Space Designer impulse response lengths in Final Cut Pro
You can use the Space Designer effect’s Length parameter to set the length of the impulse response—sampled or synthesized.
All envelopes are automatically calculated as a percentage of the overall length, which means that if this parameter is altered, your envelope curves stretch or shrink to fit, saving you time and effort.
When you’re using an impulse response file, the Length parameter value can’t exceed the length of the actual impulse response sample. Longer impulse responses (sampled or synthesized) place a higher strain on the CPU.