Dispersion -
This measures how wide or how tall a driver’s output is vs. frequency response. Like many other factors, there is no 1 best type of dispersion.
The wider a driver’s output, the wider the "sweet spot" or where a listener may be and still hear a credible stereo image. However!
First, for any given type of dispersion, speakers need to roll off more or less evenly. You don’t want to be 15 degrees off axis and only hear the mid-range. Ideally the speaker’s dispersion is even across as much of the response as possible, but usually this can only be done starting in the upper bass.
Next, the wider the dispersion, the more early reflections you may encounter, which can severely affect the frequency response and imaging. Acousticians designing a theater or monitoring room trade off dispersion vs. room treatment. A very tightly controlled speaker needs less room treatment and care.
A number of things affect dispersion, including the obvious things like wave guides (YG Acoustics, Revel’s F series, Krell, first gen. Magico) or horns, diaphragm size (larger = narrow) and crossover points.
The very large diaphragms of ESL speakers (Martin Logan/InnerSound, etc.) have fabulous clarity thanks to this effect. They can sound like you have headphones on even with very little room treatment.
Drivers with different dispersion patterns _may_ also have different rate of decay. Consider a hybrid ESL + cone woofer. The woofer radiates omni-directionally and the wavefront looses energy the fastest, while the ESL panel is a plane wave, with narrow dispersion and looses energy more slowly.
This means that changes in distance from the speaker causes the woofer to loose dB faster than the ESL panel. This has a very simple solution however: Put a volume control on the woofer.
With smaller drivers, like say 5" tall ribbons or AMT’s this difference may be too small to worry about and can be handled strictly in the crossover, though a volume control switch may also be used if absolutely required.
This measures how wide or how tall a driver’s output is vs. frequency response. Like many other factors, there is no 1 best type of dispersion.
The wider a driver’s output, the wider the "sweet spot" or where a listener may be and still hear a credible stereo image. However!
First, for any given type of dispersion, speakers need to roll off more or less evenly. You don’t want to be 15 degrees off axis and only hear the mid-range. Ideally the speaker’s dispersion is even across as much of the response as possible, but usually this can only be done starting in the upper bass.
Next, the wider the dispersion, the more early reflections you may encounter, which can severely affect the frequency response and imaging. Acousticians designing a theater or monitoring room trade off dispersion vs. room treatment. A very tightly controlled speaker needs less room treatment and care.
A number of things affect dispersion, including the obvious things like wave guides (YG Acoustics, Revel’s F series, Krell, first gen. Magico) or horns, diaphragm size (larger = narrow) and crossover points.
The very large diaphragms of ESL speakers (Martin Logan/InnerSound, etc.) have fabulous clarity thanks to this effect. They can sound like you have headphones on even with very little room treatment.
Drivers with different dispersion patterns _may_ also have different rate of decay. Consider a hybrid ESL + cone woofer. The woofer radiates omni-directionally and the wavefront looses energy the fastest, while the ESL panel is a plane wave, with narrow dispersion and looses energy more slowly.
This means that changes in distance from the speaker causes the woofer to loose dB faster than the ESL panel. This has a very simple solution however: Put a volume control on the woofer.
With smaller drivers, like say 5" tall ribbons or AMT’s this difference may be too small to worry about and can be handled strictly in the crossover, though a volume control switch may also be used if absolutely required.