You're missing clarifications about Bass Enhance that came from Lexicon after this FAQ (which is not an official Lexicon document) was written. Not your fault, but it is the reason why I specifically suggested reading "the first few pages" of the FAQ. This newer information is also why I stated things that were contradictory to statements made in the last few pages of the FAQ: e.g., subwoofers need not be directly to sides of the listening position in order to take advantage of Bass Enhance. Also, you don't lose the LFE channel; it is simply folded into the derived bass being sent to both subwoofers. In fact, you don't even lose control of the LFE content; even when it's not being sent to its own dedicated subwoofer, Lex processors still allow the user to control the volume of LFE channel (discrete bass) independently of the subwoofer (derived bass) volume. Oh yes it is, and that's all it is.

From a 1998 interview that AIG's Gordon Brockhouse conducted with Mr. Carver himself:

GB: Is sonic holography essentially crosstalk cancellation?

BC: Yes. The crosstalk cancellation has been adjusted to produce a realistic presentation on regular stereo recordings. Years ago, Harry Pearson wrote a wonderful series of articles on generating a soundstage with a stereo system. What you want is a sense of layered depth on a soundstage that extends behind the speakers and is wider than the speakers. I've adjusted Sonic Holography to really give a soundstage in spades using Harry Pearson's treatise as a model. In real life, for every sonic event we have two sound arrivals: one for the each ear. Every time I snap my fingers, you hear two sounds: one in your left ear, one in your right. In three-channel playback, every time I snap my fingers, you might hear six Ä one in each ear for each of the three speakers. Those unwanted sounds need to be cancelled if we're to generate a replica of real life.

You can read the entire interview here:

http://www.audio-ideas.com/interview/carver.html

The Ambiophonics web page also discusses Sonic Holography, and other crosstalk cancellation technologies:

http://www.ambiophonics.org/welltuned.htm

"Polk, Carver and a few other companies took up the challenge of spatial realism in the "80s by, for example, supplying the right speaker with a "shadow" version of the left speaker's sound, timed and tonally shaped so that it cancels it at the right ear. Among the limitations inherent in Polk's early "Stereo Dimensional Array" and Carver's "Sonic Holography" techniques is the fact that the shadow signal not only appears, in this case, at the right ear, where it's needed, but also, at the left ear, where it's decidedly not. Modern digital processing, like that used in the "Panorama" in Lexicon's CP-series surround processors, can cancel this new distortion by supplying the left speaker with a shadow of the right shadow, then the right speaker with a shadow of the left's shadow of the right's shadow. It sounds crazy, but it works rather well, considering it really a new take on the old cat- chasing-its-tail theme, an provided you keep your head in just the right spot."


Also see the description of Sonic Holography here:

http://www.bmwworld.com/audio/carver.htm So what? Dialing in speaker distances, during initial set-up of a pre-pro, uses "time-arrival manipulation" (signal delays) to give the psychoacoustic impression that all your speakers are the same distance away. Does that make time alignment the same thing as Sonic Holography or Bass Enhance?

I don't understand why you continue to insist that Sonic Holography and Bass Enhance are similar. Bass Enhance does not generate ANY crosstalk cancellation signals. Listening space parameters such as room size, bass modes, and surface reverberance all serve as perceptual cues contributing to realistic bass. A room where all these parameters are contributing to terrible bass response could easily swamp the effects of Bass Enhance (just as an overly reflective or oddly shaped room can kill proper soundstaging and imaging). Elsewhere, in rooms where asymmetry and/or other factors contribute to naturally "stereo" sounding bass, the Bass Enhance circuit will do very little to improve the situation. I mean, the stereo effect already exists. It is rooms and set-ups, which conspire to create monophonic sounding bass, where Bass Enhance will really help.

However, room interaction is not the same thing as precise placement of speakers and listener. They may work off each other, but they are separate parameters. To that end, Bass Enhance is less affected by imprecise placement than it is by the contributions of the listening room. Truth be told though, the effects of Bass Enhance are most dependent on the recordings. I've heard well recorded live classical music where Bass Enhance's effect was negligible. I've also heard studio pop recordings where the effect was very pronounced and easily noticeable. Bass Enhance works with more than "a center-placed LF signal". It works with stereo bass too, especially in situations where a bad room is reducing the effect of well recorded stereo bass. Keep in mind that Bass Enhance is simply a tool to correct problems that may occur when playing back audio in less-than-optimal, real-world rooms. Nothing more, nothing less. For what it sets out to do, it is extremely successful. But you would have known that had you ever heard the effect. And with all due respect to your many hours of research, your "position" is of zero significance to me. I simply posted in this thread to correct inaccurate statements you made about Dr.G and Bass Enhance. I'm not (nor do I have any interest in) debating the importance of a discrete LFE system. I'm confused by the second advantage that Lexicon apparently lists in their manual. Follow: take any Lexicon processor, hook it up to only 2 main speakers (no sub) and play any source with a .1 LFE channel. The processor will fold down any number of channels into two, and mix in the LFE. However, the user can adjust the LFE level; there are separate parameters for discrete bass (labeled LFE Mix Level) and derived bass (labeled Subwoofer Level). Agreed, they haven't. But they may not have that sort of clout in the industry.

Best,
Sanjay

[This message has been edited by sdurani (edited April 21, 2003).]