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Chapter 10 Convolution Reverb: Space Designer 141
The reason why we can actually perform the necessary calculations in real-time these
days is due to a mathematical operation known as the FFT (Fast Fourier Transform). For
filters (and we use the term filters here as this is what is effectively happening—the
input sound is being filtered by the impulse response) with lots of nonzero values, it is
easier to compute the convolution in the spectral domain. Here’s how:
If we want to convolve our music function (the sound you wish to process) against our
filter function (the impulse response), this results in another sound (the convolved
results). This convolved sound has a spectrum that is equal to the product of the
spectrum of the music function and the filter function.
Put another way, the Fourier coefficients of the convolution can be computed by
simply multiplying together each of the Fourier coefficients of the music and filter
functions.
The End Result?
Knowing the ins and outs (mathematics) behind convolution doesn’t really matter too
much. The important thing is to have a large library of great impulse responses—the
best sounding cathedrals, recording studios, concert halls, railway tunnels, electronic
reverb units or even resonance bodies of instruments … you name it!—and you can
simulate any space for any sound.
Thankfully, we’ve created and included a number of Impulse Responses to get you
started, and you may find that they’re all you’ll ever need.
If you wish to create your own, the Internet is a great place to share them with other
Space Designer users from around the globe.
Whatever way you decide to go, either using the factory IRs, downloading another
user’s efforts or rolling your own, Space Designer makes it easy to get that perfect
reverb sound.