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Topic: Center and surround channel

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Posted by Romy the Cat on 07-12-2021
I had a very interesting experience last Sunday. I visited my local audio guy and had a phenomenal listening session. He is horn guy and had a good sound in his dedicated room. He is for year playing with surround sound that I never cared about and mostly listened his 2-channel playback with properly designed and installed (very seldom happens) 45Hz. So, this time he did another dive into his surround sound craze but this time it was different result: it was very good.
 
It is some kind of new large French processor. I do not know what kind 3d algorithm sit runs, there are many of them out there but that was not what impressed me. I was very surprised with the quality of the sound from that thing: the DACs were way better what is expected from a surround processor. His lower bass was very interesting as well which is very strange. As the person who is listening time-alight open baffle for years I can literally laugh about any bass topology out there. Still, if was very music bass in him room, if the source was good. He holt me that he used 8 sub-woofers channels with meticulous time align all of them around the room. Very good idea and very well implemented.
 
The imaging in the room was beyond spectacular, in fact it was not imaging but rather sound could and it was very interesting. I have my issues with some aspect of his implementation but the spacing and imaging the system does variant him to sell ticket in his room, juts to demonstrate what is possible.
I do not want to render surround model in my own listening room, but I certainly get some inspiration from what I hear yesterday. I am conceptualizing 2+3 3D model that I might try…


Anyhow, I never felt that my objective was to recreate the same experiences as people have while they are listening in concert hall, I feel that it is incorrect objective. Still, if I was having that objective what the imaging I experiences yesterday was the closest imaging to live sound that I even experienced in audio

Posted by Paul S on 07-13-2021
I continued to correspond with the late J Gordon Holt after he stopped doing Sterophile stuff. Gordon continued on as a recording engineer who infamously insisted on sonic verisimilitude, by which he meant that the system should "correctly" reproduce the recording. He did understand that this requirement is "loaded". He eventually wound up a staunch proponent of surround sound; not the typical, garden variety 5.1, but what he considered to be an advanced iteration of this format. He was convinced that "space", etc. could not be properly recreated with just two channels. I, myself spent several years exploring a center channel before throwing in the towel, due to old age vs the difficulties of adding distribution algorithms without ruining the sound. I still remember fondly time spent with my brother in his home heater room, watching/listening to operas and Broadway musicals. Depending on how one is listening, there seem to be advantages to surround sound that - situationally -  can overcome innate sonic limitations of popular surround formats. I know nothing of the French system, but if I were betting, I'd bet it's like the old Beta vs. VHS format "wars". We all know how that's turned out. A friend who had tons of money wrapped up in reel-to-reel just recently sold out, lock, stock and barrel to a well-heeled overseas buyer/fanatic. At the time of sale, my friend had fewer than 50 master tapes and 1st dubs, and most were not of performances he would have chosen, other than the format. Not saying the French surround will go this way; but I would not be surprised or over-committed if it does.


Paul S

Posted by Romy the Cat on 07-13-2021
I am not exactly taking about the surround sound as it understood by video people. In fact, I believe that surround sound for video is a bad conceptually as it contradicts in my view some cinematographic objectives. I imply the “surround sound” and a purely audio tool to alters the acoustic signature of my listening environments. I have does it in pass using delay channels for midbass. I am doing it now dealings my migbass channels. As I did it in past it was very promising but not what I wanted and in addition to provide some benefits it had also some negative sonic characteristics. I do not mind playing with it again but in a different way then how it understood in “surround sound” world. I will write it up later.

Posted by Romy the Cat on 07-14-2021
I keep thinking about my new idea of more than 2 channels and room acoustic reinforcement but in natural and organic way, without using DSP.  I have invited my friend who did it from last week to collaborate the idea and to bound some of my concepts against his multichannel experience. He went fully DSP with surprisingly good new processor, but I still would like to not use DSP but acoustic mixing and delays.
 
So, the idea if to have a center channel that would do cross phase injection from right to left (in the way how Lamm L1 did). Also, to have back and top channels drive by delays not by DSP extraction.
 
So, here is what I need, and I started to investigate it. Feel free to pitch me ideas if you know what I am looking:
 
A center channel. Approximately 4-6 feet long and as thin in 2 other dimensions as possible, 3-4” preferably with two horizontal line arrays, the more drivers are better. In a way similar to Yamaha YSP-5600 in configuration but completely passive and with very good MF drivers. The good 3-4” MF drivers are hard to get and to see a sound bar bult out of them is not what I see available. The people who use sound bars care about bass and comfort and I am not. I do not need to go under 100Hz and all that I need is no compression, tone and a few other things. I might bult some like this, but it would take a LOT of experiments and I would rather to buy it.

A processor with 3-5 channels that would do AD, delays and DA. This will be for back and top channels, and it might be some kind of commercial receiver if I find the one that do not compress sound. I really would like this the has a microphone feedback and would allow me to celibate the time arrival but I can do it manually as well
 

Posted by Paul S on 07-14-2021
Romy, during my own quest for a center channel I met (the late) James Bongiorno, all of which I've written about before at GSC. James was a passionate proponent of the center channel, and to that end he developed the Trinaural Processor, which is analog. James is gone now, and these might be hard to find, but they are the only analog center channel processors I know of. Conversely, when, over lunch, I talked about a center channel to a retired movie sound producer I know, he actually drew a passive mixer network on a napkin for me, and there wasn't much to it, basically scrubbing the gain from merging the channels and preventing blow-back. By telling this, I mean to say it CAN be done very simply, but that would not include the "cross phase injection" algorithm you've mentioned, and that James Bongiorno insisted was necessary to make acceptable "center fill" from stereo, which is processed in its own right in order that it be stereo, which JB believed is an un-natural and very compromised format to start with.

https://www.sst.audio/new-products/trinaural-processor


Best regards,
Paul S




Posted by Romy the Cat on 07-14-2021
Thanks, Pall, this is very interesting and it was exactly what I was looking for. well, not exactly, I'm looking forward to pass right and left channel still not obtrusive to any processing but I would like to have analog mix of right and left channel and form from it a new central channel, which looks like this device does. you are correct the entire circuitry which would be responsible for this my fit in napkin as it will be only a commutation for summing or subtraction of signal difference between the main channels. The "cross phase injection" algorithm is very simple, you juts inject SOME of the right channel signal into left and vice versa. I just certainly do not want to contaminate my main signal passing it through a mixing circuit

Posted by Romy the Cat on 07-14-2021
... I would like to experiment with.

http://www.audiocircuit.com/Home-Audio/Ampzilla/Trinaural-Processor

Posted by Paul S on 07-14-2021
Well, that's the best "explanation" I've read on the Trinaural Processor, better than the SST website blurb, for sure.  Mr. Bongiorno was very warm and generous in person, and his verbal explanation to me was actually the best I got. I guess I "understand" it only in broad terms. He kept as proprietary the exact re-allocation values, attenuation, and isolation methods and values he used. For what it's worth, he was "well known" in LA recording circles.

Paul S

Posted by Romy the Cat on 07-14-2021
Well, since Mr. Bongiorno is not around, and his units are not available to experiment then it is what it is. I have no doubts that this version of semi-binaural possessing works well. What I do not know if it compromises what we get from 2 channels. This is why I call it “2+3 surround sound” as the main playback is still 2ch stereo and center channel and back channels are juts complimentary that do” something” but they do not make the main channels worse. I do not have a clear vision how to feed the center channel and back channels. I would not trust the Mr. Bongiorno’s device as well. You see if I try it have a negative result then I would not know if it was a conceptual problem, or the problem was with this specific mixing device and the Bongiorno’s implementation.
 
So, I would like to make my own judgment. Years back there was a devise Yamaha DSP-E800 that was center channel and back-channels extractor and that have delay options. I do not know how they did it, most likely digital but if it was all that the DSP does then I can deal with it. The phase manipulation is perfectly fine on DSP level, the key is that DSP should not attenuate or filter. I do not know how good AD/DA in there and I do not think that it will be the last solution. Still, I feel it much be “enough” for back channels, at least to experiment.
 
Also, I would like to look into the requirement for center channel. I do not think that I will be able to find a good one ready to go with the demotions I have in my mind. To build is complicated. I know exactly what tweeter to use in there to decompress sound, but I have no knowledge of a good 4” MF driver. I also do not know how full-range my center channel should be. I think I will take a pair of good JBL monitors, form from it a center channel and will see what it takes me.
 
I did some listening today using Bose Solo as center channel. I certainly had an interesting stereo effects but as soon I begin to “hear” Bose the sound went sound very rapidly.  For sure that Bose Solo with it’s phase vandalizing is not proper devise to experiment, but I wanted to test it right the way…

Posted by Paul S on 07-14-2021
I think I remember James saying that the center channel should be the strongest channel, and if this is the case he might not scrub the full 6 dB from the L+R "sum". James did say the device "corrects" for mistakes embedded in the original, wrongly-conceived stereo signals. I cannot say if this means his device changes the composition of left and right channels as it creates a new center channel. To be honest, I got stuck on this aspect of the design, also on the idea that I'd need another speaker that's better than my present speakers. Reading the only "review" I've seen on this device made me wonder if it really would not work with stereo LPs! 

https://forum.audiogon.com/discussions/review-spread-spectrum-technologies-trinaural-processor-surround-pre

As for 4" - 5" drivers, I am not sure what you're after in terms of sound, but there are better drivers out there again, as long as one avoids the common, overreaching MTM designs that no driver could save. Anyway, I decided to stay with stereo and just build another giant pair of speakers that I hope will flood my room a little better. Spoiler: there will be a cd/horn included (very short and fast, as much a wave guide, but a horn...).


Paul S



Posted by Bill on 07-16-2021
I feel that the correct objective of home music listening should be to reproduce as closely as possible what one can enjoy in a great concert hall with great musicians.Thus, I have been a advocate for surround processing for years. As stereo replaced mono, so should surround replace stereo.
I never go to Outdoor concerts as I prefer listening to music in a concert hall. A recording engineer friend who has done recorfdings in every major New York concert hall did some measurements and showed that most of the sound you hear in a concert hall is from the hall itself and not the musicians unless one sits in the first couple of rows. While stereo can give a perceived image of a concert stage with a back and possibly some side wall, it cannot give the effect of the concert hall side and back walls, ceiling and surrounding furniture and people reflections and sounds that makes up the concert listening experience.
Of course, like with stereo replacing mono, correct recording and playback is necessary with proper but not excessive multimiking and processing, as with stereo.
About 30 years ago, before digital processing, to get some hall sound, I used the so-called Hafler effect. One put a speaker in the back of the room and either used the plus side of each stereo front channel output to the two inputs of the back speaker, or sent the left and right signals through the use of the pass through of the front preamp to a rear amplifier and connected the two positive outputs to the speaker. Thus the rear channel would play back some of the room sound recorded while blocking out most of the front information.
As for the front center channel you could place two speakers, one on top of the other, tweeter next to tweeter, and play left and right channels through them. Or get a preamp with a mono mixer and feed to one speaker placed a couple of feet behind the left and right speaker., still using the original analog output to the main speakers.
Of course, all this could be precluded by doing digital signal processing using a top notch processor with as many surround channels as required. You could even feed your analog signals directly to the front left and right channels to keep their purity. 
 I went the other way, digitized all of my analog 15 ips master tapes and vinyl  with an ampex 351 tape deck and walker proscenium turntable and curl phono stage to 24/ 88 or 96 and now use a Trinnov processor for 16 channels. I believe Romy was impressed with the effect.

Posted by Bill on 07-16-2021
For instance one could use this Eico preamp from the early days of stereo to get the center and Hafler surround channel:
https://skyfiaudio.com/products/eico-hf-81-hf81-vintage-tube-integrated-amplifier-fully-restored-1960s-magic

Posted by Romy the Cat on 07-17-2021
Well, Bill, I disagree what you're saying. I disagree with surround sound, I disagree with the concert Hall experience and I disagree with objectives to reconstruct concert Hall experience. I'm not denying concert Hall experience itself I'm just saying that it is not objective in audio at least for me. Reconstruction of concert Hall experience is a method, one of expressive tools but not ultimate objective. The ultimate objective is to "load” musical experiences, aesthetical, ethical and subconscious encodings of musical event into the human brain. If we have other avenues to do it then trick ears ten we would do it. Some musicals “get” it by reading score, etc… Yes, in the high end audio we operate under presumption that if we reconstruct musical Hall experience then we automatically reconstruct all wonderful things which taking place there. I disagree with this as I was many times in wonderful concert Halls I did not “get” the  Communication event, because multiple circumstances. And I had many odd experiences when quality of the sound was horrendous and there was no even implication over any high-end sound production and I have spectacular music consumption experiences.
  
Do not take me wrong, the Reconstruction of concert Hall experience is very noble and very complex concept in Audio and we can spend our lives to achieve it and still to be not there. Still it is a concern about the logistics of "method" not about fulfilling the true objective of a ceremony. It is if you a priest and your objective to distribute message of God and you focus on polishing candles in your church then you do something similar to accomplishing the Concert Hall feeling in audio. Saying all of it, I'm not in being even remortly critical of what you've done. In fact what you have done in my view should be shown to anybody who has interest in the subject because it is beyond spectacular. In a way it is a freak show as knowing what I know about Audio there it is absolutely unimaginable to receive this space information from your room. If your room where 10 times bigger then it NOT be be 10 times better as you would need to spend 50 times more money and energy  to sound reinforce your room in a completely different domain of sound reproduction. 
 
I have seen similar experiences and I even back at 90s experimenting I was experimenting with it myself. I had five first original Revel channels, with two large subwoofers driven by five Lamm amplifiers.  I used Thieta processors, with separate low frequency delay channels. I had very good result. However, if you compare what I achieved it was unfortunate and it was still severely compromised compared to two channels direct experience. I used that setup only for movies but then I get disappointed with distribution of sound to the listening environment during film watching and I got rid of it all.
 

I did not detect, and it was a big surprise to me, those typical artifacts of multi-channel processing in your room. In your room and some aspect of space presentation where absolutely beyond anything that I heard. Is it something new conceptually or it is due to the fact that you very smartly, intentionally or not, dialed down the expressivity of your channels? I do not know the answer and the final result was very satisfactory. 
  
Now, I naturally ask myself is a question. In design of my system I focus on slightly different aspects of audio expressiveness and I feel that an objectives that I have my system does well. I wonder if possible to incorporate what I have, without compromise, with what you archived in terms of space information and notes connectivity. This is why I would like to invite you to hear my playback and have the discussion on the subject.  
  
I personally I have my suspicion is that your secret is not magical French processor, even though I would love to experiment with their DAC as I feel should be very good. I think that with all your 18 channels and that super precise French calibration machinery you beat me in the game of time alignment. I think your channels are much more I accurately aligned then mine because is this French device offer better options for this and  my old style analog alignment just cannot offer that quality of measurements. I unleashed a project to beef up my time alignment capacity and I will see where it will lead me. Also, I did ordered some equipment to have Back and Central channels as complementary channels but I have quite a lot of suspicious that with the means available for me for time alignment I will not be able to get results similar to what you did. Your French machine use pendulum time alignment and it is very difficult to do manually, possibly but too tedious and difficult.  
  
So, let's see where it will lead me. In meanwhile you should sell tickets to your listening room as it is truly mind expanding and thought provoking experience.

Posted by Romy the Cat on 07-18-2021
Another very interesting idea proposed by a friend of mine with whom I just discussed the notion. He asked if my find with center channel will work out then why wouldn’t I use my Injection channels as a center channels, all that I need to do is to reposition them….

Posted by Paul S on 07-18-2021
I was thinking, 4 - 5" drivers might be "too small" for proper tone and "space" for it; better to use as large as possible vs. as small as possible. Your injection channels will satisfy my curiosity on that score, anyway. Good luck with DPOLS for it.

Paul S

Posted by rowuk on 07-19-2021
I too believe that "reproduction" has nothing to do with my audio experience as there is nothing to reproduce. There is so much missing in any recorded signal that the "original" geometry can not even be close to restored. At best, we could create a plausible image that satisfies our imagination as to the size and space. It is a new "creature" however with little semblance of the original.
If geometry were the only goal, perhaps the industry could have done something. I am a professional trumpet player and for me, geometry is NOT the only goal. Playback is more about communication between the musicians themselves and their communication with the audience. In many cases, a "musical" mono recording can offer satisfaction that moves our soul, more than a high resolution stereo version.
I am have had very good experience with the Dynaco/Hafler/Polk extraction of the out of phase information but am not decided if the "ambience" is better used as a type of rear channel or if like with the Polk SDA series, the additional speakers are used to cancel interaural crosstalk. I have had some pretty spectacular results with the latter, extending the image to a 180° spread. I will have to experiment, but it will take a while before I am willing to mess with the currently very well working results.

Posted by Paul S on 07-19-2021
It seems to happen often enough that I have some idea of how I want to change my system, broadly in terms of sound, but it takes me a while to figure it out and get it done. I remember quite a few "ambience systems" over the years, including the original 4 channel. I have seen and heard LPs in that format.  My own take away after listening to this stuff was that while something was gained, something was lost; ie., it was at best a wash. It's been repeated many times here, the Magician's Axiom: "Don't call up what you can't put down." To that I'd add, "Don't throw out the baby with the bath water." If we stay focused, who knows what we might discover. If we don't look up for a while, who knows where we'll be when we do look up. I keep hearing how people are getting their best sound ever by digitizing everything and re-processing it. Has this really increased the trove of great source material, along with the Sound Quality to bring it Home? Who knows what the future will bring us. I'm waiting for Signs.


Paul S

Posted by Romy the Cat on 07-19-2021
I think to call what Bill made  as surround sound is make huge the service not only to the concept but to ourselfs. I wrote quite extended review of my thoughts on the subject and I was about to publish it but it is not in the computer that I have access now. I care less about surround and unfortunately surround sound is the only vocabulary that we have. I don't know if it was Bill's objective but I was not impressed with the surroundness of his sound but I was hugely impressed but surrounding of his space. Rowuk, sad that he is a trumpet so ask him how he's trumpet sound in closet. In reality whatever we do in out there is very much closeted sound and acoustically in order to have proper acoustic harmonic balance we need to have a reverberation time over 1.5 seconds. Even those of us who have large listening rooms let's say 600 to 1200 ft we not even remotely close to 1 second of reverberation time. What is the most beautiful thing that Bill did, besides that time  alignment about which I will be posting later, voice acoustically extending the dimension of his listening space. I wrote quite detail analysis what I think is going on, I will post it later. You my question methods he choose to implement it but there is no doubt of my mind that this direction is hugely, hugely beneficial. There is another side of that medal. If Bill or anybody else did have 10k-15k listening room then to make a playback to sound in that environment at the high quality would be astonishingly difficult. The best results people in those rooms do by designing acoustic Islands and make literally near feald listening in huge rooms, or play outside. And then we got hit by a thousand other problems, like terminal distortions in high power amplification and many others.

Posted by Paul S on 07-19-2021
It seems we are trying to fill our listening spaces with enough "relevant" information (in the form of Sound) to allow us to participate in a Musical performance. I agree that it's extremely difficult to charge a large space, and the bigger the space, the harder it is. Yes, the "accurate" reverberation "is not possible". We work around that and many other problems, not the least of which are the recordings we start with. In some cases, a certain sort of "ambience" is "built into" a recording, and I wonder how often this benefits from "further ambience measures". Of course I'm open to tricks, always happy to fool myself. Never say Never.


Paul S

Posted by Romy the Cat on 07-20-2021
With is my kids we frequently play a game "what does it mean". It is a situation when they exposed to something new and they try to name it, justified new in a context to what they already know. If we apply the same principle to sound, I experienced in Bill’d room, then I would like to have a few words to say. That is not a sound review in any way, but it is some food for thoughts for the people who did not experience what Bill did.  The “what does it mean" game identifies a single verbal element which describes a concept. I was keep thinking “what does it mean" in context of Bill's room sound. And the answer is “Sonic Accommodation”. Let me to step back a little and explain what it means. It is possible that this thing's already exist and have some kind of scientific and well research definition. I care less about it and I perfectly comfortable to propose it as my discovery, particularly because I'm talking about it for over 25 years.   

When we use our vision, we have an ability to do optical accommodations which is well known phenomena. For instance, if you look at some events which take place let's say 300 ft away then our perception can tune out from all the rest of the world and focus on the events 300 ft away. In terms of hearing, it acts very similar. You can seat a very last row of Carnegie Hall and see the stage half kilometer away, almost from Moon, but your hearing perfectly in combination with your eyesight can filter out external irritation and focus of performance essence of the orchestra in the stage. Yes, sound is not perfect in this scenario, but our brain somehow can remove focus from listening discomfort and perfectly compensate for it by making you feel that you are among musicians, in this case brains does what I call Distance Delegation. Well, it is happening in real life in most of the cases, but it's NEVER happens in audio.  Well, never say never but in situation of what Bill demonstrated I recognized that it is possible in audio. I do not know if it was in a combination with video that Bill showed but I do not think so. He played a very known to me video of Gunter van conducted Bruckner 4 and I was able to make it to sound spectacular in my own room. From sonic perspective it sounded horrible in Bill system but in the same time, despite of unpleasant sound it did demonstrated that nice acoustic accommodation. I focus my playback to get listener by “impressive” sound. Bill system demonstrated that unique Sonic Accommodation while presenting less impressive sound in my view but the overall experience is identically interesting. That opens in Pandora box from very different thinking what kind expressive means I play back might employ. 

  If you remember years back, I wrote about hierarchical approach to Sonic Assessment. At the level 2 of listening perception we deal with harmonic, rhythmic, dynamic, chromic sensations  etc… and from where I stay the Bills system did not particularly overwhelm me in there.  The theory that I pushed that only indelible success at the level 2 assures a listening perception move to level 3, the aesthetic level. That is a principle upon which I was building my playback. What Bill demonstrated is that the success at the level 2 is desirable but not mandatory and it does not block any listening advance to the level 3 and 4 (ethical level).  So somehow, I feel that Bill's play back was able to bypass aesthetical level, without compromising following levels. Interesting isn’t it? I'm not saying the Bills sound had low aesthetic payload. In my view it was aesthetically challenged but in the same time it did not create a listening deficiency which made me to worry or pay attention to this deficiency. It is like falling in love, it does not provide any answers, but it's eliminates the sharpness of the questions. I do feel that longer reverberation time in Bill room unleashed all of those effects and I would like to experiment with it more.

  Anyhow, it was what in my head and it is possible that Bill, accidentally or not, discover something that did not know enough: it is possible to get Sonic Accommodation in Audio is to get the things done properly in time and RT60 domains.

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