What is the ideal directivity pattern for stereo speakers?

[gedlee]

Hello Markus

Isn't it obvious?? Multichannel surround gives you most "natural" sound field from the get go. If anything has a chance at getting it right that seems to be the direction to go if your aim is the recreation of the original space.

Rob

And what if there is no "original space" as almost 95% of all music is done.

 

[Elias]

I agree, I don't think that Moulton's ideas have stood the test of time. They have been pretty much forgotten.

Then of course there is
BeoLab 5 - Bang & Olufsen
which employs Sausalito Audio Works patent (by Moulton et al)

 

[gedlee]

Don't forget the Audi B&O sound system. Another ground breaker.

 

[Elias]

Don't forget the Audi B&O sound system. Another ground breaker.

Does it follow Moulton's ideas ?


.

 

[graaf]

We concluded that people will adapt to any errors in a sound system and come to expect them as "good". To me this means that one should adapt to what is the most objectively accurate.

or rather one should adapt to

to unamplified life sounds.

When you do this, you hear all the flaws in other systems quite clearly, even though others take these same flaws to be "good" things. It is an insidious circle.

or rather

Unbiased listeners have no difficulty recognizing accurate sound reproduction, even with hearing damage or with hearing aids.

quotes from Linkwitz, another wacko?

 

[graaf]

Don't forget the Audi B&O sound system. Another ground breaker.

and don't forget that Moulton is quoted by Toole, another wacko?

 

[Omholt]

I appreciate Linkwitz' contribution in several areas but he's not an acoustician and his ideas about acoustics is basically circled around the idea that no treatment is possible and find something that works ok in those lines.
In other words, far from an optimal approach. And either way, I think a horn is a lot easier to get to play well in a room with no treatment. Plus you get dynamics.

The B&O Beolab 5 by the way doesn't measure flat. I have the polars. The CBT which also disperses wide is far better and avoids the detrimental front wall contribution. Who has ever seen a study that showed frontwall reflections to be beneficial?

What's important is not the name but whether what is said can be backed up by something serious. Moulton ideas are far out.

 

[graaf]

I appreciate Linkwitz' contribution in several areas but he's not an acoustician and his ideas about acoustics is basically circled around the idea that no treatment is possible and find something that works ok in those lines.

"ok"? how so?

isn't it absurd and wacko?

The CBT which also disperses wide is far better and avoids the detrimental front wall contribution.

how so?

What's important is not the name but whether what is said can be backed up by something serious. Moulton ideas are far out.

Who is the certified judge of "serious" or "far out"?

 

[Omholt]

Sorry, but I'm not going to waste more time on you Graaf. I have seen this attitude and way of discussion before from you. Some people are just trying to win a debate which makes it impossible to have meaningful discussion.

 

[ScottG]

Instead we are striving for a better condition for the re-creation of a spacious condition - the condition on the recording.

I'm afraid that's not impossible with just two speakers and no additional processing. While strong listening room reflections can create a sense of spaciousness, this is NOT the spaciousness of the recording space. One would need to extract spatial information from the recording and present it over additional loudspeakers from different direction than ±30°. Not a trivial task because important spatial information is lost in stereo recordings. For example no specific room response for let's say 90° can be extracted. There are processors that try that stunt though, e.g. Dolby PLII or NEO:X.

Of course it's possible to improve upon the condition for re-creating what's on the recording.

It's simply a matter of time and intensity from one ear vs. another. ie. the left channel is "hotter" on the left side of the room, and the right channel is "hotter" on the right side of the room. Of course a large absorber-wall bisecting the room would be far more effective (ie. the classically absurd wall of mattresses between the speakers a'la ambio..)

Note: I'm not AT ALL describing creating a sense of spaciousness. In that sense I agree with you - it requires something different by way of multi-channel manipulation or a very odd stereo setup where direct sound is substantial lower in level at higher freq.s when compared to the ipsilateral reflections.

 

[graaf]

Sorry, but I'm not going to waste more time on you Graaf. I have seen this attitude and way of discussion before from you. Some people are just trying to win a debate which makes it impossible to have meaningful discussion.

"Meaningful discussion"? You mean Your "wacko designer" type of arguments?

Then no need to be sorry really, rather I would like to thank You!

I'm just putting forth balancing counterarguments to the view that seems to be prevailing here.

"Whenever you find yourself on the side of the majority, it is time to pause and reflect", right?

Actually I am neither Moulton's fanboy nor Linkwitz's. Not at all.

I agree mostly with Mr Ohlsson's opinion quoted earlier: "The problem with room tuning and early reflection absorption is that they are oversimplifications that have little to do with how we actually hear."

Actually over the years I came to think that perhaps the guy who has the best approach to the subject could be Michael Green of Michael Green Designs

peace!
graaf

 

[ScottG]

What is that based on? Your personal preference?

How does that relate to "are NOT contrary to the notion of improving sound with side-wall reflections".

Either I misinterpret or it looks like you contradict yourself.

Sounds doubtful. Two absorbents? Two bookshelves would probably be better since they also isolate more from outside noise.

What I can however see as one reason that contribute to why many prefer removing sidewall reflections is that their speakers aren't very constant in their response and sidewalls are close in most rooms.

Personal preference? No. I prefer something more. But generally I've found (both for myself and with others) that 5 feet works reasonably well as long as both speakers are about that distance away from their near wall. Of course the modal region is still a crap-shoot, and that particular location may be horrendous at lower freq.s. for a given listening position.

The point I was trying to make is that room reflections can be both beneficial and also detrimental - the key is lowering the detrimental portion and potentially improving the beneficial portion. Beneficial is generally ipsilateral, detrimental is contralateral.

When describing "room noise" I was referring to noise other than produced by the loudspeakers.. ie. HVAC noise attenuated by room absorption and generally absorption creating a more isolated environment from noise outside the room.


Yes, another is reason as Graaf mentioned by-way-of listener quote is power response (with a potentially "bright" result or a potentially "dull" result as a tonal imbalance).

Additionally expanding on the loudspeaker's directional characteristics, there is a reasonable claim to be made concerning the ability of the listener to better "filter-out" reflections if they are more "uniform". "Uniform" would likely include similar intensity among a greater number of axis vs. a smaller range of more "dominate" axis.

 

[ScottG]

Exactly. The notion that capturing the direct sound AND all room reflections regardless of direction in one or two channels, presenting them through one or two speakers and perceiving the spaciousness of the recorded space is absurd.

In stereo you'll never perceive the spaciousness accurately.

You will however perceive spaciousness on the recording - your statement is over-broad.

I've heard some setups however that have (recording dependent), been astonishingly close (though still having that "mirror" effect). This even includes hearing cues beside and behind the listening position. And yes, that was with 2 speaker stereo.

 

[Omholt]

Yes. A more uniform speaker response will lead to less coloration from the room. The CBT is probably the first speaker I think sounds very well with reflected sidewalls. The image suffers obviously.

Something to also consider is the fact that absorbents never absorps evently 100%. They will always to some degree function as a filter. With splayed walls or proper designed angled panels, one avoids this and get a perfect redirection without this filtering. This is how the best studios are built. Combined with diffusors in the rear, the diffuse energy is increased that way and hence an increase of spaciousness too. I don't think those who have experienced this find stereo to sound unatural or lacking much in a spacious soundfield. This is simply far better IMO then only reflected sidewalls because one completely avoids the negative effects such has.

 

[graaf]

Something to also consider is the fact that absorbents never absorps evently 100%. They will always to some degree function as a filter. With splayed walls or proper designed angled panels, one avoids this and get a perfect redirection without this filtering. This is how the best studios are built. Combined with diffusors in the rear, the diffuse energy is increased that way and hence an increase of spaciousness too. I don't think those who have experienced this find stereo to sound unatural or lacking much in a spacious soundfield. This is simply far better IMO then only reflected sidewalls because one completely avoids the negative effects such has.

this time I agree 100%

believe me or not - actually the "redirecting panels + diffusion in the rear" solution is the one I find the most reasonable and convenient in a domestic listening environment, I always recommend it

 

[ScottG]

Yes. A more uniform speaker response will lead to less coloration from the room. The CBT is probably the first speaker I think sounds very well with reflected sidewalls. The image suffers obviously.



..I don't think those who have experienced this find stereo to sound unatural or lacking much in a spacious soundfield.

This is simply far better IMO then only reflected sidewalls because one completely avoids the negative effects such has.

But does the image suffer as a result of those reflections?

The critical part here is that most assume this to be the case, and yet the research on this not only does NOT support this, but rather disproves this notion - at least with respect to a "reasonable" distance from those walls.

Instead go with the experts conclusions: just look at the direct sound's behavior (in its entirety).

I've listened to setups like the control room (including control rooms). The best have been private home theaters - but even they have uniformly had limited sound-field expansion beyond the walls of the room. I tend to "hear" the room or it's lack of reflections with substantial absorption and it creates cues that make it impossible for me to "suspend disbelief". Also, the images are often "pin-point" regardless of position - essentially having "size" problems.

 

[markus76]

In stereo you'll never perceive the spaciousness accurately.

You will however perceive spaciousness on the recording - your statement is over-broad.

I think you're talking about "reverberation". That's not the same as spaciousness. In natural listening both are closely tight to each other but in sound reproduction they are not.

I've heard some setups however that have (recording dependent), been astonishingly close (though still having that "mirror" effect). This even includes hearing cues beside and behind the listening position. And yes, that was with 2 speaker stereo.

Close to what? Close to realistic-sounding or close to the original? The former can be done (although not in a consistent manner and not without unattractive trade-offs), the latter needs a change in recording and reproduction practices.

 

[ScottG]

I think you're talking about "reverberation". That's not the same as spaciousness. In natural listening both are closely tight to each other but in sound reproduction they are not.

Close to what? Close to realistic-sounding or close to the original? The former can be done (although not in a consistent manner and not without unattractive trade-offs), the latter needs a change in recording and reproduction practices.

Reverberation creates a sense of spaciousness.

I didn't realize there was a uniformly agreed upon definition for spaciousness with sound reproduction. Please show some cites.


Close to realistic as in the original performance. Memory and binaural as the "check".

 

[markus76]

Reverberation creates a sense of spaciousness.

I didn't realize there was a uniformly agreed upon definition for spaciousness with sound reproduction. Please show some cites.

Reading through the available psychoacoustic literature there is a clear distinction between reverberation and spaciousness. As far as I recall Wittek showed a good summary in his thesis.
Are there many hobbyists that make that distinction? No. They rather like to fight about their beliefs than sit down, listen and experiment.

Listen to a recording with a lot of reverberation over headphone. You'll hear reverberation. It sounds like a large room or a small room or anything in between. Is there any sense of spaciousness? No.
Now listen to these example over your speakers. Is there any reverberation? Only reverberation of your listening room. Is there spaciousness? Yes! If the reflections would come from different locations spaciousness would increase.

There was a study about it by Reichardt/Schmidt in 1966 titled "Die hoerbaren Stufen des Raumeindrucks bei Musik". They found "14 discernible 'steps of spatial impression'. 50 years later and we're still discussing the same old stuff.

 

[ScottG]

Reading through the available psychoacoustic literature there is a clear distinction between reverberation and spaciousness.

As far as I recall Wittek showed a good summary in his thesis.

Are there many hobbyists that make that distinction? No. They rather like to fight about their beliefs than sit down, listen and experiment.

Listen to a recording with a lot of reverberation over headphone. You'll hear reverberation. It sounds like a large room or a small room or anything in between. Is there any sense of spaciousness? No.
Now listen to these example over your speakers. Is there any reverberation? Only reverberation of your listening room. Is there spaciousness? Yes! If the reflections would come from different locations spaciousness would increase.

There was a study about it by Reichardt/Schmidt in 1966 titled "Die hoerbaren Stufen des Raumeindrucks bei Musik". They found "14 discernible 'steps of spatial impression'. 50 years later and we're still discussing the same old stuff.

Who is Wittek and where is his thesis, and just where does he make this distinction? Also, is it derived from a great number of other sources on this particular topic?

Your non-reverb tracks do not display "spaciousness" to me, rather they display the quality I ascribe to as presence.

Sadly I'll have to pass on the German paper - I can't read German.