Concert Hall sound

[Fitzcaraldo215]

I completely agree with @stc and @esldude.  Forgive me if I merely restate their points.

 

Concert hall sound has been a somewhat elusive goal over the history of audio.  Some insisted they could hear a good replica of it in mono days.  Some insist they can hear it in stereo.  Yes, listener imaginings on their home systems are effective in convincing people of many things,  not all of them true, and they may be quite happy with reproduced sound within the limitations of their systems and recordings.

 

But, we know quite well from measurements over many years in concert halls some essential aspects of concert hall sound.  While stereo systems and recordings today can be thoroughly enjoyable, they do not replicate at all many aspects of sound in the concert hall.  Direct sound from the stage may be reproduced with superb fidelity in stereo.  But, the main thing it lacks is proper reproduction of the contribution of the hall's reflected sound field.

 

Amar Bose famously measured direct and reflected sound decades ago in concert halls.  He came up with his 8:1 reflected/direct energy ratio, enshrined in his 901 speakers.  Though the speakers had their fans and he made $millions, it was a crude and ineffective way to replicate concert hall sound in stereo.  As @stc says, the listening room does not have nearly sufficient reverb time, and also the resulting angular dispersion of reflections from just the front wall was totally incorrect vs. the concert hall.  The listening room just cannot do it close to accurately from 2 speakers.

 

Our ear/brain hears in 3 dimensions, not just the width plus phantom depth provided by stereo.  And, we do not hear with equal acuity in all those 3 dimensions.  We are most sensitive in the front hemisphere and somewhat less so to the sides and rear.  Height acuity is less sensitive than frontal width or depth.  But, what we hear in the concert hall is direct sound from the stage plus much reflected energy from the sides, rear, ceiling, etc.  Our attention is focused on the direct sound heard by our sensitive frontal hemisphere, and it dominates our conscious perception.  But, there is also an important, more diffuse reflected and reverberant sound coming from all other directions which we are not really fully conscious of.  However, that diffuse, reflected sound field is very high in acoustic energy per Bose and many subsequent researchers.  Unfortunately, stereo recordings must truncate and discard most of it for reasons cited by @esldude and @stc.

 

The most accurate, commercially viable approach to date to recording this is discrete Mch, which starts with a similar recording setup to stereo for the direct sound but with additional more distant mics to capture the direct and reflected sound field from that perspective while maintaining reasonably accurate  directional information via direct and via phantom imaging between the Mch speakers on playback.  Among many other things, this overcomes the short RT time in the listening room and reproduces the long RT time of the hall.  Hence, this is a major step in recreating concert hall sound.

 

Current 5.1 or 7.1 Mch operates only in the X-Y dimensions.  I have found it quite effective and quite preferable to stereo for over a decade, much as stereo is preferable to mono.  I want my listening to be based on a more comprehensive and accurate transfer of the sonic information from the recording venue to my listening room.  I much prefer that to trying to have my imagination fill in what is missing.

 

I also have not personally found stereo to Mch upmixing to be very satisfying.  It is OK, but I much prefer discrete Mch recordings, which are abundant in classical. 

 

So, what about 3D immersive?  I am all for it, but only when it becomes commercially viable as a music format.  I find much more to get excited about with Auro 3D, which was developed by a large, successful Belgian music recording studio.  Dolby Atmos, and its object orientation, seems focused on object motion in 3D, as in movie effects,  so I do not see it as a good fit for "concert hall realism" with music, which is more static in performance.  We do not need clarinets flying around the listening room.

 

 

 

[Fitzcaraldo215]

1 hour ago, gmgraves said:

Actually, one doesn't want one's listening room to have any set reverb times or angular dispersion modes. The ideal listening room is acoustically dead. All of the ambience cues should, ideally, be provided by the recording and reproduced by the playback system. That way when listening to a recording made in England's Watford Town Hall, or The Royal Albert Hall, those would be the acoustic environments that the listener is transferred to while listening. If, on the other hand, one is listening to a recording made in a night club (like Jazz At The Pawnshop), the  dead acoustic signature of the listening room should facilitate the accurate recreation of that acoustic space as well. 

I see the apparent logic of what you are trying to say.  But, I don't think it squares with listening experiments.  People just don't prefer listening in dead, anechoic rooms, regardless of the recordings.  I personally have heard many rooms that were too dead to be enjoyable.  Toole talks about "listening through the room", where the brain compensates for the room's reverb and reflections, making the room "disappear".  But, there are obviously finite limits to that.  Some rooms are better than others.

 

There is also an excellent case to be made for speaker/room setups where, while the room is not dead in terms of reflections, the frequency response is smoothly downward sloping, with bass frequencies EQed to be flat or near flat to eliminate room modal variations, which are often huge.  Toole prefers EQing just the bass below about 500 Hz and using speakers with smooth directivity so that room reflections do not alter frequency response.  Others, like me, use full range DSP EQ to control frequency response at the listening position.  But, Toole is no fan of that approach.

[Fitzcaraldo215]

46 minutes ago, fas42 said:

 

As people have been pointing out, mics don't discriminate; they pick up all the sound energy that is impinging on their diaphragms ... we are the ones that separate the content, and choose to focus on what's important, to us ...

 

Mics being closer to the "instruments" doesn't stop the acoustics pickup, dead - it just means that the contribution of the latter is lower in level - and that requires a higher standard of replay for those acoustics to register, when listening. To appreciate this, one needs to have a rig working at a level where one can play a recording which is a studio mix of various instruments, all recorded separately - and one can turn one's focus on each of those sounds in turn, and "see" the acoustic where each one was located; a complex recording is a layering of acoustics, each of which still retains its identity within the whole.

 

Rule of thumb: poorer quality playback == listening room is everything; convincing standard playback == listening environment is irrelevant.

Nonsense, as usual, Frank.

[Fitzcaraldo215]

13 hours ago, STC said:

 

Excellent write up. In concert halls, the ambiance acoustics is everything. That's what reaches our ears by more than 8 fold of direct energy. Although, there are some research that suggest we are particularly sensitive to the 45 degree (sic) frontal reflection, I personally feel the rear half reflection is more important for orchestra. However, the front half is useful to smoothen the room response provided the reflection itself is perfect.

 

Despite falling in love with multichannel SACD's in the early 2000s, I never pursued that direction due to lack of material at that time. However, now with some of the 2L 5.1 label, I think the rear ambience could be reproduced more accurately via halls impulse response using stereo and a much better presentation with utilizing both front and rear channels of 5.1. Even with stereo, I would still say a proper setup to recreate the concert hall ambience require at least 30 over channels. 

Thank you.  

 

As far as channel count is concerned, yes, we know that real images from speakers are more precise than phantom images between speakers, and also that phantom images are better and more precise over a smaller distance = a narrower angle between them.  Hence, 5.1/7.1 offer an improved frontal soundstage over stereo or '70's Quad due to the center channel.  That is in addition to better handling of dialogue in relation to the screen on video material than can be done with phantom center imaging.

 

But, there are sharply diminishing returns from adding additional channels.  Toole's experiments show the channel count has to be increased substantially in order to make much perceptable difference to listeners.  So, your guess of 30 channels would be consistent with that.  The downside, of course, is the difficulty of recording that way discretely and of distributing files with such large channel counts.  

 

Artificial simulation of that increased surround channel count is possible, except can it be done in a natural way without artifacts or an imposed single sonic signature?  So far, I don't find artificial upmixing algorithms to be the equal of discrete Mch recordings, and I distrust upmixing.

 

There is another aspect to this also.  Contrary to popular belief, the surround channels in discrete Mch recordings do not just contain diffuse reflected sound.  If you think about it from the perspective of a distant surround mike, what is picked up is inseparably both the direct sound from that perspective plus the diffuse reflected sound from that perspective.  This is clear from listening to surround channels up close.  On playback, that combination of direct plus reflected sound creates phantom images heard by the listener as a result of interaction with the front channels and other surround channels.  

 

The effect is to not only bring the diffuse hall sound to the listener, but also to enhance the frontal soundstage in terms of width, depth and dimensionality.  I personally find that discrete Mch recordings pull the frontal soundstage out into the room somewhat in front of the plane of the front speakers.  A sense of added natural sounding depth and dimensionality over stereo playback is notably apparent to me, since the front speaker array can, like stereo, simultaneously produce phantom depth behind the front speaker plane.

 

My point is it may not be quite so simple to introduce added algorithmic channels that naturally convey the sound in the hall.  One must consider both the direct sound output of those channels and their interaction via phantom imaging with other speaker channels in the array.

[Fitzcaraldo215]

Duplicate post.

[Fitzcaraldo215]

15 hours ago, gmgraves said:

I think you're missing my point, my friend. It wouldn't be a "dead room" when the music is playing because recordings designed to be played in such an ideal listening room would bring with them an approximation of the venue acoustics in which the performance was played. That is to say, that the acoustics of a standard living room would be replaced by the acoustics of the place where the recording was made. Ostensibly, the room would then be a place that transported the listeners to the performance rather than bringing the performance into one's living room where the acoustics of the performance are overlaid by that room's acoustics (good or bad).

.

As is true in the concert hall, what we hear in our rooms is an inseparable combination of direct plus reflected sound.  Speakers have a dispersion pattern, a directivity index which is very much part of what we hear.  Eliminating that reflected component by deadening all reflections produces sound that is unpleasant and not preferred, even with music.  Experiments have established  this with listeners.  Scientists and engineers who work with speakers in anechoic chambers do not go home and try to make their listening rooms anechoic.

 

Yes, aspects of uncontrolled room reflections can be detrimental, such as room modal variations, floor bounce, glare at certain frequencies, etc.  But, other aspects of room reflections are positive contributions to the sound that we like.  And, listening anechoically would require much more amplifier power and speaker efficiency.  That, in addition to being costly and potentially ugly.

 

Attenuating the bad aspects of the reflections while keeping the good aspects does result in the venue acoustics on the recording overriding and masking the listening room acoustics.  Partly, this is helped by our brain adapting to and "listening through" the room, which we do quite naturally and subconsciously.  It produces a very good and enjoyable "you are there" illusion of the concert hall in Mch, much more so than in stereo, I have found.

 

 

 

[Fitzcaraldo215]

1 hour ago, semente said:

Yet many audiophiles prefer listening through headphones.

Do they prefer it because they have lousy speakers, a bad room, grouchy neighbors, kids who go to bed early, etc.? Or, do they really think it sounds, in the context of this thread, more like "concert hall realism" than even a decent stereo?  If it is the latter reason,  all I can do is shake my head and wish them listening enjoyment.  I don't think most of them listen to classical music, or if they do, they have little experience with live concerts.

 

I used headphones in the '60's for many of the former reasons.  I quickly outgrew it never to return as I acquired a decent stereo.  It simply does not image properly with normal, non-binaural recordings.  Plus, it is fatiguing.

[Fitzcaraldo215]

15 hours ago, gmgraves said:

I have no dispute with that, but ideally, the best result would be multi-channel recordings (pure stereo for the two front channels, ambience only in the side, rear and overhead channels [separate subwoofer channels optional])played in a room with no acoustical signal of it's own. Such a listening experience would be totally immersive, and from the standpoint of the concert experience startlingly real. Of course, binaural sound does that to some degree. I've been listening to the BBC Proms from the Royal Albert Hall in London streamed in binaural AAC sound. At times the result is almost spooky, but you can't move your head, or the illusion disappears like being awaken from a dream. 

George - a "room with no signal of its own" is an anechoic chamber that kills all reflections.  That is not what we want.  What we want is a speaker/room that has no sonic signature that imposes itself on the the signal via reflections.  There is an important difference.

 

Most of the issue is purely in the frequency domain.  We do not want the speaker/room to distort the frequency response, even if there are reflections in the room, and we don't want to or need to kill those reflections as long as they are not distorting frequency response.  The reflections are then actually desirable.  They help amplify and spread the sound.

 

Sometimes, there are also time domain issues, ringing, etc. These are sometimes harder to deal with, though often, for example, pulling down modal bass peaks in the frequency domain will tame them in the time domain, as well.  

 

So, killing all the reflections is draconian and leaves us with an unpleasant sounding, totally dead room.  Taming the frequency and time domain issues caused by reflections but allowing the reflections eliminates their imposition on the sound, which is what we want.  That allows us to better hear through the room to the acoustical cues on the recording.

 

[Fitzcaraldo215]

12 hours ago, STC said:

 

 

I maybe wrong but I always thought where the phantom image is further towards the side the more accurate they are.

 

 

I am not sure which Toole's experiment you are referring to. For front sound reproduction, the more channels will allow you you to precisely recreate the actual soundfield . However, it is impossible to have a similar setup as that means an accurate representation will only be possible with similar arrangement of the speakers as the recording. It is not practical and hard to be consistent with the varying number of instruments.

 

When I mention 30 channels, I was referring to the ambience cues for recreating the hall's ambiance. That's to recreating the reflecting walls of the concert hall. This require as many channels as possible to replicate the actual reflecting sound coming from multitude angles in the concert hall.  Right now, I am only using reflecting for every 15 degrees at 23 degree elevation. Prof Farina created one for every 10 degrees. Technically, with these impulse response you can create infinite number of virtual concert halls. IMO, 30 channels is good enough. I use 144* channels. Ideally, when I get another Motu I will increase another 144 channels provided my computer and Reaper could handle this. The more the channels are the smother the frequency response is as it flatten the dips and peak caused by the room.

 

* Previously, I mentioned 72 channels. It should be 72 times two as each set of IRs caries both left and right channels. So in total it should be 144 channels.

 

 

A good diffuse reflected sound will actually sound like the rear ambiance speakers of multichannels.  That's the reason why a concert hall sound is unique. Here is a quick video where at 1:00 I have mute all the speakers except for the ambiance speakers. In this video, I was using 36 channels of different IRs.

 

 

Actually, it is as simple as that. leave whatever recorded sound as it is and pay attention to the room acoustics. The IRs is dealing with the room/hall acoustics. The front channels remain as it is -untouched. Think this as more elaborate and precise method of doing room treatment. 

 

[Fitzcaraldo215]

14 hours ago, STC said:

 

 

I maybe wrong but I always thought where the phantom image is further towards the side the more accurate they are.

 

 

I am not sure which Toole's experiment you are referring to. For front sound reproduction, the more channels will allow you you to precisely recreate the actual soundfield . However, it is impossible to have a similar setup as that means an accurate representation will only be possible with similar arrangement of the speakers as the recording. It is not practical and hard to be consistent with the varying number of instruments.

 

When I mention 30 channels, I was referring to the ambience cues for recreating the hall's ambiance. That's to recreating the reflecting walls of the concert hall. This require as many channels as possible to replicate the actual reflecting sound coming from multitude angles in the concert hall.  Right now, I am only using reflecting for every 15 degrees at 23 degree elevation. Prof Farina created one for every 10 degrees. Technically, with these impulse response you can create infinite number of virtual concert halls. IMO, 30 channels is good enough. I use 144* channels. Ideally, when I get another Motu I will increase another 144 channels provided my computer and Reaper could handle this. The more the channels are the smother the frequency response is as it flatten the dips and peak caused by the room.

 

* Previously, I mentioned 72 channels. It should be 72 times two as each set of IRs caries both left and right channels. So in total it should be 144 channels.

 

 

A good diffuse reflected sound will actually sound like the rear ambiance speakers of multichannels.  That's the reason why a concert hall sound is unique. Here is a quick video where at 1:00 I have mute all the speakers except for the ambiance speakers. In this video, I was using 36 channels of different IRs.

 

 

Actually, it is as simple as that. leave whatever recorded sound as it is and pay attention to the room acoustics. The IRs is dealing with the room/hall acoustics. The front channels remain as it is -untouched. Think this as more elaborate and precise method of doing room treatment. 

Yes, phantom imaging between two speakers becomes more accurate as the apparent, panned sound source approaches the speaker to one side or the other.  Also, the centered phantom image between two speakers with a 60 degree angle between them will be less accurately conveyed than if the angle was 30 degrees.  

 

There is also a special case of sounds from front dead center and slightly either side of that.  Due to our head related transfer function and ears to the sides of our head, there is a large drop at upper middle frequencies when heard from phantom imaging by two front speakers.  The same signal when played by a single center channel speaker eliminates that.  That is important for imaging at the front of the soundstage for music, and also for dialog articulation on video.  It is a frequency response problem with center imaging in stereo we have just gotten used to.

 

I think all  this is in Toole's latest book: Volume 3 of Sound Reproduction.  But, phantom imaging is obviously vitally important to stereo and all forms of Mch.  They would not work adequately without it.  I also believe that phantom imaging, imprecise though it may be,  can be perfectly adequate to convey the diffuse reflected and reverberant sounds from Mch surround channels.  That is, I think, why Toole believes adding surround channels requires a huge increase in channel count in order to make much perceivable difference.  Adding height speakers is a different matter because that is adding additional location and dimensional information in the Z-direction.

 

Incidentally, Toole is a big fan of Mch sound.

 

I also disagree with you about what signal is present in Mch surround speakers on recordings.  I will go through it again.  In a simple Mch mic setup, there are stage mics for the front channels plus more distant hall mics, usually omnis, for surround channels.  Focus on one of those distant mics for a moment.  Imagine sitting where one of those mics is.  What will they pick up?  Obviously, they will pick up much reflected hall sound, given their location.  But, there is no way to block them from picking up or to suppress the direct sound from the stage at that more distant perspective.  Ergo, they contain signal that is an inseparable combination of reflected hall sound plus that more distant direct sound from the stage, just as you would hear if sitting there.  That direct sound component cannot be erased, nullified or removed from the signal via editing, mastering, etc. 

 

On playback, that combined direct plus reflected signal from the distant mic goes to a surround channel.  It reproduces the desired hall ambience picked up from hall reflections.  But, that direct sound is also there, delayed, somewhat down in level, and altered somewhat in frequency response relative to the front main and center channels by air/distance attenuation.  But, it interacts with the sound from the main channels, producing a phantom image mainly in the front to rear direction into the room.  The diffuse reflected energy component in the surround channel does that, too, but to a lesser degree.  

 

That phantom image of the direct sound from front and surround speakers is closer to the front speakers, because the front channels are somewhat louder, having been recorded closer to the performers.  This is why I hear the sound being "pulled into the room" in front of the front speaker plane in a way stereo does not do.  It is also why I find that discrete Mch provides a greater apparent depth of the frontal soundstage.

 

Oversimplified, that is what I believe is going on in Mch.  It also exactly reflects what I hear when I listen to the signal from surround channels in discretely recorded Mch - diffuse reflected sound plus direct sound from the stage.  And, properly done, it works.   I think it is the best approach yet to recording and reproducing a successful illusion of live music in the concert hall.

 

[Fitzcaraldo215]

1 hour ago, gmgraves said:

I never said that such an arrangement would be practical. It might take 8 or 10 discrete channels to make such a scheme work, and then maybe still, a lot of DSP computing power to boot. I mean this is just a "thought experiment" and, as such, is more of a question than an answer.

George - you can test your theory with a bit of work.  Set up your system outdoors on a sunny day on a soft grassy surface.  There will be essentially no reflections, just like your ideal.  Let us know how you like the sound.

[Fitzcaraldo215]

1 hour ago, shtf said:

 

Where do you get this from?  Take your computer to your water closet and listen to the music in your first video again and then go sit in your backyard and listen once more and once again in your listening room. 

 

If the music in the video sounds even reasonbly different between locations then you just might have a point.  If not, then you're way off base regarding the significance of the listening room's acoustics and their contributions.

Yes, he went way overboard in suggesting that MP3 could sound great with great room acoustics.  But, from much personal experience, it's clear that you are going to an opposite extreme.  Listening room acoustics absolutely affect the sound that we  hear in major ways.  There is so much empirical science to back this up, I don't even begin to know where to direct you for starters.

[Fitzcaraldo215]

15 minutes ago, fas42 said:

 

 

Wrong direction? The amount of awful sound I've heard from ambitious systems over the years is pretty depressing - my interest is in trying to inject some sanity into the audio game, and move the thinking towards getting playback to, well, play back the recording with full integrity; rather that having rigs which are Yet Another Effects Unit.

 

Yes, Frank, you are definitely the voice of sanity in the audio game.

[Fitzcaraldo215]

2 minutes ago, fas42 said:

 

The empirical science has always used playback systems that weren't of sufficient standard - "In the 1930's scientists tried to fly faster than the speed of sound, using every aircraft that was readily available - and failed. They confidentally stated, 'It's impossible to break the sound barrier, because we have tested for that possibility' ".

Ah, I see.  The problem is they were not using a Franknfas-approroved system in their testing.

 

I have a better idea, though.  Instead of wasting your time on trivial playthings like audio, why no go and show them how to cure cancer.  There is Nobel Prize in it for you.  I am sure you have what it takes.

[Fitzcaraldo215]

13 hours ago, shtf said:

 

I should clarify a bit.  A listening room’s acoustics do have some limited effect on playback sound via it’s dimensions, etc, but there is a quite an impact depending on the speakers’ inferior or superior placement within the room.

 

More specifically, I was implying that listening room acoustic treatments are of little value – provided the listening room itself is deemed reasonable enough – i.e. lacking serious room deficiencies and/or absurdities.

 

But I’m curious.  Aside from a speaker’s superior placement within a given already reasonable room, what are some of these “major” ways a room’s acoustics impact the sound we hear?

Room acoustics is a complex subject.  Again, in recent readings, I highly recommend Toole's Sound Reproduction V3, which also goes into many aspects of speaker performance, etc.

 

The  major influence of the room is in the bass due to modes Induced by reflections based on room dimensions, construction, materials and speaker placement.  It is virtually impossible to design a listening room of typical size that is not influenced by these modes, though their magnitude might be partially mitigated somewhat by room design.  

 

I have measured several "good" rooms, one used by a music and equipment reviewer.  Modal variations were in the range of +- 8 to over +- 20 dB. That is quite a major impact that would not be tolerated in a speaker or in audio electronics. These were cleaned up nicely by the application of DSP EQ, much to the satisfaction of all listeners.  Yes, I agree, bass modes of this magnitude are very difficult to control via passive absorption, especially below 100 Hz.  

 

Above the Scroeder or Transition frequency of typically 300-500 Hz, the room reflections typically play less of a role and the speaker predominates.  But, early reflections due to speaker placement or highly reflective materials, like glass, can still cause frequency response issues, as can speakers without a fairly uniform directivity index.

 

The real point is reflections play a natural and inseparable part in sound as we hear it. They alter the sound and have a large effect on the sound we perceive. That is true in the concert hall and in the listening room.  But, listeners are generally unaware of them as their consciousness is preoccupied by the direct sound from the stage or from their speakers, as well as the sight cues from those sound sources.  Some listeners therefore don't believe reflections are significant, but they would be wrong in that.

 

 

[Fitzcaraldo215]

13 minutes ago, semente said:

 

That's wild. What was the smoothing used for plotting that measurement?

That was at 6 dB per octave.  Likely it would have been greater with less smoothing.

 

Wild?  From what I have seen in Toole's book and numerous times elsewhere, it is quite typical.  But, amazingly, people just don't know unless they measure.  And, when they hear it cleaned up via DSP, they love the result.

[Fitzcaraldo215]

4 minutes ago, semente said:

 

In my opinion and understanding, one cannot put live and reproduced in the same bag.

 

In a live performance, say a piano recital, there's a sound source, a room with a particular acoustic signature and a listening spot where both direct and reflected sound arrives.

 

In reproduction, we wish to accurately recreate a soundfield, roughly similar to what the listener would have experienced, picked up by a mic onto two-channel stereo (to make things easier).

Since both direct and refelected sound will be reproduced from the same spot, the original soundfield cannot be recreated.

But, to accurately reproduce the signal one should as @gmgraves mentioned position the system in a dead or near-anechoic environment; otherwise the listening room's own reflections of the reproduced sound will add a layer of confusion which will probably affect tonal balance as much as imaging.

Cinema rooms, which unlike performance rooms are also used for reprodcution, have a lot of absorbtion built into their walls.

 

People may prefer, and many do, room reflections but this is a matter of taste and perception, not of accuracy. Listening room reflections are not cues of the original event ambience. But they enhance the soundstage-effect or 3D-ness by creating phantom images: phantom images.pdf

Well, as I said to Geroge, set up your stereo system outdoors and see how you like it.  I am willing to bet you will not.  I also said scientists and engineers who work with anechoic chambers do not go home and attempt to make their listening rooms anechoic.  Toole, the leading anechoic speaker testing guru on the planet, sure does not.  And, there are always headphones, if you like those.  I don't.

 

Once again, all listening room reflections are not "bad", as you and George would have it.  They only become "bad" if they distort the frequency and time domains excessively and perceptably.  Room modal variations inevitably do that, but that is controllable without killing all the reflections.  Some of those reflections amplify bass frequencies in good ways, so you don't want to kill all of  them.

 

Also, our ear/brain has been well equipped since we were cave dwellers to adapt to and listen through much of room acoustics, though not all.  For example, room reflections cause major comb filtering in the high frequencies.  But, there is beyond ample science that shows our hearing integrates this comb filtering, so we don't consciously hear it at all.  That is why something like 1/6 octave smoothing is used for HF measurements, because that is more like how we actually hear.

[Fitzcaraldo215]

3 hours ago, Abtr said:

A stereo version of what you describe is known as a Blumlein pair or Blumlein stereo:

https://en.wikipedia.org/wiki/Blumlein_pair

http://www.regonaudio.com/MICROPHONE THEORY word.htm

Blumlein and related coincident  or near-coincident pair micing schemes are as old as the hills.  Most every classical recording engineer is fully aware of them, and probably has tried them experimentally.  There are reasons why they have not succeeded commercially, one being the need for an unusual +-45 degree speaker setup on playback.  They remain largely a footnote in the annals of recorded history.

 

The Waterlily Acoustics label has remained dedicated to this approach for decades.  Engineer Kavi Alexander was frequently assisted by his acolyte, Robert E. Greene, in making these  recordings, some with symphony orchestras.  I have some of those, and I have listened to them with the proper speaker placement.  My opinion is that they are so-so, not worth the cost or effort.  In terms of providing a successful illusion of Concert Hall Sound, they fall far short of huge numbers of available, commercial Mch 5.1 recordings, woefully, in fact.

 

Greene once attempted to add synthesized surround to Kavi's Blumlein fronts on some Mch SACDs with the Leningrad Philharmonic.  The results are embarrassingly poor, frankly.

 

 

 

 

[Fitzcaraldo215]

9 hours ago, Blackmorec said:

I’m really having some difficulty agreeing with a lot of the posts in this thread. 

 

The purpose of a sound system and listening room is to reproduce what’s on the recording and really nothing more. If a recording is made in a hall, the longer reverb times are part of the recording and have nothing to do with the listening room. In your room you should hear the original note coming from a specific origin, you should hear its decay, which has direction and you should hear the reflection (time delayed and opposite decay direction). What tells you the recording is in a large concert hall is the directionality of the decay and the timing of the reflection.  If you have a large, lively listening room with high rt  what you hear is both the recorded venue’s acoustic and your room’s acoustic. Very confusing. 

As for room boundaries, they should play no role in terms of sound stage size. The sound stage is created in your head, not your room and the brain uses reflection time, direction of decay, phase and relative amplitude to ‘visualise’ the venue. In nature sounds behave in a ‘natural’ way....and your brain uses all the information related to the sound to characterise what made it, where it came from, how far away it is and whether it was made in a room, hall or open space. To sound ‘real’ a sound recorded in an enclosed space needs to have the correct spectral balance,  a clear pinpoint source, an acoustic delay, a reflection and the correct amplitudal relationships between original sound and reflection. The timing of the reflection and its amplitude need to ‘agree’ with what happens in nature.

Take a large hall with high RT.  The recording should have a pinpoint start (all sounds in nature emanates from a single location), should decay in the direction of the reflection, should have a high amplitude reflection which should have a more diffuse character and should decay in the opposite direction. When all those characteristics of the sound have the right relationship to one another, your brain will assign size, and relative reflectivity of the recording venue and assign a degree of ‘realness’ according to how all the attributes of the music match what would occur naturally if you were actually seated in the venue with the musicians. 

As for high rt recordings sounding muddled, this should not be the case if its a well made recording and if your system is resolving and reproducing all its detail. If it does sound muddled that’s a very good indication that your brain is missing some sonic clues, meaning that your system is failing to fully resolve all the recording’s information or your listening room is distorting the information with too many high amplitude reflections reaching your ears

Very well said.  However, I disagree that room boundaries have no effect on the image we hear.  It is well known in acoustic theory and indisputable that room modal variations in the bass and their normally very large, narrow band frequency peaks and dips are a function of reflections based on room dimensions, construction and materials.  Also, for example, at higher frequencies apparent soundstage width is affected by side wall reflections via speaker placement and toe in/out, depending on speaker directivity.

 

Yes, absolutely, we want the sound of the recording, including spatial and acoustic cues from the hall, to override the sonic signature of the listening room, both in stereo and Mch.  That does not require an ugly and unpleasant sounding anechoic listening room.  It merely requires a room in which the effects of the listening room are controlled to be sufficiently neutral, well behaved and down in level relative to direct sounds from the speakers.  And, no it does not require excessive absorption or passive treatments.

 

As far as Concert Hall Realism goes, nothing is perfect.  But, there are decidedly different degrees of plausibility of the image conveyed to home listeners between conventional stereo and Mch.  As has been restated numerous times, discretely recorded Mch achieves this best by far as a result of capturing more information on more channels about the size and acoustic of the hall and by preserving much of this in playback to the 360 degree hearing our ears are naturally capable of.

 

I dare say that those who argue that stereo is just as or nearly as good have not made a comparison using a properly set up Mch system or they lack familiarity with sound live in the concert hall.  I find the difference plain as day, repeatedly on numerous Mch systems.  And, there are very large numbers of extremely well engineered hirez Mch recordings that easily illustrate this.

 

 

 

 

[Fitzcaraldo215]

It never ceases to amaze and confound me in discussions like this, that the focus seems to shift to extremes.  We seem in this thread to have identified the reasons that 2channel stereo cannot adequately provide a  satisfactory image of live concert hall sound.  I do expect, however, that many stereo-centric listeners are still in total disbelief of that premise, even though they may not have heard alternatives that clearly demonstrate otherwise.

 

We seen to jump from there to experimental paradigms.  STC has his 64 channel  artificial synthesis scheme, overlaying and superceding 2.0 and 5.1/7.1 source material.   Semente proposes the spherical mic/playback 3D model, which he has himself not implemented, while, of course, essentially no commercial recordings provide that.

 

My own personal interest is in plonking myself down and listening to a wide variety of music that more faithfully recreates a satisfactory sonic illusion of the live concert experience.   The  experimental approaches are of little help, and there are or have been numerous others proposed  beyond those mentioned above, none commercially viable.  Artificial synthesis and upscaling via  commercially available DSP from 2.0 or higher are to me inadequate and unsatisfactory.  

 

There is a quite adequate, well supported paradigm available commercially in huge numbers via discretely recorded Mch 5.1 hirez SACD.  BDs and downloads extend that, sometimes to 7.1.  I have thousands of such recordings on my NAS, and most are highly successful in recreating a much better image of live concert hall sound than stereo was ever capable of.   "3D Immersive" schemes - Atmos, Auro, DTS:X - seek to expand on that in the height direction, but they have not demonstrated commercial viability, available releases or relelevance for music recordings.  

 

But, nothing fancy and no special processing need be done to enjoy these recordings, other than setting up an adequate Mch system.  That is not a trivial task, but it is far from rocket science.  And, the same system can support Mch video quite nicely and compatibly. 

 

So, I remain mystified why these thousands of commercially available hirez Mch recordings are simply ignored in favor of speculative schemes.  Those of us who have heard many of these recordings know they deliver a far better replica of live concert hall sound.  But, what is wrong with them, such that we need to endlessly speculate on extreme alternatives that have no commercial presence?  Those available Mch recordings  I have heard through a properly set up Mch system are very good and very satisfying to me, as well as to many concert going friends.

 

 

 

 

[Fitzcaraldo215]

Duplicate post.

[Fitzcaraldo215]

18 hours ago, semente said:

If you look closely those " Mch recordings are simply ignored in favor of" 2-channel recordings.

 

To me, immersive 3D audio is a gimmick just like 3D video. Mch is too expensive and the material is let's be honest scarce.

 

The reason I discussed mic and speaker arrays is because they would be the closest you'd get to the real thing though we'd probably have to ignore problems caused by the interaction of so many drivers.

 

Finally, as @gmgraves  @cookiemarenco  and others with recording experience would attest, tampering with the signal will reduce its quality and ultimately realism.

As for 3D Immersive formats, amplifying what I said,  if they can demonstrate audible benefits that bring us closer to concert hall sound as well as commercial viability for music, they might be of interest.  Otherwise, not to me.  Gimmick?  I don't see that in Auro, which was developed by a major European music recording studio.  But, for music, Atmos and DTS:X do not seem suitable, though they might succeed with cinema.  However, I have heard diminished returns from an added height dimension in auditions of Auro simply because our ears naturally have diminshed spatial acuity in that dimension vs. X-Y.

 

The question of whether existing 5.1/7.1 Mch is too expensive is a personal decision.  Since clearly you have not heard it and its degree of improvement over the limitations of stereo, you seem to be relying on blind prejudice rather than experience in judging it.  Also, the spherical recording/playback technique you espouse strikes me as even more complex and costly than, say, 5.1 Mch on both the recording production and playback sides.  We have no idea whether the proposed benefits of spherical arrays are worthwhile or not.

 

Incidentally, 5.1/7.1 is not scarce at all.  It seems you have not looked for such releases.  Certainly the catalog is not as extensive as stereo CD, which has existed for decades longer than Mch formats.  But, as I said, I have thousands of such Mch recordings on my NAS, and they continue to be released on SACD, BD-A, BD-V and downloads.  Discs are easily available from Amazon and numerous other retailers.  A simple search for Mch recordings at this site might reveal how extensive the catalog is:

 

https://www.hraudio.net/

 

Your mindset seems dead against more than two mics.  Good luck finding recordings that fit your ideal, and I am willing to wager that they are vastly outnumbered by discrete Mch recordings.  Even in the '50's, RCA, Mercury and others were using 3 mics, which BTW sound noticeably better on their SACD remasters in 3.0 than in 2.0.   And, if additional mics for Mch in the hall are capable of capturing reflected hall ambience with proper directional cues, why are they a bad thing?  If they overcome stereo's known limitations to providing concert hall sound by providing more of the natural sonic information from the venue, why dismiss them? 

 

Ok, you have not heard these Mch recordings on a proper Mch system, so you imagine faults they must have simply because the idea offends you.  You are fully entitled to your views, as are we all, but yours would have more credibility if they were based on actual listening experience.

 

 

 

 

[Fitzcaraldo215]

2 hours ago, semente said:

 

I have no doubt about the advantages of multi-channel just as I have no doubt that it's implementation is more expensive.

It's got nothing to do with personal decisions. Imagine a budget of say 10k; isn't it obvious that if you have to buy twice as many speakers and amplification these will be of lower performance? A Mch system will also need more floorspace than what is commonly available in European homes.

 

 

I'm just being realistic. I can buy a better 2-channel system for the same amount and even though I'm a classical music listener I doubt that more than 2% of my ~2500 albums exists in Mch. Some (maybe a lot) or the music does exist but not the recordings of performances by my favourite artists.

It's OK for you because you only listen to recent recordings but I value artistic over sound quality.

Yes, cost is an absolute number, and often a Mch system would cost more than a stereo.  But, $10k to you might have very different significance to me.  In Annie Hall, the shrink asks Annie how many times a week they have sex.  Annie's says, oh, all the time, like 3 times a week.  Same shrink asks Woody, and he says, hardly at all, like 3 times a week. So, in that sense it is personal.   Also, if you look at things in terms of value - perceived benefits minus cost - it becomes even more of a subjective personal issue.

 

Long, long story: I have been a dedicated classical music lover, recording collector and audiophile for decades.  I was always seeking higher fidelity, a better replica of live concert hall sound.  I upgraded and upgraded trying to achieve that, but I always felt something was missing and that the upgrades were at best incremental, and something was still missing.  I also had some good friends who are prominent equipment reviewers for major magazines.  I heard their > $100k rave  review rigs, but something was still missing.  I attended limited VIP demos personally supervised by Dan D'Agostino,  Dave Wilson, etc., etc.  Same problem.  I have listened to $millions worth of stereos just over the past 20 years, but good as they were, they were still quite short of the elusive goal of concert hall sound.

 

Just over 10 years ago, my own stereo had an MSRP of over $50k using carefully selected and auditioned components.  But, I was ready to add HiDef TV, Bluray and Mch sound to make my system a hybrid stereo music system plus home theater.  I planned to continue music listening via stereo CD, but with added center + surround channels only for Mch from videos.  The main front channels would be shared, but my old stereo component chain would be unaffected by an HT prepro and universal player for video.

 

Just after system setup, I wanted to see how the Mch audio was sounding.   It was excellent with movies, but what about with music?   My  $169 Oppo player was intended for video, but it could also play SACD, in Mch even.  So, I bought a few SACDs for the first time, including the Mahler 6th with the Philadelphia Orchestra under Eschenbach.  I had been in the audience when it was recorded live a year or so earlier.  

 

I have heard many audiophiles extol some miraculous experience from upgrading their audio, but never completely credibly.  But, it did not take 30 seconds to realize I was hearing by far the greatest sonic improvement I have ever heard in my life, and by a huge margin.  I was so excited and almost speechless for days. All of a sudden, that missing element, an incredibly good replica of that ever elusive concert hall realism was there for me to enjoy.

 

My life changed dramatically as a result.  Listening to my old CDs via my old, pricey stereo frankly did not compare in listening trial after trial.  It was right there, side by side for AB testing, in the same room using the same amp and speakers as my new Mch rig.  I voraciously acquired hirez Mch discs, and I abandoned CD stereo.  I haven't bought one in over a decade.  My stereo-only front end - Levinson, Audio Research, Theta Digital, etc.  was all sold.  Miraculously, those sales yielded about the same $10k that the Mch audio upgrade had cost!  But, it would have easily been worth it to me in terms of sonic improvement even without recouping any of my investment in Mch.

 

Many things were learned in this upgrade.  Of course, the main thing was just how good Mch was, even from an incredibly cheap Oppo player.  The extraordinary power of DSP Room EQ - Audyssey then, Dirac Live now - was built into my HT prepro, another absolutely indispensable discovery of huge significance.  But, I also learned once and for all in spades that spending big bucks on stereo was just not achieving any significant strides toward better reproducing concert hall sound.  I have the good fortune to be able to continue to listen to prestige, high cost stereos.  They do not compare, in my view, to even much more modest Mch systems with discrete Mch source material.  Mch gives a plausible replica of live concert hall sound.  Stereo simply does not.

 

And, BTW, old, classic Reiner on RCA, Dorati on Mercury, etc.  do sound noticeably better in 3.0, as recorded, than as 2.0, as mixed down.  However, recordings made over the past 15 years or so in discrete hirez Mch are simply the best by far sonically 

I have ever encountered.

 

But, if you are stuck on old performances, meaning old recordings, then aspiring to live concert hall sound is just not gonna happen.

[Fitzcaraldo215]

4 hours ago, semente said:

 

 

Amused to Death is an interesting exercise of spatial/ambience manipulation but it has very little realism in it (it's an effect). Which I think is what happens when you add "ambience-enhancement" (for want of a better word) to a stereo recording performed in a real reverberant space. And apparently I'm not the only one who feels like this.

 

 

I don't see how this can be done unless the recording was made in an anechoic chamber (i.e. Denon CD). A recording made in a reverberant space will have spatial information which need to be reproduced unprocessed to be accurately reconstructed.

We agree.  I walked out on an advance demo of Amused to Death conducted by the remastering team in Mch.  The field of crickets was good.  But, the rest was mediocre sonically and, dare I say it, musically.  

 

Probably the the main reason Mch, while huge for home theater, is not more popular for music is because it cannot do much for multitrack mixes from acoustically dead studios or PA equipped concert rock music.  Yes, it can do "artistic" but synthetic panning effects to surround channels.  But, that hardly makes it a must have.  The novelty of that artificial "surround" effect loses luster, as on Dark Side of the Moon, probably the top selling Mch SACD.   I must say, though, that the two Allman Brothers, Quad-era remasters from live concerts - At the Filmore East and Eat a Peach - are really pretty good at capturing the sense of live rock, though from a fairly close in perspective.  They are my favorite Mch rock albums.  Terrific music, too, while the great Duane Allman was still alive.

 

But, looking at the available Mch music recordings on hraudio.net, it is clear that there is relatively much less rock or other genres and a whole lot of classical.  Classical is already a small niche in the market and Mch a niche within the niche.  Yet, discretely recorded classical Mch persists because some dedicated labels with excellent engineering and the small niche audience remain steadfastly loyal to it.  

 

And, the reason, of course, is not gimmicks.  The reason is it captures and reproduces a more faithful replica of live, natural  concert hall sound than stereo through the added sonic information in the additional, carefully arrayed channels.  It captures the hall and its effects on the sound the audience hears, whereas stereo of necessity must truncate and discard much of it, as already discussed.

 

I also wish STC much success and enjoyment in his synthetically augmented 72 channel setup.  I have not heard it or anything like it, except for 14.2 channel, discretely recorded Auro 3D, which was impressive, but not sufficiently so to make me want to embrace it or to change my love affair with 5.1/7.1 Mch.  It simply was not compelling enough to me.

 

Also, the thought of, not to mention the budget for, even a fraction of 72 channels does not appeal.  I don't see why the natural ambiance of the hall as captured by surround mics is insufficient, or how or why we need to synthesize some fantasy in our heads of a more perfect hall than the real thing.  I have no doubt the effect is striking, even if not real.  But, rather than tinkering with the setup and DSP adjustment of such a system, I'd rather be listening to some beautiful 5.1/7.1 discrete recordings with very good reproduction of natural concert hall sound.

[Fitzcaraldo215]

2 minutes ago, GeneZ said:

  Your missing my point. Yes,  a good hall reflects sound plentifully.  But a good hall does not reflect 18000 hz from the back of the hall.  Upper midrange on down to the lowest is what those halls that make you feel good reflect.  It gives the band that nice warm deep sound,  while the high notes emanate from the stage in front of you.   I do not speaks of rock bands today who amplify everything.  They are too loud.  That's not music.  Its sacrifice ritual ceremonies designed to drown out the screams of those being sacrificed...  ?

Yes, concentrating on halls without PA or other reinforcement, the sound fields in many good halls have been  measured at points out into the audience seating area.  There is HF rolloff of both the direct and reflected sound with increasing distance from the stage.  The sound increasingly is dominated by bass and midrange, giving a "warmer" sound that people have preferred over the ages. This is natural and desirable.  Good stereo recordings attempt to adjust for this by mixing in more hall sound along with EQ.  Discrete Mch recordings already include more of this warmer hall sound naturally.