AcourateFlow

“Background:
it is known since quite a long time that with stereo playback there is
a weak point. With a given interchannel level difference the phantom
sound moves towards the louder speaker. But playing different
frequencies with the same ILD does not necessarily give the same
phantom position. So low frequencies tend to come more from the center
between the speakers, whereas high frequencies are located closer to
the louder speaker.
Now with real music we have a mixture of frequencies. Thus a stereo
image is not really focused but is more diffuse in comparison to a
real sound source between the speakers. This keeps our brain busy.

A solution for this weakness is to change the ILD depending on
frequency. The target is to get a better focus.
Changing the ILD dependent on frequency is basically the introduction
of a frequency dependent crosstalk. This is technically possible. Of
course the result will also require some skills on the applied amount
of 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. We
install dual mono amplifiers to reduce crosstalk. We expect to have
systems 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 know
that the pickup system do have a lousy crosstalk behaviour. A
crosstalk attenuation of about -30 dB, also with even a higher
crosstal at high frequencies.
We just have to bring the ends together: the analog vinyl playback
sounds more pleasing because of the crosstalk ! By random the pickup
crosstalk is compensating the first described weakness of stereo
playback.

In the meantime I’m convinced that the digital playback sounds digital
because of the good crosstalk reduction in digital systems. The analog
playback does not sound good because there is no frequency limitation
by sampling or resolution limitation by bitdepth. It simply sounds
better because the inherent crosstalk causes a better focusing of
phantom sources.

Indeed with the added crosstalk the playback requires less effort to
listen, it is more smooth, the music is more flowing.

Based on this idea I have implemented a function AcourateFLOW in my
program AcourateNAS. AcourateNAS is a program to batch process music
tracks offline with room correction filters. Furthermore it allows a
normalisation to avoid clipping and intersample clipping. Tracks can
be stored as 24 bit flacs.
AcourateFLOW contains a test procedure. You can play three chirp
signals and adjust the phantom location. The simple target is to
locate the frequencies at the same position. With the found parameters
you can then treat the music tracks with crosstalk according to your
own playback situation (the test tracks have got an assumed average
crosstalk). AcourateNAS can treat your music tracks just with
AcourateFLOW, the room correction filters are not required.
connect an ASIO soundcard to the computer.
Start AcourateNAS and there the test function of AcourateFLOW. Select
the 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 from
center between speakers and the selected speaker. Now set the sliders
to 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 the
position where the tones have about the same position. Don’t take it
too serious, you cannot pinpoint the direction.

Stop the playback if you are happy and close the window. AcourateNAS
will ask to take the parameters. Then activate Flow and calculate some
tracks. Compare to the original ones.

If you do not find a good parameter setting with the test tones simply
try 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 with
registration and you need to register once again. I’ll send you an
email for the activation.