Random Stuff About Surround Sound

[jaybird100]

I’ve not seen any matrix format that has a delay parameter in its decoding equations.

Back in the day, no matrix system-- not SQ, not QS-- used any kind of delays. That didn't come until Dolby Surround was applied to movies.

 

[MagnumX]

Without delays, you must sit exactly center between all the speakers. Otherwise, the Precedence Effect will cause problems, pulling panning towards the closer speaker set for correlated information present in multiple channels (applies even to discrete systems for panning). In other words, just because SQ/QS didn't use delays back then that doesn't mean they shouldn't have used them. Not everyone can set up a perfect square for quad in their room.

 

[par4ken]

Without delays, you must sit exactly center between all the speakers. Otherwise, the Precedence Effect will cause problems, pulling panning towards the closer speaker set for correlated information present in multiple channels (applies even to discrete systems for panning). In other words, just because SQ/QS didn't use delays back then that doesn't mean they shouldn't have used them. Not everyone can set up a perfect square for quad in their room.

I don't believe that delays are are necessary nor desirable in a typical listening room. Delays can be used in a DSP based system to optimise sound in your particular listening position but IMHO that is mostly unnecessary. I don't always sit in the sweet spot but my analog system always sounds great! A perfect square isn't always the best sounding speaker arrangement either.

 

[Soundfield]

Without delays, you must sit exactly center between all the speakers. Otherwise, the Precedence Effect will cause problems, pulling panning towards the closer speaker set for correlated information present in multiple channels (applies even to discrete systems for panning). In other words, just because SQ/QS didn't use delays back then that doesn't mean they shouldn't have used them. Not everyone can set up a perfect square for quad in their room.

If you apply fixed delays to your speaker signals the best you can hope to do is move the sweet spot from being equidistant from all speakers apparently to some other position. It has no effect on absolute image location nor on speaker dispersion characteristics. It is just a room specific fudge.

 

[MagnumX]

If you apply fixed delays to your speaker signals the best you can hope to do is move the sweet spot from being equidistant from all speakers apparently to some other position. It has no effect on absolute image location nor on speaker dispersion characteristics. It is just a room specific fudge.

Look up the Precedence effect in regards to panning phantom images. It absolutely affects imaging to a very strong degree and it's caused by sound sources arriving at different times with correlated information.

Your brain perceives the image coming from the first arrival source until up to 70% of the volume difference overrides it. This can be heard with a panned left-to-right sound on simple stereo. Sit closer to one speaker than another and it pulls hard to that speaker until the image is panned around 70% to the other and then it quickly rushes to that side. Sit in the middle and it pans evenly. Change the delay time so the sounds arrive at the same time for sitting off-center and it pans evenly.

You cannot have it perfect for more than one location. That is precisely why the center channel speaker was invented, but without discrete information, it only cuts the panning error in half and yes, delays are for the MLP. Everything else has varying degrees of imaging error.

Delays only correct room layout issues for one seat, but it can fix a room where an evenly spaced layout doesn't work. Given most home theaters are corrected for one seat, it might be helpful to have delay settings to match since 5.1 or 7.1 in bypasses all/most receiver settings, although I'm not sure if delay is included.

Even my 17.1 channel theater only images everything "perfectly" for one seat (Imaging is more accurate for the 2nd row center seat than off-axis seats as at least it's centered in the horizontal plane.

 

[jaybird100]

Without delays, you must sit exactly center between all the speakers. Otherwise, the Precedence Effect will cause problems, pulling panning towards the closer speaker set for correlated information present in multiple channels (applies even to discrete systems for panning). In other words, just because SQ/QS didn't use delays back then that doesn't mean they shouldn't have used them. Not everyone can set up a perfect square for quad in their room.

It's possible that, if matrixed quad had continued to evolve, adjustable delays might have been introduced at some time. These delays would also have been defeatable, since not everybody needs to use them. I listen to my system while moving about in the room, not always sitting in the so-called "sweet spot", and I get great imaging from discrete, QS, and SQ. On paper, what you say about the "Precedence Effect" looks to be true, but in actual use, I don't agree with it at all.

 

[MagnumX]

It's possible that, if matrixed quad had continued to evolve, adjustable delays might have been introduced at some time. These delays would also have been defeatable, since not everybody needs to use them. I listen to my system while moving about in the room, not always sitting in the so-called "sweet spot", and I get great imaging from discrete, QS, and SQ. On paper, what you say about the "Precedence Effect" looks to be true, but in actual use, I don't agree with it at all.

You can defeat it on receivers easy enough, just set all delays to zero. I'd rather have the option to use it than not have it at all.

I personally think it's more noticeable with horizontal panning than front-to-back or at least more annoying. If I sit on the right side of my room, though surround effects that are evenly spread sound like mostly closer to me and more discrete sounds are coming from the left side of the room so I think it applies off-axis horizontally even for surrounds.

 

[Soundfield]

Lots of confusion apparent on this thread over the roles of signal delays in surround sound encoding / decoding and room correction!

 

[MidiMagic]

I’ve not seen any matrix format that has a delay parameter in its decoding equations.

Dolby Surround, and PL I and II. They actually decode material in any panning position without speakers at those positions. I have been using this effect for years.

And I thought someone said that SM had a pre-fetch to select the correct decoding.

 

[chucky3042]

Look up the Precedence effect in regards to panning phantom images. It absolutely affects imaging to a very strong degree and it's caused by sound sources arriving at different times with correlated information.

Your brain perceives the image coming from the first arrival source until up to 70% of the volume difference overrides it. This can be heard with a panned left-to-right sound on simple stereo. Sit closer to one speaker than another and it pulls hard to that speaker until the image is panned around 70% to the other and then it quickly rushes to that side. Sit in the middle and it pans evenly. Change the delay time so the sounds arrive at the same time for sitting off-center and it pans evenly.

You cannot have it perfect for more than one location. That is precisely why the center channel speaker was invented, but without discrete information, it only cuts the panning error in half and yes, delays are for the MLP. Everything else has varying degrees of imaging error.

Delays only correct room layout issues for one seat, but it can fix a room where an evenly spaced layout doesn't work. Given most home theaters are corrected for one seat, it might be helpful to have delay settings to match since 5.1 or 7.1 in bypasses all/most receiver settings, although I'm not sure if delay is included.

Even my 17.1 channel theater only images everything "perfectly" for one seat (Imaging is more accurate for the 2nd row center seat than off-axis seats as at least it's centered in the horizontal plane.

You are mostly correct regarding the precedence effect, we use it extensively in our SST (Sweet Spot Technology), regarding left to right it does in fact have a close to perfect image consistent in all points of the room left to right. In a recent demo we had 6 people in the room, I asked them to go to a bunch of random positions all throughout the room left to right/ front to back. I then asked them to close their eyes and point to one of the instruments, when they opened their eyes they all were pointing to the same spot in the frontal stage- all with no center channel.

 

[ar surround]

You are mostly correct regarding the precedence effect, we use it extensively in our SST (Sweet Spot Technology), regarding left to right it does in fact have a close to perfect image consistent in all points of the room left to right. In a recent demo we had 6 people in the room, I asked them to go to a bunch of random positions all throughout the room left to right/ front to back. I then asked them to close their eyes and point to one of the instruments, when they opened their eyes they all were pointing to the same spot in the frontal stage- all with no center channel.

Regarding that Sweet Spot Technology, is that used in Involve 4.1 or only in the TSS mode?

 

[chucky3042]

Regarding that Sweet Spot Technology, is that used in Involve 4.1 or only in the TSS mode?

Its not in The Surround Master, its used in our Y4 system with our Y speakers- its a 10 channel system internally - actually the amp has 1812 components in it, just like the overture!

 

[DuncanS]

Its not in The Surround Master, its used in our Y4 system with our Y speakers- its a 10 channel system internally - actually the amp has 1812 components in it, just like the overture!

So Overture is made up of 1812 bits? the $6m dollar man?

 

[par4ken]

Dolby Surround, and PL I and II. They actually decode material in any panning position without speakers at those positions. I have been using this effect for years.

And I thought someone said that SM had a pre-fetch to select the correct decoding.

No different with discrete or QS. Even SQ can be made to pan anywhere with a position encoder. I have never heard any Dolby system that did anything special, and stereo synthesis is terrible via Dolby. As I've said before Dolby reinvented the wheel but made it square. If you hear no side imaging then perhaps your speakers are too far apart. Just as widely spaced stereo speakers might sound good but produce hole in the middle stereo. I'm sure that the Surround Master being digital has the ability to look ahead to be able to react faster than an analog decoder but what does that have to do with selecting correct decoding?

 

[Sonik Wiz]

No different with discrete or QS. Even SQ can be made to pan anywhere with a position encoder.

Agreed but how it encodes in theory vs what a person actually hears is not always the same. It seems we're talking a bit about side imaging here, as an example. While a real speaker feed to center left or center right will be heard precisely, phantom imaging only works when your facing that direction straight on. That is, center front. Turn your head to the side 90 deg and that sharp image goes away.

I have never heard any Dolby system that did anything special, and stereo synthesis is terrible via Dolby. As I've said before Dolby reinvented the wheel but made it square

Good saying, about the Dolby wheel. It was a giant step backwards to those used to enjoying good quad performance through the better gear. DPL II was a step forward. Nice that it can be set to decode QS but still no QS-like stereo synth function.

I'm sure that the Surround Master being digital has the ability to look ahead to be able to react faster than an analog decoder but what does that have to do with selecting correct decoding?

I can't answer that question but I do want to emphasize The Surround Master does not have any delay digital or analog on the control signal path to enable it to "look ahead". It is a digital/analog hybrid system where, per Chucky, "all the maths" is done digital & what we hear stays analog. Utilizing a tri-band decoder with well chosen time constants the processing does not need look ahead. The patent shows 30/60 mSec attack/ decay for the low band, 10/30 mSec for the middle band, and 1/5 mSec for the high band. They could have changed this in practice or used variable attack & decay, only Chucky could tell us. But under these conditions there seems no need for look ahead. Although it was clever in the days of all analog & I think Jim Fosgate originated it.

 

[par4ken]

Agreed but how it encodes in theory vs what a person actually hears is not always the same. It seems we're talking a bit about side imaging here, as an example. While a real speaker feed to center left or center right will be heard precisely, phantom imaging only works when your facing that direction straight on. That is, center front. Turn your head to the side 90 deg and that sharp image goes away.

I don't exactly agree, while side images are not nearly as precise as front images they still exist even without turning your head, The effect is much better if the front and rear speakers are closer together. In a long deep room you will of course get the hole in the middle effect and hear the image from the closest speaker, or perhaps hear two distinct sources. Ambisonics might be able to remedy that but how is Dolby encoding or decoding going to change anything? I prefer having the rear speakers placed off to the sides rather than behind me, the rear left and right signals are then clearly heard to the sides and panned signals move more clearly front to back across the sides.

 

[MagnumX]

While a real speaker feed to center left or center right will be heard precisely, phantom imaging only works when your facing that direction straight on. That is, center front. Turn your head to the side 90 deg and that sharp image goes away.

Why would you turn your head? Phantom imaging works perfectly fine in all directions and axis here including vertical. I've got demos and songs that go around in complete circles or rectangles around the room at different height levels even here with 17 speakers.

If phantom imaging didn't work in every direction, sounds wouldn't move smoothly around the room. With PS4 gaming (Standard multi-channel 5.1/7.1 output, not Atmos or anything), I can rotate my character 360 and a sound like a fire crackling moves around me in a smooth circle.

I almost jumped out my chair once when one of the characters in Dragon Age Inquisition suddenly yelled something right behind my left shoulder (that's where he was standing relative to my character) because it sounded so real (phantom image; there is no speaker where his voice came from).

In other words, turning your head is not a good indication of phantom imaging, but hard imaging.

 

[par4ken]

Why would you turn your head? Phantom imaging works perfectly fine in all directions and axis here including vertical. I've got demos and songs that go around in complete circles or rectangles around the room at different height levels even here with 17 speakers.

If phantom imaging didn't work in every direction, sounds wouldn't move smoothly around the room. With PS4 gaming (Standard multi-channel 5.1/7.1 output, not Atmos or anything), I can rotate my character 360 and a sound like a fire crackling moves around me in a smooth circle.

I almost jumped out my chair once when one of the characters in Dragon Age Inquisition suddenly yelled something right behind my left shoulder (that's where he was standing relative to my character) because it sounded so real (phantom image; there is no speaker where his voice came from).

In other words, turning your head is not a good indication of phantom imaging, but hard imaging.

I'll bet that you have a reasonable (not overly large) listening room. Glad that you hear pans so clearly, remember that it is still all an illusion, but what a wonderful one at that. I would suggest that for clear panning and side imaging effects in a large room one would need more speakers to fill the empty spaces. For me I'm happy with just four channels!

 

[ar surround]

Why would you turn your head? Phantom imaging works perfectly fine in all directions and axis here including vertical. I've got demos and songs that go around in complete circles or rectangles around the room at different height levels even here with 17 speakers.

If phantom imaging didn't work in every direction, sounds wouldn't move smoothly around the room. With PS4 gaming (Standard multi-channel 5.1/7.1 output, not Atmos or anything), I can rotate my character 360 and a sound like a fire crackling moves around me in a smooth circle.

I almost jumped out my chair once when one of the characters in Dragon Age Inquisition suddenly yelled something right behind my left shoulder (that's where he was standing relative to my character) because it sounded so real (phantom image; there is no speaker where his voice came from).

In other words, turning your head is not a good indication of phantom imaging, but hard imaging.

I've seen people turn their heads when they hear a sound that they believe is coming from a side location. I've done it myself. Why? Perhaps it's that a sound from the side is a distraction for which one wants to turn their head?

 

[MagnumX]

I'll bet that you have a reasonable (not overly large) listening room. Glad that you hear pans so clearly, remember that it is still all an illusion, but what a wonderful one at that. I would suggest that for clear panning and side imaging effects in a large room one would need more speakers to fill the empty spaces. For me I'm happy with just four channels!

It's about 24' long and 12' wide. I use the full length and have three rows of seats (if you can call one centered recliner in the back a row). I've got 11 speakers on the floor and 6 overhead and two overhead play a mix of L/C/R for dialog/screen lift so it sounds like the speakers are behind the screen instead of under it.

I often play many 5.1 albums with only the two lift speakers and matrixed front wides across half the room so pans across the side surrounds don't pass through the rear surrounds in an arc instead of a straight line. So its more like 7.1 Plus (or 6.1 for quad albums). The mixed front wides allow smooth imaging around the sides without any speakers to the sides (surrounds are behind me) and I can have seating closer to the side walls since the speakers are between rows of seats. This reduces the used part of the room to 12'x12' and one row of seats.

With >5.1 or upmixed 2.0 or greater the entire room is used which with Atmos encoded albums like Kraftwerk's 3D-The Catalogue or Yello's Point, sounds can and do appear and pan literally anywhere in the room including ghost imaging right through me or flying in a straight line just over my head front to back (Big Boys Blues on Point) like something actually is there (freaky effect really with your eyes closed).

Others have told me they don't hear that effect like that (spottier sounding with less consistent panning) so I think careful alignment and levels are important to get a more holographic-like sound. My goal has been to get something close to binaural without using headphones. Atmos/X/Auro finally makes that possible or very close to it, at least, I think.