"Cogging" Discussion

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MidiMagic

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Can you explain "cogging"

When multiple speakers are placed to the sides of the listener, the following happens.

With two speakers on the same side of the listener, each speaker sends audio to both the left ear and the right ear.

The human hearing system creates a separate image location for each speaker. Unlike image fusion when a sound is
panned between speakers on opposite sides of the head, either front or back, the two side images never fuse.

So when a sound is panned from (e.g.) left back to left front, the image that is louder becomes the heard position of the
sound. The other image is perceived to be a reflection. So as the sound is smoothly panned from LB to LF, the perceived
image suddenly jumps (or cogs) from one speaker to the other.

You have to turn your head to hear the smooth pan correctly. Sitting between the back speakers also reduces the effect.

With 7.1, the cogging jump is smaller, but it happens twice once from LB to LS and again from LS to LF.

Some matrix systems also cog.

Dolby Surround and the Pro-Logic versions (when set up properly) do not cog. The delay provides the missing location
information coming from the other side.

SQ has reduced cogging due to the quadrature phases in the diagonally opposite speakers.

QS through the QS decoder has reduced cogging for the same reason. But QS played through an EV decoder cogs.

Some people on this forum say they do not hear the cogging. Maybe they found a way to trick their ears into properly
integrating the two images from the side. But I can't get rid of the effect.

I am designing a system with added delay speakers to try to remove the cogging.
 

LuvMyQuad

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When multiple speakers are placed to the sides of the listener, the following happens.

With two speakers on the same side of the listener, each speaker sends audio to both the left ear and the right ear.

The human hearing system creates a separate image location for each speaker. Unlike image fusion when a sound is
panned between speakers on opposite sides of the head, either front or back, the two side images never fuse.

So when a sound is panned from (e.g.) left back to left front, the image that is louder becomes the heard position of the
sound. The other image is perceived to be a reflection. So as the sound is smoothly panned from LB to LF, the perceived
image suddenly jumps (or cogs) from one speaker to the other.

You have to turn your head to hear the smooth pan correctly. Sitting between the back speakers also reduces the effect.

With 7.1, the cogging jump is smaller, but it happens twice once from LB to LS and again from LS to LF.

Some matrix systems also cog.

Dolby Surround and the Pro-Logic versions (when set up properly) do not cog. The delay provides the missing location
information coming from the other side.

SQ has reduced cogging due to the quadrature phases in the diagonally opposite speakers.

QS through the QS decoder has reduced cogging for the same reason. But QS played through an EV decoder cogs.

Some people on this forum say they do not hear the cogging. Maybe they found a way to trick their ears into properly
integrating the two images from the side. But I can't get rid of the effect.

I am designing a system with added delay speakers to try to remove the cogging.
I only use 5.1. The rears are just barely behind the axis of my listening position. The system can definitely set up perceivable side images between the fronts and rears. However when something is quickly panned, front to rear on the same side, it does sound more like a jump instead of a smooth pan. Is that the kind of thing you are describing?
 

newslane

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When multiple speakers are placed to the sides of the listener, the following happens.

With two speakers on the same side of the listener, each speaker sends audio to both the left ear and the right ear.

The human hearing system creates a separate image location for each speaker. Unlike image fusion when a sound is
panned between speakers on opposite sides of the head, either front or back, the two side images never fuse.

So when a sound is panned from (e.g.) left back to left front, the image that is louder becomes the heard position of the
sound. The other image is perceived to be a reflection. So as the sound is smoothly panned from LB to LF, the perceived
image suddenly jumps (or cogs) from one speaker to the other.

You have to turn your head to hear the smooth pan correctly. Sitting between the back speakers also reduces the effect.

With 7.1, the cogging jump is smaller, but it happens twice once from LB to LS and again from LS to LF.

Some matrix systems also cog.

Dolby Surround and the Pro-Logic versions (when set up properly) do not cog. The delay provides the missing location
information coming from the other side.

SQ has reduced cogging due to the quadrature phases in the diagonally opposite speakers.

QS through the QS decoder has reduced cogging for the same reason. But QS played through an EV decoder cogs.

Some people on this forum say they do not hear the cogging. Maybe they found a way to trick their ears into properly
integrating the two images from the side. But I can't get rid of the effect.

I am designing a system with added delay speakers to try to remove the cogging.
A system that includes the delay and removes the unwanted added image to the "off ear" already exists, and Bob Carver invented it in the 80's - sonic holography. It works amazingly well, but the speakers have to be positioned perfectly.
 

MidiMagic

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A system that includes the delay and removes the unwanted added image to the "off ear" already exists, and Bob Carver invented it in the 80's - sonic holography. It works amazingly well, but the speakers have to be positioned perfectly.

I tried that when it came out. It works for stereo, but not for quad. It did nothing to remove the side cogging. Instead, it makes a tense feel in the sound.
 

LuvMyQuad

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I tried that when it came out. It works for stereo, but not for quad. It did nothing to remove the side cogging. Instead, it makes a tense feel in the sound.
When I tried it, it expanded the front stage nicely, but at the expense of the phantom center image, which became more diffuse. In the end, I opted out.
 

gene_stl

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I have (it's for sale if anyone wants it) a carver preamp that has a couple of Sonic Holography buttons. I couldn't hear anything when I operated them.
Others swear its wonderful. None of the Carver instructions that I have ever seen (which include the owners manual for the preamp) shed any light on how it works or how to use it to its' best advantage.
 
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kfbkfb

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It did nothing to remove the side cogging

The THX people seem to have solved this puzzle, in the mid-1990s, I saw one of the Star Wars movies at a THX theater, in one scene, the sound smoothly panned out from the screen, around to the back of the theater and then back to the screen, it's the smoothest sound pan I've ever heard.

Last fall, I saw the James Bond movie at the B&B theater (one of their smaller theaters), the movie was obviously in surround sound, but the sound jumped around, no smooth sound pans.


Kirk Bayne
 

newslane

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I have (it's for sale if anyone wants it) a carver preamp that has a couple of Sonic Holography buttons. I couldn't hear anything when I operated them.
Others swear its wonderful. None of the Carver instructions that I have ever seen (which include the owners manual for the preamp) shed any light on how it works or how to use it to its' best advantage.
I created the Carver Sonic Holography Facebook page, and there are quite a few of us who can help you set it up correctly. It's also a great place to sell your preamp. What is the model number? Войдите на Facebook
 

newslane

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I tried that when it came out. It works for stereo, but not for quad. It did nothing to remove the side cogging. Instead, it makes a tense feel in the sound.
That's exactly right - it only works for stereo. But when set up correctly, with a well-mixed record it can make stereo seem almost like quad, an incredible thing when you realize how many stereo albums/CDs you may have.
 

newslane

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When I tried it, it expanded the front stage nicely, but at the expense of the phantom center image, which became more diffuse. In the end, I opted out.
When it's set up correctly, each instrument is placed discretely in place where it was in the mix, and there is no phantom center channel. Vocals and bass tend to be in the center of the mix, appearing exactly where they were placed. One can hear them within 12-18 inches or so of their exact location. For example, If straight ahead is 12 o'clock, I can hear a vocal at 11:30 and ten feet behind the speakers, because that's where it was placed in the mix. Listening in complete darkness can be an amazing experience with certain tracks - A Saucerful of Secrets, for example, fills 170 degrees or so of the entire front hemisphere.
 

par4ken

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I think that this is an non issue! If speakers are close enough together as in a vehicle (or small room) there is no "cogging" (despite statements by others) pair wise mixing works fine. In a larger room you will hear the effect because of the large separation of the sound sources. The same goes for regular stereo. It's the hole in the middle stereo effect. It's why in large venues like a movie theatre you need a centre speaker.

For quad in a more normal listening room the back speakers can be placed more to the sides (or even slightly to the front), in that manner there is no cogging effect, just greatly widened stereo. Assuming that most listening is to enhanced "synthesized" stereo this is a great choice.

Personally I'm not bothered by so called cogging as long as I have my surround. Most discrete quad mixes from the seventies are heavy on corner sound placement, so phantom side images or the lack of them is not realty an issue IMHO.
 

ar surround

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Dolby Surround and the Pro-Logic versions (when set up properly) do not cog. The delay provides the missing location
information coming from the other side.

SQ has reduced cogging due to the quadrature phases in the diagonally opposite speakers.

QS through the QS decoder has reduced cogging for the same reason. But QS played through an EV decoder cogs.

Some people on this forum say they do not hear the cogging. Maybe they found a way to trick their ears into properly
integrating the two images from the side. But I can't get rid of the effect.

I am designing a system with added delay speakers to try to remove the cogging.

Most discrete quad mixes from the seventies are heavy on corner sound placement, so phantom side images or the lack of them is not realty an issue IMHO.

Expanding on this a bit: I thought I read somewhere that placing a phantom image between the side speakers (i.e. LF and LB) was not a good idea as the brain would have a hard time localizing the sound? Panning is different as the sound moves rather than being fixed as a center side image. I've noticed cogging with certain panned sounds but I've also noticed smooth panning as well.

Regarding psycho-acoustical phenomena, the Surround Master definitely puts a hard panned left or right sound in both the front and rear speakers. However, by keeping one's head facing forward, it appears that the sound is either in the front or rear speaker, not in both. Turn one's head a bit and it becomes obvious that the sound exists in both the front and rear speakers.
 

MidiMagic

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I only use 5.1. The rears are just barely behind the axis of my listening position. The system can definitely set up perceivable side images between the fronts and rears. However when something is quickly panned, front to rear on the same side, it does sound more like a jump instead of a smooth pan. Is that the kind of thing you are describing?
Yes.
 

MidiMagic

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The THX people seem to have solved this puzzle, in the mid-1990s, I saw one of the Star Wars movies at a THX theater, in one scene, the sound smoothly panned out from the screen, around to the back of the theater and then back to the screen, it's the smoothest sound pan I've ever heard.

Last fall, I saw the James Bond movie at the B&B theater (one of their smaller theaters), the movie was obviously in surround sound, but the sound jumped around, no smooth sound pans.


Kirk Bayne
That was a version of Dolby Surround. Dolby Surround, Pro-Logic I and Pro-Logic II fixed the problem. Going to discrete broke it again.

I have Dolby Surround copies of the Indiana Jones movies. In one scene, the sound of a metalworker is heard at left back. As the camera pans around to face the metalworker, the sound of his working pans smoothly from LB to F.
 
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kfbkfb

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This was in the mid-1990s, it was either a Dolby Digital or DTS soundtrack, there were a few other THX theaters in this area, but I don't recall any movies I saw at them having this kind of imaging in the soundtrack.


Kirk Bayne
 

jimfisheye

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What you are calling cogging - our blind spot as it were in front vs back perception - that requires interactive listening in moving your head around a bit. This is the reason you can't just translate (non-ambisonic) surround mixes to ambisonic binaural. Without adding additional reverb for cues anyway. And this is what led to the 115 to 125 deg rears placement.

That's kind of an aside itself. What I want to suggest is any relationship to a lossy format is a non sequitur. The lossy sound degrades the recording and this may help reveal other artifacts. But the lossy format (be it modern lossy digital or old school lossy analog matrix) doesn't exaggerate cogging specifically.

I think especially circular pans are prone to perception issues. We're sensitive to early reflections to determine sound location. A live room reflection could create a Haas effect for the listener and ruin (overpower) a pan effect. Just for another example.
 

ar surround

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Whether I perceive front to back cogging or not, what I find far more annoying is sound panned from a main speaker to the center speaker. This issue is likely due to my mains being much larger than my smaller (58 lbs!) center speaker despite having the same drivers. Also, the center speaker placed below the TV rather than 'embedded' in the screen isn't ideal as we all know. Music is way more important to me than film, so it's a calculated compromise. I suspect that this matter could be remedied by the film mixer placing a phantom image in the mains for the center as well as the dedicated center dialog channel. Just a thought.
 

J. PUPSTER

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Been working with this some doing up-mixes; and getting the correct phantom center fade ins & outs is tricky. Using "Adjustable Fade" in Audacity, and it takes a lot of trial and error to get it sounding smooth. Mid-fade Adjust (%) for both up and down is critical. Still trying to get a handle on it for 5.1, and of course every situation is different.

Adjustable Fade
This has a dialog box where you can choose the shape of the fade in or fade out to be applied. You can also create "partial" fades to and from other than silence and original volume. An example of this might be a fade in from 20% of the original volume to 80% of the original volume. The "Handy Presets" at the bottom offer a choice of six pairs of fade in or fade out shapes, fading between silence and original volume.

Accessed by: Effect > Adjustable Fade...

1652461900496.png
 

Sonik Wiz

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A few points on cogging in no particular order…

1. Some audible cogging may come from the decoding / separation enhancement methods. In legacy gear it was a challenge just to get those weak separation specs to match stereo quality. You know, try to get a spec that says “up to 25 dB maximum separation “ similar to that of a stereo phono cart. Fine points like constant power when panning was not much thought of as, say, SQ Logic did it’s best to shift sound from front to back, or vice versa. The Surround Master does an excellent job of keeping power levels appropriate in pans. For example do a test on the SM Involve/QS mode for left front output measured at 1V. Switch to right front output at 1 V. Now input a mono center front signal & you’ll see the front outputs are now at -3dB or .707 V compared to single channel. Constant power is maintained and the unit does so in any single to pair wise combination. The pans should be smooth in any direction if levels & speaker set up is done correctly.

2. Midi says even discrete has cogging. This may be to incorrect mixing in production. Now in a simple stereo example a sound panned properly left to right will also be at -3dB in the middle, like stated above. Using stereo gear for quad mixing there’s no guaranty that a proper pan pot might be used front to back. It could be just as easily a sound in left back faded out and faded in on left front which would not maintain constant power or be a smooth pan.

3. Speaker placement can contribute or minimize this effect. I will differ with @par4ken on his comment:

If speakers are close enough together as in a vehicle (or small room) there is no "cogging" (despite statements by others) pair wise mixing works fine. In a larger room you will hear the effect because of the large separation of the sound sources.

The closer a speaker is to the listener, the more that speaker draws attention which would exacerbate any cogging in the play back. A larger room with a larger speaker lay out will tend to smooth out those effects.

4. And in a similar vein to the above comments, I recognize many folks are using rear surround speakers any where from center left/right of the listener to just a bit behind. Theoretically introducing delay to the rear to chs to artificially match front speaker distance should fix that. It doesn’t as, once again, the rear speakers are not integrated into the acoustic environment the same way the front speakers are. So this would not be optimum for smooth pans in a soundfield.

Both my front and rear speakers are 9’ apart measured from their center line. Front to rear speaker distance is 16’. So a rectangle more than a square. But the sweet spot is dead in the middle. And tho there certainly some rough pans to be heard ( Santana: Abraxas, anybody?) nothing that is a chronic problem.
 
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