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Time vs Intensity Image Stability Experiment

tallbeardedone

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For those who can add a computer as a source, can you please try this experiment and report back.

Recently I was told that sound images placed using level-difference are more "stable" (less prone to shift as you move around relative to your speakers) than images places via time-difference.

To test this I used this time-intensity trading applet. I placed the image to the left of the soundstage as shown in the photos. First with -4dB level difference, then with -0.44ms time difference. Then I shifted my head to the RIGHT until the image disbanded and I could hear the sound from the right speaker.

To my ear BOTH IMAGES SHIFTED THE SAME AMOUNT. That is, neither image was more "stable" than the other.

Can others please try this same experiment in their room and report back?
Is one image more stable than the other in your room?

Here's link again:


Thanks in advance! :cool:

Screenshot 2022-11-22 at 9.12.10 PM.png
 

Tim Link

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There could be some truth to the statement, depending on your configuration. If you are a good ways back from the speakers, a slight distance change won't effect the volume difference from the speakers very much, but can change the timing difference just as much as if you were closer. So if subtle timing clues are being used to establish imaging locations, these remain fragile at all listening distances, and at far distances it can be tricky to get everything set up accurately. A loudness difference used to establish panning to the left or right will not be as disturbed by a slight distance offset between the speakers, so it is more likely to maintain it's effect, even though you will have added a timing difference that will try to compete with it when you go off center.
 

Dumdum

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So time alignment will skew the high freqs and focus before shifting the low freqs because of wavelengths involved, when testing time alignment in a car for accuracy I pay attention to the higher freqs of any given speakers range

When it’s correct focus gets better and it’s best tested/set with left and right routed to both left and right channels… it’s an easy test of timing being correct… if both channels have the same freq response and good timing you should have a solid centre and only a centre, perfectly between the two left and right extremes of the stage, nothing from left or right

Levels will pan the centre around in the stage, very different to ta, all the image will shift in a lump and compress one side or the other but stay in focus

Levels being off between certain freqs will also blur the centre, but you can find problem areas with band width limited pink noise in 1/3 octave bands which should all be in the centre

When you have good timing and freq response matching the centre will stay more planted

Timing for me being off more blurs the centre of the stage and objects within it… levels move the entire centre but it’s not unrelated from one to the other, a combination of both will be used in recordings

As for your experiment I will try it tomorrow
 
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tallbeardedone

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There could be some truth to the statement, depending on your configuration. If you are a good ways back from the speakers, a slight distance change won't effect the volume difference from the speakers very much, but can change the timing difference just as much as if you were closer. So if subtle timing clues are being used to establish imaging locations, these remain fragile at all listening distances, and at far distances it can be tricky to get everything set up accurately. A loudness difference used to establish panning to the left or right will not be as disturbed by a slight distance offset between the speakers, so it is more likely to maintain it's effect, even though you will have added a timing difference that will try to compete with it when you go off center.
Hmm. My listening position is a bit more near field than normal, roughly 30cm inside of the tip of the equilateral triangle, so that may account for the similarity in image stability. I'm not sure of the physics of your theory though, as sound pressure attenuates at an inverse square to distance, whereas time difference is proportional to distance (t = d/v) so doesn't that follow that a change in distance (moving head to the side) should cause greater level attenuation than time change?
 

Dumdum

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Hmm. My listening position is a bit more near field than normal, roughly 30cm inside of the tip of the equilateral triangle, so that may account for the similarity in image stability. I'm not sure of the physics of your theory though, as sound pressure attenuates at an inverse square to distance, whereas time difference is proportional to distance (t = d/v) so doesn't that follow that a change in distance (moving head to the side) should cause greater level attenuation than time change?
Also high freqs lose more energy in air vs low freqs… the bass car you can hear from miles away but miss all the high freq information is a good example of this
 

Sokel

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Did a quick sloppy one with my stereo speakers at my usual listening position (2.8 meters apart,at the inner edge of the triangle in a 300m³ of volume room)
First two segments of time (right and left ones at -22dms)are not as the first two of amplitude (at -2db) time lacks that clarity in my setup.That's something to investigate further when I will give a more critical listening.
(I compared the segments I refer to by going diagonally too,but in every other way as well)
 

Tim Link

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Hmm. My listening position is a bit more near field than normal, roughly 30cm inside of the tip of the equilateral triangle, so that may account for the similarity in image stability. I'm not sure of the physics of your theory though, as sound pressure attenuates at an inverse square to distance, whereas time difference is proportional to distance (t = d/v) so doesn't that follow that a change in distance (moving head to the side) should cause greater level attenuation than time change?
To explain my thinking better, let's assume an 8 foot spread of speakers with an 8 foot setback from the speaker plane to the ear. This creates two triangles with a 4' leg outboard from the ear, an 8' leg forward of the ear, and a hypotenuse of 107.33", which is the distance of the speaker to the ear. If one speaker is accidentally set further back by an inch, it's distance to the ear becomes 108.22". So even if you are quite a ways back you still have nearly a full 1" time delay arrival, which is quite audible. The difference in sound level at that distance would change by 1/(108.22/107.33)^2, which equals 1/1.0083, which equals .9917, which corresponds to about -.04 decibels, which I think is too small to detect. Assuming the ears are about 8" apart, what kind of angle from straight ahead would correspond to a 1" timing arrival difference? Assuming a sound source that is far away enough to produce a mostly flat wave front across the head I think it's somewhere around 5 degrees off.
 

Sokel

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Ok,did a more focus listening.
0.22 and -022ms of time seems like they stay in the center but below (in image) than the dead center segment and not as defined.
All else works as intended.
Also tried bigger distance (3.2 meters) just outside the edge of my triangle only to make things worst for the 22 and -22ms of time.
All else seems to work fine there but not as focused as my MLP.
 

Tim Link

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I just tried the test. I found that with -2 dB of the left speaker, the right speaker continued to dominate even as a moved quite a bit to the left. With the .22ms delay it shifts rapidly as I move to the left, and is generally unstable if I don't get close enough to the speakers for the direct sound to dominate. The timing cues are very easily disturbed by room reflections in my setup. So my initial impression is that timing cues are more fragile and volume cues are more robust for my ears to determine sound direction in a 2 speaker stereo setup. If I play the timing against the volume, with the delayed speaker playing louder, it does pull the image back toward the center but it's really weird sounding and obvious that both speaker are somehow making things happen. My ears feel like they're being tricked so it has a "tricky" sound to it.
 
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tallbeardedone

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I just tried the test. I found that with -2 dB of the left speaker, the right speaker continued to dominate even as a moved quite a bit to the left. With the .22ms delay it shifts rapidly as I move to the left, and is generally unstable if I don't get close enough to the speakers for the direct sound to dominate. The timing cues are very easily disturbed by room reflections in my setup. So my initial impression is that timing cues are more fragile and volume cues are more robust for my ears to determine sound direction in a 2 speaker stereo setup. If I play the timing against the volume, with the delayed speaker playing louder, it does pull the image back toward the center but it's really weird sounding and obvious that both speaker are somehow making things happen. My ears feel like they're being tricked so it has a "tricky" sound to it.
Interesting thanks for impressions. I will do the same thing on my set up tonight and see how it compares.
 

NTK

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I just tried the test. I found that with -2 dB of the left speaker, the right speaker continued to dominate even as a moved quite a bit to the left. With the .22ms delay it shifts rapidly as I move to the left, and is generally unstable if I don't get close enough to the speakers for the direct sound to dominate. The timing cues are very easily disturbed by room reflections in my setup. So my initial impression is that timing cues are more fragile and volume cues are more robust for my ears to determine sound direction in a 2 speaker stereo setup. If I play the timing against the volume, with the delayed speaker playing louder, it does pull the image back toward the center but it's really weird sounding and obvious that both speaker are somehow making things happen. My ears feel like they're being tricked so it has a "tricky" sound to it.
I think you are confirming what Dr. David Griesinger said. (Source: http://www.davidgriesinger.com/threedpm.pdf)

panning.png
 
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tallbeardedone

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I also have to thank the OP as in the same site there is a similar test called Virtual Acoustic space which is making amazing work for the whole image.
Someone can adjust and pinpoint every direction.

Yeah that's one of the coolest (and most useful) tools on the website for sure!
 

RayDunzl

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Just ran across this:

"Without moving your head, look to your left. Now look to your right. Keep flicking your eyes back and forth, left and right.

Even if you managed to keep the rest of your body completely still, your eyeballs were not the only parts of your head that just moved. Your ears did, too. Specifically, your eardrums—the thin membranes inside each of your ears—wobbled. As your eyes flitted right, both eardrums bulged to the left, one inward and one outward. They then bounced back and forth a few times, before coming to a halt. When you looked left, they bulged to the right, and oscillated again."


 
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Tim Link

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Just ran across this:

"Without moving your head, look to your left. Now look to your right. Keep flicking your eyes back and forth, left and right.

Even if you managed to keep the rest of your body completely still, your eyeballs were not the only parts of your head that just moved. Your ears did, too. Specifically, your eardrums—the thin membranes inside each of your ears—wobbled. As your eyes flitted right, both eardrums bulged to the left, one inward and one outward. They then bounced back and forth a few times, before coming to a halt. When you looked left, they bulged to the right, and oscillated again."


That's new to me! Just sitting here listening to the refrigerator in the background I percieve a slight pitch change as I move my eyes left to right with my head in fixed position. The ringing in my ears also changes. This is true as I move my jaw around too, even more so. I wonder if the eye and jaw muscles are just interfering with the ear a bit just by proximity.
 
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