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Research on reflections

aarons915

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I've been wanting to compile some of the current research on reflections into one thread for awhile as a reference and of course some debate as I know there are differing opinions on some of this and I admit some of this going to be my own editorializing based on personal experience with various speaker designs. Much of this is dealing with music listening in stereo, I realize in a home theater or studio, fewer reflections is seen as beneficial by many people. It's also important to note that there isn't really an agreed upon standard for what exactly is "wide" or "narrow" dispersion but these globe plots of the BMR and LS50 Wireless 2 clearly show the extremes:

Screenshot (12).png


Current Research


There is countless evidence that the majority of people prefer reflections when listening to music as it gives a sense of space and sounds more like live music. Dr. Toole also speculates that since Stereo can't possibly replicate a live performances 3d sound field that reflections may help to fill in the gaps and simulate it a bit better. Further research by Toole and Sean Olive have shown that listeners not only prefer reflections but that "Early Reflections" have a higher importance than later arriving reflections and that they also need to closely match the direct sound for the highest preference in listening tests. This research is the basis for the early reflections curve in the CTA-2034 measurement spec. I would go a step further and say the while the average of all the early reflections is important, I like to see that all of the early reflections are close to that average. Dr. Toole also considers sidewall reflections to be more important than vertical reflections but there isn't much research on that and I'll show some research later that shows that we probably can't neglect vertical reflections.

Ultra Wide Dispersion Speakers

I personally think the research that shows people generally like wide dispersion has been taken too far in some cases and some speakers have prioritized "wide dispersion" at the expense of other qualities in a speaker. The most extreme examples of course are speakers showcasing the RAAL 64-10 ribbon tweeter which have the widest dispersion of any speaker on the market but are also limited vertically due to their geometry. Now I admit I have limited experience with this tweeter because I auditioned them in a smaller room where wide dispersion maybe didn't matter as much but my big takeaways were that they sounded pretty normal regarding spaciousness except it was very obvious they were lacking vertically when switching back to my LS50. The LS50 sounded "bigger" because of it which was pretty surprising considering the 64-10 is known for wide dispersion and the spaciousness that comes with it. This comparison was the 1st moment that I realized that maybe vertical dispersion is more important than conventional wisdom gives it credit for.

Dr. Toole's study that was the basis for comparing speakers in mono actually also shows something interesting about dispersion and whether ultra wide dispersion is a goal worth pursuing. Aside from showing that listening to the speaker in mono makes it easier to discern differences in sound quality, another argument can be made that when listening to just 2 speakers in stereo, these spatial differences largely disappear. This is more along the line of what I hear in my own room listening to the "narrow dispersion" LS50s in 2 and 3 channel stereo for music, they don't seem to be lacking in spaciousness at all to my ears.


Mono.JPG




Ideal Dispersion

Based mostly on my thoughts between the RAAL 64-10 and the KEF LS50 I have been wondering if there is maybe an "ideal" dispersion considering both the horizontal and vertical planes. I've heard people debate that the widest dispersion is the best or even that we should be matching the dispersion pattern to the room dimensions. Neither approach has ever made sense to me, it seems like we should be trying to simulate the dispersion patterns of real vocals and instruments as best we can to get closest to the ideal speaker directivity, assuming of course that your goal is to get closer to a live acoustic performance in your room. I've never noticed that live music in smaller venues sounds bad in one room compared to another, they all sound natural to my ears. Musical instruments are obviously complex and no speaker is going to simulate all instruments but generally the sound is radiated fairly evenly from wherever the sound originates since they will be complex patterns from multiple point sources. The human voice also has a fairly even polar pattern and most notably isn't extremely wide horizontally or vertically.

Humanpolar.jpg



Vertical Reflections

Another interesting debate is about the importance of vertical reflections where there is surprisingly very little research done on. Dr. Toole briefly mentions a study where he states "...intuition is rewarded in that the dominant audible effect of the lateral reflection was spaciousness (the result of interaural differences) and that of the vertical reflection was timbre change (the result of spectral differences)" but it isn't clear if the reflection was a perfect timbral copy of the direct sound or if it was distorted to match what would be the typical ceiling reflection from a speaker with vertically arranged drivers.

I've only found 2 other studies that give some information on vertical reflections. The first one is:
"The Effect of a Vertical Reflection on the Relationship between Preference and Perceived Change in Timbral and Spatial Attributes" where I'll quote the abstract:

This study aims to investigate a vertical reflection’s beneficial or detrimental contribution to subjective
preference, compared with perceived change in timbral and spatial attributes. A vertical reflection was
electro-acoustically simulated and evaluated through subjective tests using musical stimuli in the
context of listening for entertainment. Results indicate that the majority of subjects preferred audio
reproduction with the addition of a reflection. Furthermore, there is a potential relationship between
positive preference and the perceived level of both timbral and spatial differences, although this
relationship is dependent on the stimuli presented. Subjects also described perceived differences where
the reflection was present. These descriptors provide evidence suggesting a link between timbral
descriptions and preference. However, this link was not observed between preference and spatial
descriptions.


The interesting thing to me was even with a large dip in the vertical reflection, a little over half of the participants still preferred the tracks with the reflection, also 59 out of 78 of the total ratings were positive. This is the measurement of the reflection:

ref.JPG

The other study is called: "Influence of first reflections in listening room on subjective listener impression of reproduced sound" This study compared the effects of absorbing various first reflections and comparing the results. Basically, the fewer reflections you absorb the wider the soundstage and envelopment but you lose clarity. Absorbing reflections is similar to them being absent so it's interesting that removing the ceiling reflections lessens image width and envelopment just slightly less than removing sidewall reflections. Here are a few of the key graphs: (Rs is absorption of sidewall, Rf= ceiling)

Reflections1.JPG


Also found in the thesis paper from the above study, another study was referenced: "Auditory envelopment" (Furuya, Fujimoto, Takeshima & Nakamua, 1995) :

All experiments utilised musical stimuli and the reflection and sound field were electro acoustically simulated. In relation to this thesis investigating a singular reflection, experiment one demonstrated that as the delay time of a singular reflection increased, the sound image grows vertically in size. Regarding auditory envelopment, experiments two and three show that as long as the ratio of lateral and vertical energy remains constant up to 200ms, envelopment becomes stronger as energy arriving from above increases. The author does note however that lateral arriving energy must be the “predominant factor to perceive envelopment”.

Small Room vs Big Room:

I mentioned that I was previously in a small room (11' wide with 8ft ceilings and about a 10' listening distance) and just moved to a concrete loft that is a similar listening distance but is 15' wide with 12' ceilings. It is somewhat surprising but it didn't make the speakers sound smaller, if anything they are more spacious and the room sounds like a concert hall. I have almost no absorption in this room at the moment, just a few love seats so that may be a factor. I also feel like the sound is more clear, I speculate that I'm hearing the direct sound more clearly with the early reflections that are now arriving a bit later due to the longer distances from the walls and ceiling and then the later arriving reflections are much lower in level so the overall sound remains clear.

Conclusion

I don't think definitive conclusions can really be drawn yet until we get some more research on these issues but it is food for thought. I'd like to see the effect of vertical reflections when the reflection isn't distorted as it was in one of the studies I showed. I'd also like to see how listeners perceive overall spaciousness when listening to speakers with differing horizontal and vertical dispersion.

My personal experience with multiple listening tests (sighted and blind, all level-matched and instantly A/Bing) is that my ears agree with most of the research I have posted. I have found that once at least 2 speakers are playing, I don't notice much difference in spaciousness but I do notice a difference when vertical response is very limited. This tells me that all early reflections need to be considered when going for that live spacious sound, not just the sidewall reflection. I also believe that since early reflections seem to be mostly what matters regarding spaciousness, the large difference shown in the globe plots between a wide and narrow dispersion speaker may not perceptively sound that different when the 1st reflections are within a decibel or so in amplitude. More in the preference realm but I also find listening to music in 3 channel stereo with the center about 3-5db lower than the fronts is a great way to get even more spaciousness while also reducing the stereo imaging effect which makes music sound more like music and less like headphones.
 
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Chromatischism

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Good post.

I don't believe that wider is always better, because the sound becomes more and more reliant on a good room and good placement. Taken to the extreme you have omnidirectional speakers like those from Linkwitz and Ohm which everyone knows are good speakers which don't perform well in all spaces. Meanwhile coaxials and speakers from JBL, JTR, Dutch & Dutch, Buchardt, Arendal, Perlisten, etc – with their controlled directivity – work in more spaces.
 
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aarons915

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Good post.

I don't believe that wider is always better, because the sound becomes more and more reliant on a good room and good placement. Taken to the extreme you have omnidirectional speakers like those from Linkwitz and Ohm which everyone knows are good speakers which don't perform well in all spaces. Meanwhile coaxials and speakers from JBL, JTR, Dutch & Dutch, Buchardt, Arendal, Perlisten, etc – with their controlled directivity – work in more spaces.

Agreed and one thing I didn't mention is controlled directivity speakers can be pointed straight ahead to achieve a stronger sidewall reflection for those that want it. In my smaller rooms with 8' ceilings I've estimated all my early reflection points to be within 30-50 degrees off-axis, making wider dispersion less beneficial.

I personally think a consequence of Harman testing their speakers in mono is that wider dispersion appears to be much more important than it is in the typical room with multiple speakers playing. Not saying the testing is invalid or anything, I'm aware that Dr. Toole has stated that speakers that win in mono also win in stereo but maybe the speaker that wins both is just the more neutral speaker.
 

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Ideal Dispersion

Based mostly on my thoughts between the RAAL 64-10 and the KEF LS50 I have been wondering if there is maybe an "ideal" dispersion considering both the horizontal and vertical planes. I've heard people debate that the widest dispersion is the best or even that we should be matching the dispersion pattern to the room dimensions. Neither approach has ever made sense to me, it seems like we should be trying to simulate the dispersion patterns of real vocals and instruments as best we can to get closest to the ideal speaker directivity, assuming of course that your goal is to get closer to a live acoustic performance in your room. I've never noticed that live music in smaller venues sounds bad in one room compared to another, they all sound natural to my ears. Musical instruments are obviously complex and no speaker is going to simulate all instruments but generally the sound is radiated fairly evenly from wherever the sound originates since they will be complex patterns from multiple point sources. The human voice also has a fairly even polar pattern and most notably isn't extremely wide horizontally or vertically.

View attachment 160989

I could write thousands of words on my thoughts on this topic, and I'd love to chime in more, but I just wanted to offer one small counter to the idea of matching the natural directivity of instruments, mainly that the notion of wider directivity being preferred isn't just the Harman stuff, it's also related to acoustics in larger spaces and the idea of increasing "apparent source width" being a pleasing effect.

Listening in a large venue can cause an instrument to sound larger and help make it sound better too. So it comes down again to a question of 'realism' vs 'preference' and to me since realism is not achievable in a 2-way setup with traditional recordings preference is, well... preferable.

In terms of ideal directivity I've noted before that I think part of the reason wide directivity is maybe preferred is because it is closer to constant directivity, and we often see that even the narrower Harman speakers try to have a constant directivity portion to the FR.

I do think matching directivity to the human voice is an interesting idea, since speech is the most common live acoustic reference for all of us.

In general I agree there isn't an ideal horizontal directivity but at the same time it makes sense to me that for stereo (and esp mono), wider would generally be preferred. Contrary to popular belief I think it's actually in smaller rooms that wider directivity is most beneficial. The bigger the room, the less obvious the differences between wide and narrow speakers.

One interesting caveat with wide directivity is that it might require a bit more care in the speaker design as it is more likely to reveal resonances in the enclosure due to the louder repetitions of resonances. However how much this is an issue I do not know.

Overall, despite being a big proponent of wider directivity speakers, I also take it with a big of a grain of salt. Even in that Toole study you mentioned, the difference between the 'narrow' speaker and the others was far more dramatic than, say, a revel vs a Genelec, or a philharmonic or vs a kef. Most of what we call narrow is only relative.

Edit: One more point of discussion is whether wide directivity speakers can get away with having 'messier' directivity. This has been my experience but there isn't too much concrete to prove it. But intuitively it makes sense to me. A sense of space is established when there is a similarity between the direct and reflected sound. A directivity that tilts down smoothly may look prettier in an FR chart, but I question whether it is actually perceived as being more accurate than directivity that is a bit messier but louder overall, and less tilted.
 
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Chromatischism

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I just wanted to offer one small counter to the idea of matching the natural directivity of instruments, mainly that the notion of wider directivity being preferred isn't just the Harman stuff, it's also related to acoustics in larger spaces and the idea of increasing "apparent source width" being a pleasing effect.
Doesn't this mean, less pinpoint imaging? Because pinpoint imaging is a pretty addictive quality once you've heard it.
I do think matching directivity to the human voice is an interesting idea, since speech is the most common live acoustic reference for all of us.
I'm not quite sold on this idea. We use room dimensions and constructions to "enhance" sound in many ways, for example opera houses and concert halls. Those are hardly "natural" sounds compared to day to day conversation.
In general I agree there isn't an ideal horizontal directivity but at the same time it makes sense to me that for stereo (and esp mono), wider would generally be preferred. Contrary to popular belief I think it's actually in smaller rooms that wider directivity is most beneficial. The bigger the room, the less obvious the differences between wide and narrow speakers.
This is interesting. I remember @echopraxia 's observations were the opposite of that between his Genelecs and Salon2's and he had a pretty big room. Maybe he has something to add here.
 
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Dennis Murphy

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I think we can all agree that the current research on directivity, and horizontal vs. vertical in particular, is inadequate, In the meantime, we have to go with personal experiences, and mine don't match the OP's. If they did, I would be offering a very different speaker than the BMR. I've been comparing speakers with different radiation patterns for over a decade using a volume-compensated A-B-X switching preamp. The results are always the same. In mono, I don't have a strong opinion. The BMR's, for example, sound different than a speaker with narrower horizontal dispersion but wider vertical dispersion (and I've designed many of the latter for Jim Salk), but I'm not sure I could say which is " better." I can hear voicing differences if they exist, but my speakers are voiced very similarly to begin with. In stereo, it's an entirely different outcome. On well-recorded acoustic music with natural ambiance (and we're not talking breathy young ladies singing way too close to the mic in a multitrack studio recording), the speaker with wider horizontal dispersion has a deeper sound stage and also a taller one, even though it's vertical dispersion is more restricted. . Inevitably, when I switch from the wider horizontal-dispersion design to the narrow, the soundstage gets squished vertically. The effect is very dramatic on good recordings of symphonic and jazz recordings in a natural venue. (On Nora Jones, the speakers will sound equally annoying.) If you happen to be near Rockville MD on Nov 5-7, stop by room 306 at the Capital Audio Fest and I'll demonstrate this for you.
 

aac

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Studio designs are often directed at increasing direct/reflected ratio.
Makes sense if one wants to achieve "high fidelity" reproduction rather than use room as a "mechanical sound processor".
I don't see a reason why this does not apply to speakers. So higher fidelity speakers are narrower directivity speakers (for all frequencies, which requires larger woofers or some sophisticated design).
 

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How does room dimensions, especially width, impact preference?

How does room decay time impact preference?

How does listening distance impact preference?

How does speaker distance to sidewall impact preference?

What if sidewall distances are asymmetric?

I have my own observations, but TBH I don't care if there is ever a comprehensive study on dispersion preferences. Two channel recordings aren't meant to be state of the art. They are a compromise for mass adoption. Surround sound and binaural are the next steps. For those use cases, either dispersion width doesn't matter much or even narrower can be preferred. In the case of surround sound, even the speakers don't matter much.
 
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aarons915

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Listening in a large venue can cause an instrument to sound larger and help make it sound better too. So it comes down again to a question of 'realism' vs 'preference' and to me since realism is not achievable in a 2-way setup with traditional recordings preference is, well... preferable.

In terms of ideal directivity I've noted before that I think part of the reason wide directivity is maybe preferred is because it is closer to constant directivity, and we often see that even the narrower Harman speakers try to have a constant directivity portion to the FR.

I do think matching directivity to the human voice is an interesting idea, since speech is the most common live acoustic reference for all of us.

In general I agree there isn't an ideal horizontal directivity but at the same time it makes sense to me that for stereo (and esp mono), wider would generally be preferred. Contrary to popular belief I think it's actually in smaller rooms that wider directivity is most beneficial. The bigger the room, the less obvious the differences between wide and narrow speakers.



Overall, despite being a big proponent of wider directivity speakers, I also take it with a big of a grain of salt. Even in that Toole study you mentioned, the difference between the 'narrow' speaker and the others was far more dramatic than, say, a revel vs a Genelec, or a philharmonic or vs a kef. Most of what we call narrow is only relative.

Just a few thoughts. I agree with much of your thoughts and of course someone's preference is just that and won't be changed. Dr. Toole talks about "neutrality" being the most important aspect of a speaker regarding its frequency response but I feel like there is neutrality in dispersion patterns as well and that a neutral speaker will more closely mimic the dispersion patterns of real sounds.

I'm not saying you're wrong but larger rooms will have longer arrival times for the reflections so it seems like the stronger off-axis response would be preferred in larger rooms intuitively.

Good point about relative directivity, I've said that many times myself. Like I said in the original post though you can clearly see a large difference in the globe plots, I just don't know how much that all matters. If the early reflections are mostly what matters regarding "dispersion" then most speakers are within a decibel or 2 of each other and I don't see how that would make any large difference in spaciousness.
I'm not quite sold on this idea. We use room dimensions and constructions to "enhance" sound in many ways, for example opera houses and concert halls. Those are hardly "natural" sounds compared to day to day conversation.

True but Dr. Toole mentions frequently that we "hear through the room" or even outside. The brain is good at processing reflections so that you still recognize familiar voices. For the same reason, I believe that if a speaker reproduces those vocals with a similar dispersion pattern as a real person then it should sound natural in any space.
I think we can all agree that the current research on directivity, and horizontal vs. vertical in particular, is inadequate, In the meantime, we have to go with personal experiences, and mine don't match the OP's. If they did, I would be offering a very different speaker than the BMR. I've been comparing speakers with different radiation patterns for over a decade using a volume-compensated A-B-X switching preamp. The results are always the same. In mono, I don't have a strong opinion. The BMR's, for example, sound different than a speaker with narrower horizontal dispersion but wider vertical dispersion (and I've designed many of the latter for Jim Salk), but I'm not sure I could say which is " better." I can hear voicing differences if they exist, but my speakers are voiced very similarly to begin with. In stereo, it's an entirely different outcome. On well-recorded acoustic music with natural ambiance (and we're not talking breathy young ladies singing way too close to the mic in a multitrack studio recording), the speaker with wider horizontal dispersion has a deeper sound stage and also a taller one, even though it's vertical dispersion is more restricted. . Inevitably, when I switch from the wider horizontal-dispersion design to the narrow, the soundstage gets squished vertically. The effect is very dramatic on good recordings of symphonic and jazz recordings in a natural venue. (On Nora Jones, the speakers will sound equally annoying.) If you happen to be near Rockville MD on Nov 5-7, stop by room 306 at the Capital Audio Fest and I'll demonstrate this for you.

I agree not everyone's experiences match mine but that's why I try to inject some kind of research into the discussion. That's odd that you don't notice a strong difference in mono, for anyone that remembers my blind test of the LS50 and Revel M105, I basically had them at a stalemate in sighted listening in stereo but once I went to mono and blind there were clear differences and my results were unanimous and reached very quickly.

No explanation for hearing a wider soundstage in a vertically limited speaker. The difference was easily noticeable when I did the same comparison and the blind study where the ceiling reflection was absorbed showed a lower envelopment rating among the participants.
I have my own observations, but TBH I don't care if there is ever a comprehensive study on dispersion preferences. Two channel recordings aren't meant to be state of the art. They are a compromise for mass adoption. Surround sound and binaural are the next steps. For those use cases, either dispersion width doesn't matter much or even narrower can be preferred. In the case of surround sound, even the speakers don't matter much.

Agreed, I mentioned that I prefer music in 3 channel stereo to reduce the stereo effect, it sounds artificial to me and not like real music being played. Wide dispersion may be a band aid for stereo but I agree that if we want to get closer to real music being played in a small venue then we're going to need more speakers.
 

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Some of the best research on reflection perception was done by Soren Bech during the Archimedes project with Kef and B&O.

I linked the documents in this post

https://www.audiosciencereview.com/...nd-measurements-audioholics.23519/post-791482

As Dennis writes above the program material is a huge confounding factor in people's preferences across the board. I have tested my own preference in early reflections by either absorbing them broadband or letting them reflect. On some material I can understand the preference for increased source width and spaciousness but my overriding preference is for reduced early reflections and pin point imaging as described above which I find corresponds with my general preference for studio multitrack recordings.
 

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The other study is called: "Influence of first reflections in listening room on subjective listener impression of reproduced sound" This study compared the effects of absorbing various first reflections and comparing the results. Basically, the fewer reflections you absorb the wider the soundstage and envelopment but you lose clarity. Absorbing reflections is similar to them being absent so it's interesting that removing the ceiling reflections lessens image width and envelopment just slightly less than removing sidewall reflections. Here are a few of the key graphs: (Rs is absorption of sidewall, Rf= ceiling)

View attachment 160991
It's very hard to draw any conclusions from an abstract. I believe that it's possible that you might not have represented Rf correctly. Rs may be side wall absorption, Rf both front and ceiling absorption, and Rb back wall absorption, at least for early reflections.

I found a description of the study: "It can be also concluded from the study of Imamura et al. [26], that absorption of the first reflections on the side walls causes "the width of sound image" to be narrower and "Envelopment" to be lower. Absorption of the first reflections on the front wall and ceiling make "the width of sound image" narrower and "Clarity" increase. Absorption of the first reflections on the back wall also makes "the width of sound image" narrower and "Clarity" increase."

Another description (bolded emphasis mine): "Imamura, Marui, Kamekawa, and Nakahara, (2013) recently carried out an experiment to see how this directionality of early reflections within a sound field is perceived by a listener. Using a dummy head, nine impulse responses were taken with various patterns of acoustic treatments using absorptive panels. These were then convolved with three music stimuli. The author notes that the difference of RT was almost equal throughout the patterns and therefore, specifically focused on early reflections. Through headphones, subjects were asked to rate stimuli against each other using evaluative terms on individual listening impressions. Terms used were: timbre brightness, width of sound image, envelopment, clarity, timbre naturalness, reverb suitability and listeners preference. Out of these, width, envelopment and clarity displayed significant differences throughout the nine arrangements. It was concluded that as more first lateral reflection points are covered with absorption, width of sound image will narrow and also envelopment will lower. Vertical panels were not added individually, but simultaneously with front wall absorption thus the influence of early ceiling reflections cannot be solely assessed. However, the author points out that absorption at these points not only decreased sound image width but increase clarity."

I've never listened to music through headphones using convolved impulse responses taken using a dummy head.

Regarding the first study, could you possibly provide any details? "A vertical reflection was electro-acoustically simulated and evaluated through subjective tests using musical stimuli in the context of listening for entertainment."

Young-Ho
 

test1223

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Hello,

interesting discussion. There are many aspects to consider.

One important aspect is the listening distance, position and the room. By adding the directivity of the speaker to the equation you get the important ratio of direct sound to later reflections at the listening position.
You have envelopment and exactness, which are difficult to achieve at the same time, since you need more direct sound for exactness and strong diffuse later reflections for envelopment.

So the perfect speaker is room dependent.
Here are some thoughts about it.

Best
Thomas
 

R Swerdlow

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Ultra Wide Dispersion Speakers

I personally think the research that shows people generally like wide dispersion has been taken too far in some cases and some speakers have prioritized "wide dispersion" at the expense of other qualities in a speaker. The most extreme examples of course are speakers showcasing the RAAL 64-10 ribbon tweeter which have the widest dispersion of any speaker on the market but are also limited vertically due to their geometry. Now I admit I have limited experience with this tweeter because I auditioned them in a smaller room where wide dispersion maybe didn't matter as much but my big takeaways were that they sounded pretty normal regarding spaciousness except it was very obvious they were lacking vertically when switching back to my LS50. The LS50 sounded "bigger" because of it which was pretty surprising considering the 64-10 is known for wide dispersion and the spaciousness that comes with it. This comparison was the 1st moment that I realized that maybe vertical dispersion is more important than conventional wisdom gives it credit for.
The BMR speaker is a 3-way speaker, and the KEF LS50 is a 2-way. By considering only the dispersion of the RAAL 64-10 tweeter of the BMR, you ignored the significant off-axis contribution of the BMR's mid-range driver. I find it difficult to make any useful conclusions in comparing them to the LS50.
 
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aarons915

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It's very hard to draw any conclusions from an abstract. I believe that it's possible that you might not have represented Rf correctly. Rs may be side wall absorption, Rf both front and ceiling absorption, and Rb back wall absorption, at least for early reflections.

I found a description of the study: "It can be also concluded from the study of Imamura et al. [26], that absorption of the first reflections on the side walls causes "the width of sound image" to be narrower and "Envelopment" to be lower. Absorption of the first reflections on the front wall and ceiling make "the width of sound image" narrower and "Clarity" increase. Absorption of the first reflections on the back wall also makes "the width of sound image" narrower and "Clarity" increase."

Another description (bolded emphasis mine): "Imamura, Marui, Kamekawa, and Nakahara, (2013) recently carried out an experiment to see how this directionality of early reflections within a sound field is perceived by a listener. Using a dummy head, nine impulse responses were taken with various patterns of acoustic treatments using absorptive panels. These were then convolved with three music stimuli. The author notes that the difference of RT was almost equal throughout the patterns and therefore, specifically focused on early reflections. Through headphones, subjects were asked to rate stimuli against each other using evaluative terms on individual listening impressions. Terms used were: timbre brightness, width of sound image, envelopment, clarity, timbre naturalness, reverb suitability and listeners preference. Out of these, width, envelopment and clarity displayed significant differences throughout the nine arrangements. It was concluded that as more first lateral reflection points are covered with absorption, width of sound image will narrow and also envelopment will lower. Vertical panels were not added individually, but simultaneously with front wall absorption thus the influence of early ceiling reflections cannot be solely assessed. However, the author points out that absorption at these points not only decreased sound image width but increase clarity."

I've never listened to music through headphones using convolved impulse responses taken using a dummy head.

Regarding the first study, could you possibly provide any details? "A vertical reflection was electro-acoustically simulated and evaluated through subjective tests using musical stimuli in the context of listening for entertainment."

Young-Ho
I don't actually have access to the AES journals anymore so I was really re-posting things I've posted in the past and compiling it all in one thread, I listed the names of the studies for people who want to dig a bit deeper. I didn't recall Rf being both the ceiling and front wall but remember the front wall receives very low amplitude reflections relative to the others so I doubt it has much of an impact on Rf, it would still be nice to see it by itself. Comparing the plots of a bare room and absorbing reflections, it's clear to see that absorbing any reflection increases clarity at the expense of envelopment. Sidewall reflections appear to have the largest single impact but my point was that the vertical reflections still showed the same behavior and can't be ignored.


The BMR speaker is a 3-way speaker, and the KEF LS50 is a 2-way. By considering only the dispersion of the RAAL 64-10 tweeter of the BMR, you ignored the significant off-axis contribution of the BMR's mid-range driver. I find it difficult to make any useful conclusions in comparing them to the LS50.
I didn't listen to the tweeters alone so of course I compared the whole speakers, being a 2 way or 3 way is kind of irrelevant also. The main point that example was showing was that at least from my impressions are that dispersion is about more than just the horizontal direction.


Yes I've seen that before, the narrow mode impressions are definitely interesting.
 

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your goal is to get closer to a live acoustic performance in your room

I see the reasoning for this, but it makes no sense.
- there is ambience in the recording. this totaly kills the idea of hearing an instrument like it is played in your room
- our rooms sound awfull
 

oivavoi

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FWIW, Beolab 90 in narrow mode is better controlled and behaved than in wide mode. It's still good in wide mode, but not like in narrow mode. In narrow mode the directivity is basically identical from all the way down to all the way up. In wide mode it's somewhat more "bloated", with wider directivity in the mids and the lows than in the treble, which means that the reflected sound gets a somewhat different timbral character from the direct sound. Plus some more areas where it's a tiny bit uneven. Wide mode is still good compared to most other loudspeakers, though, whereas omni mode is not good at all.

Showed the directivity graphs in this post from some time back: https://www.audiosciencereview.com/...ectional-loudspeakers.6552/page-3#post-466562

With all the Beolab speakers with variable directivity (90, 50 and 28) I have consistently liked narrow mode the best.
 

youngho

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I don't actually have access to the AES journals anymore so I was really re-posting things I've posted in the past and compiling it all in one thread, I listed the names of the studies for people who want to dig a bit deeper. I didn't recall Rf being both the ceiling and front wall but remember the front wall receives very low amplitude reflections relative to the others so I doubt it has much of an impact on Rf, it would still be nice to see it by itself. Comparing the plots of a bare room and absorbing reflections, it's clear to see that absorbing any reflection increases clarity at the expense of envelopment. Sidewall reflections appear to have the largest single impact but my point was that the vertical reflections still showed the same behavior and can't be ignored.
It looks like this paper was discussed on ASR last year: https://www.audiosciencereview.com/...s/evidence-based-speaker-designs.6441/page-49, also a copy of the paper was linked on that page, as well.
 

dasdoing

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don't know how someone expects to have a good image if when what is supoused to come from the right is copied on the left and vice versa. the nearer wall reflction might be constructive, but the oposite wall reflection is terribly desctructive
 
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