What makes speakers "disappear " and can it be measured?

[Kal Rubinson]

Sean Olive pointed out to me that it’s rare people only ever listen to multichannel. So while my approach to designing more dead multichannel rooms to avoid distractions from the small room might work well for surround, it would be a lousy room for two channel. Since the more appropriately treated room retaining some meaningful reflections will largely be ignored with multichannel, it makes more sense to design all rooms to retain some amount of reflections.

For a long time, that's been my recommendation to people who express concern about having good stereo and multichannel reproduction in the same room.

 

[Duke]

I had talked to Floyd about this and at one time advocated for making multichannel dedicated spaces very dead. Floyd pointed out that our brain is very adaptable to environments. In this case, when the brain is faced with cues from both a large and small acoustical space, he noted the brain tends to ignore the cues of the smaller space. Meaning when we get signals from the walls (small room cues) and signals from the speakers (meaning large room cues) our brain will tune out those room reflections and presume it is in the larger space. A great trick for not really requiring a dead room. [emphasis Duke's]

The "competition" between the "small room signature" of the playback room and the "venue acoustic signature" on the recording (assuming a good one) is a topic which interests me a great deal. We might call a good presentation wherein the playback room dominates the feeling of space a "they are here" presentation, and a good presentation wherein the venue acoustics on the recording dominate a "you are there" presentation.

Contrary what seems (to me) to be implied by the quoted bolded section above, I find "you are there" presentations to be more elusive than "they are here" presentations. In other words, it seems to me that, in the presence of both direct and reflected sound from the speakers, it's more common for the small room signature to dominate. Am I missing something?

Matt and @Floyd Toole , in the context of two-channel (in "normal-sized" home audio rooms), I have a couple of questions:

Do early versus late reflections make differing contributions to the feeling of space (aside from the increase in apparent source width from early same-side-wall reflections)? I think so, but would like to hear from either of you.

And if so, should either be deliberately encouraged (or suppressed) moreso than the other?

 

[BenB]

The "competition" between the "small room signature" of the playback room and the "venue acoustic signature" on the recording (assuming a good one) is a topic which interests me a great deal.

...

Do early versus late reflections make differing contributions to the feeling of space? I think so, but would like to hear from either you.

And if so, should either be deliberately encouraged (or suppressed) moreso than the other?

Good questions Duke. I anticipate that it might be time to make an important distinction between two different levels of audio foolery that I'll refer to as "understood" and "convinced". (These labels probably need some work.)

For me, the most obvious demonstration of these 2 concepts comes when listening to binaural recordings. Those recordings don't actually work for me. I suppose my auditory system is too different from the median, or something like that. At any rate, when I listen to these recordings, I can often come to an "understanding" of what it is they are trying to get me to perceive. I hear how the high frequencies get filtered, and I know they want me to perceive some sound as coming from behind me. However, they have failed to actually "convince" my senses that something is really coming from behind me.

Everything I've read would indicate that the earlier, authentic reflections of the small playback room would override the inauthentic, later reflections provided by a few speakers. Of course, I'm always happy for additional reading on the subject.

I have never found any of the surround-sound acoustic emulators to be convincing. I may "understand" that they are trying to make my space sound like a different space, but I don't find the illusion convincing. Admittedly, I haven't heard every single version of surround upmixing, etc. What I've heard has been poor enough that I have become skeptical, and don't anticipate ever finding them to be convincing. I prefer stereo to unconvincing surround sound.

When someone proclaims that "It was like being at the recording venue" I have to wonder if they mean they understood the desired deception, or if they were actually convinced.

 

[rdenney]

I think it’s reasonable to expect a willing suspension of disbelief. I know I’m not at Powell Hall, even with my eyes closed. But I can transcend that awareness because I have experiences at places like Powell Hall from which I can draw.

But the recording I mentioned (another thread? I’m losing track—a CD of Gene Pokorny playing a Bach flute sonata on a tuba, unaccompanied, on the stage at Powell Hall). That recording didn’t include the room effects of Powell with the objective of transporting me there. It included them because tubas need room effects to sound like their orchestral performers want them to sound (the art, as Dr. Toole would say), and they knew they weren’t going to get those effects in my living room. And they preferred the real reverb of that hall to digital effects reverb they would have to add if he recorded it in a dead studio. I am a tuba player and I can fill in those blanks, as I would if Gene was actually playing here in my home, but not everyone can.

Rick “capable of playing along with the illusion” Denney

 

[Thomas_A]

im using your post to make a point, these comments are to agree with what you say.

An anechoic listening room has no spatial reinforcement. all spatial cues would have to come from the speakers. 2-channel playback is fundamentally missing those cues and could not possibly present the spatial environment of the original musical event. That may be useful in applying a microscope to the music for editing purposes but is not a useful way to listen to music.

such environments could be good for surround sound. A surround system can reproduce spatial cues far more accurately than the room can mimic it. Stereo reproduction with 2 speakers is just an illusion of the real thing and not a very good one.

I had talked to Floyd about this and at one time advocated for making multichannel dedicated spaces very dead. Floyd pointed out that our brain is very adaptable to environments. In this case, when the brain is faced with cues from both a large and small acoustical space, he noted the brain tends to ignore the cues of the smaller space. Meaning when we get signals from the walls (small room cues) and signals from the speakers (meaning large room cues) our brain will tune out those room reflections and presume it is in the larger space. A great trick for not really requiring a dead room.

Sean Olive pointed out to me that it’s rare people only ever listen to multichannel. So while my approach to designing more dead multichannel rooms to avoid distractions from the small room might work well for surround, it would be a lousy room for two channel. Since the more appropriately treated room retaining some meaningful reflections will largely be ignored with multichannel, it makes more sense to design all rooms to retain some amount of reflections.

which is all to say, in average rooms it often makes sense to just leave them alone. Good speakers make a far bigger improvement than the room itself ever will. Absorbing all the reflections is counter-productive. It destroys the sense of spaciousness.

that doesn’t mean treatments have no place. Dedicated rooms are, for example, anything but average spaces. They have no natural sources of diffusion or absorption. You need to add it. In the last year alone I have been asked to make residential rooms sound good which had RT60 times from 2-3 seconds. These were fully furnished rooms. My first fix was to ensure they had good speakers. The second fix was really just about getting the decay time down to something reasonable and so absorption was added. But not at first reflection points. I wasn’t trying to remove reflections. I was simply trying to help the sound decay faster to avoid the overwhelming reverberant sound. In most of these rooms I add diffusion. It has some real advantages when used correctly and when you have nothing else in the room to break of reflections, you have to add it.

Much agreed. In my experience, putting panels 10 cm glass fiber covered with perforated masonry, and 6 cm acoustic foam on the wall directly behind the main speakers (speakers placed as close as possible) about 1-1,2 m wide and from floor to roof, but leaving the area between the speakers reflective, "transforms" the dynamics, IMO, and increases detail. It was like a window opening to the event when I heard it the first time. For the rest of the room, damping more than normal furniture has not worked any better, just worse.

Just one more added note regarding two-three channel audio vs surround. This is a choice whether you want to be transferred to the event or if you and your room is transferred to the event, the room acting as a lounge. A preference of model.

 

[Frgirard]

An anechoic listening room has no spatial reinforcement. all spatial cues would have to come from the speakers. 2-channel playback is fundamentally missing those cues and could not possibly present the spatial environment of the original musical event. That may be useful in applying a microscope to the music for editing purposes but is not a useful way to listen to music.

it's false regarding the Non environmental design as praticed by Northward Acoustics and of course with my room.

Much agreed. In my experience, putting panels 10 cm glass fiber covered with perforated masonry, and 6 cm acoustic foam on the wall directly behind the main speakers (speakers placed as close as possible) about 1-1,2 m wide and from floor to roof, but leaving the area between the speakers reflective, "transforms" the dynamics, IMO, and increases detail. It was like a window opening to the event when I heard it the first time. For the rest of the room, damping more than normal furniture has not worked any better, just worse.

The thickness minimum is 8" with the good gas flow resistance 8000-6000 rayles. Other is a bad diy. No works, no study, no knowledge is no gain.

 

[Thomas_A]

it's false regarding the Non environmental design as praticed by Northward Acoustics and of course with my room.



The thickness minimum is 8" with the good gas flow resistance 8000-6000 rayles. Other is a bad diy. No works, no study, no knowledge is no gain.

BBC has done a lot of publishing including covering with perforated hardboard:

http://downloads.bbc.co.uk/rd/pubs/reports/1992-11.pdf
Edit: there are a lot of cmmercial ones as well, e.g.
https://www.decustik.com/en/perforated-acoustic-panels

 

[Frgirard]

BBC has done a lot of publishing including covering with perforated hardboard:

http://downloads.bbc.co.uk/rd/pubs/reports/1992-11.pdf
Edit: there are a lot of cmmercial ones as well, e.g.
https://www.decustik.com/en/perforated-acoustic-panels

beautiful

https://www.amazon.fr/Acoustic-Absorbers-Diffusers-Theory-Application/dp/0415471745

 

[Matthew J Poes]

it's false regarding the Non environmental design as praticed by Northward Acoustics and of course with my room.



The thickness minimum is 8" with the good gas flow resistance 8000-6000 rayles. Other is a bad diy. No works, no study, no knowledge is no gain.

I have seen very few measurements from non-environment rooms. I don’t want to draw conclusions from my limited experience with them. The design, as I understand it, makes little sense to me as a listening room. I would love to see your ETC measurement to see if there is evidence that the room is preserving the reflections necessary to produce as sense of envelopment. My hunch is no and the few rooms I have experienced did not. They produced an anechoic path of direct sound and then attenuated all 2nd order and higher reflections so extensively that the room would have been effectively anechoic at mid and high frequencies.

I think the idea was based on some good assumptions, but the few I saw in practice were too small to work. One of the principles is that there is a large gap between the initial direct sound from the speaker and the first reflection. For that to be true the room must not produce any very early reflections at or around the speaker. Those lateral first reflections are typically redirected behind the listener and then diffused and absorbed. At the mic position you effectively see an anechoic path for the first 20ms and then what might look like relatively diffuses sound. In practice it usually has no meaningful reflections at all. The proceeds of redirecting, diffusing, and absorbing in a moderately small space leaves the room dead.

there is also a fundamental problem with this approach in my view. The direction of the reflections matters to our perception of space. Reflections from the front, back, floor, and ceiling provide a largely monophonic signal. They don’t support our sense of apparent source width and are only a part of our sense of envelopment. Lateral reflections are key to that. Lateral reflections need to be relatively strong, not intensely mitigated, to give that widening of the source effect and greater sense of envelopment.

a more sensible way to make a room sound bigger than it is would be to simply use a multichannel setup. In the absence of that possibility, diffusing lateral reflections can create greater phase randomization of the cues which better mimics how a larger room would be perceived and gives a similar sense, but is an imperfect solution itself.

in my opinion, the non-environment room isn’t one that makes a lot of sense and ultimately misses the forest for the trees.

 

[Frgirard]

I have seen very few measurements from non-environment rooms. I don’t want to draw conclusions from my limited experience with them. The design, as I understand it, makes little sense to me as a listening room. I would love to see your ETC measurement to see if there is evidence that the room is preserving the reflections necessary to produce as sense of envelopment. My hunch is no and the few rooms I have experienced did not. They produced an anechoic path of direct sound and then attenuated all 2nd order and higher reflections so extensively that the room would have been effectively anechoic at mid and high frequencies.

I think the idea was based on some good assumptions, but the few I saw in practice were too small to work. One of the principles is that there is a large gap between the initial direct sound from the speaker and the first reflection. For that to be true the room must not produce any very early reflections at or around the speaker. Those lateral first reflections are typically redirected behind the listener and then diffused and absorbed. At the mic position you effectively see an anechoic path for the first 20ms and then what might look like relatively diffuses sound. In practice it usually has no meaningful reflections at all. The proceeds of redirecting, diffusing, and absorbing in a moderately small space leaves the room dead.

there is also a fundamental problem with this approach in my view. The direction of the reflections matters to our perception of space. Reflections from the front, back, floor, and ceiling provide a largely monophonic signal. They don’t support our sense of apparent source width and are only a part of our sense of envelopment. Lateral reflections are key to that. Lateral reflections need to be relatively strong, not intensely mitigated, to give that widening of the source effect and greater sense of envelopment.

a more sensible way to make a room sound bigger than it is would be to simply use a multichannel setup. In the absence of that possibility, diffusing lateral reflections can create greater phase randomization of the cues which better mimics how a larger room would be perceived and gives a similar sense, but is an imperfect solution itself.

in my opinion, the non-environment room isn’t one that makes a lot of sense and ultimately misses the forest for the trees.

My room is not a NE room. I have un edt at 0,27 and limite my reflection hunting under - 15 dB.
You forgot when you need to create a stereo image on a recording, you don't need the room plays.
You forgot the differential time arrival to the ears is an important part to the illusion of the stereo picture.
For the opinion, i prefer trust in professionals who works and design NE room.

 

[Kal Rubinson]

Contrary what seems (to me) to be implied by the quoted bolded section above, I find "you are there" presentations to be more elusive than "they are here" presentations. In other words, it seems to me that, in the presence of both direct and reflected sound from the speakers, it's more common for the small room signature to dominate. Am I missing something?

Probably more than 2 channels.

I have never found any of the surround-sound acoustic emulators to be convincing. ........................................... I prefer stereo to unconvincing surround sound.

Agreed. An ad hoc (as opposed to one created from original mic feeds) synthetic simulation has a hard time competing with the local acoustics.

Just one more added note regarding two-three channel audio vs surround. This is a choice whether you want to be transferred to the event or if you and your room is transferred to the event, the room acting as a lounge. A preference of model.

Perhaps but not always. The 3 channel Living Stereo SACDs are a big step from the stereo to a more embracing "you are there."

 

[Thomas_A]

Perhaps but not always. The 3 channel Living Stereo SACDs are a big step from the stereo to a more embracing "you are there."

Have not heard it, unfortunately. There are probably other system-solutions like the Bremen system with a center an two front-side speakers. Point is that it is a fine line between me being there, me and and my room being there, or they being here.

 

[Kal Rubinson]

I have no idea what the "Bremen system" is but I was referring to recordings made with 3 channels from 3 discrete mic feeds. I requires no more than three channel playback and no additional processing.

 

[Thomas_A]

I have no idea what the "Bremen system" is but I was referring to recordings made with 3 channels from 3 discrete mic feeds. I requires no more than three channel playback and no additional processing.

I understand. i was referring to that three-channel gives only frontal direction of sound, being pure three-channel recordings, or processed. So your room is still there around you. Full monty with speakers all around you gives ambient information from other angles than front. The Bremen system is some kind of in between, a center speaker and speakers on the sidewalls.

 

[Frgirard]

I understand. i was referring to that three-channel gives only frontal direction of sound, being pure three-channel recordings, or processed. So your room is still there around you. Full monty with speakers all around you gives ambient information from other angles than front. The Bremen system is some kind of in between, a center speaker and speakers on the sidewalls.

Have you a link about you called Bremen system.
I don't find on the net.
Thanks

 

[Thomas_A]

Have you a link about you called Bremen system.
I don't find on the net.
Thanks

There is not much info since it is still under development. It has been demonstrated a few times on shows. Basically it can be used as a two-channel system or a three-channel system with a processor. I have not heard it, but those who have says it is quite remarkable.

http://www.bremen.se

 

[Kal Rubinson]

I understand. i was referring to that three-channel gives only frontal direction of sound, being pure three-channel recordings, or processed. So your room is still there around you. Full monty with speakers all around you gives ambient information from other angles than front.

Understood but the difference between 2-channel stereo and 3-channel is in the expansion of the width of the soundstage despite the lack of surround information.

 

[JWAmerica]

I'm a big fan of music upmixed to 3ch, but not 5ch (or more). 5ch sounds okay for orchestras, but for regular band recordings I can't get used to it, even when it's mastered in multichannel. The band is always playing in front of you, even when you're in the front row at a stadium concert. I don't know why I'd want to hear the bass guitar coming from the side speaker. Maybe for karaoke...

 

[Thomas_A]

I have no idea what the "Bremen system" is but I was referring to recordings made with 3 channels from 3 discrete mic feeds. I requires no more than three channel playback and no additional processing.

i understand. i was refereing to

I'm a big fan of music upmixed to 3ch, but not 5ch (or more). 5ch sounds okay for orchestras, but for regular band recordings I can't get used to it, even when it's mastered in multichannel. The band is always playing in front of you, even when you're in the front row at a stadium concert. I don't know why I'd want to hear the bass guitar coming from the side speaker. Maybe for karaoke...

Side channels should only try to extract side and back room ambience, but it does not always work so good. Reflections are from all over the place around the event.

 

[JWAmerica]

The only enjoyable multichannel music recordings I've liked have used the crowd noise and reflections/reverb from the venue for the side channels. All music came from the front three.