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Perceptual Effects of Room Reflections

patate91

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...Same impression here, even though it was not originally intended, when installing absorbers and diffusors...but just to get rid of this "harshness"...

Sure a lot of people like headphones : no reflections, clarity, details. Same thing goes for critical listening session and ABX test, it's easier with headphones.

Like I said earlier no one complains that there headphones are too dead or dull.
 

eliash

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Sure a lot of people like headphones : no reflections, clarity, details. Same thing goes for critical listening session and ABX test, it's easier with headphones.

Like I said earlier no one complains that there headphones are too dead or dull.

It also depends if a recording brings some intended ambience with it, or is made from artifically positioned instruments and effects. In the latter case, with some additional ambient sound or envelopment from listening room reflections may improve personal experience certainly...
 

patate91

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It also depends if a recording brings some intended ambience with it, or is made from artifically positioned instruments and effects. In the latter case, with some additional ambient sound or envelopment from listening room reflections may improve personal experience certainly...

I'm not an expert but I'm almost sure that instruments are always artifically positioned.

Samething goes for ambience it's created during the mixing.
 

Kal Rubinson

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I'm not an expert but I'm almost sure that instruments are always artifically positioned.

Samething goes for ambience it's created during the mixing.
That is unfortunate but it really depends on what recordings you are listening to.
 

Duke

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If there is one thing I learned in this forum it is that people can actually enjoy room reflections... for a single source I actually prefer the reflections. The treated room requires a stereo triangle

Very interesting. This might be related to why, when Harman evaluated the Quad electrostatic in mono, its score was terrible: Not enough reflections for the narrow-pattern Quad to be enjoyable. Then when they evaluated it in stereo its score improved significantly, BUT it still ranked third out of the three which were being compared. Toole draws the conclusion that the ranking is not changed by stereo listening but is more differentiated in mono listening, therefore mono listening is preferred for evaluation purposes. And in general I agree... BUT one can also draw the conclusion that mono listening penalizes some types of loudspeakers, as evidenced by the significant (though not decisive) rise in the Quad's score when auditioned in stereo.

My remaining question would be, at what point too much room reflections (the ones recorded in the studio plus the ones added at home) become annoying, in a way as we discussed above?

In my opinion, in a home audio listening room there is, in effect, a COMPETITION between two sets of spatial cues:

1) The (highly desirable) spatial cues on the recording, whether they be real or engineered or both; and

2) The (generally undesirable) cues inherent to our relatively small, inadequate playback rooms.

At the risk of oversimplifying, the ear will select whichever set of cues seems most plausible. Unfortunately this tends to be the "small room signature" of our playback rooms. What we'd like to do is, have the spatial cues on the recording dominate. This is easier said than done, because we only have a poverty of recording venue cues, relative to our playback room's inherent small-room-signature cues. [I can hear Kal Rubinson saying, "There's a fix for that, ya know..."]

Simply absorbing or otherwise nullifying all reflections in the playback room doesn't work. In order to most effectively convey a sense of immersion in the acoustic space on the recording, we need to have high quality (spectrally correct) reflections arriving from many directions. The multi-channel guys got THAT right!! So if we're doing two-channel, then we NEED a lot of spectrally-correct in-room reflections in order to effectively present the recording venue cues from many directions.

But it's not quite that simple. We need to MINIMIZE the "small room signature" conveyed by playback room, without simultaneously minimizing all those desirable spatial cues on the recording. Remember, we want the recording venue cues to dominate so we can enjoy that delicious sense of envelopment, assuming a suitable recording.

My understanding is that the EARLIEST reflections play a disproportionately large role in conveying the size of a room. The reverberation tail also plays a role. We want a fairly long (but not too long) reverberation tail because it conveys ambience cues from the recording, so we need to focus on minimizing the early reflections while encouraging the later ones. Done correctly, this results in the spatial cues which are on the recording dominating over the otherwise default "small room signature" cues. This is something good multichannel does very well... better than we can do with two-channel, but imo we can still make worthwhile improvements.

(One source I came across, and unfortunately did not record, stated that the ear looks at the time gap in between the first-arrival sound and the "center of gravity" of the reflections to judge the size of the room. To the extent that we can push that "center of gravity" back in time, we can reduce "small room signature", and unmask the spatial cues in the recording. I find this paradigm to be particularly useful, just wish I could remember where it came from.)

One way we can do this in a two-channel system is to set up along a room diagonal. This geometrically precludes early lateral reflections in the listening area, without reliance on absorption. Floyd Toole used this technique in one of his listening rooms in a house he used to live in. There are other techniques of course; the main point is to be aware of the general principle of avoiding early reflections, while encouraging later ones.

In this context, I consider "early reflections" to be those arriving less than about 10 milliseconds behind the first-arrival sound, and Geddes is my source for this number. Linkwitz suggested 6 milliseconds. There is an EBU standard which mentions 15 milliseconds, which was taken into consideration when Harman designed their speaker-shuffling Multichannel Listening Lab. So there is arguably some uncertainty about exactly where the target lies, but I think the general concept is valid.

Note that the playback room does not need to have a 100+ millisecond decay time in order to convey the sense of envelopment that we might get in a concert hall, as long as that 100+ milliseconds of decay is on the recording. The playback room is the DELIVERY SYSTEM for that 100+ milliseconds of decay, we just need to get the playback room's own signature out of the way as much as we reasonably can.
 
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patate91

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That is unfortunate but it really depends on what recordings you are listening to.

I know there's some ****** mixes out there, like Red hot chili peppers albums, they sound good in the car and horrible on my system.
 
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tuga

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I know there's some ****** mixes out there, like Red hot chili peppers albums, they sound good in the car and horrible on my system.

Studio mixes hardly ever have any room sound as they're close-mic'ed, mostly in mono, pan-potted into position and then effects like reverb etc. are added.

A minimally-mic'ed classical music recording on the other hand...
 

JoachimStrobel

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We have but, since you inserted a relevant comment, I felt it appropriate to add mine.

That is not relevant to me since I have no interest or serious experience in the matter. In the little experience I have had with it (Avatar), I found it technically flawed. OTOH, logically, I would say that there is a likely parallel between the senses in this regard. However, the mass market seems already to have dismissed 3D video.

Agreed.
I'll let you know if and when I find out. :)
I find 3d great and I own one 3d Mch Blu-ray. 3D needs a bright projector and a screen and you need to keep your head upright - tough requirements. It is an too early technology for a not-ready client base. 4K is easy, just add a new TV. It hence dies as Quadrophonie did because of similar reasons. And yes, I would say 3d and Mch go together for an 1-2 hour experience without doing anything else.
 

JoachimStrobel

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Studio mixes hardly ever have any room sound as they're close-mic'ed, mostly in mono, pan-potted into position and then effects like reverb etc. are added.

A minimally-mic'ed classical music recording on the other hand...

Yes, but studio mixes can create a unique Mch experience by whirling instruments to all speakers and hence enabling complex musical scenes to be deciphered.That would not make sense for classical, it has been written for a concert body. Having the Violine and the piano occupying different speakers adds little musical understanding.
 

eliash

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Very interesting. This might be related to why, when Harman evaluated the Quad electrostatic in mono, its score was terrible: Not enough reflections for the narrow-pattern Quad to be enjoyable. Then when they evaluated it in stereo its score improved significantly, BUT it still ranked third out of the three which were being compared. Toole draws the conclusion that the ranking is not changed by stereo listening but is more differentiated in mono listening, therefore mono listening is preferred for evaluation purposes. And in general I agree... BUT one can also draw the conclusion that mono listening penalizes some types of loudspeakers, as evidenced by the significant (though not decisive) rise in the Quad's score when auditioned in stereo.



In my opinion, in a home audio listening room there is, in effect, a COMPETITION between two sets of spatial cues:

1) The (highly desirable) spatial cues on the recording, whether they be real or engineered or both; and

2) The (generally undesirable) cues inherent to our relatively small, inadequate playback rooms.

At the risk of oversimplifying, the ear will select whichever set of cues seems most plausible. Unfortunately this tends to be the "small room signature" of our playback rooms. What we'd like to do is, have the spatial cues on the recording dominate. This is easier said than done, because we only have a poverty of recording venue cues, relative to our playback room's inherent small-room-signature cues. [I can hear Kal Rubinson saying, "There's a fix for that, ya know..."]

Simply absorbing or otherwise nullifying all reflections in the playback room doesn't work. In order to most effectively convey a sense of immersion in the acoustic space on the recording, we need to have high quality (spectrally correct) reflections arriving from many directions. The multi-channel guys got THAT right!! So if we're doing two-channel, then we NEED a lot of spectrally-correct in-room reflections in order to effectively present the recording venue cues from many directions.

But it's not quite that simple. We need to MINIMIZE the "small room signature" conveyed by playback room, without simultaneously minimizing all those desirable spatial cues on the recording. Remember, we want the recording venue cues to dominate so we can enjoy that delicious sense of envelopment, assuming a suitable recording.

My understanding is that the EARLIEST reflections play a disproportionately large role in conveying the size of a room. The reverberation tail also plays a role. We want a fairly long (but not too long) reverberation tail because it conveys ambience cues from the recording, so we need to focus on minimizing the early reflections while encouraging the later ones. Done correctly, this results in the spatial cues which are on the recording dominating over the otherwise default "small room signature" cues. This is something good multichannel does very well... better than we can do with two-channel, but imo we can still make worthwhile improvements.

(One source I came across, and unfortunately did not record, stated that the ear looks at the time gap in between the first-arrival sound and the "center of gravity" of the reflections to judge the size of the room. To the extent that we can push that "center of gravity" back in time, we can reduce "small room signature", and unmask the spatial cues in the recording. I find this paradigm to be particularly useful, just wish I could remember where it came from.)

One way we can do this in a two-channel system is to set up along a room diagonal. This geometrically precludes early lateral reflections in the listening area, without reliance on absorption. Floyd Toole used this technique in one of his listening rooms in a house he used to live in. There are other techniques of course; the main point is to be aware of the general principle of avoiding early reflections, while encouraging later ones.

In this context, I consider "early reflections" to be those arriving less than about 10 milliseconds behind the first-arrival sound, and Geddes is my source for this number. Linkwitz suggested 6 milliseconds. There is an EBU standard which mentions 15 milliseconds, which was taken into consideration when Harman designed their speaker-shuffling Multichannel Listening Lab. So there is arguably some uncertainty about exactly where the target lies, but I think the general concept is valid.

Note that the playback room does not need to have a 100+ millisecond decay time in order to convey the sense of envelopment that we might get in a concert hall, as long as that 100+ milliseconds of decay is on the recording. The playback room is the DELIVERY SYSTEM for that 100+ milliseconds of decay, we just need to get the playback room's own signature out of the way as much as we reasonably can.

Indeed, very interesting discussion here, really appreciate it!

Looking at the additional acoustical wave travel distances from the mentioned delay times (15ms ~ 5m; 10ms ~ 3.5m; 6ms ~ 2m ) one may derive 2 typical classes (assuming a typical rectangular listening room with speakers close to the sidewalls):
- adjacent wall reflection diversion (6ms ~ 2m)
and
- opposite wall reflection diversion (10-15ms ~ 3.5-5m)

My personal impression regarding harshness perception is that the short diversion, adjacent reflections contribute most to that effect, opposite wall reflection more to imprecise stereo base resolution.
 
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dasdoing

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Indeed, very interesting discussion here, really appreciate it!

Looking at the additional acoustical wave travel distances from the mentioned delay times (15ms ~ 5m; 10ms ~ 3.5m; 6ms ~ 2m ) one may derive 2 typical classes (assuming a typical rectangular listening room with speakers close to the sidewalls):
- adjacent wall reflection diversion (6ms ~ 2m)
and
- opposite wall reflection diversion (10-15ms ~ 3.5-5m)

My personal impression regarding harshness perception is that the short diversion, adjacent reflections contribute most to that effect, opposite wall reflection more to imprecise stereo base resolution.

yep, the main problem is the oposite wall reflection. you could treat only that one with a absorber wall in the middle of front part of the room lol
 

fredoamigo

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One way we can do this in a two-channel system is to set up along a room diagonal. This geometrically precludes early lateral reflections in the listening area, without reliance on absorption. Floyd Toole used this technique in one of his listening rooms in a house he used to live in. There are other techniques of course; the main point is to be aware of the general principle of avoiding early reflections, while encouraging later ones.
I use the diagonal (in the lengthwise direction of the workpiece) placement mode at home, it is with this method that I obtain the best result for ASW .
https://www.audioasylum.com/scripts/d.pl?audio/faq/audiophysic.html
 
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Igor Kirkwood

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I've noticed that the speakers are not toe'ed in.
Pehaps it's not very important because that Harman room is for monophonic listening ?

I use the diagonal (in the lengthwise direction of the workpiece) placement mode at home, it is with this method that I obtain the best result for ASW .

I use near diagonal loudspeakers position ( 1 meter behind diagonal) . My listening room is 6 meters large ( Harman's room 6,58 meter)
 
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Kal Rubinson

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I find 3d great and I own one 3d Mch Blu-ray. 3D needs a bright projector and a screen and you need to keep your head upright - tough requirements.
It also needs someone who cares. I am not really interested in video.
 

Plcamp

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Using Open Baffles, I have followed a ‘rule’ * that reflections are not perceived as problematic to the human brain if...

1 The reflections have full spectral content of the primary wave, and
2 The reflections are delayed by at least 6 ms.

This requires they be 1m from back wall, I found 140 cm best.

I have also talked to folks that swear diffraction panels behind their open baffles make immediate improvement because they help fulfill both criteria.

* from Linkwitz site as I recall.
 

JoachimStrobel

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It also needs someone who cares. I am not really interested in video.
... not even a concert? I find that seeing instruments and musicians beats everything. Seeing that Diana Krall sings while playing piano lets me value here singing more. I love to see musicians while playing.
 

Kal Rubinson

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... not even a concert? I find that seeing instruments and musicians beats everything. Seeing that Diana Krall sings while playing piano lets me value here singing more. I love to see musicians while playing.
Only once. I have hundreds of music/concert BDs but, after one play, I prefer to ignore the video or just play the ripped audio from my server.
 

tuga

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Igor Kirkwood

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In listening room generaly loudspeakersstrereo or multichanel toe'ed in.

If Harman room cannot do that it's not very good ?
 
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