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In Reply to: Why not go for a truly omnidirectionnal loudspeaker system ? posted by Lambda on November 14, 2006 at 10:27:32:
The problem at least at high frequencies is that the room boundaries absorb sound selectively as a function of frequency. In general, the higher the frequency, the greater the absorption. While an omnidirectional loudspeaker array would be a definite improvement over the conventional single tweeter box speaker or even a speaker wtih just one rear firing tweeter, it won't provide the ideal result of both flat FR from direct radiation and from indirect reflections meaning flat total power response. To achieve that, the sound directed at the room boundaries must be independently adjustable so that they generate more energy at frequencies where sound is absorbed most. That means that the indirect tweeters would likely have a rising output as frequency increases. A simple way to achieve this is to place a capacitor across the front firing tweeter which will roll its HF off and then boost the treble of the entire array with an equalizer. The front tweeter will flatten out and the indirect tweeters get the boost. Aiming the indirect tweeters at the ceiling should also be tried. This is the arrangement I have for my main system, three 3/8 poly's crossed over at 6khz in parallel (91 db sensitivity) and a single 3/4" front firing tweeter set to -6db relative to 89 db sensitivity. This achieves around the 12:1 ratio I found worked best in my somewhat on the live side rooms.Most woofers are nealy omnidirectional. It's very difficult to restrict the dispersion of the bass because the wavelength is very large compared to the diameter of the woofer cone. My AR9s have a dipole arrangement, 2 side firing 12" acoustic suspension woofers. As for the midrange, the dispersion at those frequencies will substantially also affect the perceived sound. Bose 901 is an extreme case. The sound is interesting, different, but living with a modified version now, I can't say which is actually better. I'm considering designing a speaker system where all of these parameters are adjustable.
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- Re: Why not go for a truly omnidirectionnal loudspeaker system ? - Soundmind 15:54:24 11/14/06 (0)
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