Simplified REW Setup and Use (USB Mic & HDMI Connection) Including Measurement Techniques and How To Interpret Graphs - Page 355 - AVS Forum
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post #10621 of 11649 Old 06-27-2014, 07:07 PM
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Guys,

I have just recently taken delivery of a new sub from Rythmik (F12G) which is supposed to be very accurate with low distortion. It's replacing a HTiB sub that got a lot of headache inducing distortion and is very boomy.

The HTiB sub has been retired and F12G has taken over it's position. Initial set-up using Audyssey has distance as the same, the trim is slightly different due to level the level position on the sub amp. The change in sound quality is not subtle.

I intend to carry out low frequency measurements of the new F12G and will compare it to the HTiB (have previous measurements of this). Will post results back here for comparison and let you all advise/critique/suggest improvements.

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post #10622 of 11649 Old 06-28-2014, 06:21 AM
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Originally Posted by artur9 View Post
How so? Rock vs classical? Electronic vs acoustic? Or ... ?
I did mean what cfraser said. As an extreme example if you interested in action films than you can probably tolerate a lot more distortion than someone who is into more musically complex content.

You may also want to consider the relative amount of different harmonics rather than just thd as the higher harmonics won't be masked in the way the lower ones can be.
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post #10623 of 11649 Old 06-28-2014, 09:03 AM
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You may also want to consider the relative amount of different harmonics rather than just thd as the higher harmonics won't be masked in the way the lower ones can be.
I only posted with the THD because adding all the other harmonics makes for a more complicated image but didn't seem to add a lot of insight.

I realize that some of the harmonics (say 3rd) are more problematic than others. In the measures I posted above the 3rd harmonic usually contributed the most to THD.
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post #10624 of 11649 Old 06-28-2014, 10:01 AM
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As if we don't have enough on the plate already, let me add another course anyway, Speaker Toe-in.

First let me say that the way the soundstage presents itself is one my most highly regarded qualities in sound reproduction to me. A really convincing soundstage is what separates mid-fi from hi-fi You could have a great FR and perfect ambiance, but if the soundstage is lacking, I am unimpressed.

That said, I have been placing special attention to it in the last few days and critiquing it. My first impression was that I loved everything happening between the speakers, but I thought I could improve what was happening beyond each. So I increased the speaker to speaker distance by 2". May not seem like much, but there was a noticeable difference. While the soundstage was a bit wider, it sounded a bit like it was curving.
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While this is a inaccurate simplification, it represents sorta my impression of the shape of the soundstage.

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So I decided to change the toe-in. That is to say, have less of it. And now my impression is more like this.

FYI, Where 0 degrees represents the speaker pointed directly at your ear, before my toe-out was about 4 degrees. And now it is about 12 degrees.

--- --- --- --- --- --- --- --- --- ---

A few thoughts on toe-in in general. Most reading has you toe-in so that the focal point is a foot or two behind your head. Also described as having the speaker point directly a few inches to each side of each ear. This is the configuration I have had mostly up to this point.

I am bringing this up partly just to see if anyone else has done experimentation in this area. I have seen other peoples setups vary from the speakers pointing directly at you to the speakers facing directly forward. Obviously, the speakers and room play a major role in what works best here. But my early findings suggest that excessive toe-in, that being pointing close to directly at you, while helping the middle in some cases, seems to make the soundstage outside the speakers seem a bit unnatural to me.

In any case, I am interested in any stories any of you may have on the topic.

--- --- --- --- --- --- --- --- --- --- --- --- ---

As far as how this relates to the thread topic, one will find that the high end roll off is generally greater as you toe-out. This may happen as well in the area where the mid/tweeter XO occurs for the midrange may roll off a bit more towards its upper range. This will be VERY speaker dependant, or more precisely, driver dependent. It is also true that some drivers are a bit flatter a bit off axis. So some may see a flatter response due to greater toe-out. Again, very speaker/driver dependent.

But for those who feel your system a little bright, a little more toe-out may help you.


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post #10625 of 11649 Old 06-28-2014, 10:27 AM
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Originally Posted by jim19611961 View Post
First let me say that the way the soundstage presents itself is one my most highly regarded qualities in sound reproduction to me.
Ditto. This is why I am so interested in understanding the ETC. A poor ETC correlates pretty directly with a poor soundstage, AIUI.

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Originally Posted by jim19611961 View Post
I am bringing this up partly just to see if anyone else has done experimentation in this area.
As I've tamed the reflections as shown by ETC the soundstage has firmed up quite a bit.

The other thing I've done is to measure toe-in using a high frequency tone. I tried to maximize the volume at the MLP that way. Sadly, it's a very delicate thing as the frequencies that show the most effect have wavelengths measured less than 5 inches.

Finally, something that helped me with setting toe-in are the LEDR audio files as described by Stereophile.

My speakers are Vienna Acoustics which are well-known for their sensitivity to both toe-in and vertical tilt. The distributor used to advertise a special class for properly setting them up to maximize their sound.
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post #10626 of 11649 Old 06-28-2014, 10:50 AM
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Finally, something that helped me with setting toe-in are the LEDR audio files as described by Stereophile.
That article is from 1989. I can't find the Prosonos CD listed on the internet. Do you actually have that CD? Any chance of ripping that test track and making it selectively available to us here?

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post #10627 of 11649 Old 06-28-2014, 10:53 AM
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That article is from 1989. I can't find the Prosonos CD listed on the internet. Do you actually have that CD? Any chance of ripping that test track and making it selectively available to us here?
I don't have the full CD but I got copies of the LEDR files from AudioCheck.net.

Sorry for not linking those earlier.
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post #10628 of 11649 Old 06-28-2014, 10:55 AM
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That article is from 1989. I can't find the Prosonos CD listed on the internet. Do you actually have that CD? Any chance of ripping that test track and making it selectively available to us here?
http://www.audiocheck.net/audiotests_ledr.php

Personally, I found these to have limited value. They don't translate very well to how music sounds. Of course, if your system fails these tests miserably, that probably points to something a muck.


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post #10629 of 11649 Old 06-28-2014, 11:13 AM
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Originally Posted by jim19611961 View Post

In any case, I am interested in any stories any of you may have
I follow the same general guidelines you mentioned. I place a piece of cardboard approximately two feed behind the MLP with a vertical line representing the midpoint between the left and right speakers. I then use a laser pointer to adjust toe-in so it is on the center line, crossing just behind the MLP.

Analyzing the soundstage is a topic that I have struggled with for quite some time. My ability to analyze audio depends on being able to devise A/B tests that I can toggle back and forth. I can't, for example, listen to a music passage, stand up, adjust toe-in, sit down and listen to the same music passage, and assess audible changes to the soundstage attributable to the change. I don't know why this is difficult for me, but it is.

So, for those of you with Golden Ears, walk me through how you assess a system's soundstage. Do you have a particular piece of music you are very familiar with? What exactly do you listen for? Is your audio memory good enough that you can adjust something and immediately assess the impact of the change?

If someone were able to coach me through how to optimize my soundstage, I would be forever indebted. Wouldn't this be good advice for anyone reading this thread?
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post #10630 of 11649 Old 06-28-2014, 11:24 AM
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Originally Posted by AustinJerry View Post
I follow the same general guidelines you mentioned. I place a piece of cardboard approximately two feed behind the MLP with a vertical line representing the midpoint between the left and right speakers. I then use a laser pointer to adjust toe-in so it is on the center line, crossing just behind the MLP.

Analyzing the soundstage is a topic that I have struggled with for quite some time. My ability to analyze audio depends on being able to devise A/B tests that I can toggle back and forth. I can't, for example, listen to a music passage, stand up, adjust toe-in, sit down and listen to the same music passage, and assess audible changes to the soundstage attributable to the change. I don't know why this is difficult for me, but it is.

So, for those of you with Golden Ears, walk me through how you assess a system's soundstage. Do you have a particular piece of music you are very familiar with? What exactly do you listen for? Is your audio memory good enough that you can adjust something and immediately assess the impact of the change?

If someone were able to coach me through how to optimize my soundstage, I would be forever indebted. Wouldn't this be good advice for anyone reading this thread?
As you quite rightly point out, you cant A/B speaker toe-in for obvious reasons. While I agree memory isnt too reliable when it comes to evaluating the soundstage as whole in all its details, I do find that if I focus just on certain elements, on a piece of music that I am VERY familiar with, I can discern differences caused by toe-in or other minor soundstage differences. In my case, I was only focusing on what was happening outside the speakers while mostly ignoring all else.

As for Golden Ears, it is my claim that such has little to do with ones ears, and everything to do with how well you can focus your hearing on specific elements. If you can pinpoint exactly where just a couple specific things appear in the soundstage, then its not as hard to see if they move 5 minutes later. Where most fail, is trying to take it ALL in and then make the comparison to ALL that maybe new after some change. This, I cannot do either very well.

I do not know of any scientific way to make assessments of the soundstage. If for no other reason, its an illusion to begin with. How do you measure an illusion?

Edit: That said, we can measure some of the things that contribute to the systems ability to create the illusion. These I think your familiar with. Early high gain reflection attenuation. Channel tracking precision. Left to Right room symmetry. Left and Right ETC symmetry. Exact speaker distance from LP. Exact toe-in angles. And so on.
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post #10631 of 11649 Old 06-28-2014, 11:26 AM
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Do you have a particular piece of music you are very familiar with?
Not a golden ears hear but one of the things I use is a copy of Anthing Goes sung by Patti LuPone. At one point there's a tap dancer that goes from the right hand to the left hand sides of the stage. I try to get that to travel as smoothly as possible.
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post #10632 of 11649 Old 06-28-2014, 05:03 PM
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Not a golden ears hear but one of the things I use is a copy of Anthing Goes sung by Patti LuPone. At one point there's a tap dancer that goes from the right hand to the left hand sides of the stage. I try to get that to travel as smoothly as possible.
Haven't tried it out - but I always remember the fantastic left right left pan in Jimi Hendrix' version of "All Along the Watchtower."

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post #10633 of 11649 Old 06-29-2014, 02:18 AM
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Fwiw there is a new rew beta which adds that zero phase filter option for etc as well apparently removes the need for workarounds on the mac. The latter especially may be of interest to some people who buy laptops purely for rew.
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post #10634 of 11649 Old 06-29-2014, 10:03 AM
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I do not know of any scientific way to make assessments of the soundstage. If for no other reason, its an illusion to begin with. How do you measure an illusion?
Exactly. Likewise for the other desirable "audiophile" qualities, which is mainly why the audiophile world is eschewed by pure objectivists.

I do appreciate soundstage, so I put up with the physical/operational inconvenience of front speakers that are not my "best", or even second best, but kill for soundstage. You either value something or not, and weight things accordingly. Since it's a psychoacoustical effect, it would require some model of the brain/ears and "numerous" (more than 1 anyway) microphones...perhaps the next REW beta.

I certainly do notice that since I've treated my room, the soundstage has been narrowed somewhat (expected), and the depth is about the same. This is OK as I feel the width is more under control now. I don't listen to orchestral music so don't know how that might be affected, since there are a lot more instruments to be placed and perhaps they're getting more scrunched together than they should be...I would have no way to even know (from real life). Whereas for the music I listen to, I can throw in a BD concert and see where everybody is and get a sense of how it might really sound, assuming the mix is representative. All very airy fairy...

Certainly the decay/reflection parts of REW are somehow indicative of what you can expect though. First you have to get rid of the junk reflections that are just messing up the sound. Then we get into the ambience type of reflections/diffusion that are contributing positively to the experience. This is very difficult to judge, for me, and I think I went just a tad far with wall absorption (my room is too small/cramped to use diffusion effectively). The only way to know if you went "too far" is to listen and then pull back, I'm not sure if you can judge in advance just by the graphs/numbers. The "too far" panels aren't wasted, I put them in neutral places where they're decorations until I can put them on the ceiling or get some new insight.
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post #10635 of 11649 Old 06-29-2014, 10:49 AM
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http://www.moultonlabs.com/more/prin...ntom_image/P2/



I was curious how phantom delays are created in the first place. If we are to enhance our soundstage, we need to preserve those factors that contribute to it. While this is not the entire story, what this link and graph tell me is that left and right speaker to LP timing is CRITICAL.

For instance, if one speaker were 1.5" further away than the other, that would make the further one delayed in time by 0.111 ms. Looking at the graph, that would be enough to move all the phantom images by several inches on the soundstage.

If one looks at this from another view, speaker design, more specifically, driver placement in regards to depth make a similar, but different type of delay. The timing of each driver depends on the voice coil location. Typically, the voice coil position of a tweeter is different than that of a woofer if both are mounted on a flat plane. If you have ever heard of speakers that are time aligned, this is what they are talking about. The drivers in such a speaker have there voice coils matched in depth in order to provide time continuity across the frequency range. Most speaker do not provide this. While none time aligned speakers do not pose any R to L delay per say, the frequencies provided from the tweeter, mids, and woofers will arrive at different times in a spectral sense.


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post #10636 of 11649 Old 06-29-2014, 01:18 PM
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^
99,9% of all recordings don't utilize interchannel time differences but interchannel level differences. Highly recommended read:
Lipshitz, "STEREO MICROPHONE TECHNIQUES: ARE THE PURISTS WRONG?"
Send me a PM if you're interested.

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post #10637 of 11649 Old 06-29-2014, 01:26 PM
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I came across another comment on distortion measurements today in the Toole book



I think it's fair to say he's not a fan of THD as a measurement judging from that quote

The text referenced as a good overview is described as

Voishvillo, A. (2006). “Assessment of Nonlinearity in Transducers and Sound Systems — From THD to Perceptual Models,” 121st Convention, Audio Eng. Soc., Preprint 6910.

I can't find this except via AES. I did find a ppt presentation from the author on the subject though (haven't read it yet) - http://www.almainternational.org/yah....106173319.pdf
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post #10638 of 11649 Old 06-29-2014, 05:34 PM
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^ I would interpret that as meaning the THD/IMD measurement numbers don't correspond directly with how we hear. I am pretty sure Dr. Toole is a fan of reproduction devices reproducing what he sends them. And believes that THD/IMD is some imperfect indication of them not. [If not, then pretty much everything he's ever done in the field is meaningless, because it wouldn't matter what the speakers output, or what they sounded like.]

IOW written like a scientist rather than an engineer. Those who are either can easily tell this. I can tell you that scientists typically look down on engineers, at all levels but especially in academic institutions. As one of the latter who has worked with more of the former, we are definitely on the down side of the pecking order. Flawed/bad "scientists" lol. Never mind that the scientists wouldn't be able to do a fraction of what they do without the work of the engineers (instruments for a start, never mind being able to get to work). Engineers need some numbers to work with, something real, otherwise it's hard to tell if you're making progress. Scientists are perfectly capable of working totally within their minds. But I digress...
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post #10639 of 11649 Old 06-29-2014, 09:34 PM
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^ Guys,

Came across this website: http://soundoctor.com/whitepapers/subs.htm regarding how to integrate sub(s) into the system. Scroll down to the part about "THE RECORDING PROCESS" which tells the sad tale of how music is now mastered to obtain soundstage.

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Nice article. Not that I would agree with everything that is said there but nonetheless it is a good overview of the complexities involved setting up speakers in rooms.

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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post #10641 of 11649 Old 06-30-2014, 04:32 AM
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^ I would interpret that as meaning the THD/IMD measurement numbers don't correspond directly with how we hear. I am pretty sure Dr. Toole is a fan of reproduction devices reproducing what he sends them. And believes that THD/IMD is some imperfect indication of them not. [If not, then pretty much everything he's ever done in the field is meaningless, because it wouldn't matter what the speakers output, or what they sounded like.])
No one is advocating adding distortion where none exists or that distortion is irrelevant, rather the questions have been how much distortion should one tolerate? (where distortion has largely been discussed in THD terms). If recent research says that THD is almost useless for predicting sound quality then that seems quite a strong argument against spending time attempting to incrementally improve distortion performance. I can't say I am familiar with any recent research beyond the previous links though so perhaps there are contrary views out there.
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post #10642 of 11649 Old 06-30-2014, 05:01 AM
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No one is advocating adding distortion where none exists or that distortion is irrelevant, rather the questions have been how much distortion should one tolerate? (where distortion has largely been discussed in THD terms). If recent research says that THD is almost useless for predicting sound quality then that seems quite a strong argument against spending time attempting to incrementally improve distortion performance. I can't say I am familiar with any recent research beyond the previous links though so perhaps there are contrary views out there.
I agree with what you are saying. Side question: have we discussed how one might incrementally improve distortion performance? Other than making sure sound levels are kept below levels that cause increased distortion, or replacing audio components that have higher inherent distortion, what else can we do? It has been interesting developing an understanding of how to measure distortion, but I have been taking the measured levels as a "given", because I am not likely to start swapping out audio components.

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Side question: have we discussed how one might incrementally improve distortion performance? Other than making sure sound levels are kept below levels that cause increased distortion, or replacing audio components that have higher inherent distortion, what else can we do? It has been interesting developing an understanding of how to measure distortion, but I have been taking the measured levels as a "given", because I am not likely to start swapping out audio components.
I had been considering that question too & could only think of the same treatments (where "keeping output below a threshold" can also mean "choosing a different correction curve in your EQ tool of choice").
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post #10644 of 11649 Old 06-30-2014, 07:43 AM
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Originally Posted by AustinJerry View Post
I agree with what you are saying. Side question: have we discussed how one might incrementally improve distortion performance? Other than making sure sound levels are kept below levels that cause increased distortion, or replacing audio components that have higher inherent distortion, what else can we do? It has been interesting developing an understanding of how to measure distortion, but I have been taking the measured levels as a "given", because I am not likely to start swapping out audio components.
In absence of any audio processing devices, I would agree, mostly. But things like Audyssey and DSP can radically increase distortion in areas where they EQ the signal. Furthermore, how much gain you apply to your subs vs your mains is something to look at also as Artur documented in his system. Even the XO point may have effects on distortion. And lastly, I pointed out already that certain elements in multi-amped, multisub apps can very well introduce distortion in one element before the others.

In summation, if you have tons of headroom in every amped element well beyond the levels you listen at, then distortion probably isnt an issue for you. But let me remind everyone that in dynamic recordings, peaks can be 16-20db (requiring 40X - 100X amp power) above your average power level in order to produce them cleanly. And our sine sweep distortion tests make no attempt to document peak distortion.

In regards to Dr. Toole, I think he is saying we don't have good psychoacoustic facility to know how we hear distortion or whats its effects are. Not that distortion is irrelevant.

I do think that in terms of getting better sound out of our system, distortion level analysis isnt in the top 5 things we should be concerned about. To me, though, the topic has been relevant and helpful given some have discovered 30%+ distortion in there systems at typical listening levels at certain frequencies.


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post #10645 of 11649 Old 06-30-2014, 08:31 AM
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Originally Posted by 3ll3d00d View Post
I had been considering that question too & could only think of the same treatments (where "keeping output below a threshold" can also mean "choosing a different correction curve in your EQ tool of choice").
...or adding more output potential (another sub?) if your preferred EQ curve is causing you to exceed desired distortion levels in that region.


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post #10646 of 11649 Old 06-30-2014, 08:45 AM
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Originally Posted by markus767 View Post
^
99,9% of all recordings don't utilize interchannel time differences but interchannel level differences. Highly recommended read:
Lipshitz, "STEREO MICROPHONE TECHNIQUES: ARE THE PURISTS WRONG?"
Send me a PM if you're interested.
My point here was that small differences in timing (distance) in L & R mains can cause image shift.


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Yes and you can hear it by rotating your head and/or by moving sideways.

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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post #10648 of 11649 Old 06-30-2014, 09:03 AM
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^
Yes and you can hear it by rotating your head and/or by moving sideways.
Do you have a reference that shows image shift based on level differences?


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post #10649 of 11649 Old 06-30-2014, 09:27 AM
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Originally Posted by jim19611961 View Post
I do think that in terms of getting better sound out of our system, distortion level analysis isnt in the top 5 things we should be concerned about. To me, though, the topic has been relevant and helpful given some have discovered 30%+ distortion in there systems at typical listening levels at certain frequencies.
completely agree with this & hence why I think it should be possible to write something in the guide around how to measure. The most obvious and unambiguous use for this info is to get warning signs around headroom but also a warning that something might be wrong with your measurement chain. As an example of the latter, I've seen some measurements recently where the frequency response looks quite normal (and consistent from measurement to measurement) but the impulse has a load of preringing (and is not consistently repeatable) and this appears to surface as anomalous distortion spikes in particular frequency bands.

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...or adding more output potential (another sub?) if your preferred EQ curve is causing you to exceed desired distortion levels in that region.
yes that as well for sure.

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Do you have a reference that shows image shift based on level differences?
I can only offer an anecdote on that score. My room correction clearly has the effect of firmly fixing the stereo image in the right place, uncorrected (but still level matched as best as possible) there is a clear bias to the R side of the room.
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post #10650 of 11649 Old 06-30-2014, 09:42 AM
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Originally Posted by 3ll3d00d View Post
No one is advocating adding distortion where none exists or that distortion is irrelevant, rather the questions have been how much distortion should one tolerate? (where distortion has largely been discussed in THD terms). If recent research says that THD is almost useless for predicting sound quality then that seems quite a strong argument against spending time attempting to incrementally improve distortion performance. I can't say I am familiar with any recent research beyond the previous links though so perhaps there are contrary views out there.
Yes, exactly what I said, following on from comments on what Toole said. THD is not useless in predicting sound quality because if you have any you have decreased sound quality, by definition of the word distortion, and our understanding of quality in this context. Toole is making a scientist's argument (theory), we are using the engineer's argument (practice). Those who are neither probably don't get it, they are very different. That's why I mentioned what I did. Do you want to do something, or just think about it?

Edit: As for the distortion that Audyssey (specifically XT32, what I was using then) may cause, that is exactly what I was talking about when I brought up the REW distortion capabilities several months ago. It was completely ignored IIRC. Look, I know many people are almost completely immune to it, until it gets to almost clipping. I have heard their setups, good ones at least from the quality perspective, yet they are missing it.

As others have said, it's something that people may only notice when it's there after they've heard it not there. I even said I find it difficult to pick out in the bass region, where I most appreciate what Audyssey does, but I can easily tell when it's not there. It sort of creeps up on me as muddying and an eventual fatigue, and I expect younger ears (that can go lower in freq for a given level) can more easily pick it out, if they know what to listen for. Most below 25Hz is hard for me to hear unless it's a rather high level. But it seems like a good idea to have as little distortion as possible, but not to go to massive lengths, since it's sucking up amp power and the distortion harmonics are easier for me to hear. And in my particular case, was muddying the mid-bass while trying to reproduce the lower bass (my front speaker capability is not good down there, worse than any other speaker in my 7.1 setup). People have to give their own weighting to things, based on what sonic attributes they appreciate, and which ones that really annoy.

Last edited by cfraser; 06-30-2014 at 10:06 AM.
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