequencies (rather than absorb them), the Primacoustic Razorblade is dense and rigid.

The design is based on the quadratic residue sequence for the prime number 17, making the Razorblade an N=17 QRD diffuser. It is a 1D hemi-disc diffuser, meaning it disperses reflections by spreading sound energy left and right in the horizontal plane.

Use the Primacoustic Razorblade to control problematic reflections, while simultaneously enhancing spaciousness to make your room sound larger.

SKU: PRIMA-RAZOR. Category: . Tag: .

Product Description

A brilliant invention by Manfred R. Schroeder, quadratic residue diffusers are based on elegant mathematics and are still popular today because they are so effective. QRD diffusers, like the Razorblade, achieve optimum scattering at integer multiples of the design frequency, and achieve very good diffusion in between these frequencies.

The Razorblade is an N=17 QRD diffuser, meaning the design is derived from the quadratic residue sequence for the prime number of 17. 17 wells of different depths (determined by the mathematical sequence) create a reflection phase grating that sends acoustic energy back toward the listener with varying time delay. This provides both temporal dispersion (breaking up sound waves with respect to time) and spatial dispersion (distributing sound energy in space).

Because some of the wells blend together, the 17 “wells” in the Razorblade diffuser visually appear to be 15 wells separated by fins.

The depth of the deepest well is 8 inches, which controls the low frequency cutoff (about 400 Hz). The width of the wells facilitates the high frequency diffusion performance (up to about 5.5 kHz). In practice the Primacoustic Razorblade will scatter sound over 5.5 kHz and as low as 200 Hz.

The Primacoustic Razorblade is designed to be positioned at least 6 feet away from the listening position, but we recommend a minimum listening distance of 9 feet.

The design is modular so that you can place multiple Razorblade QRD diffusers side-by-side to create a large diffusive surface. A typical application for this is to scatter reflections on the back wall of RFZ (reflection free zone) and live-end, dead-end control rooms.

One-dimensional sound diffusers like the Primacoustic Razorblade are not only useful in recording studios and concert halls. Musicians, audiophiles and hi-fi enthusiasts use them in music rooms,  listening rooms and  home theatres to control reflections and enhance ambience.

Diffusion helps you create an enveloping sound stage and balanced acoustics so that your room sounds natural, spacious and alive.

Additional Information


Satin black finish


48″ x 24″ x 8″


Furniture grade baltic birch plywood and MDF


One (1) N=17 QRD diffuser




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