How it differs from a QRD
Instead of `n² mod N`, a PRD uses a primitive-root sequence `g^n mod N`, which visits every non-zero residue exactly once — so there is no zero-depth (flat) well. The payoff is a dip in energy reflected straight back toward the source at the design frequency and its harmonics. See QRD vs PRD vs skyline for a side-by-side.
Geometry, fins, and the usable band are otherwise the same as a 1D QRD. A PRD has N−1 wells (no null well) rather than N.
s_n = g^n mod N, d_n = s_n · λ₀ / (2N)g = least primitive root of the prime N. The sequence is a permutation of 1…N−1, so no well has zero depth.
Best for
- Setups where a strong straight-back echo is the problem
- Anyone who wants a QRD alternative with a different scatter signature
Not the tool for
- Low-frequency problems (use an absorber)
- When you specifically want the simplest, most-documented panel (QRD)
Start from a common size
N is the number of wells (a prime). More wells scatter more smoothly but make a wider, deeper panel. Pick one to open the designer pre-set: