"Official" Audyssey thread Part II - Page 120 - AVS Forum | Home Theater Discussions And Reviews
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post #3571 of 7078 Old 08-14-2017, 07:08 PM
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Originally Posted by mthomas47 View Post
Thank you, Feri! That's a good point! I don't know as much as I would like to about some of the other RC systems, so I don't know how much calibration technique affects the final result. I would expect that technique might matter more where the automated system is doing more, but I'm not sure. I am pretty sure, though, that good set-up would yield better results with virtually any system of automated EQ.

Perhaps this is circuitous thinking to some people, but I have always felt that the fact that Audyssey reveals defects in speaker positioning, that we don't necessarily hear without Audyssey, is a good thing rather than a bad thing. Every change I ever made due to a problem that Audyssey exacerbated (and made more noticeable to me) actually resulted in better overall sound quality even without Audyssey engaged. I realize that's a YMMV sort of thing, but that was my experience.

When speakers weren't toed-in just right, for instance, Audyssey would do strange things to the sound (usually making the mid-range or high frequencies sound harsher.) When I experimented with adjusting the speaker toe-in to remove the artifacts that Audyssey had created, either the tone improved slightly, or the soundstage sounded fuller, or both. I probably wouldn't have ever noticed if Audyssey hadn't pulled my attention to those speakers. Maybe I'm just a glass half-full type, but that's how I always looked at it.

Regards,
Mike
A glass half full type? I've been accused of being a glass half empty type; my response is usually, "Let's fill up the glass!" Sometimes this is a PITA, but OCD helps some of us fine tune things. Having good advisors like the members of this forum multiplies one's chances. I think good results are either the result of the infinite taking of pains or good luck. I think adjusting room treatments, mic positions, etc. until one's significant other(s) think you are ready to be certified is worth the effort. A little luck wouldn't hurt.

I just found my notes from my early tinkering around with Audyssey. It turns out that the reduction in deep bass imposed by Audyssey was objectively true, not just my pining away for missing bass peaks caused by room anomalies. Comparing playback with Audyssey ON to Audyssey OFF, Aud. ON cut the bass an average of 7 dB below 70 Hz, i.e., 7 dB below the 0 line, according to REW measurements I took a few years ago, before I was a forum member. Oddly, I don't have to turn up the sub a full 7 dB to get the 7 dB back -- but, because of my preference, I turn up the sub to an even higher level.

Another oddity is that music, and especially movie soundtracks, seem to sound a bit better from the side seats of our 5 seat couch (i.e., from the far left seat or the far right seat); the soundstage isn't as wide, but the tonality, for want of a better term) seems slightly better. I'm quite happy with my system and Audyssey, but I still ponder these things from time to time.

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post #3572 of 7078 Old 08-14-2017, 11:10 PM
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Individual handling of the measurement process is - most of the time - the name of the game because ones situation at home might not follow the general path often suggested. Some even must experiment during that process. But some knowledge about physics and acoustics usually helps ( a lot).

All common (low cost) measurement (room EQ) systems are based upon certain models of a common room. As soon as the individual room and the personal setup deviates more than a certain amount from the basic parameters set by that model it might get somewhat tricky to find an ad hoc solution. One of the main reasons why the setup guide etc. published in this thread has became so enormous and huge. Some will never make it, because of personal taste, expectations, prejudice and some not so common acoustical parameters like reverberation times. It's to be expected...

That's nothing special for Audyssey and if you look at the other room EQ threads for YPAO, MCACC, Dirac etc. it gets not better as soon as something is "different", although many don't realize this at 1st.
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post #3573 of 7078 Old 08-15-2017, 03:49 AM
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Originally Posted by drh3b View Post
Typically, the circuitry in sub woofers delays the signal a tiny bit, which makes the subwoofer appear further away to Audyssey. Don't worry about it.
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Originally Posted by mthomas47 View Post
Hi,

As you know, Audyssey is simply measuring timing as opposed to actual distance. Your speakers are all powered by your amplifier(s). But, as you noted, your subs have internal amplifiers with their own internal processing which is usually several milliseconds behind your AVR. Since the sounds from all your sources need to arrive at your MLP at the same time, Audyssey will typically set subwoofer distances further away in order to speed up the subwoofer sound arriving at the MLP. Your speakers are set to operate the same way. A speaker further away will actually start it's sound a millisecond or more before a speaker nearer to the MLP, so that the sounds will arrive at the same time.

It's always a good idea to raise crossover, preferably to about 80Hz, or at least to about one octave higher than the reported F3 point. In this case, that would be 80Hz.

Regards,
Mike
Thank you both! That is of course completely obvious once you state it. But I'd turned myself in a circle in what Audyssey was doing with the measurements. I have DSP amps for the subs which of course will add delay in the lines increasing their apparent distance.

Now to scan the FAQ and see what it says about measurement approach for multi-row seating, high-ish back leather chairs, and all that good stuff
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post #3574 of 7078 Old 08-15-2017, 07:10 AM
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Just to add to that.
Audyssey normally adjust the phase of both the sub(s) and the corresponding speaker at the pre-determined (-3db) lower corner frequency by adding some further delay to correct for phase differences.
This will make the sub(s) look further way because of that additional delay. Due to the large wavelength at bass frequencies this may add up to several feet. If you need further information about this please look at the published patent literature of Audyssey. Unfortunately this will only hold true for the suggested minimum crossover frequency. If one changes that crossover frequency to his liking and to make further use of the subs capabilities you may have to fine-tune that subwoofer delay somehow to compensate for the differences, i.e. from minimum suggested 60 Hz to 80 Hz. If not, this might introduce a small (measurable) dip in the crossover region but with rather limited consequences...
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post #3575 of 7078 Old 08-15-2017, 07:24 AM
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Originally Posted by gurkey View Post
Just to add to that.
Audyssey normally adjust the phase of both the sub(s) and the corresponding speaker at the pre-determined (-3db) lower corner frequency by adding some further delay to correct for phase differences.
This will make the sub(s) look further way because of that additional delay. Due to the large wavelength at bass frequencies this may add up to several feet. If you need further information about this please look at the published patent literature of Audyssey. Unfortunately this will only hold true for the suggested minimum crossover frequency. If one changes that crossover frequency to his liking and to make further use of the subs capabilities you may have to fine-tune that subwoofer delay somehow to compensate for the differences, i.e. from minimum suggested 60 Hz to 80 Hz. If not, this might introduce a small (measurable) dip in the crossover region but with rather limited consequences...
Do you feel that is you have a dip at crossover freq (measured) due to the above you should leave it be or adjust (in my case add a couple feet) to get a measurement without the dip?

Edit: My most recent audyssey measurement showing the dip at crossover, aud flat vs aud flat with sub distance +3ft


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post #3576 of 7078 Old 08-15-2017, 07:37 AM
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You might try to fill a larger dip (or wiggle) by changing the subs delay somewhat and measuring / checking the resulting frequency response afterwards. This might need some experimenting to be successful. But if it's rather small I probably wouldn't bother. Thus it depends. If you want to try it, see if you can fill that appr. -6db to -7db dip. It could be the result of other causes too, but you wouldn't really know, if you didn't try...
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post #3577 of 7078 Old 08-15-2017, 09:35 AM
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Originally Posted by gurkey View Post
You might try to fill a larger dip (or wiggle) by changing the subs delay somewhat and measuring / checking the resulting frequency response afterwards. This might need some experimenting to be successful. But if it's rather small I probably wouldn't bother. Thus it depends. If you want to try it, see if you can fill that appr. -6db to -7db dip. It could be the result of other causes too, but you wouldn't really know, if you didn't try...
Maybe I am misunderstanding your post, but I did fill the dip, red line is audyssey stock, blue line is after I changed the distance on the sub (delay). Maybe I miread your post, I thought you were saying sometimes its better to leave the dip than to mess with the settings.
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post #3578 of 7078 Old 08-15-2017, 04:09 PM
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Originally Posted by grendelrt View Post
Do you feel that is you have a dip at crossover freq (measured) due to the above you should leave it be or adjust (in my case add a couple feet) to get a measurement without the dip?

Edit: My most recent audyssey measurement showing the dip at crossover, aud flat vs aud flat with sub distance +3ft

Did you measure this at one single point (probably at the MLP) or this is a result of multi-point measurement averaged in REW?
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post #3579 of 7078 Old 08-15-2017, 04:37 PM
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Did you measure this at one single point (probably at the MLP) or this is a result of multi-point measurement averaged in REW?
I did a check from 2 other points (Seat spots) with and without the 3ft and there was less dip using the 3ft extra delay on those spots.
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post #3580 of 7078 Old 08-15-2017, 05:11 PM
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I did a check from 2 other points (Seat spots) with and without the 3ft and there was less dip using the 3ft extra delay on those spots.
If you are doing single point measurements just in order to check you will be really misguided by what REW will show you.

Doing a multi-point measurement and averaging them in REW will bring you much closer to what is happening in your room.
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post #3581 of 7078 Old 08-17-2017, 06:22 AM
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A few days ago I added a second identical sub to an older single-sub-out MultEQ AVR. I have a ton of experience with Audyssey and all the settings on this receiver. The subs are not equidistant. One is farfield, and the new one is nearfield. The subs do not have phase switches, just delay dials. They are connected via a Y adapter.

When I first received the sub, I didn't bother re-running Audyssey. I simply plugged it in and ran with it. It was obvious there were cancellations going on, as it seemed quieter with 2 than with 1. So I just added delay by ear on the NF sub until it was awesome and I was certain the house was going to fall down.

Then I decided to run Audyssey so I could get the benefit of EQ. I first used REW to more precisely time align the NF sub and had the frequency responses summing together nicely. Then, I re-ran Audyssey, and it more than doubled the subwoofer distance I had when I only had the FF sub (from ~11' to ~24') . And, now it doesn't sound that great, with the tactile response completely gone.

What should I try next?

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post #3582 of 7078 Old 08-17-2017, 08:01 AM
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Originally Posted by mdameron View Post
A few days ago I added a second identical sub to an older single-sub-out MultEQ AVR. I have a ton of experience with Audyssey and all the settings on this receiver. The subs are not equidistant. One is farfield, and the new one is nearfield. The subs do not have phase switches, just delay dials. They are connected via a Y adapter.

When I first received the sub, I didn't bother re-running Audyssey. I simply plugged it in and ran with it. It was obvious there were cancellations going on, as it seemed quieter with 2 than with 1. So I just added delay by ear on the NF sub until it was awesome and I was certain the house was going to fall down.

Then I decided to run Audyssey so I could get the benefit of EQ. I first used REW to more precisely time align the NF sub and had the frequency responses summing together nicely. Then, I re-ran Audyssey, and it more than doubled the subwoofer distance I had when I only had the FF sub (from ~11' to ~24') . And, now it doesn't sound that great, with the tactile response completely gone.

What should I try next?
Hi,

In this case, if I were you, I would run Audyssey to allow it to set filters, and then I would use REW and the individual delay dials on the subs to tweak things to my satisfaction. I often hear advice to make tweaks before running Audyssey, and it's possible that it works well to do that in some cases. But, there is always the possibility that Audyssey will undo something, and particularly something related to phase or to delay, so I would try making that kind of tweak post-Audyssey.

Edit: Just to clarify something, adjusting the delay settings on the subs (or changing the sub gains) will not interfere with the control points that Audyssey set. So, you will still have the benefit of Audyssey's best efforts to smooth out peaks and valleys in the frequency response. You will simply be overlaying your own tweaks on top of the EQed response.

Regards,
Mike
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* The Guide linked above is a comprehensive guide to Audio & HT systems, including:
Speaker placements & Room treatments; HT calibration & Room EQ; Room gain; Bass
Preferences; Subwoofer Buyer's Guide: Sealed/ported; ID subs; Subwoofer placement.

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post #3583 of 7078 Old 08-17-2017, 08:28 AM
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Originally Posted by mthomas47 View Post
Hi,

In this case, if I were you, I would run Audyssey to allow it to set filters, and then I would use REW and the individual delay dials on the subs to tweak things to my satisfaction. I often hear advice to make tweaks before running Audyssey, and it's possible that it works well to do that in some cases. But, there is always the possibility that Audyssey will undo something, and particularly something related to phase or to delay, so I would try making that kind of tweak post-Audyssey.

Edit: Just to clarify something, adjusting the delay settings on the subs (or changing the sub gains) will not interfere with the control points that Audyssey set. So, you will still have the benefit of Audyssey's best efforts to smooth out peaks and valleys in the frequency response. You will simply be overlaying your own tweaks on top of the EQed response.

Regards,
Mike
Thanks for replying.

the thing is, setting the delay on the near sub first is required for the "real" frequency response to be visible to audyssey. If I leave the delay at 0 on both subs, there are huge nulls from 30-60 hz. So then Audyssey would boost that range. But then if I were to add the delay manually after the fact, those nulls would be resolved anyway and have a huge peak.

I'm thinking what I need to do is start over from the beginning and run Audyssey with only the far field sub on to set its "audyssey distance" in the AVR. Then run REW to set the delay knob on the near sub relative to the audyssey distance of the far sub. Then, run audyssey again with both subs on. It might not make a difference. Previously I set the delay knob on the near sub while the far sub had the default AVR distance setting.

1) Run audyssey on far sub to get a real distance setting.
2) disable multeq so no eq is applied
3) Turn on near sub, use REW to dial in near sub's delay relative to far sub.
4) re-run audyssey

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post #3584 of 7078 Old 08-17-2017, 10:47 AM
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Hmmm...would this work?

Adjust the delay knob and run Audyssey until you get a distance setting in the AVR of "0" (or close to it)? Wouldn't that then be the "correct" distance knob setting??

Correct me if this is not the right way to think about it....
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post #3585 of 7078 Old 08-17-2017, 10:49 AM
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Originally Posted by mdameron View Post
Thanks for replying.

the thing is, setting the delay on the near sub first is required for the "real" frequency response to be visible to audyssey. If I leave the delay at 0 on both subs, there are huge nulls from 30-60 hz. So then Audyssey would boost that range. But then if I were to add the delay manually after the fact, those nulls would be resolved anyway and have a huge peak.

I'm thinking what I need to do is start over from the beginning and run Audyssey with only the far field sub on to set its "audyssey distance" in the AVR. Then run REW to set the delay knob on the near sub relative to the audyssey distance of the far sub. Then, run audyssey again with both subs on. It might not make a difference. Previously I set the delay knob on the near sub while the far sub had the default AVR distance setting.

1) Run audyssey on far sub to get a real distance setting.
2) disable multeq so no eq is applied
3) Turn on near sub, use REW to dial in near sub's delay relative to far sub.
4) re-run audyssey
You are very welcome! I don't know whether the specific method you are outlining will work or not. I think that some of this just has to be a trial-and-error process. What I am saying, though, is that you simply need to do whatever is necessary for Audyssey to run its calibration process. If that means setting delays first, so be it. But, after Audyssey has run, be prepared to redo that delay setting procedure using REW, and listening to the result. The changes you make to the delays and to the sub gains, post-calibration, will not affect the control points that Audyssey's set. So, you can have your cake and eat it, too.
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* The Guide linked above is a comprehensive guide to Audio & HT systems, including:
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Originally Posted by Alan P View Post
Hmmm...would this work?

Adjust the delay knob and run Audyssey until you get a distance setting in the AVR of "0" (or close to it)? Wouldn't that then be the "correct" distance knob setting??

Correct me if this is not the right way to think about it....
Won't work. Audyssey doesn't measure distance, it measures the time delay between its test tone and the mic return. That delay in microseconds is converted to a distance using a value for the speed of sound. If you adjust the delay knob on the sub, all you can do is dial in more delay than the delay already occurring due to distance and the sub's internal circuitry. You can never get Audyssey to deliver a distance setting of 0 unless you stick the mic right in front of the sub's driver and the other data measuered is then going to be useless plus the time delay setting is going to be off.
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post #3587 of 7078 Old 08-20-2017, 05:46 PM
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I've been using audyssey for years and I can't really recommend it anymore unless you are thoroughly testing the results with REW. It just doesn't work right half the time and sometimes causes larger problems regardless of mic position, sofa, and speaker/sub placement. I've been messing with my new dedicated HT setup for days now. I'd consider myself pretty experienced in this field, but Audyssey keeps making things worse.

Red/Purple = no audyssey
Green = audyssey XT32

Audyssey smooths out some minor problems in the low end, but creates a major problem at 40hz. Even the PEQ on my subs can't fix the 40hz dip it creates. You aren't going to notice a -/+ 5DB difference in real content, but you will notice a -20db null at 40hz, so I am just giving up on Audyssey unless someone has any tips on fixing this issue. It sounds fantastic without it enabled and it does basically nothing noticeable 400hz and above.

I am in a fully treated 23x17x10 room (about 35% coverage), so I'd imagine that's why audyssey doesn't need to do much. To my eyes, the non-audyssey seems good. Audyssey produces better results in the 60-200hz range, so if I can fix it from creating that dip then that'd be preferred.
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post #3588 of 7078 Old 08-20-2017, 07:33 PM
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I've been using audyssey for years and I can't really recommend it anymore unless you are thoroughly testing the results with REW. It just doesn't work right half the time and sometimes causes larger problems regardless of mic position, sofa, and speaker/sub placement. I've been messing with my new dedicated HT setup for days now. I'd consider myself pretty experienced in this field, but Audyssey keeps making things worse.

Red/Purple = no audyssey
Green = audyssey XT32

Audyssey smooths out some minor problems in the low end, but creates a major problem at 40hz. Even the PEQ on my subs can't fix the 40hz dip it creates. You aren't going to notice a -/+ 5DB difference in real content, but you will notice a -20db null at 40hz, so I am just giving up on Audyssey unless someone has any tips on fixing this issue. It sounds fantastic without it enabled and it does basically nothing noticeable 400hz and above.

I am in a fully treated 23x17x10 room (about 35% coverage), so I'd imagine that's why audyssey doesn't need to do much. To my eyes, the non-audyssey seems good. Audyssey produces better results in the 60-200hz range, so if I can fix it from creating that dip then that'd be preferred.
I wonder what Audyssey is reacting to that causes that 40 Hz dip? Or could it be an artifact of using fewer mic positions for REW than for Audyssey? Can your REW mic be in a 40Hz null? Are you using just one mic position when you run REW, or are you using the same number and location with your calibrated mic as you use with the Audyssey mic, and averaging them? I think Chris K. of Audyssey advocates a more complex RMS way of simulating Audyssey results with REW. My tentative understanding is that there is a big difference between using a few mic positions and using the full Hateful Eight in some rooms, and not in others.

If all the listening is going to be done from one or two seats, have you tried clustering the mic positions within that small area, rather than spreading them out?

Since you have used Audyssey for years, did it perform better in former rooms than it does in your new HT?

I agree that Audyssey seems to improve response between 60 to 200, but it also seems to help between 4K and 9K. In my set-up, one of the biggest improvements is Audyssey knocking down a broad peak centered at about 8K. Clarity and smoothness seem much improved.

My "problem" [it's not really much of a problem] in my room (25 x 16.75 x an average of 10.16 feet for the ceiling which is sloped up toward the back) is the opposite of yours; I have a broad peak at 40 Hz when measured from the MLA, but not so much at other mic positions.
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post #3589 of 7078 Old 08-20-2017, 08:00 PM
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I wonder what Audyssey is reacting to that causes that 40 Hz dip? Or could it be an artifact of using fewer mic positions for REW than for Audyssey? Can your REW mic be in a 40Hz null? Are you using just one mic position when you run REW, or are you using the same number and location with your calibrated mic as you use with the Audyssey mic, and averaging them? I think Chris K. of Audyssey advocates a more complex RMS way of simulating Audyssey results with REW. My tentative understanding is that there is a big difference between using a few mic positions and using the full Hateful Eight in some rooms, and not in others.

If all the listening is going to be done from one or two seats, have you tried clustering the mic positions within that small area, rather than spreading them out?

Since you have used Audyssey for years, did it perform better in former rooms than it does in your new HT?

I agree that Audyssey seems to improve response between 60 to 200, but it also seems to help between 4K and 9K. In my set-up, one of the biggest improvements is Audyssey knocking down a broad peak centered at about 8K. Clarity and smoothness seem much improved.

My "problem" [it's not really much of a problem] in my room (25 x 16.75 x an average of 10.16 feet for the ceiling which is sloped up toward the back) is the opposite of yours; I have a broad peak at 40 Hz when measured from the MLA, but not so much at other mic positions.
Audyssey and REW mics are setup in the exact same spot using a tripod. I used one mic position for that specific test, but I moved the mic around that area doing ~6 other readings afterwards and there was no difference. I only care about the MLP so my 8 audyssey mic positions are closely cluster as you described. In past rooms, audyssey has been a hit or miss for me. This is the first room i've had that is this flat without any calibration, so audyssey has to do it's job more to improve upon that.

Maybe next weekend I will mess with it more.

Last edited by Tyrindor; 08-20-2017 at 08:05 PM.
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post #3590 of 7078 Old 08-20-2017, 09:03 PM
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Audyssey and REW mics are setup in the exact same spot using a tripod. I used one mic position for that specific test, but I moved the mic around that area doing ~6 other readings afterwards and there was no difference. I only care about the MLP so my 8 audyssey mic positions are closely cluster as you described. In past rooms, audyssey has been a hit or miss for me. This is the first room i've had that is this flat without any calibration, so audyssey has to do it's job more to improve upon that.



Maybe next weekend I will mess with it more.


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post #3591 of 7078 Old 08-21-2017, 01:58 AM
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What crossover are you using?
80hz on everything. Audyssey sets my fronts to Large but I change them to Small/80hz since I have dual PB13 Ultra subs.

If I had to guess why this is happening, Audyssey is likely trying to tame that mild 50hz peak and in doing so creates a large null in the 40hz range. This is why i've always wondered why Audyssey doesn't test it's corrections and fine tune them further. It guesses, and sometimes it guesses really wrong because it's impossible for the software to know the results of an EQ tweak without measuring again afterwards.

It takes literally forever to do 8 audyssey positions with 7.2.4 setup, so I'll try to work on it further this next weekend. I don't see why it'd be any different though, I can't imagine it picked up background noise or anything. I put the mic on a tripod, and I leave the room completely before running each test. My noise floor in the room at the time was only 21-23dB which is absurdly quiet.

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Audyssey and REW mics are setup in the exact same spot using a tripod. I used one mic position for that specific test, but I moved the mic around that area doing ~6 other readings afterwards and there was no difference. I only care about the MLP so my 8 audyssey mic positions are closely cluster as you described. In past rooms, audyssey has been a hit or miss for me. This is the first room i've had that is this flat without any calibration, so audyssey has to do it's job more to improve upon that.

Maybe next weekend I will mess with it more.
Did you do the averaging of REW readings as Gary suggested?
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post #3593 of 7078 Old 08-21-2017, 02:10 AM
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Did you do the averaging of REW readings as Gary suggested?
The chart was the center of the MLP on a tripod. I then moved the mic a foot in each direction around that and they were all the exact same results in the 0-200hz range. A +/- 1dB difference on a couple frequencies, so averaging them would pretty much look the same. The 40hz dip was the same in each result.

These are the same mic positions I use for Audyssey too, since I really only care about the main listening position. My only guess is it is trying to tame 50hz, and wrecks 40hz in the process. This weekend I will try to use the PEQ on my subs to tame the 50hz peak before running audyssey and see if it still happens. Also, if I turn the phase control to 180 on both my subs AFTER running audyssey, the 40hz dip is mostly fixed. If I run Audyssey again with phase 180, the dip comes back. Hope it's not a faulty mic or something.

Overall though, my non-calibrated result seems flatter than 99% of rooms I think? Not in a huge rush to fix minor problems that I may not notice in real content. Leaving audyssey off might not be a terrible idea, I don't use DyanmicEQ anymore because the new HT is soundproof and I basically watch everything at reference (or very near it) anyway.

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post #3594 of 7078 Old 08-21-2017, 07:32 AM
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The chart was the center of the MLP on a tripod. I then moved the mic a foot in each direction around that and they were all the exact same results in the 0-200hz range. A +/- 1dB difference on a couple frequencies, so averaging them would pretty much look the same. The 40hz dip was the same in each result.

These are the same mic positions I use for Audyssey too, since I really only care about the main listening position. My only guess is it is trying to tame 50hz, and wrecks 40hz in the process. This weekend I will try to use the PEQ on my subs to tame the 50hz peak before running audyssey and see if it still happens. Also, if I turn the phase control to 180 on both my subs AFTER running audyssey, the 40hz dip is mostly fixed. If I run Audyssey again with phase 180, the dip comes back. Hope it's not a faulty mic or something.

Overall though, my non-calibrated result seems flatter than 99% of rooms I think? Not in a huge rush to fix minor problems that I may not notice in real content. Leaving audyssey off might not be a terrible idea, I don't use DyanmicEQ anymore because the new HT is soundproof and I basically watch everything at reference (or very near it) anyway.
Hi,

I'm sorry that XT-32 seems to be introducing a big dip at about 40Hz, and I can't account for it. XT-32 has 4096 control points (taps) available to the .1 channel, though, which allows for fairly precise adjustments to the frequency response. I am having a hard time believing that Audyssey aimed at 50Hz and hit 40Hz instead. But, I don't have another explanation to suggest.

Presumably your subs are already in the best positions you can put them before Audyssey attempts to EQ the response? I ask because I see a lot of peaks and valleys above 50Hz, both with and without Audyssey. Room treatments certainly help, but below about 120Hz it takes fairly thick bass traps, and perhaps a lot of them, to have a very significant effect on the FR.

To your point of just leaving Audyssey off, though, I think that is always an option with any version of Audyssey. Measurements notwithstanding, I think that our ears need to be the final judge of what Audyssey is doing. For instance, I have fairly extensive bass trapping (among other treatments) in my large room. The good news is that I have excellent bass reinforcement and low frequency containment in the room. The bad news is that the irregular geometry in the room creates a lot of peaks and dips which I just can't tame without room correction.

The other day, I decided to experiment with some things again, and tried turning XT-32 off for the first time in a while. My bass below about 80Hz or 100Hz sounded very occluded without Audyssey. After becoming used to a clearer sound, that boomier sound is just unlistenable to me. Irrespective of other portions of the frequency range (and Audyssey also helps with my mid-range frequencies, and doesn't adversely affect my treble) I would use Audyssey solely for the mid-bass frequencies and below.

But, that is the bottom line for me. If you can't hear a difference with Audyssey on, then it doesn't matter whether it's on or not. If the sound is definitely better with it off, and you are convinced that you can't improve it with further experimentation, then just leave Audyssey off.

I wish I could offer some additional trouble-shooting suggestions, but other than initial subwoofer placement, I can't think of any.

Regards,
Mike
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Wasn't XT32 using > 10.000 (10.240 to be exact; 512 *20) control points for each channel as being published by Audyssey ?
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Wasn't XT32 using > 10.000 (10.240 to be exact; 512 *20) control points for each channel as being published by Audyssey ?
They never specified a number. Their charts always showed that XT-32 had 512 times "X", with X being 2EQ. But, they never told us what X was. My own speculation about X had been that the earliest version of Audyssey was similar to a parametric filter, with anywhere from 8 to 12 control points per channel. A couple of years ago someone on an audio theory thread looked up the specific chip that XT-32 uses (I believe he looked at the patent) and found that it has 4096 control points per filter (channel). That number corresponds well to previous speculation that 2EQ would have had about 8 to 12 taps, as 4096 / 512 = 8.
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Audyssey MultEQ® XT32 is the most advanced and accurate room correction solution to remove acoustical distortion. It uses equalization filters with more than ten thousand individual control points...

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Audyssey MultEQ® XT32 is the most advanced and accurate room correction solution to remove acoustical distortion. It uses equalization filters with more than ten thousand individual control points...

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That corresponds to what Keith put in the FAQ. I'm just not sure that it is correct. Of course, depending on how you interpreted what Chris said, several filters (at 4096 control points per filter) would add up to more than 10,000.

I'm not sure how much effort we want to put into this issue, anyway though, when it comes to the subwoofer channel. Even if we assume that XT-32 is EQing every individual frequency from 200Hz (or 400Hz if any subwoofers can make meaningful sounds that high) down to 10Hz, it is difficult for me to understand how the algorithm could use more control points than there are individual frequencies to control. (400 - 10 = 390.) So, it seems to me that for the .1 channel, whether there were 10,000 taps, or "only" 4096, XT-32 would only be able to use a fraction of the number of control points available to it.

Regards,
Mike
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...So, it seems to me that for the .1 channel, whether there were 10,000 taps, or "only" 4096, XT-32 would only be able to use a fraction of the number of control points available to it.

Regards,
Mike
Haven't seen that claim in more recent publications, and it appears to be presented as a total; could be marketing hokum. Not to quibble, frequencies, similar to any numerator x-0, are divisible.

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post #3600 of 7078 Old 08-21-2017, 12:38 PM
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That corresponds to what Keith put in the FAQ. I'm just not sure that it is correct. Of course, depending on how you interpreted what Chris said, several filters (at 4096 control points per filter) would add up to more than 10,000.

I'm not sure how much effort we want to put into this issue, anyway though, when it comes to the subwoofer channel. Even if we assume that XT-32 is EQing every individual frequency from 200Hz (or 400Hz if any subwoofers can make meaningful sounds that high) down to 10Hz, it is difficult for me to understand how the algorithm could use more control points than there are individual frequencies to control. (400 - 10 = 390.) So, it seems to me that for the .1 channel, whether there were 10,000 taps, or "only" 4096, XT-32 would only be able to use a fraction of the number of control points available to it.

Regards,
Mike
Mike,

I think you're counting 20 Hz, 21 Hz, 22 Hz and up as individual frequencies but those frequencies aren't the only frequencies. 20.1 Hz is a different frequency to 20 Hz, and 20.15 Hz is a different frequency to 20.1 Hz and so on. There's way more frequencies between 20 Hz and 200 Hz than you're thinking of, in fact there's an infinite number of frequencies within the range.

Having said that, there's also only 3 and a half octaves or so between 20 Hz and 200 Hz and that only amounts to 42 or so notes of the musical scale but that number needs to get multiplied a few times since there are several different tuning standards in existence. Everyone thinks of A= 440 Hz for the tuning standard but period instruments for baroque and renaissance classical music use a couple of other standards with A tuned lower and there are also modern orchestras using a couple of higher tuned standards. If there are 181 exact "x.0" frequencies between 20 Hz and 200 Hz, there's probably more than 200 musical note pitches in use between 20 Hz and 200 Hz because of the different tuning standards in use. Of course, when you start to look at instruments like the double bass and cello and trombone which allow the player to glide their pitch smoothly between different notes, and that is actually done at times, you could also say that there are an infinite number of musical pitches between any two adjacent notes of the musical scale, just as there are an infinite number of frequencies.

I don't think counting frequencies or musical pitches within a given frequency range is the way to look at what may be needed in tap points for room correction.

I learnt the start of my very basic understanding of room acoustics from Everest's "Master Handbook of Acoustics". In it he refers to a study which showed that an empty Coke bottle, acting as a Helmholtz resonator, absorbs 5.9 Sabins at its resonant frequency of 185 Hz but that the absorption has a bandwidth between +/- 3 dB points of only 0.67 Hz. If you are going to try to correct for deviations like that in a room response then you may have to have correction points at intervals of less than 1 Hz in order to make a smooth response. Most room problems have much wider bandwidths than that and I also can't see many rooms having several problems as narrowly defined as the absorption suckout from a Coke bottle but correcting for a deviation in room response like that might require several tap points within a fairly narrow frequency band so I suspect that more tap points might be required for low frequency room correction than we think.

Even so, like you I find it difficult to see how as many as 4096 tap points could be used to correct the .1 channel, though I can understand why a lot more tap points may be needed than we might initially think.


Addition: I just realised that someone may read the above and object that we tend not to correct for dips but only for peaks. That's true, but we correct for peaks by adding dips and some physical correction is done using Helmholtz resonators designed and tuned to absorb a peak at a specific frequency. Tailoring an electronic correction that reproduces the correction achieved by a precisely tuned Helmholtz resonator may actually require more than a single tap point. Several tap points may be required to correct for a single peak so looking at a room response curve with x number of points requiring correction may well require the use of several times that number of tap points given that the correction has to be tailored to produce a smooth response and the deviations being corrected may not be symmetrical in behaviour around their nominal frequency.

Last edited by David Aiken; 08-21-2017 at 12:55 PM.
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