““Optimize xSub phase” and “Phase Align Engines” setting add latency to the x-sub, and quite a lot (in total about 16ms or 790samples).”
The thing with optimising the phase of xSub, is that when you press a new note x-Sub will not reset its phase immediately as that would cause an abrupt click…instead it waits until the wave crosses zero and then waits again until the main synth waveform is out of phase by a preset amount and restarts from zero. This prevents a loud click in the sub-bass and also achieves the enhancement of the subs that fulfils what we describe in the blog post here:
There are two things at play here:
- We always want x-sub to not cause a click by resetting its phase immediately, as this is something that people requested we do. We therefore cross fade out x-Sub when a new note is played. We then reset the phase to zero, but we don’t output any sound until the x-sub crosses zero again and then we start output audio from x-Sub. The wait is related to how much out of phase we want to be in relation to the main synth oscillator.
new note → fade out x-sub → reset its phase → wait until we are out of phase by a per-determined amount with the main synth oscillator and then start from 0 phase again. We then have no clicks and also an optimal phase between xSub and the main oscillator as described in the blog post.
- For the phase, we have optimised it so that it doesn’t eat all the headroom. If you were to reset both x-Sub and synth waveforms to zero at the same time, you would have both waveforms in near perfect phase creating a peak and audio overload. Instead we delay x-sub so that it enhances the synth waveform. We get the same perceived loudness, but preserve headroom as per the technique in the blog post.
AFAIK no other synth on the market does this type of phase enhancement and click reduction for simple sine wave sub-bass.