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In Reply to: RE: Early reflections: 5 ms time window for sound source localisation? posted by KlausR. on July 08, 2010 at 01:30:12
"I consider the message that there is no principle need for reflection treatment as really good news, since such treatment in domestic living rooms have extremely low WAF and will therefore in most cases inevitably lead to problems."
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.
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
Follow Ups:
“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
This is, of course, what high-end aficionados think. Having read the relevant scientific/technical literature, I think that there are many, too many, myths around room acoustics, myths because there's no supporting evidence, the myth of principally bad early reflections being just one of them. Read Floyd Toole's paper "Loudspeakers and Rooms for Sound Reproduction--A Scientific Review", read the literature quoted therein, read the literature listed here , then conclude.
Klaus
Are you disagreeing with my statement that the room is the most important component or are you just commenting on details?
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
> Are you disagreeing with my statement that the room is the most important component? <
Yes, I do!
You will obtain very different results in different locations of the speakers within the same room:
Olive et al. (1994), “The effects of loudspeaker placement on listener preference ratings”, J. of Audio Eng. Soc., p.651
Bech (1994), “Perception of timbre of reproduced sound in small rooms: influence of room and loudspeaker position”, J. of Audio Eng. Soc., p.999
You will obtain very different results in different locations of the listening chair within the same room:
Salava (2004), “Imperfections at low frequencies – how much are they audible or annoying?”, Audio Eng. Soc. Preprint 6144
The room doesn’t change, but the result does. Behaviour and perception of bass depend on placement of speakers and listening chair. Effects of early reflections depend on placement of speakers and listening chair and on the speakers’ off-axis behaviour. Since there is interaction of room and speakers you cannot separate the two and say the room is most important, placement is most important, the speakers are most important. You can put the best speakers in the world in a room built to all the audiophile standards you know, if you put speakers and yourself in the wrong place, the result may be disappointing.
In the same room, badly designed speakers will cause more problems than well designed speakers. Most people don’t know or don’t care, yet think that high-end is a label for quality.
Klaus
I don't believe that we are really disagreeing. There is no doubt that speakers interact with rooms and that location is very important. As you say, the bass varies according to location, as does early reflections. In addition, even if the room does not need treatment the WAF still affects the location of speakers and listening position, since the layout of all furniture in a room is likely to be affected by the location of speakers and listening chair/couch.
While we are at it, I would expand the list of interacting components to include the power amplifier(s) as well as the speakers and room.
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
> I don't believe that we are really disagreeing. <
If “room” includes the interaction between room and speakers, hence placement and the speakers’ off-axis behaviour, then we indeed agree.
> In addition, even if the room does not need treatment the WAF still affects the location of speakers and listening position, since the layout of all furniture in a room is likely to be affected by the location of speakers and listening chair/couch. <
When living rooms are used for music listening, WAF inevitably is a parameter, unless you’re single. That’s why I said that the fact that there is no principle need for reflection treatment is actually good news. No treatment always has the highest possible WAF. You have to select the loudspeakers accordingly though. In this respect the discussion on whatsbest is interesting. Bass boom and room mode issues can be addressed electronically, again with highest possible WAF.
> While we are at it, I would expand the list of interacting components to include the power amplifier(s) as well as the speakers and room. <
In particular cases certain amps may intact audibly differently with certain speakers
E. Brad Meyer, “The amp/speaker interface”, Stereo Review June 1991, p.53
In such cases it may be worth paying attention. This problem, however, is elegantly solved in active speakers . No more complex loads for the amps, each amp is optimized for the driver he is powering.
Klaus
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