Tghanks Karen
Here are a few extracts from the Space Designer section of the manual:
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.
Activating the " preserve length " button preserves the length of the impulse response when the sample rate is changed.
Another benefit of reducing the sample rate is that processing requirements drop significantly, making half-sample rate settings useful for large, open spaces.
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.
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.
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If it ain't broken.....