- Aug 18, 2017
I mean, the same result happens no matter whether it's loopback or even just applying Pro-Q3 filter or anything else useful.
So for example, take the GS original WAV, apply a single Pro-Q3 instance (probably the single most used/respected EQ plugin in the Music production world right now) with a 5dB (24dB/octave) cut at 15khz and compare:
L - diff -59.02dB [-63.42dBA], PKMetric RMS=-56.8dBr
Stereo - diff -34.24dB [-34.19dBA], PKMetric RMS=-43.3dBr
OK, 15kHz is still within audible range, so it will have some effect on audibility (PKMetric) and certainly on the RMS null metric since that includes the full bandwidth.
You can specify a Low-pass filter in DeltaWave set to 15kHz to see how similar/different the two are below that frequency, but I also suspect that the filters in Pro-Q3 are IIR and not particularly precise, so might affect lower frequencies, below 15kHz, as well as, phase. Post a spectra delta and phase delta plots to see what effect these filters have on the waveform. I wouldn't be surprised if the Pro-Q3 also resamples the audio as part of the internal processing, a lot of "pro" filters do this automatically.