Warp69 wrote:stian wrote:valhallasound wrote:I define "true stereo" as anything that doesn't mix to mono before being processed by a reverb network. By this definition, algorithms that have stereo early reflections, but mono input late reverbs, aren't true stereo
I definitely agree with you there, Sean. While experimenting with different reverb designs for Verberate, I was actually surprised to find out how important true stereo processing is also in the late reverberation in order to achieve a sense of space even if other techniques are used to de-correlate the outputs.
So this very simple setup would not produce "True Stereo"?
The ER engine could have any numbers of taps and/or allpass filters and/or something else. The above would create 4 completely different outputs which equals "True Stereo".
If the ER engine has decorrelated outputs for left and right that are being sent to the late reverb, this isn't really summing to mono. Simply delaying the right input from the left by 11 msec or so will decorrelate things to some extent. However, this will also cause some sort of comb filter coloration when summed to mono, and this coloration will be present in all of the late reverb. More complicated L/R input decorrelation will create a more complicated comb filter, but it will still be a comb filter.
Meanwhile, a late reverb network with separate left and right inputs (or N channels of input) will have a potentially HUGE number of comb filter outputs, to the point where no fixed coloration is heard. The left and right inputs will be combining in some manner, whether it is through parallel output taps, or via residual energy hanging out in an FDN or allpass delays, but this can sound much better than a single mix of left and right...
That is, better for stereo miked signals. For mono signals, or for mono signals that are panned in the stereo image, these sort of cancellations won't happen when summed to mono. So a mono input reverb, or a reverb with stereo early reflections and a mono late reverb, will work fine there. In such a case, having different delayed/allpassed signals for left and right channels, that are summed to mono, could add coloration that wasn't in the original signal.