Simplified REW Setup and Use (USB Mic & HDMI Connection) Including Measurement Techniques and How To Interpret Graphs - Page 429 - AVS Forum
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post #12841 of 12858 Old Yesterday, 01:10 PM
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If I missed it in the guide, I apologize but I can't seem to find the part to interprete distortion graph. I am trying to understand my graph below. Thanks.

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post #12842 of 12858 Old Yesterday, 01:22 PM
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Originally Posted by tvuong View Post
If I missed it in the guide, I apologize but I can't seem to find the part to interprete distortion graph. I am trying to understand my graph below. Thanks.
do you understand what harmonic distortion is? have you read the REW help on the subject?

the graph is basically just telling you how loud the various components of harmonic distortion are & how they vary by frequency, i.e. it's exactly the same information as a frequency response chart but showing the harmonic distortion instead
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post #12843 of 12858 Old Yesterday, 02:10 PM
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I wonder if it's possible to add such examples to the guide?

Has anyone here had ringing this bad? Most of the graphs I've seen here have only a few frequencies extending out past 450ms. This one has seems to have it going every 35Hz or so.

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No, THIS is modal ringing

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post #12844 of 12858 Old Yesterday, 02:34 PM
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Maybe I am just not understanding things correctly, but does the fact that this graph is showing down to 20 db and in the noise floor have something to do with the resonance?
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post #12845 of 12858 Old Yesterday, 02:38 PM
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No. It is that big long peak at around 35hz that's the point of interest, and that is well out of the noise floor.
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post #12846 of 12858 Old Yesterday, 02:52 PM
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Originally Posted by ssjp55 View Post
Maybe I am just not understanding things correctly, but does the fact that this graph is showing down to 20 db and in the noise floor have something to do with the resonance?
The measurement isn't level calibrated and as Audionut said, the interesting part is the mode at 33Hz that rings on forever.

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post #12847 of 12858 Old Yesterday, 03:15 PM
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Originally Posted by tvuong View Post
If I missed it in the guide, I apologize but I can't seem to find the part to interprete distortion graph. I am trying to understand my graph below. Thanks.

Click on the graph. It will show at the bottom the various distortion figures for the frequency you click on. The numbers on THIS graph are meaningless without knowing where the target was when you saved the pic.

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post #12848 of 12858 Old Yesterday, 03:34 PM
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Quick question about water fall graph. Its X-axis shows Hz and Y-axis shows db. Based on room floor noise, we ignore anything under that noise (since its not audible). Is there also a limit on X-axis that we can ignore?

In other words, Assuming floor noise = 50db, if we have a decay of 45 at 40Hz, we can ignore it since its below floor noise. Similarly is there a point on X-axis that we don't need to worry about below certain point even if it exceeds 50db?

thx.
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post #12849 of 12858 Old Yesterday, 03:59 PM
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Quote:
Originally Posted by artur9 View Post
I wonder if it's possible to add such examples to the guide?

Has anyone here had ringing this bad? Most of the graphs I've seen here have only a few frequencies extending out past 450ms. This one has seems to have it going every 35Hz or so.
If everyone thinks there is value, I can add this example to the guide.
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post #12850 of 12858 Old Yesterday, 04:14 PM
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Quote:
Originally Posted by artur9 View Post
I wonder if it's possible to add such examples to the guide?

Has anyone here had ringing this bad? Most of the graphs I've seen here have only a few frequencies extending out past 450ms. This one has seems to have it going every 35Hz or so.
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Originally Posted by AustinJerry View Post
If everyone thinks there is value, I can add this example to the guide.
I am not sure we all agree on how to read the graph. IMO, its not about what extents out to 450ms, or any other time (within reason), but when the ridge starts both in time and in magnitude. But I do feel we will all agree the graph with the 35hz ridge is a good example of a very BAD result. That is an extreme example though. Likewise, its easy to look at graphs with no ridges or extension and agree that would be a good one. At the other extreme. But 99% of us are going to be between these extremes. And that is where help will do some good in graph interpretation.

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post #12851 of 12858 Old Yesterday, 07:27 PM
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Quote:
Originally Posted by jim19611961 View Post
Click on the graph. It will show at the bottom the various distortion figures for the frequency you click on. The numbers on THIS graph are meaningless without knowing where the target was when you saved the pic.
Got cha. What order(s) of harmonic distortion (2nd, 3rd, etc...) is most important that I need to pay attention to? 3rd? based on Dood's comment below?
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Originally Posted by 3ll3d00d View Post
Generally speaking there is some debate about the absolute audibility of distortion at low frequencies. However what isn't up for debate is that high levels of distortion are a clear sign of impending distress for your sub, in my experience you are in the danger zone when you by past 10% and then really clearly in trouble at 30%. This percentage refers to how much quieter the distortion is vs the fundamental tone, 10% distortion = -20dB and 30% = -10dB.
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Originally Posted by 3ll3d00d View Post
I mention 60Hz as you seem to have a clear spike in the distortion there upto ~5%, this must be audyssey boosting. You can then see you reach ~10% distortion at ~16Hz so this is getting the limits of your system at reference. Note that 3rd harmonic is escalating rapidly under 20Hz, AIUI 3rd harmonic is predominantly mechanical non linearity (i.e. magnet losing control of driver aka reaching xmax) so this shows that ~12Hz or so sees your drivers losing it.
Dood, Based on your comment about the 10% distortion limit, If I interprete correctly, I am safe down to 14Hz (I based it on the THD)? Seem fine @60Hz, is it not?
Thanks so much.











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post #12852 of 12858 Old Yesterday, 07:30 PM
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Is there a need to do soundcard calibration for REW setup if I were to use HDMI to my AVR and UMIK1 mic.

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No, THIS is modal ringing

Is this in a concrete bunker?
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post #12853 of 12858 Old Yesterday, 08:09 PM
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Is there a need to do soundcard calibration for REW setup if I were to use HDMI to my AVR and UMIK1 mic.

-----



Is this in a concrete bunker?
Soundcard calibration is not required when using the USB/HDMI Kit.
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post #12854 of 12858 Old Today, 12:35 AM
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Quote:
Originally Posted by jim19611961 View Post
I am not sure we all agree on how to read the graph. IMO, its not about what extents out to 450ms, or any other time (within reason), but when the ridge starts both in time and in magnitude.
Yes, this is the important message for people trying to understand waterfall graphs. They need to understand that each single waterfall slice contains not only energy from that specific point in time but from several hundreds of milliseconds before (rise time) and after (window).

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post #12855 of 12858 Old Today, 12:39 AM
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Is this in a concrete bunker?
Most basements in Europe are poured concrete so this is unfortunately rather the norm than an exception. Those wooden tents Americans call their homes are much better for good bass reproduction

Markus

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post #12856 of 12858 Old Today, 04:13 AM
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Looks like they are cubes also.
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post #12857 of 12858 Old Today, 04:53 AM
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Quote:
Originally Posted by tvuong View Post
Got cha. What order(s) of harmonic distortion (2nd, 3rd, etc...) is most important that I need to pay attention to? 3rd? based on Dood's comment below?
generally speaking

* the higher the harmonic, the more noticeable it will be hence you need to keep them to a relatively lower level than lower harmonics.
* harmonic distortion is relatively less noticeable at v low frequencies (though might be much much more audible when you get into infrasonics)
* I don't think there is a straight answer to individual preference/tolerance for different levels of distortion

Quote:
Originally Posted by tvuong View Post
Dood, Based on your comment about the 10% distortion limit, If I interprete correctly, I am safe down to 14Hz (I based it on the THD)? Seem fine @60Hz, is it not?
seems a reasonable conclusion to me
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post #12858 of 12858 Old Today, 07:40 AM
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^^ thanks again.
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