Thanks for the reply Nicolas. I guess equipment like the Tact RCS will always be due to discussion because it alters the music no matter how advanced it is done.
That's not really the best way of looking at it. If you want to phrase it in those terms, it is the
listening room that "alters the music". Applying acoustic treatments will help reduce the extent to which the room "alters the music". A system like TacT tries to
compensate for the way that the listening room "alters the music" by introducing modifications of its own such that when you add the alterations of the room and the alterations of correction system together, they cancel each other out: the music is restored back to what it would have been
without the alterations caused by the room.
Basic parametric EQ systems don't always do a very good job of this, because all they do is apply corrections to volume based on sound frequency. For example, if there's a standing wave at 40Hz, then a 40Hz sound played at 60dB from the speakers might be heard as 75dB because the room amplifies it. The parametric EQ system thus scales a 60dB signal down to 45dB, so that the room amplification scales it back up to the correct value.
But there are a lot of problems with this. For starters, the amplification effect of the room varies depending on where you are sitting. If you're sitting at a standing-wave maximum then the sound is louder, but another person sitting at a minimum would hear the sound as being much
quieter so the EQ won't help them - quite the reverse. Second, the standing waves have an effect that varies with time as well as frequency: the length of time it takes for a loud sound to decay away to silence, for example, is much longer if there is a resonant standing wave than it is for sounds of other frequencies.
The TacT system goes way beyond parametric EQ, though - it applies correction that varies with time as well as frequency. It can even (I think) compensate for sound reaching the listening position by bouncing off walls rather than taking a direct path (which messes up the "sound stage", for example because sounds that originate from the left speaker end up reflecting off the right hand wall and approaching the listener from his right, which messes up the directionality).
