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Posts: 4429
Location: Princeton, Texas
Joined: March 31, 2000
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I routinely use aggressive toe-in, ballpark 45 degrees, such that the speaker axes criss-cross a couple of feet in front of the listening area. The speakers I do this with are woofer/horn hybrids, with a constant-directivity horn having a 90 degree wide pattern (-6 dB limits) in the horizontal plane, crossed over to the woofer in the frequency region where their patterns match up in the horizontal plane. These are gentle waveguide-style horns, which do not use diffraction for pattern control, as diffraction horns can sound harsh. This extreme toe-in configuration combined with this type of speaker offers at least two advantages: 1. Very wide sweet spot. The ear localizes sound by two mechanisms: Arrival time and intensity. For an off-centerline listener, the near speaker of course "wins" arrival time, but with our strong toe-en, the far speaker "wins" intensity, at least in the frequency range of greatest interest for imaging. The off-centerline listener is well off-axis of the near speaker, but is on-axis, or nearly so, of the far speaker. The secret to this working well is the pattern control of that near speaker: Its response must fall off smoothly and fairly rapidly as we move off-axis, and this is accomplished by the 90-degree constant-directivity characteristic from the crossover region on up. Listeners will still get a reasonably good soundstage from well off-centerline, and the spectral balance will hold up well across a relatively large area. Of course imaging will still be best up and down the centerline. 2. Reduced near-side-wall interaction. Because of the pattern width and approximately 45 degree toe-in angle, there is very little sidewall reflection off the near side wall. In fact, the first significant sidewall reflection of the left speaker is the long bounce off the right side wall, and vice-versa. Because of the way the ear processes reflections, this contributes to low coloration and improves sense of immersion in the acoustic space on the recording: Early-arrival same-side reflections tend to be interpreted as coloration, but later-arriving opposite-side reflections tend to be interpreted as spaciousness and ambience. Accomplishing this is often a goal of room acoustic treatment, but we can pretty much get there just with the right kind of speakers and the right kind of setup. If you are getting a "ping-pong" effect, that is an indication the speakers are too far apart. You might try them closer together, keeping the axes criss-crossing a little bit in front of the central sweet spot. Duke
Me being a dealer makes you leery?? It gets worse... I'm a manufacturer too.
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