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Speaker Asylum General speaker questions for audio and home theater. |
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Speaker Asylum General speaker questions for audio and home theater. |
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In Reply to: Frontal Horizontal Directivity Measurements of a speaker ?.. posted by audiophile919 on July 24, 2015 at 15:54:01:
One of the main reasons loudspeaker directivity matters is, unless we listen nearfield or under approximately anechoic conditions, most of the sound that reaches our ears is reverberant energy - that is, energy that has reflected one or more times off of room surfaces. This reverberant energy can do a lot beneficial things if we get it right: It can enhance timbre, clarity (according to Toole), and sense of immersion in the acoustic space of the recording. The speaker's off-axis response is the main source of this reverberant energy, so it matters a lot.
Let me back up and state what I believe to be a reasonable goal, acknowledging that it may not be everyone's goal: I believe that a reasonable goal would be to approximate the perception of hearing a live performance. In order to do that, we need to not only get the first-arrival sound right (from a perceptual standpoint; waveform fidelity would be nice but isn't essential), but also get the reverberant field right. And by getting the reverberant field "right", I mean we want to approximate what we'd find at a decent venue - the spectral balance of the reverberant field shouldn't be skewed; the reverberant field should be highly diffuse; and the onset of significant reverberant energy should occur after a fair amount of time delay relative to the first-arrival sound.
Getting the reverberant field "right" is a cat which can in more ways than one be skinned, and I won't go into them all here, but djk's post is worth repeating:
"Many, many years ago Audio did tests to determine what kind of directivity factor sounded best in a typical room.
"They found that a Q=7 gave the best results (a typical 90°x 40° horn at the time).
"Horns have been improved a lot over the years, but I would wager that the Q=7 still holds true, the modern horns would just be a lot less colored.
"Crossing the woofer over where the directivity matches the HF also helps with realism."
So following this line of thought, a 90°x 40° low-coloration constant-directivity horn, crossed over to a midwoofer array whose radiation pattern is approximately the same as the horn's in the crossover region, would arguably be a strong candidate for getting the directivity right.
In my opinion this, or something conceptually similar, would be an excellent starting point. It arguably has some room for improvement, and a case can be made for different radiation pattern shapes, which I can do into if anyone is interested, but the basic principle is to make sure the off-axis energy is working WITH, rather than AGAINST, the first-arrival sound.
Duke
Me being a dealer makes you leery?? It gets worse... I'm a manufacturer too.
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Follow Ups
- Loudspeaker directivity should be a top priority - Duke 20:23:31 07/26/15 (4)
- John Volkmann RCA - Kloss 04:41:24 07/27/15 (0)
- Another reason - Duke 21:10:12 07/26/15 (0)
- RE: Loudspeaker directivity should be a top priority - genungo 21:03:08 07/26/15 (1)
- RE: Loudspeaker directivity should be a top priority - Duke 21:36:00 07/26/15 (0)
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