"Official" Audyssey thread (FAQ in post #51779) - Page 2527 - AVS | Home Theater Discussions And Reviews
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post #75781 of 75786 Old Yesterday, 05:25 PM
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Originally Posted by AustinJerry View Post
The measurement technique is correct now. I don't see a significant difference in the default distance and the tweaked distance, at least not enough that would cause an audible difference. I would leave it at the default.
Okay. Thanks.
Just want to make sure that I was looking at the right thing.
The default distance has roll off at crossover point (90Hz).
My tweaking was such that it becomes as flat as possible at 90Hz without significant drop in the 20-90Hz range. Is this the correct way to tweak?

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post #75782 of 75786 Old Today, 07:15 AM
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Originally Posted by AustinJerry View Post
The measurement technique is correct now. I don't see a significant difference in the default distance and the tweaked distance, at least not enough that would cause an audible difference. I would leave it at the default.
I concur.


I would however crank that sub trim up a bit. Probably sounds a little anemic right now.

AVR: Denon 4520ci, FL/R: Klipschorn, CC: Klipsch RC-64ii, SUR: Polk LS/FX x4, FH: Klipsch RB-51ii x2, SUB: PSA T-18 x2, DISP: Mitsubishi WD-73740, BluRay: PS3 & BDP-S5100, Remote: URC MX-700
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post #75783 of 75786 Old Today, 07:20 AM
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Originally Posted by aaranddeeman View Post
Okay. Thanks.
Just want to make sure that I was looking at the right thing.
The default distance has roll off at crossover point (90Hz).
My tweaking was such that it becomes as flat as possible at 90Hz without significant drop in the 20-90Hz range. Is this the correct way to tweak?
Yes, you are correct. However, you don't really have a problem at the crossover (lucky man!) to begin with so that's why the tweak didn't seem to do much.

Here's a more dramatic example of how the distance tweak can help a big dip over the crossover:


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AVR: Denon 4520ci, FL/R: Klipschorn, CC: Klipsch RC-64ii, SUR: Polk LS/FX x4, FH: Klipsch RB-51ii x2, SUB: PSA T-18 x2, DISP: Mitsubishi WD-73740, BluRay: PS3 & BDP-S5100, Remote: URC MX-700
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Getting Started with REW
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Audyssey FAQ
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post #75784 of 75786 Unread Today, 08:06 AM
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Originally Posted by mthomas47 View Post
I was sort of hoping that you wouldn't ask, as the answer is a little complicated. On the other hand, this question comes up from time to time, so it's probably worthwhile to try to provide a comprehensive explanation. So, here's my take on it.

There are sound waves bouncing around your head (and off it) from the leather sofa back, from the ceiling, from the floor, etc. all the time. You simply don't pay much attention to those sound waves for several reasons. First, if they are very high frequency waves, and many of them are, they are short in wavelength (less than an inch) and transient in duration. Unless there are a lot of them grouped together, our hearing just isn't sensitive enough to notice them. Second, there are psycho-acoustic phenomena in play. We tend to pay the most attention to the first arriving sound (the Precedence Effect: see Haas), so the sound we really notice is coming from the general direction of the speaker(s) playing it. And our brains are actually quite adept at filtering out extraneous noise, as we do when we talk on the telephone, or work, or talk to someone in a crowded restaurant. So, those spurious sound waves bouncing off your sofa and into your ears are largely unnoticed by your hearing, and ignored by your brain.

Ideally, Audyssey, and particularly XT-32, should ignore them as well. What you don't want Audyssey to do is to try to be fussy in the upper frequencies. There are graphs in the Addendum to the FAQ which show the difference between XT trying to over-correct the upper frequencies, and XT-32, doing less up top. The philosophy between the two versions is different. XT-32 attempts to disregard minor deviations in the upper frequencies, and only deal with variations that span across let's say 50-100hz. It's very different at the low end, though, where Audyssey will try to detect and correct issues involving only a few hertz. But, when Audyssey attempts to make so many minor adjustments up high, the result can be a garbled, or harsh sound. So, we want to avoid creating a situation where Audyssey will try to over-adjust in the high frequency range.

The Audyssey microphone doesn't hear the way our ears do; it is far more sensitive. And it doesn't have a psycho-acoustic mechanism like our brain, which will allow it to disregard what it hears in quite the way we can. So, if the mic. gets too close to a hard surface during calibration, the short waves bouncing off the surface into the mic. will "spoof" Audyssey into trying to "fix" a problem that doesn't really exist. Due to the close proximity, the sound waves will seem more prominent, and problematical, than they really are. And in trying to correct for that non-existent problem, Audyssey will create a lot of unnecessary filters (hair) in the upper frequencies. That is called comb filtering due to it's shape, and it is a form of distortion which Audyssey can inadvertently introduce. That's why users are advised to keep the Audyssey microphone about 18" away from hard surfaces. But, trying to stay so far away may not present an ideal calibration, so people came up with the idea of temporarily using a blanket.

When you use a blanket, or towel, during calibration, you can position the mic. close to hard surfaces without worrying about spurious reflections "spoofing" Audyssey into over-correcting. And when you remove the blanket after calibration, you will go back to your normal situation in which the relatively lesser acuteness of your hearing, and the psycho-acoustic phenomena discussed earlier, will protect you from hearing (or noticing) the spurious reflections bouncing around you. A lot of us have tried it and found that to be the case. To summarize, this procedure of using a blanket during calibration has been endorsed by Chris K,. the inventor of Audyssey, and well established empirically by numerous members of the thread. It makes sense acoustically, and it works. Win, Win, as they say.

Regards,
Mike
Awesome write-up Mike. How close can you get with the blanket? I think I read 3 inches somewhere, does that sound correct? Thanks.
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post #75785 of 75786 Unread Today, 10:07 AM
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Originally Posted by johnnymacIII View Post
Awesome write-up Mike. How close can you get with the blanket? I think I read 3 inches somewhere, does that sound correct? Thanks.
Thank you! I don't know that I have ever heard of a specific distance limitation. I generally keep the microphone about 4"-6" away from the blanket, but I think you would probably have to experiment to find out what works best for you. Depending on how much you lean back when you watch/listen, your ear canals are going to be about 4" or so from the back of the chair or couch, anyway. I have never felt that having the mic. 6" away from the back of my chair made any difference to the sound. Now, getting 18" away on the other hand, does make a difference for me.
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post #75786 of 75786 Unread Today, 10:31 AM
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Originally Posted by Alan P View Post
Yes, you are correct. However, you don't really have a problem at the crossover (lucky man!) to begin with so that's why the tweak didn't seem to do much.

Here's a more dramatic example of how the distance tweak can help a big dip over the crossover:

Ah. looks like I am in much better shape (may be due to my sub is nearfield).
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