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The info comes from the speakers - not reflections - right?


Please help me understand - I'm not being argumentive, but I can't wrap my head around the idea that we want some absorption but not too much (as seems to be conventional wisdom) in a stereo or surround playback environment.


The way I understand stereo speaker playback is as follows (please correct me if I have something wrong in my understanding):


The speakers reproduce as closely as possible what two stereo microphones recorded (or surround mics in the case of a surround recording). If the recording was in a cathedral there would be reverb and echo ALREADY IN THE RECORDING, and that is what I would want to hear. If you recorded someone speaking in an anechoic chamber, the recording would sound dead.


Either way - the information I want to hear is contained within the recording. Right? Any additional information reaching my ears from room reflections (whether direct reflections or diffusion) is not contained in the original recording.


So why would I want to hear it?


And thus, it seems to me, that the goal should be to make a theater room as dead as possible. Because all the information I want to hear is in the surround speakers and the sub.


The goal, I would think, would be to create an environment as close as possible to you, sitting in an atmosphere with no walls ceiling or floor of any kind, so that sound waves which don't hit your ears simply travel on away from you.


To be clear, I can see why one would not want to make a recording environment too dead. Because then you'd have a dead sounding recording.


But in a playback environment the "liveness" should come from whatever the speakers produce. Right?


This seems analogous to how we want to see, visually, what the director intended, and no more. So to the extent we can, we darken our theaters, with many people feeling that the ideal is the "bat cave."
 

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Oh its certainly possible to have too much absorption. Sadly most home theaters that I see are way to dead.

All your high frequency energy gets absorbed.

Leaving you with a room that is dead and lifeless with no snap and booming bass.

It also will take an inordinate amount of additional energy from your speakers/amps to achieve a reasonable SPL.

In real life we hear a ton of reflected sound as well as direct sound.

In fact this is how we take our auditory cues about texture, space, distance, direction etc.

If you have ever been in an anechoic chamber that has no reflected sound its very disconcerting and disorienting-you want to get of the space as fast as you can.


I'll see if I can find some links that go into more detail.


.
 

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Quote:
Originally Posted by chrisreeves  /t/1523161/how-is-too-much-absorption-of-sound-in-a-theater-room-possible#post_24499409


The info comes from the speakers - not reflections - right?


Please help me understand - I'm not being argumentive, but I can't wrap my head around the idea that we want some absorption but not too much (as seems to be conventional wisdom) in a stereo or surround playback environment.


The way I understand stereo speaker playback is as follows (please correct me if I have something wrong in my understanding):


The speakers reproduce as closely as possible what two stereo microphones recorded (or surround mics in the case of a surround recording). If the recording was in a cathedral there would be reverb and echo ALREADY IN THE RECORDING, and that is what I would want to hear. If you recorded someone speaking in an anechoic chamber, the recording would sound dead.


Either way - the information I want to hear is contained within the recording. Right? Any additional information reaching my ears from room reflections (whether direct reflections or diffusion) is not contained in the original recording.


So why would I want to hear it?


And thus, it seems to me, that the goal should be to make a theater room as dead as possible. Because all the information I want to hear is in the surround speakers and the sub.


The goal, I would think, would be to create an environment as close as possible to you, sitting in an atmosphere with no walls ceiling or floor of any kind, so that sound waves which don't hit your ears simply travel on away from you.


To be clear, I can see why one would not want to make a recording environment too dead. Because then you'd have a dead sounding recording.


But in a playback environment the "aliveness" should come from whatever the speakers produce. Right?


This seems analogous to how we want to see, visually, what the director intended, and no more. So to the extent we can, we darken our theaters, with many people feeling that the ideal is the "bat cave."

If the above hypothesis were entirely correct then the ideal listening room would always be an anechoic chamber. Been there done that and so have many others and the vote is in: FAIL!


My experience is that a good sounding room that allows you to hear into a recording well combines absorption, reflection, and diffusion in balanced amounts. Every real world room is sufficiently unique all by itself that the precise proportioning and locations of those elements varies. Loudspeaker differences, personal preference and practical exigencies further the need for a unique approach for every room. I can't overemphasize the benefits of diffusive elements, for example.
 

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An anechoic chamber reproduces only the source material with nothing added by the room. Reflections in the room add to the sense of "space" in the sound and most people find that pleasing. The catch is to not significantly alter the sound the producer intended, but of course in general there is no way to know that. My room is very dead and I prefer it that way; I have large panel speakers in a 7.1 system and the sound is quite enveloping without the room intruding. It's a smallish room so I am fairly close to the speakers (about 8'). Different speakers, different room, and a different arrangement might not sound as nice.


In the past I have preferred larger rooms and some reflective content, though as Arny mentions I much prefer diffusion to absorption. The catch is diffusors tend to be more expensive, and a mix of both generally provides the smoothest frequency response IME. Someplace between the anechoic chamber and the batcave is probably best, but the choice is user-dependent. Again in the past, different rooms (but similar components), I found the amount of room response I liked depended upon the source, both the mix and the type of music. A big orchestra filling the room sounded pretty good; a small jazz trio (recorded with a single pair on a small club stage), not so much.


Most folk find the extremes sound bad, whether a totally dead media room or an echo chamber. Ideally I'd love to be able to program the amount of reverberation, reflection, diffusion, etc. but the rooms I have seen that have that flexibility run toward commercial concert halls with systems well beyond what I can afford. At one time I built absorbers with simple window blinds that allowed the user to play with adding reflections; it was somewhat successful. I modified the slats to provide a bit on non-regularity (randomness) to the reflections. Not a real diffusor, but better than just regular slats.


FWIWFM - Don


Edit: After all is said and done I realized I pretty much echoed Arny's response. Also, one thing I have seen only rarely are systems that use a multitude of speakers to recreate a sound field. I have heard some research systems using that approach (tens to hundreds of speakers) and it can work well in an anechoic chamber, you'd never know the room is "dead", but is not practical for most of us. That said, my Maggie 7.2'ish system gets pretty close. The room is dead, but listeners don't realize it.
 

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Quote:
Originally Posted by chrisreeves  /t/1523161/how-is-too-much-absorption-of-sound-in-a-theater-room-possible#post_24499409


The info comes from the speakers - not reflections - right?

I'm with Don, deader is mostly better. You are correct that all the desired ambience is already present within the recording, so adding more - especially lousy sounding "small room" ambience - can only detract from the sound. People wrongly claim that reflections from the listening room are needed to add space and depth. But if that were true, listening through headphones would sound small. I think we can all agree that headphones usually sound larger than speakers! Now, you don't need to make a room totally anechoic. What matters most is killing all of the early reflections. That, and taming the inevitable peaks and nulls and ringing at bass frequencies. More here:

Early Reflections


This short article is mainly about home recording, but all the same principles apply to hi-fi and home theater acoustics too:

Acoustic Basics


--Ethan
 

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Quote:
Originally Posted by Ethan Winer  /t/1523161/how-is-too-much-absorption-of-sound-in-a-theater-room-possible/0_50#post_24503969


I'm with Don, deader is mostly better. You are correct that all the desired ambience is already present within the recording, so adding more - especially lousy sounding "small room" ambience - can only detract from the sound. People wrongly claim that reflections from the listening room are needed to add space and depth. But if that were true, listening through headphones would sound small. I think we can all agree that headphones usually sound larger than speakers! Now, you don't need to make a room totally anechoic. What matters most is killing all of the early reflections. That, and taming the inevitable peaks and nulls and ringing at bass frequencies. More here:

Early Reflections


This short article is mainly about home recording, but all the same principles apply to hi-fi and home theater acoustics too:

Acoustic Basics


--Ethan

What I find is most rooms that kill early reflections kill all the later arriving ones also. Its tricky to preserve the later ones in such a case. But unlike HT or 2 ch live recordings, often times 2 channel studio recordings sound very dry and sterile in a dead room. In the case where the so-called dead room turns out to be a room that is only dead from a 1000hz and up, these rooms are most unbalanced and unsatisfactory sounding.


For Theater, dead is probably ok if the deadness is broadband enough.
 

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Quote:
Originally Posted by Ethan Winer  /t/1523161/how-is-too-much-absorption-of-sound-in-a-theater-room-possible#post_24503969

I think we can all agree that headphones usually sound larger than speakers! 
I am afraid that we all do not agree with that.  
 

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I used to think super dead was the way to go until I heard a room designed by Russ Berger.

Absent was all the tell tale array of heavy absorption. It was very live, more so than I had ever thought enjoyable.


But this experience was completely different-the music was so alive, extremely dynamic with a sense of space and immediacy that I had never heard.


The "there there" was astonishing. I was totally transported to the concert hall.


Since then my approach has been significantly less heavy handed with a much more balanced approach.


For those who are not familiar with Russ http://rbdg.com
 

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assuming an "anechoic chamber" is created when one merely wishes to minimize room contributions from the source at a given receiver position within the bounded acoustical space is merely a form of operator error. the room can be modified to create an effectively-anechoic speaker/listener response while maintaining a non-anechoic listener/room response, limiting the "uncomfortableness" of a highly damped space some may experience.


there's two "perspectives" at play here. associating an NE or FTB room (for example) with an "anechoic chamber" is entirely erroneous.


and for 2ch stereo, this is exactly that of which the LEDE concept was developed - resultant also from that of Dr. Manfred Schroeder's measurements of Europe's best (highest perceived) concert halls. an established Inter Signal Delay gap (Initial Time Delay (ITD) in concert hall acoustics) yields an acoustically larger space than what the room's boundaries naturally allow, increasing the perceived size of the reproduction space. the attenuated high-gain early arriving signals maintain accuracy of the direct signal with respect to intelligibility, localization, and imaging. a later-arriving sound-field is presented via that of broadband, 1-dimensional reflection phase grating diffusers (QRD or PRD variety) with the wells oriented vertically to produce a lateral-arriving, exponentially decaying semi-diffuse sound-field - emulating that of natural reverberation in concert halls. the lateral returns provide envelopment and that of a form of passive surround sound.


for multi-channel setups, the existence of active sources provide the surround sound. an effectively-anechoic response can still be achieved without the use of porous absorption, as illustrated by that of Blackbird Studio C (which provides a reflection-rich, highly diffused first-order sound-field that is -30dB below direct signal). the room, however, does not impose an "anechoic chamber" feel to the listeners.
Quote:
Originally Posted by trans_lux  /t/1523161/how-is-too-much-absorption-of-sound-in-a-theater-room-possible/0_60#post_24504705


I used to think super dead was the way to go until I heard a room designed by Russ Berger.

Absent was all the tell tale array of heavy absorption. It was very live, more so than I had ever thought enjoyable.

But this experience was completely different-the music was so alive, extremely dynamic with a sense of space and immediacy that I had never heard.

The "there there" was astonishing. I was totally transported to the concert hall.

Since then my approach has been significantly less heavy handed with a much more balanced approach.

For those who are not familiar with Russ http://rbdg.com

+1 for Russ Berger; he was involved heavily in the LEDE development days and subsequent workshops.
 

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Note in case the anechoic comment was directed my way due to my lack of clarity:


1. I used an anechoic chamber as an example to bound the problem; and,

2. I have performed numerous tests in actual anechoic chambers (albeit that the vast majority were RF tests, not audio).
 

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Quote:
Originally Posted by localhost127  /t/1523161/how-is-too-much-absorption-of-sound-in-a-theater-room-possible#post_24505380


assuming an "anechoic chamber" is created when one merely wishes to minimize room contributions from the source at a given receiver position within the bounded acoustical space is merely a form of operator error. the room can be modified to create an effectively-anechoic speaker/listener response while maintaining a non-anechoic listener/room response, limiting the "uncomfortableness" of a highly damped space some may experience.


there's two "perspectives" at play here. associating an NE or FTB room (for example) with an "anechoic chamber" is entirely erroneous.


and for 2ch stereo, this is exactly that of which the LEDE concept was developed - resultant also from that of Dr. Manfred Schroeder's measurements of Europe's best (highest perceived) concert halls. an established Inter Signal Delay gap (Initial Time Delay (ITD) in concert hall acoustics) yields an acoustically larger space than what the room's boundaries naturally allow, increasing the perceived size of the reproduction space. the attenuated high-gain early arriving signals maintain accuracy of the direct signal with respect to intelligibility, localization, and imaging. a later-arriving sound-field is presented via that of broadband, 1-dimensional reflection phase grating diffusers (QRD or PRD variety) with the wells oriented vertically to produce a lateral-arriving, exponentially decaying semi-diffuse sound-field - emulating that of natural reverberation in concert halls. the lateral returns provide envelopment and that of a form of passive surround sound.


for multi-channel setups, the existence of active sources provide the surround sound. an effectively-anechoic response can still be achieved without the use of porous absorption, as illustrated by that of Blackbird Studio C (which provides a reflection-rich, highly diffused first-order sound-field that is -30dB below direct signal). the room, however, does not impose an "anechoic chamber" feel to the listeners.

+1 for Russ Berger; he was involved heavily in the LEDE development days and subsequent workshops.

+1

Even if you can't get to the point of having "the gap" there is no reason to not go in that direction. The way I see it is to "manage" the unwanted reflections to try to work in your favor. Nothing wrong with just going dead, but a room that has some life that is "controlled" is pretty outstanding.

There is a heck of a balancing act you have to play, depending on the room and so on.
 

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There is another thing to consider, and that is the speakers that are being used in the sound system.  Normally, my preference is more toward the dead end of the spectrum than the live end for a room (though I do not ever want absolute extremes, at least I have never wanted either extreme so far).  But I have a pair of Apogee Stage speakers, which are dipole speakers and are made to reflect sound off the wall behind them.  In the manual , they recommend that the wall behind them have no or minimal damping material; in other words, they recommend a fairly reflective surface behind them.  (They also make several other very specific recommendations, which I will not presently comment on, except to say that I recommend that every owner of these speakers pay attention to the careful placement advice therein; every time I have tried violating their recommendations for placement, it degraded the sound.)  I have tried them that way as well as with material that diffuses/damps the sound off the back, and I think they sound much better with a very reflective surface behind them, placed at a distance in accordance with the manual.  Although I have not done any measurements, and consequently cannot be entirely certain of the details, I have an explanation for why the bass would be better with these speakers so situated.  If one looks at the anechoic response:







(this is according to Stereophile ), one can see an immediate problem, with excess bass.  And that is exactly what my subjective experience indicated with the diffuse/dampened wall behind them (though I must say, I found their bloated bass that way much less objectionable than any other speaker I have ever heard with bloated bass).  The theory of the placement and reflective wall appears to be that one place the speakers precisely in order to get the rear reflection to be out of phase with the forward bass and give a flatter in-room response.  Subjectively, at least, it seems to work quite well.


So, what works best, in my opinion, is going to depend upon the particular speakers.  Ordinarily, I think most people have rooms that are too live (judging from pictures I have seen online, with bare walls and minimal furnishing that people often seem to have in their rooms with audio gear).  But I think there are limits to what should be done, and do not want a totally dead room.  But I don't think most people need to hear that, and instead need to hear that they need to deal with excess reflections in their rooms.


 
 
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