The original RealDiff HD is a two-dimensional quadratic residue diffuser with a low frequency cutoff of 800Hz and a prime number 13 design criteria. This means that you get better diffusion due to more frequency groups being addressed in its design. Two-dimensional diffusion ensure equal scattering/diffusion in both the horizontal and vertical planes. This is ideal for concert venues, recording studios and other environments where equal dispersion of diffuse frequencies is desireable. Additionally, the unique mounting method of the RealDiff series of diffusers means you get the job done faster and more precise than ever.