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Propeller Head Plaza Technical and scientific discussion of amps, cables and other topics. |
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Propeller Head Plaza Technical and scientific discussion of amps, cables and other topics. |
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In Reply to: RE: Early reflections: 5 ms time window for sound source localisation? posted by Tony Lauck on July 8, 2010 at 09:11:19:
“The room is the most important component in an audio playback system. One can not have a high end system without a suitable room, which means either: (1) a dedicated room that is optimized for sound reproduction, (2) a shared room that is optimized for sound reproduction and the corresponding absence of a "partner" who prevents this optimization. Looking at the associated economics, one sees that the room is likely to be the most costly component, unless one happens to be single.”
This is all true with a hidden assumption.
Obviously, one can listen outside where there are no walls and no ceiling, no room gain and no reverberant field.
A suggestion I made is to actually try that to see what difference the room makes with a given set of speakers. Normally with hifi speakers it makes a big difference.
Your assumption is on the speaker’s directivity or lack of.
To the degree the sound radiation could be confined to avoid any close reflections, then one is approaching the condition one hears outdoors where the direct sound is much louder than the first or following reflection sound. This is the proverbial “nearfield” condition.
If one measured two speaker systems that had an identical amplitude response (and all other things equal) BUT one was a wide dispersion speaker and the other narrow, they would measure identically outdoors. Once in the room however, the response curve taken at the listening position (a place that actually matters more than at one meter) will be much worse for the wide dispersion speaker as it contains much more room sound. With a narrow speaker, in a living room, one can measure a variance of say + -3dB greater than the one meter curve while a dome /cone system in the same location is more like + - 10-20dB.
Directivity at the source is doing what massive room absorption does for a non-directive system.
Unfortunately for home audio, for the most part the importance of directivity is not widely recognized and more importantly, directivity is only achieved with physical size commensurate to the wavelength being controlled and that does not lead to pretty shoe boxes, making constant directivity more difficult yet.
The larger the acoustic space, the more important all of this consideration of where the sound goes becomes.
To properly measure ‘where the sound goes” takes hundreds of measurements taken over the surface of a sphere surrounding the speaker.
This is normal practice in the technical end of commercial sound as some people design sound installations based on what the speakers actually do.
For the speaker I design at work, we use the CLF data format with the measurements taken by an independent lab (the spherical measurements are too much work).
http://www.clfgroup.org/index.htm
So your room could do anything from destroy any imaging in the recording to being slightly worse than outdoors depending on the directivity and the consistency of it.
Best,
Tom
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Follow Ups
- RE: Early reflections: 5 ms time window for sound source localisation? - tomservo 15:17:29 07/09/10 (0)
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