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Junior Varsity
Low ceiling, long room - delays or louder PA?
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<blockquote data-quote="Art Welter" data-source="post: 100912" data-attributes="member: 52"><p>Re: Low ceiling, long room - delays or louder PA?</p><p></p><p></p><p>A horn may not have vertical pattern control matching it's nominal pattern even to the crossover frequency.</p><p>Horns loose pattern control when the wavelength of the frequency reproduced is longer than the mouth height (or width), for instance a 6" (16 centimeter) high horn would start to widen below 2260 Hz, while a big horn like the SH-25 would not start to open up (loose pattern control, AKA "pattern flip") till below around 450 Hz.</p><p></p><p>In a front loaded cone speaker, dispersion is determined by piston diameter, the smaller the diameter, the wider the dispersion.</p><p></p><p>Dispersion varies with frequency, a 15” speaker is about -6 dB at 60 degree at about 1.8K, a 12” at 2.2K, a 10” at 2.8K.</p><p>A 15” has a -6 dB 90 degree dispersion at about 1200 Hz. </p><p>A 12” speaker is around 180 degree at 900 Hz, 90 degree at 1200 Hz, 50 at 2400 Hz, and 30 degrees at 4000 Hz.</p><p>A 15” has a 180 degree -6 dB beam width at around 600 Hz, a 12” at about 800, and a 10” at about 1200 Hz.</p><p>The above are rough guides for pistonic cone behavior, real world cones don't behave like perfect pistons so the dispersion above the frequencies listed above can vary widely.</p><p></p><p>Dispersion patterns are easier to understand if you think in terms of lighting, given a 100 watt floodlight (90 degrees) or a 100 watt spotlight (30 degrees) the flood will illuminate everything well nearby, but having spent it's energy over a wide area won't be bright at a distance. The spotlight will not illuminate much off to the side, yet will illuminate better at a distance.</p><p></p><p>Given the same HF driver, on axis response for a 60 degree horn will be +3 dB over a 90, and a 30 degree horn +6 dB. </p><p>The 30 degree horn will be another -6 dB (roughly) at 45 degrees off axis compared to the 90 degree horn, so the front to back imbalance (inverse distance loss) can be improved by some 12 dB.</p><p></p><p>Since a 10 dB difference in level (at 1000 Hz) sounds half or twice as loud, a reduction in level difference of 12 dB would be more than "twice as good".</p><p></p><p>Wide dispersion horns can reflect around in an long empty venue and level will sound similar throughout, but when the room fills and much of the direct energy is absorbed, not much is left at the back.</p></blockquote><p></p>
[QUOTE="Art Welter, post: 100912, member: 52"] Re: Low ceiling, long room - delays or louder PA? A horn may not have vertical pattern control matching it's nominal pattern even to the crossover frequency. Horns loose pattern control when the wavelength of the frequency reproduced is longer than the mouth height (or width), for instance a 6" (16 centimeter) high horn would start to widen below 2260 Hz, while a big horn like the SH-25 would not start to open up (loose pattern control, AKA "pattern flip") till below around 450 Hz. In a front loaded cone speaker, dispersion is determined by piston diameter, the smaller the diameter, the wider the dispersion. Dispersion varies with frequency, a 15” speaker is about -6 dB at 60 degree at about 1.8K, a 12” at 2.2K, a 10” at 2.8K. A 15” has a -6 dB 90 degree dispersion at about 1200 Hz. A 12” speaker is around 180 degree at 900 Hz, 90 degree at 1200 Hz, 50 at 2400 Hz, and 30 degrees at 4000 Hz. A 15” has a 180 degree -6 dB beam width at around 600 Hz, a 12” at about 800, and a 10” at about 1200 Hz. The above are rough guides for pistonic cone behavior, real world cones don't behave like perfect pistons so the dispersion above the frequencies listed above can vary widely. Dispersion patterns are easier to understand if you think in terms of lighting, given a 100 watt floodlight (90 degrees) or a 100 watt spotlight (30 degrees) the flood will illuminate everything well nearby, but having spent it's energy over a wide area won't be bright at a distance. The spotlight will not illuminate much off to the side, yet will illuminate better at a distance. Given the same HF driver, on axis response for a 60 degree horn will be +3 dB over a 90, and a 30 degree horn +6 dB. The 30 degree horn will be another -6 dB (roughly) at 45 degrees off axis compared to the 90 degree horn, so the front to back imbalance (inverse distance loss) can be improved by some 12 dB. Since a 10 dB difference in level (at 1000 Hz) sounds half or twice as loud, a reduction in level difference of 12 dB would be more than "twice as good". Wide dispersion horns can reflect around in an long empty venue and level will sound similar throughout, but when the room fills and much of the direct energy is absorbed, not much is left at the back. [/QUOTE]
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Low ceiling, long room - delays or louder PA?
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