I’ve heard the Polk speakers and the Carver Sonic Hologram and while interesting at first listen, there are other things a lot more important in re-producing music realistically and enjoyably. Still very cool.
It’s amazing that stereo speakers work at all. Two different sound sources spaced apart by a few feet attempting to maintain separation. One has left channel-only information while the other produces right channel-only info. Problem is, as soon as they make sound in the room the channels are no longer separated. Your left ear hears a slightly delayed version of what’s on the right speaker and vice versa.
When you wear headphones this problem does not exist, which is one of the reasons headphone listening is so different than that of speakers.
The issue has a name: Interaural Crosstalk. If you’re an Audio Engineering Society member, or willing to shell out a few bucks, you can read all about it here. The paper will explain all the issues, like massive comb filtering along with frequency and amplitude issues that are anything but trivial.
Mathew Polk tried to fix some of the problems of interaural crosstalk with the introduction of the Polk SRS speakers. In this clever design, an extra set of drivers on each channel were used to deliver an out of phase signal from the opposite channel. That out of phase signal canceled some of the effects of the problem and the result was a much more realistic soundstage. In later years, Bob Carver did the same thing electronically with his Sonic Hologram generator.
And here’s the thing. Despite the problems of interaural crosstalk, our stereo speaker systems still image. Set up properly, they image great!
Just another example of how far we have to go in perfecting the art of home music reproduction.