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etc6849

Anyone else using Multi-channel stereo instead of stereo?

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Seems likely. I have always used HDMI with my theater system.

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My boss loaned me a book: "The New Stereo Soundbook" https://www.amazon.com/New-Stereo-Soundbook-Ron-Streicher/dp/0966516206?SubscriptionId=AKIAILSHYYTFIVPWUY6Q&tag=duckduckgo-osx-20&linkCode=xm2&camp=2025&creative=165953&creativeASIN=0966516206

 

In there I came across a chart, which you can see here:

https://www.semanticscholar.org/paper/Loudspeakers-and-Rooms-for-Sound-Reproduction-—-A-*-Toole/7b0e3101e1788608d75d024ac926d25a077b85bc/figure/5

 

Looking at that chart I decided as an experiment to adjust my side and center channels to be 20ms delayed and 9 decibels attenuation. That puts them in the zone of detectability by not enough to shift the image. The result is highly agreeable to my ears. It sounds like normal, good stereo in a good, larger room. Compared to running all channels at full volume and time aligned, this is much more stable. With four channels at full volume, very little head movement will change the sound appreciably. With attenuation and delay, there's much less perceived change when moving around.

 

The book also mentioned that even in anechoic chambers, when extra channels are added with time delay and attenuation, an sense of spaciousness is restored. My room is nowhere near anechoic, but it's pretty well damped at this point with lots of absorption panels and some tube traps turned with their reflectors toward the wall. I'm thinking that for small bedrooms, a highly damped room with extra spaceousness channels is a good way to go. I'm thinking I'm going to keep adding absorption to see if it's even possible to over-deaden  the room with this setup.

 

Edited by timbley2

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On 4/1/2019 at 10:59 AM, timbley2 said:

My boss loaned me a book: "The New Stereo Soundbook" https://www.amazon.com/New-Stereo-Soundbook-Ron-Streicher/dp/0966516206?SubscriptionId=AKIAILSHYYTFIVPWUY6Q&tag=duckduckgo-osx-20&linkCode=xm2&camp=2025&creative=165953&creativeASIN=0966516206

 

In there I came across a chart, which you can see here:

https://www.semanticscholar.org/paper/Loudspeakers-and-Rooms-for-Sound-Reproduction-—-A-*-Toole/7b0e3101e1788608d75d024ac926d25a077b85bc/figure/5

 

Looking at that chart I decided as an experiment to adjust my side and center channels to be 20ms delayed and 9 decibels attenuation. That puts them in the zone of detectability by not enough to shift the image. The result is highly agreeable to my ears. It sounds like normal, good stereo in a good, larger room. Compared to running all channels at full volume and time aligned, this is much more stable. With four channels at full volume, very little head movement will change the sound appreciably. With attenuation and delay, there's much less perceived change when moving around.

 

The book also mentioned that even in anechoic chambers, when extra channels are added with time delay and attenuation, an sense of spaciousness is restored. My room is nowhere near anechoic, but it's pretty well damped at this point with lots of absorption panels and some tube traps turned with their reflectors toward the wall. I'm thinking that for small bedrooms, a highly damped room with extra spaceousness channels is a good way to go. I'm thinking I'm going to keep adding absorption to see if it's even possible to over-deaden  the room with this setup.

 

I use a 5.2 setup for multichannel stereo with ELAC speakers, dual subs and a Yamaha RX-A3080 receiver.  2 Surround speakers are at right angles on either side of listening position.  I don't have flexibility on the surround speaker placement and restricted to 90 degrees at the moment.The Yamaha has a option for front/rear balance on the multichannel stereo mode, which is  a very useful feature for this mode. I run it at +1 in favor of the fronts/center vs  the 2 surrounds. It sounds amazing and makes my $$$$ 2 channel setup sound lame at times.

 

Quote

 

 

Edited by HIRES_FAN
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On 12/5/2020 at 12:23 PM, HIRES_FAN said:

 

I use a 5.2 setup for multichannel stereo with ELAC speakers, dual subs and a Yamaha RX-A3080 receiver.  2 Surround speakers are at right angles on either side of listening position.  I don't have flexibility on the surround speaker placement and restricted to 90 degrees at the moment.The Yamaha has a option for front/rear balance on the multichannel stereo mode, which is  a very useful feature for this mode. I run it at +1 in favor of the fronts/center vs  the 2 surrounds. It sounds amazing and makes my $$$$ 2 channel setup sound lame at times.

 

 

I just got a Yamaha RX-V385. I was thinking of using it with stereo CD's in 3.1 mode, Front Left, Front Middle and Front Right with a sub. What content does the processor send to the front middle? 

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Six-year-old thread, but I'll bite. I run a 5-channel prototype of this. No information on the Website any more, but it's a very high-quality stereo-to-multichannel upmix.

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On 11/22/2014 at 10:33 AM, etc6849 said:

However, is this because of the loudness increase and purely psychological?  Or does having the stereo image come from multiple speakers somehow reinforce the sound-stage and help my mind better drown out any reflected images?  

I have a full Atmos 7.2.4 (4 channels on ceiling at equal distance from my head, angled inwards. the rest is "normal" 7 channels at ear level, and 2 discrete tapped hornsubwoofers with different drivers and horn lengths. More and more, I'm enjoying the different matrix renderings of 2 channel sound with all those  43 drivers working (down from a higher number I had in a bigger space). The ceiling speakers are 2-way and the rest 3-way. Full 180 degrees vertical and 360 degrees Horizontal creates opportunity for many different sonic landscapes at the touch of a button on my Yamaha CX-A5200. I have yet to get bored with the possible sonic explorations of different material, especially some of the 5.1 recordings that "matrixed up."

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17 hours ago, Pondoro said:

I just got a Yamaha RX-V385. I was thinking of using it with stereo CD's in 3.1 mode, Front Left, Front Middle and Front Right with a sub. What content does the processor send to the front middle? 

I have that receiver as well, but used in stereo with inwall speakers. I haven’t been able to find an answer to your question, but my guess is that it sends a combined left and right mono signal to the center. 
 

You could confirm this by disconnecting the left and right speakers and listening to the center. All of the music should be there, just in mono. 
 

Hope that helps. 

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On 12/7/2020 at 6:57 PM, Pondoro said:

I just got a Yamaha RX-V385. I was thinking of using it with stereo CD's in 3.1 mode, Front Left, Front Middle and Front Right with a sub. What content does the processor send to the front middle? 

You can read about a likely implementation of your Yamaha AVR here: https://www.aes.org/journal/sample_issue/JAES_V50_11_PG914.pdf

 

It's not a simple answer if you're using a synthesized 3.1 mode. 

 

Chris

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11 hours ago, Chris A said:

You can read about a likely implementation of your Yamaha AVR here: https://www.aes.org/journal/sample_issue/JAES_V50_11_PG914.pdf

 

It's not a simple answer if you're using a synthesized 3.1 mode. 

 

Chris

That is an interesting, but very technical, article. I’m a mechanical engineer so I understand the math, but the signal processing stuff is a bit beyond me. I am very familiar with the original Klipsch article that they refer to. It appears they can improve on his simple additive method. I need to spend some serious time listening to songs in both traditional stereo and synthesized center mode. I have a pair of Heresy Ones and a single Kp-250 for the center. The KP is noticeably louder (I substituted it for one Heresy to compare), but I can adjust center channel level.

Edited by Pondoro

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I have been into multi channel music for several years. I currently own an Integra DHC-80.3 and Yamaha CX-A5200 pre-pros. I have found that having JRiver converting stereo files to multi channel provides superior results to having the pre-pros doing it. YMMV

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23 minutes ago, tromprof said:

I have been into multi channel music for several years. I currently own an Integra DHC-80.3 and Yamaha CX-A5200 pre-pros. I have found that having JRiver converting stereo files to multi channel provides superior results to having the pre-pros doing it. YMMV

Since our mileage DOES vary...........................do you do a signal pass thru using HDMI to convert to analog and feed your power amps? or how/what??? Describe your connections.

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On 12/28/2015 at 3:23 PM, boenmoen said:

Sorry, just found the answer.

Apparently if the speaker settings are ALL set to SMALL then the Subwoofer will be on.

I had my Speakers set to Large...

The terminology used is designed for the non-audiophile consumer market. Where they use dumb down the terms and never actually/technically describe, even with manuals of hundreds of pages,  what is going on with the signal output. It's been a frustrating 20 years evolving with multi channel technology, but we keep moving forward with it regardless.

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Quote

...as proposed by Klipsch [1], an additional center loud-speaker C can be fed with the sum signal [square root of 2](xL+xR),where xL and xR represent signals from left and right,respectively. The [square root of 2] factor was introduced to preserve the total energy from the three loudspeakers, assuming incoherent additive for left, center, and right sounds recorded by two widely spaced microphones.  A major drawback of this approach is that crosstalk with the left and right channels is inevitable, and therefore it will narrow the stereo image considerably.

 

This is the part that I think you need to take note of with PWK's approach (which was as complicated as he could withstand in ca. 1959 when he proposed a three-channel summing resistor network to create one of the first consumer-grade three-channel setups using Klipschorns and a center Heresy...at that time).

 

Here's perhaps a little more tractable explanation of how 2-->5 channel synthesis algorithms work, describing the different methods (without concentrating as closely on Dolby Labs and on signal processing estimation matrices and using partial differential equations).  PWK's method is the "passive surround decoding method": 

 

https://core.ac.uk/download/pdf/25789335.pdf

 

1 hour ago, Pondoro said:

I’m a mechanical engineer so I understand the math, but the signal processing stuff is a bit beyond me.

 

I'm a mechanical engineer, too (1st degree >40 years ago).  I encourage reading up.  I've found it's good for the career to continuously broaden your technical knowledge, and especially in today's hi-fi audio world.  It keeps you from being taken to the cleaners by "hi-fi carpetbaggers".

 

Chris

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13 hours ago, Chris A said:

You can read about a likely implementation of your Yamaha AVR here: https://www.aes.org/journal/sample_issue/JAES_V50_11_PG914.pdf

 

It's not a simple answer if you're using a synthesized 3.1 mode. 

 

Chris

I read through that as best I could, unlike Pondoro having no understanding of the math I also don't understand the testing procedures or statistical analyses.  I was looking for the word "Yamaha" and/or some clue as to how they implemented their algorithm so I might try to replicate the results or at least hear what they were getting at.  The only bit I could find is that they used Philips DSS940 speakers.

 

This article is from 18 years ago but perhaps now there is software that let's one enter some of those equations and play around with audio algorithms...?

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Let me give you an example, in this case from the last link I posted:

 

image.png.00882f32e55d283e4e5d5515d12c7061.png

 

Notice the center channel here is not just padded down, but a low pass filter is added.  I find this to be a problem (and I hear it in some of my multichannel recordings--and it sounds odd). I would like the sound field coming toward me to be more representative of what the microphones actually recorded, and not with a hole in the center of the soundstage that is based on frequency(...?...). I could write a lot more on this subject, but I'll refrain here.

 

If I were to try to implement the old Polk Audio SDA monitor (ca. late 1970s) "cancellation of the cross-talk between left and right channels, and left and right ears" using stereo loudspeakers only, I would send an out-of-phase right channel component to the front left (FL) channel at a low level...and the opposite to the right channel.

monitor11-01.jpg

One of the Polk SDA monitor midranges is driven by the opposite channel via a separate cable that connects the loudspeakers.

 

Bob Carver did this in the late 1970s-early 1980s to simulate the same thing but using a preamp only and analog op amps in a separate/selectable processing loop if you sit right on centerline between the left and right channels. 

 

dab862e1a7fca68d470b80e394a1ae72.jpg

 

In both cases, the apparent stereo image goes from ±45 deg to something like ±120 deg instantly--using only stereo speakers (not three channel).  But you have to sit right on-axis for it to work.  With three channel, you use a schema like the stereo-only method, but you have a bit more freedom to play with the apparent soundstage so that it is more stable if you're not sitting directly on the centerline between the two loudspeakers.

 

Additionally, the above diagram shows a ±90 deg phase-shifter on RL and RR channels.  This introduces frequency-dependent time delays on the rear channels, something that I would not like.  The simple time delay would suffice to recreate an echo-channel effect without the frequency-dependent delays. 

 

Note that all of the above is wrapped up with how humans actually hear, and not how machines/arrays of microphones  perceive the sound field.  That field is called "psychoacoustics", and anyone having much more than a passing interest in hi-fi audio really needs to understand the basics of that field, too.  I recommend Floyd Toole's book.

 

Chris

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28 minutes ago, Chris A said:

Let me give you an example, in this case from the last link I posted:

 

image.png.00882f32e55d283e4e5d5515d12c7061.png

 

Notice the center channel here is not just padded down, but a low pass filter is added.  I find this to be a problem (and I hear it in some of my multichannel recordings--and it sounds odd). I would like the sound field coming toward me to be more representative of what the microphones actually recorded, and not with a hole in the center of the soundstage that is based on frequency(...?...). I could write a lot more on this subject, but I'll refrain here.

 

If I were to try to implement the old Polk Audio SDA monitor (ca. late 1970s) "cancellation of the cross-talk between left and right channels, and left and right ears" using stereo loudspeakers only, I would send an out-of-phase component to the front left (FL) channel at a low level and the opposite to the right channel--like Bob Carver did it in the late 1970s-early 1980s to simulate the same thing, but using a preamp only and analog op amps in a separate/selectable processing loop if you sit right on centerline between the left and right channels.  The apparent stereo image goes from ±45 deg to something like ±120 deg instantly--using only stereo speakers (not three channel).  But you have to sit right on-axis for it to work.  With three channel, you use a schema like the stereo-only method, but you have a bit more freedom to play with the apparent soundstage so that it is more stable if you're not sitting directly on the centerline between the two loudspeakers. 

 

Additionally, the above diagram shows a ±90 deg phase-shifter on RL and RR channels.  This introduces frequency-dependent time delays on the rear channels, something that I would not like.  The simple time delay would suffice to recreate an echo-channel effect without the frequency-dependent delays. 

 

Note that all of the above is wrapped up with how humans actually hear, and not how machines/arrays of microphones  perceive the sound field.  That field is called "psychoacoustics", and anyone having much more than a passing interest in hi-fi audio really needs to understand the basics of that field, too.  I recommend Floyd Toole's book.

 

Chris

As Quad died in the 1970's "Time Delay" units were briefly popular. You had two channel stereo in front and variable delay in the rear two speakers. Some loved it, said it was "Quad without the format war incompatibilities", purists called it "distortion." 

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3 minutes ago, Pondoro said:

As Quad died in the 1970's "Time Delay" units were briefly popular. You had two channel stereo in front and variable delay in the rear two speakers. Some loved it, said it was "Quad without the format war incompatibilities", purists called it "distortion." 

 

Quad died?  Oh No!

https://www.quadraphonicquad.com/

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1 hour ago, tromprof said:

I have found that having JRiver converting stereo files to multi channel provides superior results to having the pre-pros doing it. YMMV

In the example that I posted above, it's clear that what's being done by different pieces of gear is not equivalent, although they're advertised as being equivalent. I hear those differences, and I don't usually like the synthesized implementations of 2-->5 channel that AVPs/AVRs use.  Finding out what they're actually doing is usually a lot more difficult than just listening to the results and judging for yourself if it is better or worse. 

 

I think the reason why some of the folks on this forum still use PWK's method, and not because it's necessarily superior, but because it's a user-controllable and known process, even though it may significantly narrow the apparent stereo soundstage.  If you set the loudspeakers along the long wall of an oblong/rectangular room, then the loss in apparent soundstage width isn't noticed as much.  I think PWK knew what he was doing in 1959 when he published the article on 3 channels from 2 channel channel sources.  He had also apparently experienced using the Bell Labs setup that was pioneered perhaps 15-20 year earlier, and he understood the pros/cons of what he was proposing.  I'm not sure about the synthesized modes that we get today in our AVPs/AVRs. 

 

Nowadays, you get the algorithms in canned fashion with bells and whistles that you didn't ask for put in, ostensibly because someone in marketing though it sounded "better than the competition" (probably using questionable recordings in the first place to make their judgments). 

 

JRiver seems to have a better handle on things in terms of the signal processing for psychoacoustical effects, but I can't say that I have first-hand experience listening to what they've done, and I certainly don't know what they've actually implemented.

 

Caveat emptor applies..."let the buyer beware".

 

Chris

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