Gentlemen, draw your swords! Multi-channel or 2-channel?

[Robh3606]

Put your ear up to a wall whether in your own listening room, a concert hall, cathedral and what do you hear coming from the wall? Nothing. The intensity of sound coming from any one direction is so low it's inaudible.

Hello Soundminded

From personal experience I have to disagree. I was at MSG for a concert a couple of weeks ago and was quite surprised just how audible the echo can be depending on where you sit. I was sitting in line with the stage and you could clearly hear the reflection from the rear coming back at the stage. It was very easy to hear. There was obviously quite a bit of energy reflected off the back walls.

I agree you shouldn't be able to locate the rears, they should just be a difuse field.

Rob

 

[edorr]

The multichannel sound system I built for my own use addresses problems of reproducing large room acoustics in a small room conventional multichannel systems don't. 1) the required acoustics are largely not in the recording and to what small degree they are they are inadequate by themselves. The reverberant acoustic field has many components arriving from many different directions. Not only is this aspect of them lost to the recording but what little is there due to microphones being placed close to the instruments can't be separated from the direct sound. Some of the direct field will therefore be heard from the speakers that are supposed to reproduce only the reverberant field. This flaw alone was enough to be a deal breaker for me insofar as quadraphonic sound and its like are concerned. 2) as soon as you point the speaker that's supposed to reproduce the reverberant field at yourself, IMO your goose is cooked. Put your ear up to a wall whether in your own listening room, a concert hall, cathedral and what do you hear coming from the wall? Nothing. The intensity of sound coming from any one direction is so low it's inaudible. But put all of it together and that's almost everything you hear. That's what you have to arrive at to duplicate it and it's no easy trick. If you can hear where the speakers are that are intended to reproduce the reverberant field, you've failed as I see it.

The best rooms to even try it in I've found are those of approximately the same proportions and shape as concert halls and the like themselves, rectangles with no large discontinuities of reflective surfaces. Even so it's not an easy illusion to create. But when it works......

On the Adele live blu ray, there is an echo when she talks to the audience between tracks. This very realistically creates the large venue illusion in my small room. I agree the surrounds should be very difuse to achieve this. In fact, when I upgraded from Paradigms to B&W 8NT in walls the surrounds simply disappeared on good MCH recordings. Hardware quality matters a lot. I am even toying with the idea of upgrading my Bel Canto S300 amp I use for surround channel to a pair of Ref 500 monos.

 

[Robh3606]

On the Adele live blu ray, there is an echo when she talks to the audience between tracks. This very realistically creates the large venue illusion in my small room.

Yes mine as well, great DVD

Rob

 

[edorr]

Yes mine as well, great DVD

Rob

The loud vocal passages have distortion in the high frequencies, which gets very annoying though. It is in the recording.

 

[NorthStar]

The multichannel sound system I built for my own use addresses problems of reproducing large room acoustics in a small room conventional multichannel systems don't. 1) the required acoustics are largely not in the recording and to what small degree they are they are inadequate by themselves. The reverberant acoustic field has many components arriving from many different directions. Not only is this aspect of them lost to the recording but what little is there due to microphones being placed close to the instruments can't be separated from the direct sound. Some of the direct field will therefore be heard from the speakers that are supposed to reproduce only the reverberant field. This flaw alone was enough to be a deal breaker for me insofar as quadraphonic sound and its like are concerned. 2) as soon as you point the speaker that's supposed to reproduce the reverberant field at yourself, IMO your goose is cooked. Put your ear up to a wall whether in your own listening room, a concert hall, cathedral and what do you hear coming from the wall? Nothing. The intensity of sound coming from any one direction is so low it's inaudible. But put all of it together and that's almost everything you hear. That's what you have to arrive at to duplicate it and it's no easy trick. If you can hear where the speakers are that are intended to reproduce the reverberant field, you've failed as I see it.

The best rooms to even try it in I've found are those of approximately the same proportions and shape as concert halls and the like themselves, rectangles with no large discontinuities of reflective surfaces. Even so it's not an easy illusion to create. But when it works......

---- Good post. I've experimented in the past (extensively) in various rooms with Trifield from Yamaha processors, and with several positions of the four surround speakers (in addition to the three main front speakers and two subs), with occasionally good enough results from certain recordings and with the appropriate parameter adjustments (delicate). ...Mainly from Classical and Jazz (some Blues too) music recordings, on CDs.

It was too much time consuming, and after few years I let things vanished.

Now, I'm older, and wiser, and simpler. I listen to the already recorded multichannel SACDs and
DVD-Audios, and Blu-ray music concerts, and simply appreciate the ones done with professional taste by the recording/mixing engineers. ...But too often I wish I was myself at the control of the mixing console and the entire recording process/project.
...Not an easy job if you want to do the right things. ...The true "artists" are rare because it is a business, a music industry which is the front runner; they simply don't have the time and luxury to truly perform their 'art'.
It's up to us, the listeners at home, to treat the recordings with 'due dignity' and our rooms appropriately. ...Some are worth it, others forget it.

Ambiance, that is the key word in realistic surround sound. Anyone who puts something else in the surround channels is out of the game in my book.

 

[NorthStar]

Hello Soundminded

From personal experience I have to disagree. I was at MSG for a concert a couple of weeks ago and was quite surprised just how audible the echo can be depending on where you sit. I was sitting in line with the stage and you could clearly hear the reflection from the rear coming back at the stage. It was very easy to hear. There was obviously quite a bit of energy reflected off the back walls.

I agree you shouldn't be able to locate the rears, they should just be a difuse field.

Rob

---- Here's the thing Rob; in a Concert Hall if you sit near the back or side walls you'll hear reverbs that are quite stong and it will affect the entire realistic soundstage, the full performance and experience. It'll 'destroy' the good things.
Remember too, near the rear of the hall you are usually sitting behind the balcony just above you, so you have a ceiling there that is much lower than sitting in front (main hall's ceiling).
The echoes (reverbs) are much much stronger, and they totally ruin the true direct essence of that live performance. ...If your goal is to have the best of the best of course.

It is primordial that you choose a good seat carefully. ..That means generally at center alleys between G & J. But some people like K, L, & M too, depending on the particular venue. ...E & F could also be fine, if the live concert is from a smaller ensemble, like chamber music; but in that case a much smaller room is preferable. ...And same for Jazz music with three to six musicians.

Furthermore, in that hall we are sitting below the actual stage where the musicians/singers are performing, or above it at the main rear balcony or side balconies.
So it is tough to grasp an actual and accurate live performance.
...You go for what is the most 'pleasant' and 'balanced' sound at the most positions possible, and you follow some basic guidelines.

I worked in a hall theater when I was young as an engineer assistant for sound & light, and I checked the sound projections from EVERYWHERE, even behind and at the sides of the main stage.

...Two totally different spaces (live hall and our room) and two totally different mediums (live and recorded music).
And you need more than 'magic' to get everything just right.

For me, both Stereo and Multichannel music have their Pros & Cons.
One can be as effective as the other if properly set up and with the right material (music mediums).
And most importantly, a properly acoustically treated room for one or the other, but not both, I truly believe.

 

[Soundminded]

Hello Soundminded

From personal experience I have to disagree. I was at MSG for a concert a couple of weeks ago and was quite surprised just how audible the echo can be depending on where you sit. I was sitting in line with the stage and you could clearly hear the reflection from the rear coming back at the stage. It was very easy to hear. There was obviously quite a bit of energy reflected off the back walls.

I agree you shouldn't be able to locate the rears, they should just be a difuse field.

Rob

For a concert hall this is an unacceptable acoustic defect. By MSG I assume you mean Madison Square Garden. This is not a concert hall, it's a sports arena. Surely you heard much of the sound through amplifiers and speakers. Even so, were you near a wall and put your ear up to it, you stil wouldn't hear the reflection. However as you move away from the wall, you ears are picking up sound from an increasingly wide angle. You are hearing a great deal of almost nothing, the emphesis being on "almost."


You sometimes hear the same thng in churchs and cathedrals and it comes as no surprise there, it's to be expected because of the very long length of the structure and consequential time delay involved. It will become more noticable as you got to the front and the time delay from the first rear reflection gets longer.

When I was in high school I went on a class trip to the then new Philharmonic Hall (now called Avery Fisher Hall) at Lincoln Center in Manhattan. We walked through a door and found ourselves in a balcony as Leopold Stokowski wa rehearsing the New York Phiharmonic. Lucky me. I was surprised that I distinctly heard the trumpet player on the right of the stage and a reflection of his sound off the left procenium arch around the stage (I don't know if it's still there, it may have been removed in one of countless renovation trying to salvage the place.) A distinct focused echo or evident reflective surface that's audibly identifiable is a design blunder. To prevent that, acoustic architects avoid concave surfaces and deliberately break up large reflective areas. Look at photos of the interior of Boston Symphony Hall someone posted elsewhere. Notice the coffered ceiling panels. Notice how the side walls are broken up and the art niches with statuary in them. The parameter Beranek and others refer to is SDI which stands for surface diffusivity index. It's a measure of how irregular surfaces break up focused or planar reflections that can cause them to be distinctly audible.

 

[MarinJim]

By multi channel, do you mean Dolby Atmos?

 

[treitz3]

You have the power to mean multi-channel anyway you want. With me not even hearing of this Dolby Atmos yet, is it really "revolutionary"? With only 16 movies out and two TBD, it is obvious that this hasn't been around the block yet. I see ten of those haven't even been released yet. Have you had a chance to experience the Atmos yet, MarinJim?

Tom

 

[Soundminded]

---- Here's the thing Rob; in a Concert Hall if you sit near the back or side walls you'll hear reverbs that are quite stong and it will affect the entire realistic soundstage, the full performance and experience. It'll 'destroy' the good things.
Remember too, near the rear of the hall you are usually sitting behind the balcony just above you, so you have a ceiling there that is much lower than sitting in front (main hall's ceiling).
The echoes (reverbs) are much much stronger, and they totally ruin the true direct essence of that live performance. ...If your goal is to have the best of the best of course.

It is primordial that you choose a good seat carefully. ..That means generally at center alleys between G & J. But some people like K, L, & M too, depending on the particular venue. ...E & F could also be fine, if the live concert is from a smaller ensemble, like chamber music; but in that case a much smaller room is preferable. ...And same for Jazz music with three to six musicians.

Furthermore, in that hall we are sitting below the actual stage where the musicians/singers are performing, or above it at the main rear balcony or side balconies.
So it is tough to grasp an actual and accurate live performance.
...You go for what is the most 'pleasant' and 'balanced' sound at the most positions possible, and you follow some basic guidelines.

I worked in a hall theater when I was young as an engineer assistant for sound & light, and I checked the sound projections from EVERYWHERE, even behind and at the sides of the main stage.

...Two totally different spaces (live hall and our room) and two totally different mediums (live and recorded music).
And you need more than 'magic' to get everything just right.

For me, both Stereo and Multichannel music have their Pros & Cons.
One can be as effective as the other if properly set up and with the right material (music mediums).
And most importantly, a properly acoustically treated room for one or the other, but not both, I truly believe.

"Remember too, near the rear of the hall you are usually sitting behind the balcony just above you, so you have a ceiling there that is much lower than sitting in front (main hall's ceiling)."

This is a very important point. When you sit under a balcony, you are in what's called an "acoustic shadow." You don't hear reflections from the part of the ceiling that's high above, especially from that part which is behind you. The ceiling below the balcony has much shorter delays and its loudness isn't nearly as great. The acoustics of a room are different at every point. In one of Beranek's 2008 papers, he re-evaluated the importance of reflections from above and behind the listener being much more important to listener envelopment than he had previously thought. He re-defined his calculation for this parameter called LEV. Being a reverb freaK all my life I enjoy hearing rehearsals in an empty or near empty hall. You're right about finding a critical balance between the direct and reverberant field. Too close to the front and you hear less of the hall relative to the direct and earliest reflections, too far back and the balance is wrong the other way. What's the perfect spot? That's stictly a matter of personal taste.

One misake it's easy for people trying to recreate concert hall acoustics to make is to assume that in a good hall since you can't hear the source of reverberation it's isotropic, that is directionless. Experience confirms what my model shows, that the directionality of different reverberant components is critical even though we're not consciously aware of them in a hall with good acoustics. It's the reason for differences in Intera-Aural-Cross-Corrolation (IACC) in different halls and the resulting Binaural Quality Index (BQI.) It may also affect Apparent Source Width (ASW.) These have to be taken ito account in simulating the acoustics of a large room electroacoustically in a small room. The multichannel systems you can buy usually have only two reverberant channels but in some cases more. One problem with those that try to extract the reverberant components on the recording from the direct and earliest components is that they can't completely get rid of the direct field. The reverberant speakers invariably reproduce some of it. You also can't make a recording where the microphones record only the reverberant sound either, they inevitably pick up some of the direct sound and play them through the speakers that are supposed to reproduce only the reverberant sound. Another is that if you have too few speaker to reproduce reverberation and/or they are pointed driectly at you, you will hear where their sound is coming from. That's not what you hear live.

Getting the process just right is difficult. First you need an understanding of how the reverberant field works and then you need a system that is capable of reproducing it. And then you need a lot of patience to get each of its components just right. Refining a machine that can do this and learning to adjust it takes considerable patience and experimentation. Is it worth it. IMO you bet it is. Once I heard it, there was no going back. In trying to figure out why it works, I came up with a kind of parameter that I think of as how powerful a sound of a given loudness and spectral content is perceived. In addition to abolute loudness and how much bass content there is, three important factors are how far away the source of the sound is (the perceived power seems to vary with the square of the perceived distance), how large the room is perceived to be (it's apparent volume) and how long it takes for reflections to die out. By that measure the perceived power of a typical source of a musical performance at a live concert in a typical concert hall is approximately 43 db greater (a factor of 20,000) than a recording of the same music played on a typical 2 channel sound system in a typical room. The factors are 3 to 4 times the perceived distance, 150 to 200 times the perceived volume, and 10 times the perceived time for the sound of each note to die out. For a cathedral it's more like 50 db or 100,000 times as great. It can be even greater. What a difference!

 

[NorthStar]

-- Another great post Soundminded.

Recording techniques from the recording engineer are into places; the reverbs in a concert hall, in order to be well recorded, require directional mikes aimed at the back wall and rear side walls, so that you don't record the direct sound from the front soundstage. ...Not easy to do at all; requires a lot of experimentation (trials and errors).
Because where you put them mikes exactly is a very tough proposition for best results.
...And also the type of mikes used. ...And how far, how deep, or closer to the walls do you put the mikes, and how high, depending of EACH venue (concert hall)? ...Not easy at all as you have billions of various combinations to experiment with. Do you have the time, to do it right, or at least the best that it can be?

You might need a "cover protector" behind the mike (between the mike and the front soundstage), but not material reflective, in order to help.

I found multichannel SACDs, some, are doing the best job so far, in that regard.

Choral music from churches, cathedrals, etc. are also falling into this category.

Personally, I love Operas, and their performances can happen in several various venues, even outdoors. ...But lets stay inside, it is by far much easier to control. :b

 

[Soundminded]

-- Another great post Soundminded.

Recording techniques from the recording engineer are into places; the reverbs in a concert hall, in order to be well recorded, require directional mikes aim at the back wall and rear side walls, so that you don't record the direct sound from the front soundstage. ...Not easy to do at all; requires a lot of experimentation (trials and errors).
Because where you put them mikes exactly is a very tough proposition for best results.
...And also the type of mikes used. ...And how far, how deep, or closer to the walls do you put the mikes, and how high, depending of EACH venue (concert hall)? ...Not easy at all as you have billions of various combinations to experiment with. Do you have the time, to do it right, or at least the best that it can be?

You might need a "cover protector" behind the mike (between the mike and the front soundstage), but not material reflective, in order to help.

I found multichannel SACDs, some, are doing the best job so far, in that regard.

Choral music from churches, cathedrals, etc. are also falling into this category.

Personally, I love Operas, and their performances can happen in several various venues, even outdoors. ...But lets stay inside, it is by far much easier to control. :b

I've considered this concept as a viable alternative to my own and it has always seemed to me to have possibilities. As you say it will be difficult. You have to somehow capture the different reverberant components from different dirctions without inadvertently capturing the direct component as well. Therefore a difficult miking problem. I think you need at least 6 channels, two for the direct field, at least 4 for the reverberant field. The technology for laying down 6 or more discrete tracks in a consumer affordable format was a real problem 40 years ago, not so today. There are any number of inexpensive ways to do it. Remember, 40 years ago we didn't even have VCRs yet. That alone gave you 7 mhz of bandwidth to use. On playback you'd face exactly the same problem my concept addresses, recreating a reverberant field that is sufficiently diffuse. It must preserve different directional components having different delay components arriiving at the listener from different directions but uniformity of intensity as a function of angle of arrival must be sufficient that its source isn't audibly identifiable. Ralph Glasgal does it (I think intuitively) in his best system by surrounding himself with panel type speakers, big Soundlabs electrostatic speakers. That is too expensive and impractical for over 99% of audiophiles and in his system, it doesn't address vertical components I cited Beranek as having arrived at as being a critical element in Listener Envelopment (LEV.) The indirect method can work well. I heard one pair of RS Minimus 7s fill up a large RS retail store of a few thousand square feet with undistorted music all buy themselves. Eight pairs in a 400 square foot room that only reproduce the reverberant field is from the standpoint of sound generating capacity huge design overkill (contrary to what one poster said on another thread.) In this concept more smaller speakers and channels are better than fewer larger ones.

In my Sams Engineering Handbook there's a chapter on acoustics including concert hall acoustics. It explains why it is necessary to rake audiences to prevent the listeners in the front row from reaching listeners behind them. It also says however if bass in the direct field is weak, bass in the reverberant field being strong will adequately compensate for it. It seems to work the other way too. The main speakers can produce all of the very deep bass without added delay satisfactorily. This allows the speakers reproducing the reverberant field to be small, in fact it seems to work better that way.

My experience with outdoor concerts is they do not sound very good. Most necessarily use amplfiiers and speakers to reinforce the sound to adequate levels. There is no acoustics to enhance the sound as with concert halls, opera houses and cathedrals. There may be exceptions such as the Hollywood Bowl. Natural amphitheaters may provide interesting but different acoustics. I've never heard one. BTW it is generally acknowledged that the fan shape hall does not work very well. That shape prevents strong lateral reflections from reaching the listener, a critical factor for good acoustics. The surround hall can present other problems for those in the audience seated behind the performers. The conventional shoebox shape seems to work best.

 

[L00k_C]

I belive the question here is like asking a mother which of the two children she loves best?

 

[treitz3]

So, it looks like with 19 more days to go until the poll ends that 2 channel is perhaps the most preferred as of right now. Still, the preference for multi-channel playback has a strong presence here. Results as of today;

If you had a stunningly well recording of a performance you just saw...which type of system would you want to use to recreate the event?

It's time to see where the forum stands at this moment in time with regards to your observations of what constitutes the most realistic playback. Have your experiences got you thinking that multi-channel is the path toward the most realistic reproduction of a performance....or has your experience got you thinking that 2-channel is the path toward the most realistic reproduction of a performance.

Multi-Channel -36.67%

2-Channel - 56.67%

Other type - 3.33%

Haven't decided yet -3.33%

 

[NorthStar]

-- ...And I didn't even vote. :b

* "Other Type", is that for Mono, Quad? ...Perhaps Headphone. ...But Stereo, or Multichannel Headphone listening? ...Most likely Stereo.

 

[treitz3]

Hello and good morning to you, members of the WBF. Just a friendly reminder, this poll will close tomorrow night at around 9:30. Thanks go to those who have participated in the poll so far.

Enjoy the music, no matter your preference.

Tom

 

[Nightlord]

Answering on the original post:

I definitely believe the most illusory reproduction of sound will have to be multichannel. BUT, I don't necessarily believe it is the channels in the current surround formats we need, it could be a completely different combination of speaker placements that should be used. I do have a classical recording made for 7.1 that's definitely a nice experience to listen to, so also current format can be utilized well with some skill.

 

[NorthStar]

-- I'm happy; I finally voted. :b ...33.33% - I'm now part of that group.