Dave, why would a CD player need impact res r oration? I wasn't aware that CD recordings were compressed.
Most people aren't aware of it. With recent recordings in particular, engineers have sacrificed dynamic range for 'loudness' in their final mix. The so-called "Loudness Wars" appear to be a result of a couple of things, FM broadcasts for one. A highly modulated FM signal reaches a wider audience in terms of transmitter range, so the bean counters have gotten engineers to sacrifice dynamics for loudness in their mix. Another audience is the rap scene, where the bigger the boom the better.
Whether those are the prime reasons or not, I am not sure. I am just repeating some information that I read about recently...some CDs are just lacking in dynamic range because the producers didn't do their job right...
At any rate, I have found my dbx gear way more useful than I imagined it would be for CD playback. I use it all the time (with considerable restraint) and it makes everything sound better. Even really good SACD recordings, like Steely Dan's "Gaucho" benefit from a tiny bit of expansion, but each case is different.
The other thing is that the old recordings that were done before CD was created were made to consider the limitations of the analog playback equipment of the day. It was simply physically very difficult to get a stylus to accelerate fast enough to capture the dynamic punch of a snare drum rim-shot or a very loud kick drum. So the dbx guys made a way around it that they call "Impact Restoration". It is said to work well, and I'm eager to get my new 3bx and the new dbx cd player next week. Both of them have this feature. Stay tuned, more info to follow...