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Effect of Loudspeaker Directivity Compared with In-room Measurements

youngho

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None of those speakers have a pattern that can work well for this. The pattern is too wide at mid-high freq, and it does not fall off sharp enough.

A radiation pattern can not be described well just using a radiation angle number, you need to look at how the pattern is across both angle and frequency.
Can you show any detailed measurements of any speakers that can work well for this? Preferably showing pattern across angle and frequency. Most of what you say is really quite vague.
 
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Kvalsvoll

Kvalsvoll

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Can you show any detailed measurements of any speakers that can work well for this? Preferably showing pattern across angle and frequency. Most of what you say is really quite vague.
I do not believe such a speaker exist.

The pattern must be much more narrow, and fall off much faster when reaching the cut-off angles.

If you do the experiment, you realize the level must be down around 8dB at 30 degrees, if the speakers are toed in on the center position. While maintaining a reasonably flat frequency response. If speakers are toed in a lot more, it will work better, but this will have other issues, it does not work well.

What does work well, is a speaker with pattern that covers the whole listening area with flat frequency response, with a moderate reduction in level going off-axis inside this area, and falls off quite sharp outside, speakers more moderately toed in towards center. A horn can be designed to create such a pattern.

This gives a spatial presentation that is not compromised in the enter position, and good tonal balance with reasonable spatial properties outside. Images will move going off center, but that is not a big problem. For movies, where a centered dialog is more important, there is already a solution - the center speaker.
 

markus

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I do not believe such a speaker exist.
One of Danley's Synergy horns should work. They even offer CLF files for download.
For movies, where a centered dialog is more important, there is already a solution - the center speaker.
There's still a ton of stereo content in movie mixes which would benefit from better "stereo speakers".
 
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markus

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Ah, my mistake. It feels strange for me to look at the Kef Wireless II (https://www.erinsaudiocorner.com/loudspeakers/kef_wireless_ii/), which has a lower directivity index for most of its response compared with the D&D 8C (https://www.erinsaudiocorner.com/loudspeakers/dutch_dutch_8c/), compare their unnormalized horizontal contour plots, but then the LS50 has a +/- 50 degree beamwidth (https://www.audiosciencereview.com/forum/index.php?threads/kef-ls50-meta-review-speaker.25574/ and https://www.erinsaudiocorner.com/loudspeakers/kef_wireless_ii/), while the D&D 8C has a +/- 80-100 degree beamwidth.

It's hard to imagine a speaker, then, that could achieve the suggested directivity in the Kates paper. Even the Beolab 90 seems to be too wide (https://www.tonmeister.ca/wordpress/2015/06/30/bo-tech-what-is-beam-width-control/)
There is a typo in the Kates paper by the way. The first column in the table I had linked earlier isn't D/Y but Y/D. For a equilateral stereo triangle you end up around 1.7. So the beamwidth should be less than around 50° (+/-25°). The Beolab 90 in "narrow mode" comes close.
 
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tuga

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I may have missed it, but can’t remember reading about the best directivity characteristics for multi-channel use in Toole’s book. Is narrow objectively better than wide for that particular application?
 
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Kvalsvoll

Kvalsvoll

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One of Danley's Synergy horns should work. They even offer CLF files for download.

There's still a ton of stereo content in movie mixes which would benefit from better "stereo speakers".
Danley could be a good choice for this. But it still will not work well. Focus is lost, and when they are toed in enough to make it work, focus is also lost in center position.

Center channel also works for stereo source material, it is a simple upmix. And then you can turn it off for music.
 
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Kvalsvoll

Kvalsvoll

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I may have missed it, but can’t remember reading about the best directivity characteristics for multi-channel use in Toole’s book. Is narrow objectively better than wide for that particular application?
Can't speak for Toole, but generally, it seems the more speakers and channels you have, the more forgiving. What I have found, is that surround channels also benefit from having controlled directivity, but with a wide pattern.
 

Inner Space

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I may have missed it, but can’t remember reading about the best directivity characteristics for multi-channel use in Toole’s book. Is narrow objectively better than wide for that particular application?
I believe Toole recommends narrow directivity speakers for multichannel. He recommends wide directivity for two-channel, because his starting position is that two-channel should be turned into faux multichannel by bouncing reflections around the room, in search of so-called envelopment.
 

thewas

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From what I think to remember he does not explicitly recommend narrow directivity loudspeakers for multichannel but writes that more absorption (for example for the side walls) can be used, which could be indirectly also interpreted as such a recommendation?
Would be interesting to hear his exact view on it though, @Floyd Toole?
 

markus

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Danley could be a good choice for this. But it still will not work well. Focus is lost, and when they are toed in enough to make it work, focus is also lost in center position.
The alternative is all images collapsing into the nearest speaker.
Center channel also works for stereo source material, it is a simple upmix. And then you can turn it off for music.
I was talking about stereo stems in multichannel movies. You'll find a ton of those. Upmix doesn't help here as there's nothing to upmix anymore.
 

youngho

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The alternative is all images collapsing into the nearest speaker.
No, you already cited two very strange alternatives like semi-cardioid turned sideways and semi-dipole rotated obliquely. Furthermore, there are other alternatives like CBT designs that change the fall-off with distance and hence all calculations/models.
 
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Kvalsvoll

Kvalsvoll

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The alternative is all images collapsing into the nearest speaker.
For some speakers, this happens. For some other speakers, it does not.

And if a speaker does not sound so good far off center, it may still serve a listener who does not care so much about that.

Some time not very long ago, I had both set up in the same room, so this was easy to experience. Along with other differences, that made for a different experience.
 

youngho

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For some speakers, this happens. For some other speakers, it does not.

And if a speaker does not sound so good far off center, it may still serve a listener who does not care so much about that.

Some time not very long ago, I had both set up in the same room, so this was easy to experience. Along with other differences, that made for a different experience.
This is very vague. Can you provide more specifics?
 
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Kvalsvoll

Kvalsvoll

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This is very vague. Can you provide more specifics?
We have some speakers, and they are different from other speakers.. Yes, not exactly descriptive.

Starting from the observation - sitting far off-center, those some-speakers tend to present a sort of soundstage, though diffuse and things have moved closer to the nearest speaker. Switching to other-speakers, the sound collapses into the nearest speaker.

So what is a some-speaker, and what is a other-speaker.

It is clear that it has to do with radiation pattern. A larger speaker with horn at least above 1-2K, can be an example of the first (some-speaker) type. A small speaker with dome tweeter can be the other-speaker type.

A pattern that manages to cover my far-off position from both L and R speaker with full frequency range coverage, is a good starting point. Then there is the shape of the wavefront - a horn with its larger radiating surface tend to maintain spl level better across a longer distance, thus keeping spl from the speaker far away from dropping.
 

markus

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No, you already cited two very strange alternatives like semi-cardioid turned sideways and semi-dipole rotated obliquely.
I was referring to Kvalsvoll's comment that a high directivity design like a Danley Synergy "will not work well" for time-intensity trading, suggesting that it's not worth the effort. That's simply not true. From all conventional designs the Danley Synergy probably works best and it's well worth the effort because if you don't do anything you get the "image collapses to nearest speaker" effect. Some don't care as they always listen alone, head-in-a-vise-style, that's ok.
Maybe he wanted to say something else? Hard to tell as all his comments are very vague at this point.

Generally I'd like to see some meaningful listening tests for time-intensity trading with stereo speakers. What we have is largely anecdotal. Personally I haven't had great results (yet?).

Furthermore, there are other alternatives like CBT designs that change the fall-off with distance and hence all calculations/models.
CBT is horizontally wide and vertically narrow. "fall-off with distance" is the same for both stereo speakers so I'm not seeing why this is relevant to the discussion of time-intensity trading?
 
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markus

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ernestcarl

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Specs say "Nominal Beamwidth 60° x 45°". Might work when flipped 90° to the side so horizontal beamwidth becomes 45°.

I was trying to look for something narrower, but this just happened to be the narrowest configuration available for the particular model.
 

markus

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I was trying to look for something narrower, but this just happened to be the narrowest configuration available for the particular model.
PA speakers usually have narrower beamwidth so for first experiments you're heading in the right direction.
 

markus

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Danley could be a good choice for this. But it still will not work well. Focus is lost, and when they are toed in enough to make it work, focus is also lost in center position.
Rereading your comment, why would you say "focus is also lost in center position"? What should cause this "loss of focus"?
 
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