"Official" Audyssey thread (FAQ in post #51779) - Page 998 - AVS Forum
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Old 08-21-2010, 11:18 AM
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Originally Posted by pepar View Post


I've looked at this before. This time I'll read it carefully. Thanks.

Great article but it doesn't invalidate your original point.

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Old 08-21-2010, 11:57 AM
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Originally Posted by nathan_h View Post

Great article but it doesn't invalidate your original point.

I guess my takeaway is term "positional optimization" and that, yes, it supports equalizing all subs as one. Beyond that, it is a Harman paper with "patent pending" for SFM on the first page and then thirty-seven more instances of SFM.

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Old 08-21-2010, 12:53 PM
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Quote:
Originally Posted by pepar View Post

Chris/audyssey has posted that their research has shown that correcting two subs AS ONE produces the best results. This may or may not be the reason, but my thinking is that doing each sub individually corrects for the interaction with the room while doing them as one corrects for their interaction with the room AND EACH OTHER.

My guess is that this has more to do with the specifics of how Audyssey determines the EQ curve than due to sub interactions. As Chris has also mentioned, they do not have to remeasure the room's response to predict the result of the corrective EQ, since it is a linear system. That same principle of superposition applies when two subs are involved.

For example, two subs can be measured and their "interaction" predicted. This is for example how BassQ works.

However, I think that since Audyssey calculates EQ filters by merging several mic positions, the amplitude and time information no longer represent any one point in space, so the ability to predict how a new stimulus, the second sub, will affect the end result over that space is not as certain as simply measuring both subs at the same time. Measuring them separately might work out fine, it might not--but measuring them together always assures a certain accuracy is attained. [/armchair analysis]

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Old 08-21-2010, 01:08 PM
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So after a week with the new firmware on my Denon 1909 I definitely notice a difference with the boomy bass....I'm happy to say it seems to be gone.

However I've noticed something else with the subwoofer which is kind of annoying. One of the main seats in my room is pretty close to the sub (basically the sub points from the side wall right at your ear, maybe 6 ft away). Well I've noticed that I constantly hear the sub kicking off (it isn't actually shutting off)....there's like a second or two of muted "white noise" type static when the audio seems to go from a scene that require bass to one that doesn't. It's particularly noticeable in this seat, less so from others just b/c it isn't particularly loud. It is quite distracting. I tried lowering the subwoofer trim from -5.5 (setting from Auto Setup) to -12.0 (the max) and it doesn't seem to improve it at all. I've tried turning Dynamic Volume on and off and don't notice a difference there either.

Relocating the sub is out of the question. It is sitting in a customized media cabinet that I had hollowed out behind it and there's no where else in the room to put it.

Any suggestions?

TIA
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Old 08-21-2010, 01:26 PM
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Quote:
Originally Posted by EricScott View Post

I've noticed that I constantly hear the sub kicking off (it isn't actually shutting off)....there's like a second or two of muted "white noise" type static when the audio seems to go from a scene that require bass to one that doesn't.

Just to make sure it isn't the sub, try playing a bassy section and then hitting the mute button on the AVR. If the noise burst remains, I'd start looking into the sub. Is it using a switching (Bash) amp?

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Old 08-21-2010, 02:22 PM
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Quote:
Originally Posted by Roger Dressler View Post

Just to make sure it isn't the sub, try playing a bassy section and then hitting the mute button on the AVR. If the noise burst remains, I'd start looking into the sub. Is it using a switching (Bash) amp?

Thanks for the reply.

When you say the "burst", I would kind of describe it as the opposite. It sounds more like it is sort of fading out but the sub seems to fade out a second or two "late" if that makes sense?

Not sure I understand your question on the sub. I have a Paradigm DSP 3100 which is connected to my Denon 1909 using the LFE out on the Denon.
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Old 08-21-2010, 02:56 PM
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Quote:
Originally Posted by EricScott View Post

When you say the "burst", I would kind of describe it as the opposite. It sounds more like it is sort of fading out but the sub seems to fade out a second or two "late" if that makes sense?

Like a reverb tail, but it's some sort of noise?

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Not sure I understand your question on the sub. I have a Paradigm DSP 3100 which is connected to my Denon 1909 using the LFE out on the Denon.

That sub has a class-D switching power amp as well as an option for DSP EQ filtering. So it's "busy" in there, and must be considered a potential source of the problem just as much as the AVR.

You mentioned this noise tail becomes audible as the bass ceases in the program. To see if it is coming from the AVR's internal signal processing or from the sub, I suggest hitting the Denon's mute button while bass is playing. If the sub goes dead silent, no noise tail, it implies the noise is inside the AVR. If the sub makes the noise tail, it suggests the sub electronics are misbehaving.

Give it a shot.

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Old 08-21-2010, 08:39 PM
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Quote:
Originally Posted by Roger Dressler View Post

Like a reverb tail, but it's some sort of noise?

That sub has a class-D switching power amp as well as an option for DSP EQ filtering. So it's "busy" in there, and must be considered a potential source of the problem just as much as the AVR.

You mentioned this noise tail becomes audible as the bass ceases in the program. To see if it is coming from the AVR's internal signal processing or from the sub, I suggest hitting the Denon's mute button while bass is playing. If the sub goes dead silent, no noise tail, it implies the noise is inside the AVR. If the sub makes the noise tail, it suggests the sub electronics are misbehaving.

Give it a shot.

So I tried a few scenes with and without a lot of bass and after hitting mute on the Denon, the sub still makes the static noise for a second or two. The noise I hear before the sub goes off completely after hitting mute is the same as the one I was describing earlier where during a scene you will just hear these dropouts (really more like pauses) in the background.

Sounds like it is probably my sub and not the Denon? On the sub I have the phase set to zero, the LPF set to "bypass"and the volume knob is at 12:00. Those haven't changed from when I ran Auto Setup. Don't think there are any other settings.

What do you suggest I do?

Thanks for the help.
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Old 08-21-2010, 11:03 PM
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Quote:
Originally Posted by EricScott View Post

So I tried a few scenes with and without a lot of bass and after hitting mute on the Denon, the sub still makes the static noise for a second or two. The noise I hear before the sub goes off completely after hitting mute is the same as the one I was describing earlier where during a scene you will just hear these dropouts (really more like pauses) in the background.

Ok. Good data.

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Sounds like it is probably my sub and not the Denon? On the sub I have the phase set to zero, the LPF set to "bypass"and the volume knob is at 12:00. Those haven't changed from when I ran Auto Setup. Don't think there are any other settings.

The settings would have no bearing.

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What do you suggest I do?

I'd give Paradigm a call. I suspect they will recognize the symptoms if it's ever happened before. What it sounds like to me is as the signal/load is removed (mute), the class-D amp relaxes as the caps reach normal charge, and the current flow tapers off, reducing the interference (either induced or maybe conducted as if there's a ground loose in there somewhere). Obviously just guessing, but no harm asking them about it.

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Old 08-22-2010, 12:48 PM
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As regards to the treatment Audyssey does in the time domain, here's some "food for thought" I found and would like to share: Excerpts from a paper by Michael Gerzon: "...One of the basic principles of science is the law of causality, that asserts that an effect cannot precede its cause. A causal filter is one in which the output does not emerge earlier than the input, and of course all real-world filters are of this type. In the digital domain, by adding an overall time delay so that one can have responses occurring before the delayed input (although after the actual input), one can simulate the effect of an acausal filter (ie one whose output responds before the input arrives), at the expense of having to wait a little..."

http://www.audiosignal.co.uk/Resourc...isation_A4.swf

I think this paper may help to get closer to understanding what Audyssey does in the time domain in our rooms by the clever use of digital filters, so to speak...(Warning: long read!) :-)

Whaddaya think?
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Old 08-22-2010, 01:51 PM
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Quote:
Originally Posted by mogorf View Post

http://www.audiosignal.co.uk/Resourc...isation_A4.swf

I think this paper may help to get closer to understanding what Audyssey does in the time domain in our rooms by the clever use of digital filters, so to speak...(Warning: long read!) :-)

Whaddaya think?

It won't tell you what Audyssey optimization is really doing because Audyssey doesn't disclose their optimization strategy. See http://www.avsforum.com/avs-vb/showt...0#post19038290

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Old 08-22-2010, 02:17 PM
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Originally Posted by markus767 View Post

It won't tell you what Audyssey optimization is really doing because Audyssey doesn't disclose their optimization strategy. See http://www.avsforum.com/avs-vb/showt...0#post19038290

Yeah, fully agree with you Markus, this is not to tell us HOW Audyssey is doing it, but to give us a hint on WHAT is to be done and treated. We all know that time domain problems are usually not exhausted by setting delays of each speaker in the system. That is rather easy to do IMHO, eh?

Time domain problems occur in our rooms in a much more complex way and that is what makes Audyssey stand out for me when compared to the competition not having such features.

And that's why I'm trying to put up this post for some further discussions on time domain issues discovered by other more knowledgable members asking them to share their experience here...
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Old 08-22-2010, 02:44 PM
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Originally Posted by Roger Dressler View Post

Ok. Good data.

The settings would have no bearing.

I'd give Paradigm a call. I suspect they will recognize the symptoms if it's ever happened before. What it sounds like to me is as the signal/load is removed (mute), the class-D amp relaxes as the caps reach normal charge, and the current flow tapers off, reducing the interference (either induced or maybe conducted as if there's a ground loose in there somewhere). Obviously just guessing, but no harm asking them about it.

Good idea. Will try them this weak. Hope my sub isn't broken. I have a feeling that they are going to tell me to disable Audyssey which obviously I don't want to do.

Any chance the measured speaker distance from auto setup could be causing / contributing to the problem? I know it is supposed to measure further than the actual distance but in my case it measured around 24' when the actual distance to the central seating area is maybe 7' - seems like a huge disparity.

Also did some more testing. On one particular 5.1 program (on FiOS) I didn't notice the sub cutting in and out and there was a lot of bass (was watching Ice Age 2 with my son). If I hit mute at any point there was still that second or two delay before it cuts out. Also watched a Blu-Ray with a DTS HD-MA soundtrack and DID notice the sub cutting out during the program, although not nearly as often as on a 2 CH program on FiOS where the den on was in DPL II Cinema mode. Those seem to be the biggest culprits. Unfortunately a lot of what we (are forced to) watch are kids shows and I have been watching a fair amount of vod which is mostly 2 CH.

To be clear I'm not worried about the delayed dropout when I hit mute (unless that is completely abnormal). It just seems to be an effective way to replicate the sound that I am hearing when the dropouts occur in the middle of a soundtrack (which is the annoying part).
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Old 08-22-2010, 03:46 PM
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Quote:
Originally Posted by EricScott View Post

Good idea. Will try them this weak. Hope my sub isn't broken. I have a feeling that they are going to tell me to disable Audyssey which obviously I don't want to do.

Maybe just as part of a diagnostic, but otherwise I cannot see that making sense.

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Any chance the measured speaker distance from auto setup could be causing / contributing to the problem? I know it is supposed to measure further than the actual distance but in my case it measured around 24' when the actual distance to the central seating area is maybe 7' - seems like a huge disparity.

Not an issue.

Quote:


Also did some more testing. On one particular 5.1 program (on FiOS) I didn't notice the sub cutting in and out and there was a lot of bass (was watching Ice Age 2 with my son). If I hit mute at any point there was still that second or two delay before it cuts out. Also watched a Blu-Ray with a DTS HD-MA soundtrack and DID notice the sub cutting out during the program, although not nearly as often as on a 2 CH program on FiOS where the den on was in DPL II Cinema mode. Those seem to be the biggest culprits. Unfortunately a lot of what we (are forced to) watch are kids shows and I have been watching a fair amount of vod which is mostly 2 CH.

To be clear I'm not worried about the delayed dropout when I hit mute (unless that is completely abnormal). It just seems to be an effective way to replicate the sound that I am hearing when the dropouts occur in the middle of a soundtrack (which is the annoying part).

If by dropout you're still talking about the noise tail that occurs after the audio has muted, ok. If there is some other sort of cutting out of the bass when it should be playing, that's a new wrinkle--to me anyway.

BTW, if they somehow want to shift the blame to the AVR, one other simple test will prove it. Disconnect the sub cable from the rear of the AVR. It should be silent. Touch your finger to the signal pin--it will buzz. Remove your finger--it should return to silent immediately. If the noise tail occurs, it could not have come from the AVR.

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Old 08-22-2010, 04:25 PM
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What would be a good way to compensate for a AVR that has MultEQ XT but not Dynamic EQ? If you normally listen at -5dB how much would you boost the sub trim and/or bass level control? How much at -10dB? Would you boost high frequency levels?
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Old 08-22-2010, 04:44 PM
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Quote:
Originally Posted by Roger Dressler View Post

Maybe just as part of a diagnostic, but otherwise I cannot see that making sense.

Not an issue.

If by dropout you're still talking about the noise tail that occurs after the audio has muted, ok. If there is some other sort of cutting out of the bass when it should be playing, that's a new wrinkle--to me anyway.

BTW, if they somehow want to shift the blame to the AVR, one other simple test will prove it. Disconnect the sub cable from the rear of the AVR. It should be silent. Touch your finger to the signal pin--it will buzz. Remove your finger--it should return to silent immediately. If the noise tail occurs, it could not have come from the AVR.

Sorry by dropout I meant the same noise tail I was describing earlier.

Tried the subwoofer cable test and the loud feedback buzz goes away instantly when I remove my finger from the cable. To be clear I simply removed the cable from the avr and did not touch the subwoofer end of it.

So I guess that means the noise tail is being generated somehow by the avr?
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Old 08-22-2010, 05:40 PM
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Quote:
Originally Posted by EricScott View Post

Tried the subwoofer cable test and the loud feedback buzz goes away instantly when I remove my finger from the cable. To be clear I simply removed the cable from the avr and did not touch the subwoofer end of it.

So I guess that means the noise tail is being generated somehow by the avr?

It's starting to make me wonder.

One thing you can do is play the sub output through something else--a headphone amp for example, so you can listen to it without the sub involved.

BTW, I fear we're off the Audyssey reservation with this topic. We can go to PM if you like. Or some other thread.

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Old 08-22-2010, 07:28 PM
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I'm not sure whether to post this hear or in the sub thread so I'll start here.

Both the Harmon Papers and Geddes strategies recommend various sub placements for positioning multiple subs to achieve the most linear frequency response. In either of those two approaches (particularly Geddes), it will be likely that one or more of the subs will NOT be the same distance from the main LP as another sub. In fact, you could end up, in a four sub room, with all four subs different distances from the main LP.

While I understand the approach of EQing all subs as one, the Audyssey SubEQ provides the ability to deal with subs where two of them are different distances from the main LP. Products like the QSC DSP 30 also provide that capability. In my case, when (using the DSP 30) i delayed the rear subs to match the distance of my front subs, the un-EQ'd FR got slightly worse.

So my question is: How important is it to compensate for distance differences when dealing with multiple subs that are placed in such a way that they are different distances from the main LP. And I ask this not from some theoretical position but rather sonically ---- can you hear it?.

Anyone reading this using multiple subs where the distance to the LP is not the same, you have EQ'd them but have not compensated for the distance differences electronically?

(I've re-read this several times and I'm not sure how clear it is but I'm not sure how to re-word the question!)

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Old 08-22-2010, 08:43 PM
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Quote:
Originally Posted by audioguy View Post

In my case, when (using the DSP 30) i delayed the rear subs to match the distance of my front subs, the un-EQ'd FR got slightly worse.

So my question is: How important is it to compensate for distance differences when dealing with multiple subs that are placed in such a way that they are different distances from the main LP. And I ask this not from some theoretical position but rather sonically ---- can you hear it?

In my feeble understanding of the Geddes approach, you use delay not to align arrivals but to smooth the response--and not just at one location. Delay settings for the subs have no real meaning as far as spatial imaging is concerned.

In Harman's world, they are not adjusting the multiple subs for best frequency response, but lowest variation in response across the seats. Then the EQ yields a good response for everyone.

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Old 08-23-2010, 01:47 AM
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Quote:
Originally Posted by mogorf View Post

Yeah, fully agree with you Markus, this is not to tell us HOW Audyssey is doing it, but to give us a hint on WHAT is to be done and treated.

If you want to know how Audyssey does it then you'll probably find that information in Chris' book. But from a user perspective the more important question is what Audyssey is doing. Audyssey doesn't disclose that information.

I'll probably post some measurements soon once I get my Onkyo TX-NR708.

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Old 08-23-2010, 01:55 AM
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Quote:
Originally Posted by audioguy View Post

So my question is: How important is it to compensate for distance differences when dealing with multiple subs that are placed in such a way that they are different distances from the main LP. And I ask this not from some theoretical position but rather sonically ---- can you hear it?.

Get a high resolution RTA, play white or pink (depends on how your RTA works) noise from all speakers and look at the steady state frequency response. You'll see it changing significantly when moving the subwoofer(s) around. You'll also notice that matching the distance setting of the sub and the mains doesn't produce the smoothest frequency response.

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Old 08-23-2010, 02:08 AM
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Quote:
Originally Posted by Roger Dressler View Post

In my feeble understanding of the Geddes approach, you use delay not to align arrivals but to smooth the response--and not just at one location. Delay settings for the subs have no real meaning as far as spatial imaging is concerned.

http://mehlau.net/audio/multisub_geddes/

Quote:
Originally Posted by Roger Dressler View Post

In Harman's world, they are not adjusting the multiple subs for best frequency response, but lowest variation in response across the seats. Then the EQ yields a good response for everyone.

Both approaches are essentially the same to me. The basic approach is to reduce seat to seat variance so EQs have the same effect at every location within that area.
There's also a metric VSA (variance of spatial average) in Welti's investigation: "This is a measure of overall amplitude response flatness for all seats."

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Old 08-23-2010, 06:35 AM
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I ran a 3 point Pro calibration with the mic in the MLP for all three measurements for each of my two subs individually. One of the subs showed a huge dip (null...or whatever) around 45 hz.....all the way to the bottom of the y-axis on the graph. The other sub showed a null there as well but not as bad.

When I run the 12 point calibration with both subs on.....the null is about 9 db before...and flat after. Can I assume that Audyssey AND the two subs somewhat smooting out the frequency response has smoothed out the null?
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Old 08-23-2010, 07:06 AM
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After running Audyssey on my Onkyo 876 and then checking the trim levels with my Radio shack SPL meter. My MK S-150 Front L/C/R speakers were showing 71db, my SS-150 L/R rears were 73db and my MK MX-350 sub was peaking at 73db. Would it be best to bring the trims for the rears and sub down to 71db or raise the fronts to 73db ? I placed my Radio shack SPL meter in exactly the same central listening position as the Audyssey mic had been to do the measurements. I could clearly hear the rears are playing louder than the fronts and the SPL meter has confirmed this as it shows them 2db louder So just want to know really if i need to bring the rears and sub down a couple of dbs or raise the fronts a couple of dbs so that all speakers and sub is level matched ? Any help would be greatly appreciated
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Old 08-23-2010, 08:02 AM
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Originally Posted by gamelover360 View Post

I ran a 3 point Pro calibration with the mic in the MLP for all three measurements for each of my two subs individually. One of the subs showed a huge dip (null...or whatever) around 45 hz.....all the way to the bottom of the y-axis on the graph. The other sub showed a null there as well but not as bad.

When I run the 12 point calibration with both subs on.....the null is about 9 db before...and flat after. Can I assume that Audyssey AND the two subs somewhat smooting out the frequency response has smoothed out the null?

First, you should measure the steady state repsonse of the two subs playing at once with a RTA. It's likely that just by using two low frequency sources the dip got filled in.

Second, I doubt that Audyssey shows diagrams that are detailed enough. The dip probably just got filled in by the way the data is presented whereas the real dip is still there.
Here are three graphs from the same measurement data.

No smoothing:



1/6 octave smoothing (Audyssey Pro?):



1/3 octave smoothing ("normal" Audyssey):



It's obvious that important details get lost.

Markus

"In science, contrary evidence causes one to question a theory. In religion, contrary evidence causes one to question the evidence." - Floyd Toole
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Old 08-23-2010, 08:08 AM
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Quote:
Originally Posted by pulse View Post

After running Audyssey on my Onkyo 876 and then checking the trim levels with my Radio shack SPL meter. My MK S-150 Front L/C/R speakers were showing 71db, my SS-150 L/R rears were 73db and my MK MX-350 sub was peaking at 73db. Would it be best to bring the trims for the rears and sub down to 71db or raise the fronts to 73db ? I placed my Radio shack SPL meter in exactly the same central listening position as the Audyssey mic had been to do the measurements. I could clearly hear the rears are playing louder than the fronts and the SPL meter has confirmed this as it shows them 2db louder So just want to know really if i need to bring the rears and sub down a couple of dbs or raise the fronts a couple of dbs so that all speakers and sub is level matched ? Any help would be greatly appreciated

What calibration signal does the 876 use? You should use band-limited (500Hz-2kHz) pink noise to minimize errors.

Markus

"In science, contrary evidence causes one to question a theory. In religion, contrary evidence causes one to question the evidence." - Floyd Toole
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Old 08-23-2010, 08:19 AM
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Originally Posted by markus767 View Post

What calibration signal does the 876 use? You should use band-limited (500Hz-2kHz) pink noise to minimize errors.

I used the test tones in the 876 to check so are you saying that the test tones in the 876 are no good for level matching then ? I thought with it being a THX Ultra2 Reciever the pink noise test tones would be ok ?
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Old 08-23-2010, 08:26 AM
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Quote:
Originally Posted by gamelover360 View Post

I ran a 3 point Pro calibration with the mic in the MLP for all three measurements for each of my two subs individually. One of the subs showed a huge dip (null...or whatever) around 45 hz.....all the way to the bottom of the y-axis on the graph. The other sub showed a null there as well but not as bad.

When I run the 12 point calibration with both subs on.....the null is about 9 db before...and flat after. Can I assume that Audyssey AND the two subs somewhat smooting out the frequency response has smoothed out the null?

Quote:
Originally Posted by markus767 View Post

First, you should measure the steady state repsonse of the two subs playing at once with a RTA. It's likely that just by using two low frequency sources the dip got filled in.

Second, I doubt that Audyssey shows diagrams that are detailed enough. The dip probably just got filled in by the way the data is presented whereas the real dip is still there.
Here are three graphs from the same measurement data.

No smoothing:



1/6 octave smoothing (Audyssey Pro?):



1/3 octave smoothing ("normal" Audyssey):



It's obvious that important details get lost.

Hi Markus,

As I understand gamelover, he was using the Pro graphs both for the 3 point and 12 point calibrations. So the graphs on 3 point calibrations were already smoothed yet the nulls were still very obvious.

I believe the nulls in the 12 point calibration were mitigated on the graphs mostly because of spacial averaging.

Larry
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Old 08-23-2010, 08:27 AM
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Quote:
Originally Posted by pulse View Post

I used the test tones in the 876 to check so are you saying that the test tones in the 876 are no good for level matching then ? I thought with it being a THX Ultra2 Reciever the pink noise test tones would be ok ?

There are likely more accurate ways to measure, but for your purposes the test signals are OK. The Radio Shack meter is likely off reference, but for all of the main channels it will be off the same amount. I wouldn't have any confidence in it at all for comparing the mains to the sub.

Are you holding the meter or is it mounted on a stand? Getting YOU away from IT will make it more accurate.

However, the tell here is probably that you hear the surrounds are too loud in relation to the mains. Whether you raise the fronts or lower the surrounds depends on where the trims are now and also which way you want to skew Dynamic EQ.

Jeff
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Old 08-23-2010, 08:27 AM
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Quote:
Originally Posted by pulse View Post

I used the test tones in the 876 to check so are you saying that the test tones in the 876 are no good for level matching then ? I thought with it being a THX Ultra2 Reciever the pink noise test tones would be ok ?

I don't know what tones the 867 is using but I know that band-limited noise is your best chance to get the most accurate reading with a SPL meter. The broader the noise spectrum, the more inaccurate the results. There are even processors out there that use white noise instead of pink noise...

Markus

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