Simplified REW Setup and Use (USB Mic & HDMI Connection) Including Measurement Techniques and How To Interpret Graphs - Page 232 - AVS Forum
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post #6931 of 11856 Old 11-14-2013, 06:37 PM
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Ok, so if measurement peak happens to at 102 or 93 then I don't need to go in and set it to 99 but just leave it scaled to peak correct?

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post #6932 of 11856 Old 11-14-2013, 06:41 PM
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Quote:
Originally Posted by Audionut11 View Post

With 'match top of scale to peak', you can ignore 'scale top' and 'scale bottom' unless you want to manually change things. If you want to see further down into the noise floor you should use 'scale range'. This won't change the top end but will simply extend the scale further into the noise floor.

I was thinking so but I wanted to be 100% rolleyes.gif

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post #6933 of 11856 Old 11-14-2013, 06:42 PM
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What is the closest I can have my UMM-6 to the back of the couch?

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post #6934 of 11856 Old 11-14-2013, 06:56 PM
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Originally Posted by jlpowell84 View Post

What is the closest I can have my UMM-6 to the back of the couch?

Place it where the middle of your ears would be.
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post #6935 of 11856 Old 11-14-2013, 07:04 PM
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Place it where the middle of your ears would be.

Ok, it just gets a little close and wasn't quite sure. Ive always ran it there prior

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post #6936 of 11856 Old 11-14-2013, 08:05 PM
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I noticed the other night my raw graph looked different from when I had moved my two subs to the 1/4 and 3/4 points on the front wall per Sanjay's prescription. So tonight I bypassed everything to get the raw measurements again. I noticed different still. So I hit invert Polarity on my mini dsp unit and the RAW 5-300 range looked familiar once again and obviously much better. The thing is I have no idea how it changed? I have never clicked on the invert polarity buttons before? Is there any way the polarity could have inverted from any of my electronics? Denon 3313, Open DRC-AN (mini dsp unit), and two Seaton Submersives. I did rerun Audyssey, change a little bit of the PEQ cuts and low shelf filter on the mini dsp and change out a speaker wire on the right main. Probably the most important note I think is that when I played a song and had the polarity inverted the bass was much stronger especially the kick drum









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post #6937 of 11856 Old 11-14-2013, 08:22 PM
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ok, i am officially confused now. These two graphs are both with two single cuts so far while developing and prepping for Audyssey.




perhaps it was right? Any reason it would be better inverted on a raw graph and not inverted with EQ added?

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post #6938 of 11856 Old 11-14-2013, 08:36 PM
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I have no idea what you are talking about. Are these PEQ settings?

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post #6939 of 11856 Old 11-14-2013, 08:54 PM
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Quote:
Originally Posted by AustinJerry View Post

I have no idea what you are talking about. Are these PEQ settings?

PEQ settings aside I was confused why my raw response looked different when no physical changes took place. I then clicked on the invert polarity buttons on my mini dsp menu. Output channel 1&2 which goes to each Submersive and the raw response looked familiar again. That is all. I was trying to provide any info of why this would take place

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post #6940 of 11856 Old 11-14-2013, 08:55 PM
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But as soon as I added two PEQ filters it went from good to bad. So I just un clicked the invert polarity buttons. Was just trying to understand is all

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post #6941 of 11856 Old 11-14-2013, 08:58 PM
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Well its only right to post these. I has thought there may have been different effects in the time domain from two different EQ options on the mini dsp PEQ page. None whatsoever IMO. One good thing is that the SUB EQ seems to give a natural house curve rise. Settings were identical just toggled from one to the other for measurements. It was inflated hope on a bonehead move of different graph values








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post #6942 of 11856 Old 11-14-2013, 09:13 PM
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Got a chance to lay some pink fluffy on the floor.



Here 0.1ms smoothed.



Extended out to 50ms. The peaks at 6-8ms are ceiling.



0.5ms smoothed.



Didn't get a chance to judge the differences with my ears, but judging by the differences on the FR plot, I was relying to much on delay on the sub to fix the dips.



Jim, I'm probably 70/30 movies/music so prefer to tend towards a dead room. Although I'm sure if I had a chance to listen in your room my preferences might change smile.gif
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post #6943 of 11856 Old 11-14-2013, 09:25 PM
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Quote:
Originally Posted by jlpowell84 View Post

It was inflated hope on a bonehead move of different graph values

Well at least you know now. Much better then the false hope that something had changed.

I don't have time for a good look, but it does appear that if you compensate for the increased amplitude below 40hz, the SubEQ results are better. Not much, but it looks like a difference is there.
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post #6944 of 11856 Old 11-14-2013, 10:20 PM
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Originally Posted by jlpowell84 View Post

Any reason it would be better inverted on a raw graph and not inverted with EQ added?

Audyssey equalizes each speaker seperately. This equalization not only changes frequency response but also creates phase shifts. Therefore the combined response of two or more speakers will be different with and without equalization.

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post #6945 of 11856 Old 11-14-2013, 10:29 PM
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Audysseysey equalizes each speaker seperately. This equalization not only changes frequency response but also creates phase shifts. Therefore the combined response of two or more speakers will be different with and without equalization.

Ok, I see. I settled on a 110hz crossover and would love to post a couple pics but for some reason I can't at the moment. Just did in the mini dsp forum so not sure what the deal is. But I had a HUGE 40 db skinny dip at the 110hz crossover. I inverted the polarity and completely gone.

Here we go I used my iPhone.


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post #6946 of 11856 Old 11-15-2013, 02:03 AM
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Originally Posted by jim19611961 View Post
 
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Yes but surely those peaks and valleys are entirely inaudible?

http://www.audioholics.com/room-acoustics/human-hearing-amplitude-sensitivity-part-1



The finding by these various studies suggest we can discriminate between 0.25 and 3db differences. And all but one suggest in the 1db - 1.5db range.

 

Yes, I've seen that article before, thanks. But these are lab conditions using tones or pink noise. On real material can we really detect these small changes in FR, such that we really need to be aiming for +/-1dB graphs? I know you are not trying to dictate to anyone how they should proceed, Jim, but you have a huge amount of experience and I value your opinion.



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post #6947 of 11856 Old 11-15-2013, 02:05 AM
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Quote:
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Yes, good point. I am +/-3dB at 1/3rd smoothing. Is that good enough then?  I am starting to get confused. And should that be for individual channels, combined L+R+subs or what?

Again, I am not hear to tell anyone whats good enough for them.

These guidelines should be applied to individual channel responses (L, R, L+sub, R+sub). Combining L+R naturally intruduces a smoothing or averaging effect upon them. But many treat the bass region differently and apply different criteria to it. For one, many low bass instruments are in mono anyway, so combined channel responses sometimes emulate whats going on anyway pretty well. Lower bass frequencies lose directionality as well.

I am not saying L+R cant be useful. But you may have to apply different goal constraints upon it.

But personally, I find +/-5db at 1/24th oct smoothing more useful and telling than +/-3db at 1/3rd oct smoothing. But many here, including self, elevate the bass region, so these +/- factors have to be modified.

 

Thanks. Yes, I take into account the bass hump usually, looking at the FR range in 'two parts' IYKWIM. I think I am starting to get an understanding of the central point - thanks.



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post #6948 of 11856 Old 11-15-2013, 02:08 AM
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Quote:
Originally Posted by Nyal Mellor View Post
 
Quote:
Originally Posted by jim19611961 View Post



Here is a very old FR of the same response in 1/3 and 1/24th.

The null at 33hz is completely smoothed over at 1/3rd. And the peak at 64hz, the same. 200hz, the same. I could hear EASILY these phenomena.

But my greater point is at 1/3rd (1/6th not being much better), you wouldn't be aware of these at all.

Your points are well founded in the low bass area. Simplistically speaking if one divides up their analysis into >250Hz and below <250Hz (corresponding to modal / specular regions) then what I stated was true above 250Hz. I will edit my post to that effect.

Do you think we can hear peaks and dips which show up at 1/24th resolution at say 800Hz? I don't think so.

As frequency goes down our frequency resolution increases. I'm not convinced it's as much as 1/24th octave though. Certainly 1/12th octave.

What's more we really don't hear the nulls like we hear the peaks. What we hear is more like a the arc drawn by say a swing bridge or cable car between two mountains.

 

Nyal - does this summarise as 1/6 smoothing >300Hz and unsmoothed <300Hz?  If it does, that is what I have been doing (albeit to the wrong combination of speakers it seems)?



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post #6949 of 11856 Old 11-15-2013, 02:12 AM
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Quote:
Originally Posted by Nyal Mellor View Post
 
Quote:
Originally Posted by AustinJerry View Post

Nyal, can you clarify what you mean by "not valid"?  In the example below, are you saying that combined L+R measurement has no useful information?


In the low bass, say <250Hz or where ever there might be the same signal playing from more than one speaker then L+R or L+R+C+Sub is valid.

Differences in mic to speaker distances will cause comb filtering when playing the same signal through multiple speakers, especially as the wavelengths get very short.

 

I thought I had a handle on this but the more I read the more uncertain I become .... so playing a mono source on a two channel system is a problem then due to this comb filtering?  I ask because I do this frequently on my separate stereo system and I don't hear anything odd even if I don't sit exactly equidistant from the speakers. 



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post #6950 of 11856 Old 11-15-2013, 02:21 AM
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Quote:
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But for the 'end result' of what the room looks like, isn’t the R+L+Subs the right thing to do?
Your L/C/R speakers are placed at the 3 nulls of your 3rd width mode so that their interaction cancels/minimizes the first 5 width modes of your room: 54Hz, 108Hz, 161Hz, 215Hz and 269Hz. The 1st width mode is below the crossover point and being addressed by your dual subs.

How will you verify that the interaction between your L/C/R speakers is reducing the next 4 modes if you don't measure the interaction between your L/C/R speakers? Measuring L+R won't let you see that. Hence Nyal's suggestion to measure all 3 front speakers (and subs) to see what is happening in the modal range.

 

Got it!  Thanks, Sanjay.  I will change my measuring parameters accordingly.

 

@Jerry

 

Jerry, is all this stuff reflected in your Guide?  I have been well off-track it seems in that I have been giving significant attention to the wrong graphs and insignificant attention to the right ones. I feel I am almost back to Square One.



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post #6951 of 11856 Old 11-15-2013, 02:25 AM
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Keith, was it established the Herb is no longer shipping worldwide? If so I thought you might want to know to change this in post #10. Just happened to see it while reading for more info.
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This Mic is only $90.00 and he charges $9.00 for shipping. He also ships Worldwide.

 

Done it - thanks. Also added that non-US residents may wish to use the UMIK-1 which is available worldwide (and which comes with its own cal file now).



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post #6952 of 11856 Old 11-15-2013, 06:32 AM
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Got a chance to lay some pink fluffy on the floor.



Here 0.1ms smoothed.



Extended out to 50ms. The peaks at 6-8ms are ceiling.



0.5ms smoothed.



Didn't get a chance to judge the differences with my ears, but judging by the differences on the FR plot, I was relying to much on delay on the sub to fix the dips.



Jim, I'm probably 70/30 movies/music so prefer to tend towards a dead room. Although I'm sure if I had a chance to listen in your room my preferences might change smile.gif

The results you obtained are very similar to what I obtained when I added the 3" of Roxsul on the floor except as my ceiling is treated it doesn't introduce any significant reflections.

It is quite amazing how the floor is often neglected as a relevant reflective surface. I suppose it is because it is so difficult to easily treat. It would be great if some company introduced effective floor treatment that you could "walk on". smile.gif

Thanks for taking the time to post these measurements. Pity you didn't get a chance to listen to the changes.

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post #6953 of 11856 Old 11-15-2013, 07:04 AM
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Quote:
Originally Posted by sdurani View Post
 
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But for the 'end result' of what the room looks like, isn’t the R+L+Subs the right thing to do?
Your L/C/R speakers are placed at the 3 nulls of your 3rd width mode so that their interaction cancels/minimizes the first 5 width modes of your room: 54Hz, 108Hz, 161Hz, 215Hz and 269Hz. The 1st width mode is below the crossover point and being addressed by your dual subs.

How will you verify that the interaction between your L/C/R speakers is reducing the next 4 modes if you don't measure the interaction between your L/C/R speakers? Measuring L+R won't let you see that. Hence Nyal's suggestion to measure all 3 front speakers (and subs) to see what is happening in the modal range.

 

Got it!  Thanks, Sanjay.  I will change my measuring parameters accordingly.

 

@Jerry - 

 

Jerry, is all this stuff reflected in your Guide?  I have been well off-track it seems in that I have been giving significant attention to the wrong graphs and insignificant attention to the right ones. I feel I am almost back to Square One.

 

Geez, tell me about it (i.e. back to square one)!

 

Perhaps I'm the only one that was confused by Nyal's advice to you but is it clear now what we are supposed to use to characterize the status of the full frequency spectrum?  Is it a 15-20k Hz response that is 1/6 smoothed of the L+Sub, C+Sub and R+Sub?  Is this perhaps a reason to use the "averaging" option in REW to generate one FR that is a combination of all 3 FR's (but that seems like it could be very misleading depending on what's going on in the room)? :confused:

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Got it!  Thanks, Sanjay.  I will change my measuring parameters accordingly.

@Jerry

Jerry, is all this stuff reflected in your Guide?  I have been well off-track it seems in that I have been giving significant attention to the wrong graphs and insignificant attention to the right ones. I feel I am almost back to Square One.

So what should the guide say? Beware of basing conclusions on measurements that include both the left and right speakers because speaker interactions can result in an accurate picture? Take separate measurements of left, right, and center speakers to gain a true understanding of the frequency response in you listening room?

My head is starting to hurt.

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post #6955 of 11856 Old 11-15-2013, 07:59 AM
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Got it!  Thanks, Sanjay.  I will change my measuring parameters accordingly.

@Jerry

Jerry, is all this stuff reflected in your Guide?  I have been well off-track it seems in that I have been giving significant attention to the wrong graphs and insignificant attention to the right ones. I feel I am almost back to Square One.

So what should the guide say? Beware of basing conclusions on measurements that include both the left and right speakers because speaker interactions can result in an accurate picture? Take separate measurements of left, right, and center speakers to gain a true understanding of the frequency response in you listening room?

My head is starting to hurt.

 

Same here. I think the Guide needs to spell out which measurements we should be taking, which I understand to be L only, R only, C only, L + Subs, C + Subs, R + Subs (in the context of this discussion). My understanding is that <300Hz should be shown with no smoothing and >300Hz with 1/6th smoothing. If I am wrong someone please correct me. I think a note as to why R+L or R+L+Subs are a no-no should be included.

 

My mistake was to look at R+L+Subs for the 'guide' to the room after all futzing was done. I shall go and measure again over the weekend using the new requirements. I'm kinda surprised we have gotten into 7000 posts and nobody has ever raised this before. Pretty much every FR graph I have posted has been 'wrong'.  Fortunately, these days I pay more attention to waterfalls, ETCs and spectros.

 

EDIT... actually, I have some good news... the OM graph I posted recently is labelled R+L+Subs - but I have just discovered that I mislabeled it - it is actually C+Subs, so I am good for that one!  It's this one, to save people going back...

 

Legend should read C+Subs, Aud On, DEQ Off, subs flat, Pgm2 (Submersive mode), 1/6th smoothing. I feel a bit better now :)



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post #6956 of 11856 Old 11-15-2013, 08:00 AM
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But for the 'end result' of what the room looks like, isn’t the R+L+Subs the right thing to do?
Your L/C/R speakers are placed at the 3 nulls of your 3rd width mode so that their interaction cancels/minimizes the first 5 width modes of your room: 54Hz, 108Hz, 161Hz, 215Hz and 269Hz. The 1st width mode is below the crossover point and being addressed by your dual subs.

How will you verify that the interaction between your L/C/R speakers is reducing the next 4 modes if you don't measure the interaction between your L/C/R speakers? Measuring L+R won't let you see that. Hence Nyal's suggestion to measure all 3 front speakers (and subs) to see what is happening in the modal range.

 

Got it!  Thanks, Sanjay.  I will change my measuring parameters accordingly.

 

@Jerry - 

 

Jerry, is all this stuff reflected in your Guide?  I have been well off-track it seems in that I have been giving significant attention to the wrong graphs and insignificant attention to the right ones. I feel I am almost back to Square One.

 

Geez, tell me about it (i.e. back to square one)!

 

Perhaps I'm the only one that was confused by Nyal's advice to you but is it clear now what we are supposed to use to characterize the status of the full frequency spectrum?  Is it a 15-20k Hz response that is 1/6 smoothed of the L+Sub, C+Sub and R+Sub?  Is this perhaps a reason to use the "averaging" option in REW to generate one FR that is a combination of all 3 FR's (but that seems like it could be very misleading depending on what's going on in the room)? :confused:

 

See my reply to Jerry. I don't know how to use the averaging thing so I never have. I naively thought that as I listen to L+R+C+Subs when listening, that is kinda what I should be showing - I now see why that isn't correct though, so progress has been made.



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post #6957 of 11856 Old 11-15-2013, 08:19 AM
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OK - after all the recent confusion (on my part) perhaps someone would care to comment on these graphs and help me understand what I can learn from them and what needs further attention.

 

L+SUBS:

 

C+SUBS

 

R+SUBS

 

BOTH SUBS ONLY

 

L+SUBS 

 

C+SUBS

 

R+SUBS

 

I have made the waterfalls to 325ms because that is where the ringing seems to start.

 

L+Subs <300Hz no smoothing

 

C+Subs <300Hz no smoothing

 

R+Subs <300Hz no smoothing

 

 

L+Subs, C+Subs, R+Subs <300Hz no smoothing

 

 

L+Subs full range 1/6th smoothed

 

C+Subs full range 1/6th smoothed

 

R+Subs full range 1/6th smoothed

 

L+Subs, C+Subs, R+Subs full range 1/6th smoothed

 

All of the above are with Audyssey on, DEQ off.

 

Are there any others that the panel would like to see?

 

TIA, Keith



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post #6958 of 11856 Old 11-15-2013, 08:24 AM
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See my reply to Jerry. I don't know how to use the averaging thing so I never have. I naively thought that as I listen to L+R+C+Subs when listening, that is kinda what I should be showing - I now see why that isn't correct though, so progress has been made.

Kinda like that old saying. The more you learn the more you realize you don't know!
So a L+R+Subs should never be done? I personally think a section or chart that lists the parameters of each measurement style would be helpful. Like a cheat sheet we can glance at and see spectrogram, waterfall, frequency response, etc...

But when measuring final response what combo do we use? Single left or right +subs?

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post #6959 of 11856 Old 11-15-2013, 08:25 AM
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It certainly makes sense measure individually to get a better idea

But if I'm going to say this is my final response then what combo? Perhaps there won't be, and just this is L or R or C with subs

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post #6960 of 11856 Old 11-15-2013, 08:26 AM
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See my reply to Jerry. I don't know how to use the averaging thing so I never have. I naively thought that as I listen to L+R+C+Subs when listening, that is kinda what I should be showing - I now see why that isn't correct though, so progress has been made.

I pity anyone picking up this thread, reading Jerry's Guide, and trying to understand why through 7000+ posts, a fair number of the graphs shown and discussed were corrupted by this comb filtering/short wavelength issue and are henceforth invalid.

So to get closure:
Are L/R+subs STILL valid for waterfalls and spectrograms in the < 300 Hz range?
For accessing frequency response of bass performance < 300 Hz, is it now, as per Nyal and Sanjay, valid to run a combined plot of L/C/R+subs as measured in that way, to capture the complete interaction of speakers for those wavelengths?

Stuart

 

Denon 4311 with XT32 and Audyssey Pro

Oppo 93 and 103

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Sherwood R-972 with its version of the Trinnov Optimizer

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PSB Imagine T2, Center, and Surrounds (as of 5/2014); HSU ULS-15 subs (2)

 

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