I have done some more extenisve testing with the latest 17.0.67 build (Convolution obviously hasn't changed since 17.0.65). I am aware that the following will probably cost me all credibility - especially after Uli's confirmation that since build .65 the convolution engine is working "mathematically correct".
As mentioned before Matt did a great job in supporting standard Convolver config files (especially relevant with multichannel/-way setups). I also do my channel delays there (Audiolense filter are channel delayed automatically - but I would still optimize subwoofer delay manually as this always was a little but relevant optimization in the XO band).
First of all lets stay objectively. I showed a measured frequency response using my calibrated mic with REW RTA. It shows a perfect match BUT the XO band is not the same. Therefor time alignment with ConvolerVST and JRiver Convolution is not the same. This should/must be the same as the same filters and config files are used, and during live measurement only the Convolution is switched. I optimized the subwoofer delay settings based on JRiver Convolution running so this shows a better result in this case (look at screenshots before - open in new browser tab and switch between tabs to easily see the difference). My first idea was that either ConvolverVST or JRiver Convolution doesn't support decimal numbers with delays (it is not specified on the Convolver homepage) and therefor they are internally calculating with different delays although the same config file is used.
BUT I have done pretty extensive listening tests over the last 3 days (so it is not a bad day syndrome). I also asked my wife to provide another - unaffected - point of view. PLACEBO is a very hard call in this case as the difference between those two convolutions is a) rather obvious in switching directly between them and b) I want my brains to like JRiver Convolution better (see the reason I started this thread ;-). What is the difference I believe to be hearing? Well - in typical audiophile terms - ConvolverVST sounds rhythmically "right", full bodied, smooth. The most immediate difference I hear is in the soundstage - ConvolverVST has more depth and more width, more spaciousness in general, the soundfield opens up. JRiver convolution sounds more analytical, "thinner", probably a little more focused but resulting in a "very" flat soundstage. Listening to it for a few moments after using ConvolverVST always gives me the impression that "something isn't right, about the rhythm, it doesn't sound "natural" to me. And yes, this is also based to double blind tests where the difference of the two options were identified in all case but one. Well, how many times have we heard words like that with snake oil, sponsored audio reviews. Well, I get no money for saying it and I know my credibility will be lost - so a lose lose situation for me. Although I decided to not withdraw from this because of the hope that Matt doesn't accept the verdict "mathematically correct and bit-perfect output" and actually LISTENS to the output. My big hope is that Uli "AudioVero" takes his time and makes a listening test against his reference system using the same filters. There is probably nobody that knows how (his) FIR-filters should sound better than him.
The difference for me between listening with ConvolverVST and JRiver Convolution is like using a very decent playback software (eg. JRiver ;-) and a rather poor one (eg. WMP) and switching between them. I am very sure you will find that the vast majority of "poor sounding" media players will still provide "bit perfect" output (given WASAPI or Kernel streaming pugins). I really don't want to, but for the time being, I will continue to use ConvolverVST exclusively. Note: this is only the second JRiver Convolution revision (built within a single week) and I will continue to benchmark further developments.
IMHO