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I know that this is topic about new versions and since in newer version there is matrix mode,
can you give me information how this stereo effect is different than ACR or stereo boost?
Because sometimes I think it's reacting too much in terms of stereo picture.
Thnx!
Long story... Basically it comes down to "I was wrong about how good stereo widening works" - multiple times. Fortunately it's not only me working here anymore, and Mathijs figured out how to do it, which led to the _new_ matrix mode. (There's also an _old_ matrix mode which is less good).
- Stereo Boost is the oldest and simplest stereo widener in Stereo Tool, it's basically just a 7-band multiband compressor on the L-R signal, which doesn't allow the L-R levels to exceed the L+R. It works but it can very easily boost reverb a lot (since reverb typically fades out and Stereo Boost will increase it when that happens).
- ACR is kinda based on older 1980's designs, it adds the L-R signal with a delay to the audio, and mainly adjusts the amount of L-R to add on louder spikes and transients. The goal here was to avoid pulling up reverb too much. Unfortunately, because of the sudden jumps it can cause a bit of a "restless" sound, and we figured out recently that if you turn the delay OFF, it actually sounds much wider. The delay was needed in the past to avoid too strong stereo which interferes with FM reception, but even for FM we can live without it now because of Stokkemask. (You can turn that on to protect against reception issues caused by loud stereo sounds).
What I understood wrong upto this point is that what gives the impression of loud stereo is not so much the constantly present difference in L vs R, but mainly the stereo effect in transients. Both Stereo Boost and ACR were actually boosting the rest of the stereo sound, and the transients least of all.
Enter matrix mode. What it does is very slowly (at the speed of the AGC) adjusting the L-R level relative to the L+R level. Since it responds very slowly it boosts transients and other sounds equally. When you use it you should turn the other two OFF. If it does too much, "L+R to L-R channel mix" controls how much of the L+R signal is measured as part of the L-R channel - setting this higher reduces the effect, especially if there's not much L-R content in which case it would be boosting to insane levels. So, increasing that slider will reduce the effect mainly in cases where it's doing a lot.