Genelec on audio science

[sergeauckland]

Agree on 'imagery'. It is still a fuzzy topic.

The main practical drawback to multi-channel is multiplicity of wiring(aesthetics) and loudspeakers( cost and aesthetics). Then, how many people can be bothered with it? Similar to the old Quadraphonic days. It is a bit like 3D TV, not so convincing.

Imagery has always been important to me with HiFi. With a real live performance if one closes one's eyes, there isn't the sort of sharp imaging we get with HiFi as mostly, we're sitting in a diffuse soundfield. With a live performance, where there is the visual confirmation of who's playing what, I suggest that imagery isn't very important. At home, however, we don;t have the visual, so accurate imaging becomes important, at least to me.

I've found that for accurate imaging, the loudspeakers have to be closely matched, and many of today's loudspeakers are not that good, several dBs difference between the loudspeakers at certain frequencies, and this screws up the phantom image. Match the loudspeakers to 1dB across the audio band, and imaging becomes very tight, and the loudspeakers 'disappear' insofar as they no longer draw attention to themselves. When I equalised my own 'speakers to +-1dB from 200Hz-20kHz and pair-matching was well under 1dB, the imaging improved immeasurably. (immeasurably as I have no idea how to measure imaging!)

I still enjoy Quadraphonics, but not because the surround is accurate, but just for the sheer fun of scraping 4 channels out of an LP. I can completely understand why it failed, three (or four) competing and incompatible systems, none of which worked very well, or not for long in the case of CD-4, and the domestic difficulty of positioning four loudspeakers correctly. Hell, few people manage to get two loudspeakers positioned properly for stereo, what chance four loudspeakers? Nevertheless, my modest collection of SQ encoded LPs is growing slowly, but I have to recalibrate my head whenever I play one as HiFi it's not.
S.

 

[Fitzcaraldo215]

An observation I have regarding stereo, and therefore possibly relevant to multichannel:

When I listen to a 'purist' stereo recording with my stereo setup, the side of the room where the speakers are appears to be transformed into a different acoustic space - it is very convincing and compelling, and worth the price of building a decent hi fi system in itself. There is no need for a centre channel because the audio 'scene' is apparently spread out throughout the end of the room with perfect stability and solidity. You can envisage getting up and walking around the individual musicians in some recordings. Turning your head, the illusion seems to be maintained convincingly.

However, it is not, as some people imagine, a 'holodeck' type synthesis of a real space. If you do get up and walk around, the image does not stay stable while you are moving. But when you do stop moving a new, plausible, image appears.

This, it now seems to me, is what should happen with stereo: as you move towards one speaker and away from another dynamically, the inter-speaker time delays shift uniformly for everything in the recording, which is not what would happen in a real 3D scene. But when you stop moving the relative delays between the individual elements in the recording re-assert themselves and a new, different scene appears. But it is not as if you have moved position and are looking at the original scene from a different angle; it is now a somewhat different scene altogether. However, because there are only two speakers, there is still a unique 'solution' to the scene that results in a new, clear, stable image.

With multichannel, am I going to get that stability and clarity of image? Can multiple channels create the stable 'unique solution' that stereo produces? Is the aim to create an impression of a 'holodeck' I can walk around, at the expense perhaps of the exquisite detail of the stereo image? Is it still meant to be enjoyed from a specific, stationary position?

An earlier reference said that surround sound was mainly about incoherent non-minimum phase delayed reflections. Can I just keep my stereo and pipe some delayed AVR 'hall preset' to a few surround speakers and achieve 90% of what multichannel is all about, anyway?

Yes, you can move around with Mch in much the same way with no problem. In my opinion, stability and clarity of image are at least as good as with stereo, actually better, in fact, because of the "anchoring" of the frontal image by the center channel, among other things. Clarity and perceived depth and dimension of the frontal image are considerably enhanced by discrete Mch. My perception is also that the listening sweet spot is actually somewhat wider than stereo in terms of delivering a satisfying image.

In my experience, no, synthesized surround does not get even close to 90% of discretely recorded Mch. It produces an immersive effect that some people like. But, its effect is more invariant in spite of program material, though that can be tweaked via interchannel balances, etc. on a recording by recording basis. Discretely recorded Mch captures and reproduces much more of the actual acoustic of the recording venue automatically.

 

[Blumlein 88]

An observation I have regarding stereo, and therefore possibly relevant to multichannel:

When I listen to a 'purist' stereo recording with my stereo setup, the side of the room where the speakers are appears to be transformed into a different acoustic space - it is very convincing and compelling, and worth the price of building a decent hi fi system in itself. There is no need for a centre channel because the audio 'scene' is apparently spread out throughout the end of the room with perfect stability and solidity. You can envisage getting up and walking around the individual musicians in some recordings. Turning your head, the illusion seems to be maintained convincingly.

However, it is not, as some people imagine, a 'holodeck' type synthesis of a real space. If you do get up and walk around, the image does not stay stable while you are moving. But when you do stop moving a new, plausible, image appears.

This, it now seems to me, is what should happen with stereo: as you move towards one speaker and away from another dynamically, the inter-speaker time delays shift uniformly for everything in the recording, which is not what would happen in a real 3D scene. But when you stop moving the relative delays between the individual elements in the recording re-assert themselves and a new, different scene appears. But it is not as if you have moved position and are looking at the original scene from a different angle; it is now a somewhat different scene altogether. However, because there are only two speakers, there is still a unique 'solution' to the scene that results in a new, clear, stable image.

With multichannel, am I going to get that stability and clarity of image? Can multiple channels create the stable 'unique solution' that stereo produces? Is the aim to create an impression of a 'holodeck' I can walk around, at the expense perhaps of the exquisite detail of the stereo image? Is it still meant to be enjoyed from a specific, stationary position?

An earlier reference said that surround sound was mainly about incoherent non-minimum phase delayed reflections. Can I just keep my stereo and pipe some delayed AVR 'hall preset' to a few surround speakers and achieve 90% of what multichannel is all about, anyway?

Yes, this was very satisfying doing recordings with just a couple well chosen and placed microphones. You open the end of the room up to sound like somewhere else.

And to my dismay, most, nearly all non-audiophiles do not like that kind of sound quality. They hear the hall, the sense of space and the other acoustic as noise between them and the music. Recordings of smaller musical groups had people complaining the band was lost in all that space they were hearing. Crestfallen was I with those evaluations. These recordings sounding very much like sitting in the actual space where those people were playing. I wonder if it is something of directional masking in play since the image and space were coming from the same two speakers as the music. I've not yet done as many mch recordings, but in those handful having the extra speakers provide that other acoustic and having the center to better anchor the music up front seems to meet with better reception from regular folks. It is not that they exclaim how good it is, they simply don't complain of the hall acoustic being in the way of the music.

 

[Floyd Toole]

Yes, you can move around with Mch in much the same way with no problem. In my opinion, stability and clarity of image are at least as good as with stereo, actually better, in fact, because of the "anchoring" of the frontal image by the center channel, among other things. Clarity and perceived depth and dimension of the frontal image are considerably enhanced by discrete Mch. My perception is also that the listening sweet spot is actually somewhat wider than stereo in terms of delivering a satisfying image.

In my experience, no, synthesized surround does not get even close to 90% of discretely recorded Mch. It produces an immersive effect that some people like. But, its effect is more invariant in spite of program material, though that can be tweaked via interchannel balances, etc. on a recording by recording basis. Discretely recorded Mch captures and reproduces much more of the actual acoustic of the recording venue automatically.

I completely agree. Upmixing is a serious compromise compared to a deliberate multichannel mix, but for me and many others it is a step up from unadulterated stereo - which is where most of the music is. I cannot understand how one can be such a stereo "purist" to think that there are no possible improvements. After all, stereo is the first, minimalist, step above mono

 

[Floyd Toole]

I wonder if it is something of directional masking in play since the image and space were coming from the same two speakers as the music.

My guess is that having the "room" sounds arriving from directions other than the front channels is the key. Then it is possible for two ears and a brain to binaurally process the combination of sounds and to perceptually stream the music sources as separate from the sounds provided by the listening venue. This is the "listening through the room" phenomenon that makes live unamplified performances so special.

 

[Blumlein 88]

I completely agree. Upmixing is a serious compromise compared to a deliberate multichannel mix, but for me and many others it is a step up from unadulterated stereo - which is where most of the music is. I cannot understand how one can be such a stereo "purist" to think that there are no possible improvements. After all, stereo is the first, minimalist, step above mono

Ahhhh!................so you summarily dismiss the mono(phile)theists among us.

No comb filtering, no preferred listening position. So many issues never even have the chance to occur. Stereo is the sin that gave birth to the abomination of multi-channel audio in a conspiracy to sell more of everything. Plus it gives a never ending upgrade path of more and more channels, more formats, more processing more more more.................

Did I mention some of the above may not represent my own views.

 

[Floyd Toole]

Ahhhh!................so you summarily dismiss the mono(phile)theists among us.

No comb filtering, no preferred listening position. So many issues never even have the chance to occur. Stereo is the sin that gave birth to the abomination of multi-channel audio in a conspiracy to sell more of everything. Plus it gives a never ending upgrade path of more and more channels, more formats, more processing more more more.................

Did I mention some of the above may not represent my own views.

I'm old enough to remember when stereo was introduced. Some diehard mono enthusiasts dismissed it as a gimmick, not necessary because everything that mattered was in a single channel - tune, lyrics, foot tapping motivation - what more could there possibly be?

 

[svart-hvitt]

I'm old enough to remember when stereo was introduced. Some diehard mono enthusiasts dismissed it as a gimmick, not necessary because everything that mattered was in a single channel - tune, lyrics, foot tapping motivation - what more could there possibly be?

That’s one quote for writing down!

 

[pirad]

Listen to “Something Cool” by June Christy. It’s in mono and stereo versions.
The mono version on good stereo systems sounds so much better IMNSHO.

 

[tomelex]

I'm old enough to remember when stereo was introduced. Some diehard mono enthusiasts dismissed it as a gimmick, not necessary because everything that mattered was in a single channel - tune, lyrics, foot tapping motivation - what more could there possibly be?

I often ask people to perform this simple experiment (well it used to be simple as all good preamps had a mono switch), play your music in mono for a week and then one day just while playing a song flip the switch back to stereo, and listen to how contrived and artificial it sounds. Many have become so accustomed to stereo they have no idea what it really is doing.

Knowing what it really does allowed me to pursue other things like choosing equipment that allowed more details to be heard in the music and also paradoxically, to listen to SET amps for their added dynamics and what I call chorus effect.

The key take away I had was a reasonable expectation of what stereo could and could not do, and lucky for me that was in my early twenties and since then I have enjoyed what it can deliver not what I expect it to deliver and kept me off the audiophile road to hell.

 

[tomelex]

Listen to “Something Cool” by June Christy. It’s in mono and stereo versions.
The mono version on good stereo systems sounds so much better IMNSHO.

stereo has the potential to sound better but I have found the the stereo with the most minimal "stereo" sounds best IMHO

 

[Guermantes]

"Satisfying" is a term that is cropping up here, and I don't think it is necessarily linked to "accuracy". Stereo is more satisfying than mono and MCh more satisfying than stereo but satisfaction is really a very personal thing, perhaps only quantifiable with analysis of the perceptions of large sample of people (as has been done with psychoacoustic encoding schemes).

Perhaps we need a separate thread on multichannel techniques -- both recording and replay -- and their success or satisfaction levels. We could also share recordings that translate well to a satisfying surround experience.

 

[Fitzcaraldo215]

I'm old enough to remember when stereo was introduced. Some diehard mono enthusiasts dismissed it as a gimmick, not necessary because everything that mattered was in a single channel - tune, lyrics, foot tapping motivation - what more could there possibly be?

Yes, I remember those days, too. I was amazed by many well-heeled audiophile friends with superb for their day mono systems in their absolute rejection of stereo as nothing but a conspiracy to sell more gear.

But, with due respect to the prologue to Star Trek on TV, it is about "space...the final frontier". Stereo took a hugely important step in that direction, from zero to one dimension commercially over 50 years ago. 2D Mch 5/7.1 took another huge and valuable step, now substantially refined and improved over many decades. And, the newest "3D Immersive" audio will someday conquer the final dimension of space in the height direction, invoking all the possible dimensional aspects of our natural hearing capability.

On 3D, I will be very interested in your observations as you get more acquainted with it. I too have heard discrete Auro 3D, and I have heard very good things about synthesis of it from Mch or even stereo sources. Personally, it was impressive in discrete form, but probably not worth waiting for in my limited lifetime in terms of a steady source of viable, commercial, discrete 3D music recordings. There seem to be clearly diminishing returns to my ears in 3D vs 2D, which is not a huge surprise. Meanwhile, my substantial library of discrete 2D Mch recordings provides much great pleasure. That may be as good as it gets for me, but I have never been remotely happier with the reproduced sound in my listening room.

 

[sergeauckland]

When discussing mono, I think we need to distinguish between mono played on one loudspeaker and when played on two loudspeakers, with a phantom central image. My AEG turntable has a mono switch which mutes the right channel, and only drives the left. Playing mono LPs, or indeed CDs of mono recordings, playing with one loudspeaker only sounds flat, dull, located in that loudspeaker, whilst playing out of both, creates a tight phantom image which I find perfectly acceptable for a mono recording.

At the time when HiFi went from mono to stereo, people would have gone from one to two loudspeakers, more or less well matched if they just bought a second channel, so comparisons between their old one ' 'speaker mono and playing their existing mono LPs in two channel wouldn't be comparable except insofar as I think few would have switched off the second channel when playing mono, so presumably the greater perceived spaciousness of the dual channel mono would have been preferred.

S

 

[Fitzcaraldo215]

"Satisfying" is a term that is cropping up here, and I don't think it is necessarily linked to "accuracy". Stereo is more satisfying than mono and MCh more satisfying than stereo but satisfaction is really a very personal thing, perhaps only quantifiable with analysis of the perceptions of large sample of people (as has been done with psychoacoustic encoding schemes).

Perhaps we need a separate thread on multichannel techniques -- both recording and replay -- and their success or satisfaction levels. We could also share recordings that translate well to a satisfying surround experience.

Ok, I am game on for that. However, recording techniques are really an area ideally spoken to by professional recording engineers.

I think I understand the de facto standard for most all available Mch music recordings, which is based on the ITU 5.0/.1 speaker layout. Others methods seem less important to me, although ITU is largely compatible with Dolby and DTS recommendations for BD home theater.

So, do you wish to start a new thread?

 

[Fitzcaraldo215]

When discussing mono, I think we need to distinguish between mono played on one loudspeaker and when played on two loudspeakers, with a phantom central image. My AEG turntable has a mono switch which mutes the right channel, and only drives the left. Playing mono LPs, or indeed CDs of mono recordings, playing with one loudspeaker only sounds flat, dull, located in that loudspeaker, whilst playing out of both, creates a tight phantom image which I find perfectly acceptable for a mono recording.

At the time when HiFi went from mono to stereo, people would have gone from one to two loudspeakers, more or less well matched if they just bought a second channel, so comparisons between their old one ' 'speaker mono and playing their existing mono LPs in two channel wouldn't be comparable except insofar as I think few would have switched off the second channel when playing mono, so presumably the greater perceived spaciousness of the dual channel mono would have been preferred.

S

I think Dr. Toole's excellent latest book covers the issue quite well. His conclusion is that mono is best reproduced by a single, centered speaker rather than by phantom imaging by two speakers. He is far from alone in that view among professionals. The supporting details are all there and quite clear. However, your personal preference for whatever reason must be respected.

 

[sergeauckland]

I think Dr. Toole's excellent latest book covers the issue quite well. His conclusion is that mono is best reproduced by a single, centered speaker rather than by phantom imaging by two speakers. He is far from alone in that view among professionals. The supporting details are all there and quite clear. However, your personal preference for whatever reason must be respected.

I have just today received Dr Toole's book, but haven't read past the introduction, so looking forward to the rest of the book. Your point is valid, insofar as I don't move my 'speakers when listening to mono, my choice is a single (left) loudspeaker or both together, and I prefer both together as then the image is central. My point also is that domestically, I would expect most people to do the same, either use one loudspeaker of a stereo pair, or both, and to have done so for the 50 years since stereo first became available.
S

 

[Pio2001]

I think Dr. Toole's excellent latest book covers the issue quite well. His conclusion is that mono is best reproduced by a single, centered speaker rather than by phantom imaging by two speakers. He is far from alone in that view among professionals.

Oh really ? But I have read also that the defects of a given loudspeaker would be much more audible if used alone in a mono configuration, than using the pair. So, if using two loundspeakers masks their defects, then a mono program listened to with two speakers should sound better, shouldn't it ?

I've just tried : it sounds good on the left speaker if I move my listening position in front of it. It also sounds good on the right one if I move the listening position towards the other side.
With both speakers, is sounds good too.

Since my room correction is the same on both channels, I can't comment on the general frequency response : it is necessarily flawed when I have only one speaker active. One of them is related with two low frequency room modes (55 Hz and 70 Hz), the other has only one (55 Hz). And my equalization corrects both of them on both channels at once.

The difference is that with both speakers, the sound is "wider". It is not concentrated inside a central phantom image. I can hear some high frequencies coming from the sides, although my configuration is narrower than the usual equilateral triangle.

So I guess that a single speaker is better if you need to create a central image, like with dialogs in movies, but two speakers are better to listen to music recorded in mono.
By the way, I've heard that using several subwoofers was a good idea, although they all play the same mono signal...

 

[pirad]

By the way, I've heard that using several subwoofers was a good idea, although they all play the same mono signal...

Several subs are used to alleviate room modes appearing below Schroeder frequency ( typically 200-300Hz).

 

[fredoamigo]

"Satisfying" is a term that is cropping up here, and I don't think it is necessarily linked to "accuracy". Stereo is more satisfying than mono and MCh more satisfying than stereo but satisfaction is really a very personal thing, perhaps only quantifiable with analysis of the perceptions of large sample of people (as has been done with psychoacoustic encoding schemes).

Perhaps we need a separate thread on multichannel techniques -- both recording and replay -- and their success or satisfaction levels. We could also share recordings that translate well to a satisfying surround experience.

In everyday language, we usually oppose illusion and truth: illusion is what masks the truth, prevents us from seeing things as they are. Yet can it not also, in some cases, be a path to the truth? or are the two things not compatible for audio mch ?