AcourateFlow is a new function developed by Uli. So far, it is still very confusing to me. So I just copy and paste some of my email exchange with Uli here for documentation. As I learn more about it, I will add more info.
“Background:it is known since quite a long time that with stereo playback there isa weak point. With a given interchannel level difference the phantomsound moves towards the louder speaker. But playing differentfrequencies with the same ILD does not necessarily give the samephantom position. So low frequencies tend to come more from the centerbetween the speakers, whereas high frequencies are located closer tothe louder speaker. Now with real music we have a mixture of frequencies. Thus a stereoimage is not really focused but is more diffuse in comparison to areal sound source between the speakers. This keeps our brain busy. A solution for this weakness is to change the ILD depending onfrequency. The target is to get a better focus.Changing the ILD dependent on frequency is basically the introductionof a frequency dependent crosstalk. This is technically possible. Ofcourse the result will also require some skills on the applied amountof correction and the shape of the correction curve. The idea of introducing some crosstalk includes IMHO some dynamite !All the developments have gone toward crosstalk attenuation. Weinstall dual mono amplifiers to reduce crosstalk. We expect to havesystems with crosstalk better than -140 dB to keep the channels clean.Now we do the opposite.And there is another idea: considering a usual vinyl playback we knowthat the pickup system do have a lousy crosstalk behaviour. Acrosstalk attenuation of about -30 dB, also with even a highercrosstal at high frequencies.We just have to bring the ends together: the analog vinyl playbacksounds more pleasing because of the crosstalk ! By random the pickupcrosstalk is compensating the first described weakness of stereoplayback. In the meantime I’m convinced that the digital playback sounds digitalbecause of the good crosstalk reduction in digital systems. The analogplayback does not sound good because there is no frequency limitationby sampling or resolution limitation by bitdepth. It simply soundsbetter because the inherent crosstalk causes a better focusing ofphantom sources. Indeed with the added crosstalk the playback requires less effort tolisten, it is more smooth, the music is more flowing. Based on this idea I have implemented a function AcourateFLOW in myprogram AcourateNAS. AcourateNAS is a program to batch process musictracks offline with room correction filters. Furthermore it allows anormalisation to avoid clipping and intersample clipping. Tracks canbe stored as 24 bit flacs.AcourateFLOW contains a test procedure. You can play three chirpsignals and adjust the phantom location. The simple target is tolocate the frequencies at the same position. With the found parametersyou can then treat the music tracks with crosstalk according to yourown playback situation (the test tracks have got an assumed averagecrosstalk). AcourateNAS can treat your music tracks just withAcourateFLOW, the room correction filters are not required.connect an ASIO soundcard to the computer.Start AcourateNAS and there the test function of AcourateFLOW. Selectthe ASIO driver. Select the connected output channels.The samplerate 44100 is fix. Then you can start the test signal. You can select left or right side.The phantom source position should be about 3/4 of distance fromcenter between speakers and the selected speaker. Now set the slidersto 0. Listen and check if all three signals (low, mid=refernce, high)have the same position. Usially the lower tone is more to the center,the higher one more to the speaker. Move the silders. Find theposition where the tones have about the same position. Don’t take ittoo serious, you cannot pinpoint the direction. Stop the playback if you are happy and close the window. AcourateNASwill ask to take the parameters. Then activate Flow and calculate sometracks. Compare to the original ones. If you do not find a good parameter setting with the test tones simplytry e.g. +2/-4 as a starting point. If you do not run V1.3.6 then please download and install again.Because of some hacker trouble I have changed something withregistration and you need to register once again. I’ll send you anemail for the activation.