FabFilter User Forum
Pro-MB being not linear phase in Linear Phase Mode?
Hey guys, I love Pro-MB. But recently I ran into a problem with a parallel compression bus resulting in a phasey sound when Pro-MB being put onto it. The linear phase mode was activated and toggling the oversampling settings or lookahead didn't change anything.
So I loaded it into PluginDoctor, set up a pure band splitting and looked at the phase response: imgur.com/a/LxcBCAB
Changing the slope (the softer the later it begins) or the frequency (up to around 1kHz) pushes this phase mess up or down in the frequency range.
A similar highpass band creates a "ditch" in phase for the lower frequency settings.
This was kind of unexpected. And yes, I know I could setup parallel compression in Pro-MB itself but there's some more stuff going on on the bus.
Don't know if I missed something or if this is just a latency compromise.
All the best,
Danny
Oh, just to clarify: the picture shows a band being solo'ed to demonstrate the phase response of the band. When not being soloed the phase response of the plugin is indeed linear.
Used on the parallel compression bus with only 2 bands and the lower one doing some compression, I can hear phasing in the highs which corresponds to the frequency range seen in the picture. This is the actual issue.
Hi Danny,
The image from PluginDoctor shows the "phase mess" in the region where Pro-MB is not letting any audio through, so the audio levels here will be very low. With very low levels, the phase can't be calculated reliably so that's why you're seeing this. It doesn't say anything about a linear or non-linear phase response.
I'm not sure why you are hearing phasing. Is it possible your host is not properly compensating for Pro-MB's latency? Or do you have any other plug-ins on the parallel bus that could change the phase? For example, an EQ will almost always do this.
Cheers,