Soundtrack Pro 3 Effects Reference (en).pdf - Help Library - Apple

• If the project sample rate is 44.1 kHz, the options will be 22.05 kHz, 11.025 kHz, and
5512.5 Hz.
Changing the sample rate upward increases—or changing it downward decreases—the
frequency response (and length) of the impulse response, and to a degree the overall
sound quality of the reverb. Upward sample rate changes are of benefit only if the original
IR sample actually contains higher frequencies. When you are reducing the sample rate,
use your ears to decide if the sonic quality meets your needs.
Note: Natural room surfaces—except concrete and tiles—tend to have minimal reflections
in the higher frequency ranges, making the half-rate and full-rate IRs sound almost
identical.
When you select half the sample rate, the impulse response becomes twice as long. The
highest frequency that can be reverberated will be halved. This results in a behavior that
is much like doubling every dimension of a virtual room—multiplying a room’s volume
by eight.
Another benefit of reducing the sample rate is that processing requirements drop
significantly, making half-sample rate settings useful for large, open spaces.
Activating the “preserve length” button preserves the length of the impulse response
when the sample rate is changed. Manipulating these two parameters as you see fit can
lead to interesting results.
The lower sample rates can also be used for interesting tempo, pitch, and retro-digital
sounding effects.
If you are running Space Designer in a project that uses a higher sample rate than the
impulse response, you may also want to reduce the impulse response sample rate. Make
sure the “preserve length” function is enabled. This cuts CPU power consumption without
compromising reverb quality. There is no loss in reverb quality, because the impulse
response does not benefit from the higher project sample rate.
You can make similar adjustments while running in Synthesized IR mode. Most typical
reverb sounds don’t feature an excessive amount of high frequency content. If you were
running at 96 kHz, for example, you would need to make use of some deep lowpass
filtering to obtain the mellow frequency response characteristics of many reverb sounds.
A better approach would be to first reduce the high frequencies by 1/2 or even 1/4 using
the “sample rate” slider, and then apply the lowpass filter. This conserves a considerable
amount of CPU power.
Setting Impulse Response Lengths in Space Designer
You can use the Length parameter to set the length of the impulse response—sampled
or synthesized.
136 Chapter 11 Space Designer Convolution Reverb