What does "speaker distance" setting actually do? - AVS Forum
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post #1 of 12 Old 05-14-2013, 08:28 AM - Thread Starter
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As the old saying, "the more I learn, the more I realize I don't know"....So, as I read many threads about set up, I realize that I do not know what setting the speaker distance setting actually does to the audio it sends out. Obviously, it is not "loudness or volume", then what is it?

I ask because I've always been a bit unsure about what "proper surround sound" should sound like. I've gone to audio stores to try and "calibrate my ears and expectations", but now I wonder if tweaking distance settings would be an improvement.

As a note, when I set up my speakers, (whether AutoCal or Manual) I do get out the tape measure and verify the distances. So, I believe I am dead on as to set up.

Sometimes I have to remind myself that I bought all this "stuff" to enjoy it!
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post #2 of 12 Old 05-14-2013, 09:03 AM
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Speaker distance settings in the AVR are time delays. Say you have surround speakers that are 4 ft from your head and your front speakers are 12 ft away. If the sound came out of all the speakers at the same time you would hear the sound from the surrounds first then you would hear the sound from your fronts. This would cause perceived distortion, muddiness, inaccuracies, or echos. So the distance setting allows all the sounds to reach your ear at the same time OR I guess I should say how the mixer intended.

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post #3 of 12 Old 05-14-2013, 09:15 AM - Thread Starter
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Originally Posted by flickhtguru View Post

Speaker distance settings in the AVR are time delays. Say you have surround speakers that are 4 ft from your head and your front speakers are 12 ft away. If the sound came out of all the speakers at the same time you would hear the sound from the surrounds first then you would hear the sound from your fronts. This would cause perceived distortion, muddiness, inaccuracies, or echos. So the distance setting allows all the sounds to reach your ear at the same time OR I guess I should say how the mixer intended.

Thanks, that description does make sense. All the more reason to make sure the distances to the listening position(s) are accurate.

Sometimes I have to remind myself that I bought all this "stuff" to enjoy it!
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post #4 of 12 Old 05-14-2013, 09:20 AM
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Yes. Now some ppl say its better to leave it where Audyssey sets it, some say its better to measure yourself. I just let Audyssey do its thing and leave it there.

Now the distance setting on the subwoofer is a lil different, most say that measuring with a tape measure is NOT the best way. Most have a higher distance set than what it truly is. For the sub what its mainly about is getting it to cooperate with your speakers around the xover point.

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post #5 of 12 Old 05-14-2013, 10:01 AM
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^^ I haven't seen advice to leave it as it is, in particular if the difference is significant. Your best bet, if you see errors in distance that are alarming, is to re-run Audyssey.

Subwoofers have their own filters that contribute to delay, and Audyssey uses these as well determine its distance. This kind of boggles my mind, but I don't argue.

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post #6 of 12 Old 05-14-2013, 04:53 PM - Thread Starter
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Originally Posted by Nethawk View Post

^^ I haven't seen advice to leave it as it is, in particular if the difference is significant. Your best bet, if you see errors in distance that are alarming, is to re-run Audyssey.

Subwoofers have their own filters that contribute to delay, and Audyssey uses these as well determine its distance. This kind of boggles my mind, but I don't argue.

Well, neither of my set ups use Audyssey; one is a Pioneer MCACC, the other Sony AutoCal. But knowing the science behind the settings helps to sort out the set ups. My primary concern is with the surrounds. The fronts/center distances tend to be stable across listening positions, as it is really a constant radius/arc type of distance.

Now the surrounds are a different story...in my main living room, the outer sections of the "arc" can be close to one surround, and far from the other, and vice versa. The "main listening position is equidistant to both.

Again, I am really trying to "calibrate my ears and expectations", and I may play with settings just to learn the differences.

Sometimes I have to remind myself that I bought all this "stuff" to enjoy it!
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post #7 of 12 Old 05-14-2013, 05:27 PM
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Quote:
Originally Posted by Nethawk View Post

^^ I haven't seen advice to leave it as it is, in particular if the difference is significant. Your best bet, if you see errors in distance that are alarming, is to re-run Audyssey.

Subwoofers have their own filters that contribute to delay, and Audyssey uses these as well determine its distance. This kind of boggles my mind, but I don't argue.

if it boggles your mind, you prabably are giving Audyssey more complicated features than it has. FOr the distance/delay settings all AUdyssey ever does is emit a sound and wait to see how much later that sound gets to the microphone. It sets distances by emitting a sound at a time it know then waiting quite a number of CPU cycles until the sound gets to the mic. WIth the normal channels, the electrical transfers are too fast (speed of light almost) to make a difference in the total time between emission of the chirp and it's arrival at the microphone position.

When it pings the sub, Audyssey does the exact same thing. It emits the sound and waits how ever many cpu cycles it takes for the sound to reach the mic. If the sub has internal processing that slows everything down, Audyssey has absolutely no idea it's there. But if the electrical signals are delayed going through the sub's processing that means the sound coming out of the sub is later than it would have been without the processing. So by the time the sound gets from the sub to the mic, the built in delay of the sub is simply there. Audyssey doesn't know if your sub's 10 feet away with sone processing delay or really 17 feet away. It only knows how long it takes from electrical signal to the mic. In modern-er receivers, that calculation show up for our information as "distance" but it was never anything but delay from chirp start to chirp reaching the mic to Audyssey. Sound has a constant velocity in air, so converting the delay time to distance is pretty simple for a computer . . .so we can see it that way. But the receiver actually implements corrections via delay of the sound from the "closer" channels. So the receiver doesn'tcare about distance either. Just the time it takes for the sound to get to the mic.
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post #8 of 12 Old 05-14-2013, 06:34 PM
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From the technical papers that I read in preparation for Audyssey it explained that the algorithm used to derive distance value takes into account the induced delay implemented by the subwoofer's processing filters. Given this, Audyssey does know it's there. Based on pure logic and your description this is how I expect it would work, but that statement on Audyssey sent logic into a tailspin. I'm guessing that it may be as simple as counted cycles and another internal formula that provides an accurate guess of the delta. That and marketing spin may be the correct analysis.

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post #9 of 12 Old 05-14-2013, 07:00 PM - Thread Starter
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Quote:
Originally Posted by Nethawk View Post

From the technical papers that I read in preparation for Audyssey it explained that the algorithm used to derive distance value takes into account the induced delay implemented by the subwoofer's processing filters. Given this, Audyssey does know it's there. Based on pure logic and your description this is how I expect it would work, but that statement on Audyssey sent logic into a tailspin. I'm guessing that it may be as simple as counted cycles and another internal formula that provides an accurate guess of the delta. That and marketing spin may be the correct analysis.

Seeing as we are speaking of micro and nano seconds here regarding time, does speaker wire length come into play? How does the AVR/Audyssey know when the signal "comes out of the speaker"? I can understand it knows when the signal is sent (from the AVR), but similar to the subwoofer "delay" it would seem wire travel would have to be taken into account in some fashion. I understand the velocity differences of electrons vs sound waves, but I'm trying to understand all the possible nuances.

So, does, or can, Audyssey get thrown off by greater speaker wire lengths, or thinner wire?

Sometimes I have to remind myself that I bought all this "stuff" to enjoy it!
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post #10 of 12 Old 05-14-2013, 07:50 PM
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Hi BizWiz,

No, you don't have to worry about cable length, because the speed of light is somewhat faster than the speed of sound, so the cable isn't significant.

The signal travels through the wire at approximately 11 inches per nanosecond, whereas the sound travels through the air at approximately 13.5 inches per millisecond. That approaches a million-to-one difference. It would take 165 miles of speaker cable to generate the same delay as one inch of speaker distance from the listener.

But even if it was significant, Audyssey works by measuring the time between it generating the "ping" until it hears the ping in the microphone, so it takes into account the aggregate of the delay, regardless of what causes the delay (which really doesn't matter). What it cares about is getting the audio from each speaker to your ears at the same instant.
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post #11 of 12 Old 05-15-2013, 12:28 AM
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My simple understanding is the 'distance' is the delay caused by physical distance and any caused by filters on top. Audyssey's team know that filters cause delay in practice but it doesn't mean during actual measurement Audyssey can determine how much delay is caused by filters and how much by physical distance. There's no need to know the individual contribution.

If you look at the 'distance' settings actually used in receivers, in the Denon it's down to an inch (IIRC) but in the Onkyo it's 6in so it's relatively crude, hardly in the micro and nanosecond territory.

Audiosceptics accept audio trials using 25 people. A recent Oxford study with over 353,000 patient records from 639 separate clinical trials shows for every 1,000 people taking diclofenac or ibuprofen there would be 3 additional heart attacks, 4 more cases of heart failure and 1 death every year.

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post #12 of 12 Old 05-15-2013, 06:24 AM
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Audyssey has no way of knowing what's inside your sub, nor does it need to. Send a pulse, wait for the response at the mic, calculate the delay, done. It can also determine the phase response to better integrate your system. Getting the phase aligned at the crossover point is most important for cohesive sound without large amplitude excursions at the crossover point.

The delay includes processing delay for all the filters in the AVR (or pre/pro), time delay through the amps and wires (usually far in the mud), etc. The most significant delays are usually acoustic, since sound travels around 1 foot per ms, but digital filters can eat up some time as well. Adjusting the delay to match the phase of the sub to the mains is also important; built-in filters and crossovers can change the phase significantly. All this may cause the physical distance and calculated distance to vary a bit, but I have not seen large differences except as the result of a bad calibration run. I would not generally expect them to be identical.

FWIWFM - Don

"After silence, that which best expresses the inexpressible, is music" - Aldous Huxley
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