My bandmates often tell me that they can perceive a sizeble latency when they try out my rig, expecially when it comes to the guitar. I use (used?) VoiceMeeter to combine Window’s audio with Cantabile and to share the same interface (Steinberg UR22mkII) between Cantabile and Reaper.
So I did a real-life test, just using my mobile phone mic. I placed the phone close to the guitar, near the point where I am picking the string. The (electric) guitar goes into a DI-box and then into the UR22. The signal enters Cantabile, where it is processed through Nembrini Nexus. Inside Nexus I have just an amp sim. By playing short muted sounds, the phone records both the sound of the pick on the string and (after some latency) the sound of the guitar coming out of the speakers.
The speakers are about 80 cm far from the phone, so sound needs about 2.4 ms to go from the speaker to the phone. I then load the audio file (as recorded by the phone) into audacity, so that I can measure the latency between the pick sound and the guitar sound.
That’s what I found (it is not an extensive experiment, I tried just a few combinations):
Samplng Rate: 44100 Hz for all tests.
Buffer Size =128 VoiceMeeter=yes Latency=21ms
Buffer Size =256 VoiceMeeter=yes Latency=33ms
Buffer Size =128 VoiceMeeter=no Latency=7ms
Buffer Size =256 VoiceMeeter=no Latency=16ms
Latency value includes the 2.4 ms mentioned above. The uncertainty on the quoted value could very well be one (even two) ms, given the way it is determined.
When using VoiceMeeter, Cantabile uses VM Virtual ASIO and VM uses Yahama Steinberg ASIO Driver.
When VM is not used, Cantabile uses the Yahama Steinberg driver directly.
I did a similar test with my keyboard and a piano sound, playing the highest octave. The results are more uncertain in this case (it is not so obvious when the piano sound starts with respect to the sound of the key being pressed). At 128 samples, no VM, I get about 25 ms, which is more than what I get with the guitar (the piano plugin is Pianoteq8), maybe due to the time needed by the plugin to calculate the waveform.
Finally, I guess my bandmates were right and I was just used to the latency. I will probably avoid using VM live from now on, expecially when playing guitar.
Gabriel
Edit: the test was done on my desktop system, I have still to try it on my laptop, which is the actual PC I use live.