Hi Earl,
If room induced ASW is the goal then strong reflections can do it. The more omni the design the better. Any deviation from constant directivity is probably detrimental. The question is if this is a relaxing situation for our brain when its "precedence processor" has to work the hardest.
Reports from LEDE rooms show that ASW is also achieveable with a terminator (a single delayed lateral reflection from the back or the front). The lack of strong early reflections in such a design is probably more desirable than flooding the room with energy that masks low level details.
Increasing ASW is clearly in contrast to improved "imaging". One seeks to create a precise image and the other no image at all. Yes, you have to decide what it is you want.
ASW is an admirable attribute for auditoriums - which it was developed for - but if the recording is not intended to create an "auditorium experience" then an increased ASW is not a positive attribute.
This all comes down to what I call the "Classical Audiophile Syndrome (CAS)" - that only classical music perform in a large auditorium is worthy of consideration as a musical source for reproduction. CAS completely distorts the objective of "accuracy", replacing instead an objective of "the creation of a false impression of spaciousness" whether or not one is intended or desired in the source material.
ASW is an admirable attribute for auditoriums - which it was developed for - but if the recording is not intended to create an "auditorium experience" then an increased ASW is not a positive attribute.
This all comes down to what I call the "Classical Audiophile Syndrome (CAS)" - that only classical music perform in a large auditorium is worthy of consideration as a musical source for reproduction. CAS completely distorts the objective of "accuracy", replacing instead an objective of "the creation of a false impression of spaciousness" whether or not one is intended or desired in the source material.
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Earl,
Yes, reverberant field is much more up to date.
Toole's Loudspeakers and Rooms for Sound Reproduction—A Scientific Review
As published in J. Audio Eng. Soc., Vol. 54, No. 6, 2006 June, Toole makes no mention of front wall reflections as negative attribute. Sec. 3.4 describes all reflections in small room are preferred, with front wall reflections showing least preference. This is far different from front wall reflection as being objectionable.
Sure, least preference can be used by speaker designer as grounds not to pursue enhancing front wall reflections, and in light of Toole's summary about maintaining spectral balance in reflections, a key point in loudspeaker rankings of preference in his paper, complications in designing for spectral balance of front wall reflections in terms of size, cost, and visual appeal are avoided by most designers.
Linkwitz and the OB dipole crowd embrace reflections with spectral balance. You don't.
You respect Toole's work, as do I, yet you attempt embellishing your designs as superior by putting "No we don't want that." in Toole's mouth.
Yes, reverberant field is much more up to date.
Toole's Loudspeakers and Rooms for Sound Reproduction—A Scientific Review
As published in J. Audio Eng. Soc., Vol. 54, No. 6, 2006 June, Toole makes no mention of front wall reflections as negative attribute. Sec. 3.4 describes all reflections in small room are preferred, with front wall reflections showing least preference. This is far different from front wall reflection as being objectionable.
Sure, least preference can be used by speaker designer as grounds not to pursue enhancing front wall reflections, and in light of Toole's summary about maintaining spectral balance in reflections, a key point in loudspeaker rankings of preference in his paper, complications in designing for spectral balance of front wall reflections in terms of size, cost, and visual appeal are avoided by most designers.
Linkwitz and the OB dipole crowd embrace reflections with spectral balance. You don't.
You respect Toole's work, as do I, yet you attempt embellishing your designs as superior by putting "No we don't want that." in Toole's mouth.
I see it that way :
Take as an example my Enviee Cardioid, That is a wideband driver that i put in a frame that has damping material on the back.
It radiates to the front and to the back.
The frontal radiation is EQed flat. I do that by putting a measurement microphone on axis of the driver and make the response as flat as i can. I call that freefield EQ, call it direct radiation if you will.
As far as i understand Zwicker the ear has a different sensitivity for sound that comes from the front and sound that comes from the side.
If we normalize the frontal curve and compare it to the side wise incidence we get Zwickers diffuse field curve. Call it reverberant sound if you will.
So my Cardoid has a back radiation too.
I put a tweeter on the back that i invert in phase and give the back rediation frequency response the shape of the Zwicker curve.
That way i destroy the impulse response to the back and it is likely that the sound that reaches my ear from the back has subjectively the same tonal balance then the sound i hear direct from the front.
When i go to the back of the speakers i can not hear the usual second phantom image that i get with dipoles. Instead the sound from the back is totally diffuse because the impuls response is random so there is no Haas effect.
I tried this over the last two years on various speakers and in various systems, also on bigger gatherings like ETF, Frickelfest. The result was always the same : Better imaging and less critical placement.
There is much more to say about this and please go ahed and take my experience apart.
I do not care. For we it was enlightening and rewarding.
Take as an example my Enviee Cardioid, That is a wideband driver that i put in a frame that has damping material on the back.
It radiates to the front and to the back.
The frontal radiation is EQed flat. I do that by putting a measurement microphone on axis of the driver and make the response as flat as i can. I call that freefield EQ, call it direct radiation if you will.
As far as i understand Zwicker the ear has a different sensitivity for sound that comes from the front and sound that comes from the side.
If we normalize the frontal curve and compare it to the side wise incidence we get Zwickers diffuse field curve. Call it reverberant sound if you will.
So my Cardoid has a back radiation too.
I put a tweeter on the back that i invert in phase and give the back rediation frequency response the shape of the Zwicker curve.
That way i destroy the impulse response to the back and it is likely that the sound that reaches my ear from the back has subjectively the same tonal balance then the sound i hear direct from the front.
When i go to the back of the speakers i can not hear the usual second phantom image that i get with dipoles. Instead the sound from the back is totally diffuse because the impuls response is random so there is no Haas effect.
I tried this over the last two years on various speakers and in various systems, also on bigger gatherings like ETF, Frickelfest. The result was always the same : Better imaging and less critical placement.
There is much more to say about this and please go ahed and take my experience apart.
I do not care. For we it was enlightening and rewarding.
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Thanks Markus. I tried to find that statement because my recollection was that he was not a fan of front wall reflections. Side walls yes, but not front wall. We all agree with side wall reflections, albeit in what time frame is issue.
The whole paragraph before that statement is exactly the point that I was making.
Joachim - I think that you are overly simplifying Zwicker, but at any rate things are only "truths" to me when the subjective is supported by the objective, and the two are connected by psychoacoustics. What you have said thus far is not supported with any objective measurements (such as polar response, etc.) but seems entirely based on your personal subjective evaluations. I have found this approach can often lead to faulty ideas. Maybe its right, but initially it seems contrary to a lot of existing data and my experience.
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Nevertheless Toole doesn't give much explanation as to why front wall absorption is a good thing. Kishinaga et al. even states "To enjoy the music, however, reflective walls yield better effect" (AES Conv. Paper #1524)
Don Davis of Synergetic Audio Concepts (SYN-AUD-CON) trademarked LEDE back in 1984, the live end dead end approach to studio control room acoustical treatment .
In an LEDE studio control room the area around the monitors is deadened, or made absorbent acoustically. The remainder of the room remains reflective.
The arrival of reflections at the mixing console then arrives in a specific (desirable) order:
1.The direct sound from the reference monitors.
2. First studio reflection (from the generally much larger recording room, as heard through the mics and monitors.
3. First control room reflection off the back wall, assuming it is 10 feet or so behind the engineer.
By staggering these arrivals, the control room reflections interfere less with monitoring recorded studio acoustics.
LEDE as applied to a listening room would make playback more similar in sound to what the engineer heard when mixing in a LEDE control room.
That said, LEDE is only one of many approaches that have been used in studio control rooms, and may not be desirable for home use, to quote Floyd Toole from this article:
http://www.wilsonaudio.com/pdf/vol2no3.pdf
“LEDE was, in any case, a design approach conceived with the particular needs of the studio control room in mind, which don’t necessarily carry over to a domestic listening environment… this doesn’t square at all with my thinking on the subject, which is to keep absorbents away from places where they will distort the spectra of early reflections."
Art
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Markus
That's true and I am trying to remember where else I heard him discuss the situation because he gave more concrete explanations.
To me the front wall reflections cannot add anything positive as they do not increase IACC, but do degrade imaging. So unlike early lateral reflections (which tend to degrade image but do enhance spaciousness), there is no trade-off (they degrade image but don't enhance spaciousness.)
Regarding Kishinaga, clearly not all reflections are the same so not all walls can be consider the same either. Ceiling and floor absorptions are a good thing (in the right places), side walls not so.
That's true and I am trying to remember where else I heard him discuss the situation because he gave more concrete explanations.
To me the front wall reflections cannot add anything positive as they do not increase IACC, but do degrade imaging. So unlike early lateral reflections (which tend to degrade image but do enhance spaciousness), there is no trade-off (they degrade image but don't enhance spaciousness.)
Regarding Kishinaga, clearly not all reflections are the same so not all walls can be consider the same either. Ceiling and floor absorptions are a good thing (in the right places), side walls not so.
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I think that we need to consider some characteristics of absorbers. It is not too hard to absorb most of a reflection above a certain frequency. If this frequency is low enough then I do not see Toole's point about "distort(ing) the spectra" because it doesn't matter. I agree if a small thin patch of absorption were used on say a side wall - which is extremely common unfortunately - is not the right thing to do because it does distort the spectra. But a large mass of absorption behind the speakers coupled with a directive set of speakers can completely null any reflections from the front wall above a few hundred hertz. The remaining reflection will not be an issue for imaging or coloration.
Quite off-topic, don't you think? Anyway, you can buy it in any "Baumarkt". Look for "Birkenmultiplex".
...and many more concepts. "Throughout all of this evolution, recorded music has survived... Maybe we are irrelevant and music is what really matters!" http://www.rpginc.com/docs\Technology\Presentations\Studio Design From Mono2Surround.pdf
I believe this is a major issue. All that energy radiated to the sides and the back of the speaker probably can't be suppressed by the precedence effect because it isn't similar enough to the direct signal. This is probably a major source of localization ambiguity. It will also contribute to perceived timbre. Worst case it will be perceived as low frequency noise, (upward) masking higher frequency details.
There is still a wall bounce even if the speakers are mounted "on" the wall. Only if there are flush with the wall does this go away and my walls are concrete, so I can't do that. Corner mounting is a possibility, but that means far too much distance between them. I'm happy with what I have.
Built-in has its issues as well. You certainly can't change them very readily. Not that I have done that in the last five or six years though.
If the enclosure is rather shallow and large there're probably minimal issues.
Would you make the corner baffle as narrow as possible?
