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The perfect speaker is room dependent - wide vs. narrow directivity and more

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#1
Hello,

I want to discuss here the differences of wide and narrow directivity of very good speakers in context with room acoustics and more.

One perfect speaker for all rooms. I don't think so.
On conclusion of the research at of @Floyd Toole and others are that a good speaker sounds good in any room. In general I will agree with this statement, but if you have a closer look at only very good speakers and different rooms and positions of the speakers and the listening position you will find that the perfect speaker is room dependent.

Listening distance
The listening distance is one of the most important parameter here. If you have a look at stereo you will find that you will need a amount of later reflections to get a feeling of "been surrounded by the sound". Omnidirectional speaker achieve this very well since there are more reflections of the room. But you will have a disadvantage with these speakers, the details of the sound will be masked by the reflections which makes the sound "soft", "washy" or "inexact". On the opposite side is a headphone. You have no additional reflections and the sound is "clear" or "exact" but you will have a poor or no feeling of being surrounded by the sound (binaural recording are different but I will not go into detail here). So there is a sweet spot of the ratio of direct sound to later reflected sound. It can be seen in the EBU recommendations on page 6 where the reverberation time at the listening position is recommended. I think this recommendations are valid.

Short listening distance wide directivity
If you follow this path you will need a speaker with wide directivity if you listen at short listening distances. Linkwitz invented a speaker which creates a good feeling of being surrounded by the sound despite the short listening distance. which is very rare to get. This is done by having a omnidirectional speaker and put them in the middle of the room.

Long listening distance narrow directivity
If you have a longer listening distance you will need a speaker with a narrow directivity to get the recommended reverberation time at the listening position with the speaker. And the speaker have do be beam a lot to achieve the goal. E.g. at 2.5m a typical 2 way speaker with 17cm bass beams a lot to wide.

There are plenty other parameter which are important
How constant is the directivity is over frequency, speaker with narrow beam and extra backfiring speaker or dipol like characteristics, first side wall reflection absorb or not, side wall reflections at 60° ideal?, unsymmetric placement is bad but what differences are still okay...

How to get perfect sound?
And the question which speaker room combination is perfect and how should the ultimate goal look like? A "standard" speaker with narrow directivity in a studio like dry room? All horns oben back in a big room with diffusing walls? Line arrays (horizontal wide and vertical narrow diretivity)?

Best
Thomas
 

richard12511

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#2
Hello,

I want to discuss here the differences of wide and narrow directivity of very good speakers in context with room acoustics and more.

One perfect speaker for all rooms. I don't think so.
On conclusion of the research at of @Floyd Toole and others are that a good speaker sounds good in any room. In general I will agree with this statement, but if you have a closer look at only very good speakers and different rooms and positions of the speakers and the listening position you will find that the perfect speaker is room dependent.

Listening distance
The listening distance is one of the most important parameter here. If you have a look at stereo you will find that you will need a amount of later reflections to get a feeling of "been surrounded by the sound". Omnidirectional speaker achieve this very well since there are more reflections of the room. But you will have a disadvantage with these speakers, the details of the sound will be masked by the reflections which makes the sound "soft", "washy" or "inexact". On the opposite side is a headphone. You have no additional reflections and the sound is "clear" or "exact" but you will have a poor or no feeling of being surrounded by the sound (binaural recording are different but I will not go into detail here). So there is a sweet spot of the ratio of direct sound to later reflected sound. It can be seen in the EBU recommendations on page 6 where the reverberation time at the listening position is recommended. I think this recommendations are valid.

Short listening distance wide directivity
If you follow this path you will need a speaker with wide directivity if you listen at short listening distances. Linkwitz invented a speaker which creates a good feeling of being surrounded by the sound despite the short listening distance. which is very rare to get. This is done by having a omnidirectional speaker and put them in the middle of the room.

Long listening distance narrow directivity
If you have a longer listening distance you will need a speaker with a narrow directivity to get the recommended reverberation time at the listening position with the speaker. And the speaker have do be beam a lot to achieve the goal. E.g. at 2.5m a typical 2 way speaker with 17cm bass beams a lot to wide.

There are plenty other parameter which are important
How constant is the directivity is over frequency, speaker with narrow beam and extra backfiring speaker or dipol like characteristics, first side wall reflection absorb or not, side wall reflections at 60° ideal?, unsymmetric placement is bad but what differences are still okay...

How to get perfect sound?
And the question which speaker room combination is perfect and how should the ultimate goal look like? A "standard" speaker with narrow directivity in a studio like dry room? All horns oben back in a big room with diffusing walls? Line arrays (horizontal wide and vertical narrow diretivity)?

Best
Thomas
Agreed.

Something else I've found to be important is the number of speakers. I've found myself preferring more narrow dispersion designs for multi-channel music listening, and wider designs for stereo or mono. My guess is that the extra surround channels are able to provide that sense of envelopment that's missing from the narrow designs in stereo or mono, that along with the extra clarity is what's leading to my preference. I don't really listen in mono often, but my guess is that I'd prefer an omni design in that scenario.

The preference for narrow/wide based on listening distance might be a little controversial. I've heard others state the opposite of what you said. They prefer wider for big rooms with long listening distances, and narrower for small rooms with short distances. It may just be that preferences differ greatly on this subject.

I tend to agree with you; I prefer wider dispersion for short distances, as I dislike the super unstable soundstage/imaging that narrow designs throw at short distance.
 
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Thread Starter #3
Yes, the more speaker you have the less room reflections are desirable. In the EBU recommendation there is also a lower reverberation time suggested for multi channel listening.

Some also say stereo can't be good, but I have heard very convincing stereo setups. An almost no very good stereo to multichannel upscale which comes close to the very good stereo setup. The sense of enveloping is only good mit auro 3D or similar setups with higher placed speakers or with setups with omnidirectional and very well places back channel speaker. With no higher places speaker you have to play with the room acoustic like in stereo to get the feeling of enveloping sound. It is harder to build this room acoustic with more speakers. Or do you know some more tricks like placing additional speakers at +/- 60°.

One other important aspect is the positioning in the room. If the speakers are not places symmetrical in the room or the first reflections provide a uneven frequency response and high power (placement close to the wall); in this cases it is better to have less reflections aka a speaker with narrower directivity even in a small room.
 
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#4
Indeed
Different opinions and personal tastes
I use excessive toe-in and like what i am hearing
Enjoy...
 

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Duke

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#5
I want to discuss here the differences of wide and narrow directivity of very good speakers in context with room acoustics and more.
Imo this is the right way to look at loudspeaker design: Taking room interaction into account.

One perfect speaker for all rooms. I don't think so.
Me neither.

But I am in favor of building some user-adjustability into the speakers, for adaptation to different room acoustic situations. Is the room acoustically dead or highly reflective or in between? How much boundary reinforcement are we getting in the bass region? One of my goals as a small speaker manufacturer is "no speakers returned for a refund", and more than once user-adjustability to deal with room acoustics has saved the day for me.

The listening distance is one of the most important parameter here. If you have a look at stereo you will find that you will need a amount of later reflections to get a feeling of "been surrounded by the sound". Omnidirectional speaker achieve this very well since there are more reflections of the room. But you will have a disadvantage with these speakers, the details of the sound will be masked by the reflections which makes the sound "soft", "washy" or "inexact".
You might also take a look at the role played by early reflections in particular, for better or for worse. They are arguably a two-edged sword. If you want early reflections (in particular early sidewall reflections), that implies using wide-pattern speakers. If you want to minimize early reflections (and again in particular early sidewall reflections), that implies either using narrow-pattern speakers or acoustic treatment of those early sidewall reflection zones.

Also, in general I have tended to prefer wide-pattern speakers in highly damped rooms, and narrow-pattern speakers in relatively reverberant rooms.

...speaker with narrow beam and extra backfiring speaker...
[Does a double-take] Hey, that sounds familiar!

...unsymmetric placement is bad but what differences are still okay...
Imo acoustic asymmetry is most detrimental when it affects the early reflections. Asymmetry (de-correlation) in the later reflections is arguably desirable.

How to get perfect sound?
And the question which speaker room combination is perfect and how should the ultimate goal look like? A "standard" speaker with narrow directivity in a studio like dry room? All horns oben back in a big room with diffusing walls? Line arrays (horizontal wide and vertical narrow diretivity)?
I don't know "how to get perfect sound", but it probably starts with asking the right questions, and I think you are on the right track.
 

JustIntonation

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#6
I think a wide dispersion speaker is to be preferred when striving for the best.
I say this both from experience and from theory.

Yes, a narrow dispersion speaker can often sound better in a bad sounding untreated room. Though I know many examples from experience where it's the opposite too.
But the preference for wide dispersion speakers becomes clear when you have a good sounding room or even a minorly treated room.

A wide dispersion speaker will throw a much bigger soundstage.
I've listened in a fairly large room with heigh ceilings which had virtually no absorption but did have a lot of diffusion and with a wide dispersion speaker the whole room came alive and the soundstage was absolutely huge. And compared this in that room with more narrow dispersion speakers which had waveguides (among them K+H O300) and the soundstage just collapsed to a mostly inbetween the speakers ordeal.

If you want to dampen the off-axis sound then a carpet and curtains against the sidewalls will already do that in the treble similar to a more narrow dispersion speaker would do on bare walls / floor. But the big difference is that with bare walls / floor the sound will keep reflecting without further absorption, while with absorption the reverb time itself shortens. I think the second way where reverb time is shortened is to be greatly prefered.

For serious listening rooms the trouble is in absorbing the deep bass, not the treble which is easy. It's both easier to get to a tonal balance and soundstage you like with absorption and diffusion with a wide dispersion speaker and the endresult will likely be better regarding reverb time and soundstage.

Goes without saying that a smooth off-axis is preferred ofcourse. With both wide and narrow dispersion speakers.
 
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#7
Wide or narrow dispersion is bandaid for situations where you can't control the placement and acoustics of the room.
 

Duke

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#9
I think a wide dispersion speaker is to be preferred when striving for the best...

A wide dispersion speaker will throw a much bigger soundstage.
I agree that wide dispersion speakers throw a bigger soundstage, but imo there are trade-offs involved. The same psychoacoustic mechanism which perceives a wider soundstage when significant early sidewall reflections are present also degrades image precision. And in my experience clarity and soundstage depth can also be degraded by early reflections. Toole's findings indicate that the benefits of wide-pattern speakers outweigh the downsides for most listeners.

Here are some arguments against early reflections, which may have implications for the wide-pattern vs narrow-pattern speaker debate. These statements may also be thought of as arguments for treatment of the early reflection zones:

"The earlier and the greater in level the first room reflections are, the worse they are. This aspect of sound perception is controversial. Some believe that all reflections are good because they increase the listener's feeling of space – they increase the spaciousness of the sound. While it is certainly true that all reflections add to spaciousness, the very early ones (< 10 ms.) do so at the sake of imaging and coloration... The first reflections in small rooms must be thought of as a serious problem that causes coloration and image blurring. These reflections must be considered in the [louspeaker] design and should be also be considered in the room as well." - Earl Geddes

"The earlier a reflection arrives the more it contributes to masking the direct sound." - David Griesinger

"When presence is lacking the earliest reflections are the most responsible." - David Griesinger
 

JustIntonation

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#11
I agree that wide dispersion speakers throw a bigger soundstage, but imo there are trade-offs involved. The same psychoacoustic mechanism which perceives a wider soundstage when significant early sidewall reflections are present also degrades image precision. And in my experience clarity and soundstage depth can also be degraded by early reflections. Toole's findings indicate that the benefits of wide-pattern speakers outweigh the downsides for most listeners.

Here are some arguments against early reflections, which may have implications for the wide-pattern vs narrow-pattern speaker debate. These statements may also be thought of as arguments for treatment of the early reflection zones:

"The earlier and the greater in level the first room reflections are, the worse they are. This aspect of sound perception is controversial. Some believe that all reflections are good because they increase the listener's feeling of space – they increase the spaciousness of the sound. While it is certainly true that all reflections add to spaciousness, the very early ones (< 10 ms.) do so at the sake of imaging and coloration... The first reflections in small rooms must be thought of as a serious problem that causes coloration and image blurring. These reflections must be considered in the [louspeaker] design and should be also be considered in the room as well." - Earl Geddes

"The earlier a reflection arrives the more it contributes to masking the direct sound." - David Griesinger

"When presence is lacking the earliest reflections are the most responsible." - David Griesinger
Agreed.
But as I wrote, the better way to reduce early reflections is by using absorption (even if it's thin absorption like thick curtains and a carpet) at those early reflection points, not by using a narrow pattern speakers.
I think the only time a narrow dispersion speaker is to be preferred is when one has a bad sounding room and one wishes to keep the walls bare, then it may give the best result (though even then not always).
 
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#12
Time intensity trading

 
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Thread Starter #13
Thank you for all the interesting replies.

I agree that wide dispersion speakers throw a bigger soundstage, but imo there are trade-offs involved.
Exactly!
I also agree to the consensus that there is a trade of between envelopment and accuracy. And envelopment is much harder to obtain with narrow directivity. The room acoustic treatment is crucial here. From my experience wide directivity speaker only sound very good in the near field. Like the approach of Linkwitz with the near omnidirectional speakers in the middle of the room. With this you will get less early reflections and more later reflections. With such setup you have some problems since you have to place the head very accurately in the middle, but the overall sound is very good accuracy and envelopment are there.

Different opinions and personal tastes
I think there is a broad consensus in what is better if you compare two actual setups. Similar to the consensus of good sounding speaker.

I use excessive toe-in and like what i am hearing
That is interesting I actually never tried this out.

Wide or narrow dispersion is bandaid for situations where you can't control the placement and acoustics of the room.
Yes you can build a room for the speaker or build a speaker for the room ;) The question is wich speaker, room, placement combinations work best...

Also, in general I have tended to prefer wide-pattern speakers in highly damped rooms, and narrow-pattern speakers in relatively reverberant rooms.
From my experience wide directivity speaker in highly damped rooms doesn't provide convincing envelopment of the sound. What is the listening distance we are talking about here?

[Does a double-take] Hey, that sounds familiar!
Yes, very obsessed audio nerds often end with all horn speaker in bigger rooms with higher listening distance. One of the downsides of such setup would be the lack of later reflections due to the high amount of direct sound, so the horn drivers form about 300Hz are not working in an enclosure to get more diffuse sound at the listening position. If it is made right it is very convincing, envelopment and accuracy are both very good.

Or are you discussing only passive speakers without room correction?
Room correction it another piece of the puzzle, but you can typically only equalize the speaker as a whole so you are not able to adjust the amount of direct to reflected sound. So that is a problem why you can not get one perfect speaker for all rooms. Room correction may help to adjust the overall tonality e.g. dry room vs. no absorption, but none of the less you have to choose the right directivity for your room and placement.

Has someone also experienced the benefit of first reflections at about 60° like in very good concert halls. I think this trick helps a lot with the sense of envelopment and sound stage in smaller rooms, if you doesn't like the extrem near field middle of the room approach. Never the less so far I think a the big room, diffusing walls all horn approach with backfiring speakers is the best oft the best....

Best
Thomas
 
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#15
Yes you can build a room for the speaker or build a speaker for the room ;) The question is wich speaker, room, placement combinations work best...
In my room I prefer the dispersion width to be optimized for the spinorama... meaning it is a side effect not a design goal.

I sit 7 ft away, rear wall is 14 ft back, early reflections absorbed, hard flooring. In this way I can get precise imaging and large soundstage.
 

JustIntonation

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#16
Wide dispersion thus more reflections may sound better, but it's certainly not about fidelity to the recording.
Agreed to a large degree. But the way to handle reflections is by absorption and diffusion / room treatment. The result will be much better than by using a narrow dispersion speaker where the initial reflection is down in the treble just like with shallow absorption but then the reverb / RT60 doesn't match that and it reverbs / rings / flutters etc on without absorption.
A wide dispersion speaker will let you know how to treat your room to make it sound great. With a narrow dispersion speaker you will have more trouble and it can easily get too dark sounding while the RT60 / reverb isn't yet damped enough.
I'm convinced that if you're serious about (stereo) audio and willing to put some minor effort into your room acoustics then wide dispersion speakers are the best solution.
More troubling though is to find a wide dispersion speaker that has an even and smooth off-axis / power response. Designed one myself for this purpose.
 

Duke

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#17
...the better way to reduce early reflections is by using absorption (even if it's thin absorption like thick curtains and a carpet) at those early reflection points, not by using a narrow pattern speakers.
Broadband absorption is imo highly preferable to "thin absorption" because the latter becomes progressively less effective as the wavelengths increase. So the spectral balance of the reflection is significantly changed, undoing all the work the speaker designer put into getting good off-axis response, with arguably much of the same effect, because now the reflections no longer sound like the direct sound. And note that this effect doesn't stop with those first reflections - rather, the absorptive material continues to have that same effect on every subsequent reflection which strikes it.

Imo either broadband absorption or diffusion makes more sense.

Now one advantage of wide-pattern speakers, which probably contributes to their general preference in listening tests, is that they also produce more later-arriving reverberant energy, which (if spectrally correct) tends to be spatially and timbrally beneficial without the downsides mentioned in post #9 above.

Wide dispersion thus more reflections may sound better, but it's certainly not about fidelity to the recording.
Imo this is an oversimplification, as taking this idea to the extreme (anechoic listening) isn't the answer either. Evidently the ear likes some reflections, just not too much and not too little, and in particular (in my opinion) not too many early ones.
 

Thomas_A

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#18
Indeed
Different opinions and personal tastes
I use excessive toe-in and like what i am hearing
Enjoy...
Me too. Wide dispersion speakers, small room, and heavy toe in. Felt around tweeters reducing > 3 kHz large angle reflections.
 

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Duke

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#19
Has someone also experienced the benefit of first reflections at about 60° like in very good concert halls.
In my opinion they would normally need to be fed a delayed signal. After reading Toole's book I made a pair of speakers that had secondary arrays dedicated to those theoretically ideal 60 degree reflection angles. I learned the hard way that they need a lot of distance to the sidewalls to work well, so it was a good speaker for long-wall placement in a wide room, but not a very good speaker for more conventional situations.

Acoustic Research made a speaker like this but with time-delayed secondary arrays called the MGC-1, but unfortunately it was not a commercial success and the company went out of business shortly afterwards.

When I made a comparison between prioritizing the secondary array's reflection arrival angle and reflection arrival time, the arrival time seemed to matter most. However by using delay you could do both.

... so far I think a big room, diffusing walls all horn approach with backfiring speakers is the best of the best....[emphasis Duke's]
Imo that's a very good idea. What made you try adding backfiring speakers to a horn system? I do the same thing (though not with an "all horn" main system).
 
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JustIntonation

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#20
Broadband absorption is imo highly preferable to "thin absorption" because the latter becomes progressively less effective as the wavelengths increase. So the spectral balance of the reflection is significantly changed, undoing all the work the speaker designer put into getting good off-axis response, with arguably much of the same effect, because now the reflections no longer sound like the direct sound. And note that this effect doesn't stop with those first reflections - rather, the absorptive material continues to have that same effect on every subsequent reflection which strikes it.

Imo either broadband absorption or diffusion makes more sense.

Now one advantage of wide-pattern speakers, which probably contributes to their general preference in listening tests, is that they also produce more later-arriving reverberant energy, which (if spectrally correct) tends to be spatially and timbrally beneficial without the downsides mentioned in post #9 above.



Imo this is an oversimplification, as taking this idea to the extreme (anechoic listening) isn't the answer either. Evidently the ear likes some reflections, just not too much and not too little, and in particular (in my opinion) not too many early ones.
My personal preference is all of the above. Broadband absorption / bass traps, thin hf absorption and some diffuse reflections.
Those narrow pattern speakers are not flat off-axis either, they slope down like thin / non broadband absorption gives. The spectral balance is altered in a similar way.
I think for a living room / listening room system one should go for reverb and early reflections that is more attenuated / absorbed at the hf to give a sloping freq / decay time.
I've owned a semi anechoic room (currently building a nearly full anechoic one) and to go truly fully dry is a different thing altogether.
 
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