Simplified REW Setup and Use (USB Mic & HDMI Connection) Including Measurement Techniques and How To Interpret Graphs - Page 94 - AVS Forum
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post #2791 of 10862 Old 05-06-2013, 06:51 PM
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Quote:
Originally Posted by AustinJerry View Post

There are two drop downs.  Choose the second output in the drop-down under "Timing Reference Output".



Thanks for the info. I wasn't sure if that was used for other measurements and would skew results or not.

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post #2792 of 10862 Old 05-07-2013, 12:27 AM
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Quote:
Originally Posted by ironhead1230 View Post

Quote:
Originally Posted by Roger Dressler View Post

Hi Mike,

Did you check if polarity of the sub helps with the dips? Could try the old method: park a sine wave at the crossover frequency. Flip polarity and or tweak delays such that at one polarity you create the deepest null possible, then invert to obtain good summation. If the sub is at different distances from the L and R speakers, find the delays needed for both then split the difference.

The submersives do not have a polarity control. I can adjust the distance for each individual sub separately in the AVR.

-Mike


My AVR has a subwoofer polarity setting built into the AVR menu.

Does your AVR have a subwoofer polarity control that you may have not noticed?
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post #2793 of 10862 Old 05-07-2013, 11:37 PM - Thread Starter
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^^ Curious which AVR you have that has this feature?

Thanks to EVERYONE that Helps Make These Threads so Awesome!

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post #2794 of 10862 Old 05-08-2013, 02:47 AM
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Originally Posted by jevansoh View Post

^^ Curious which AVR you have that has this feature?

My Onkyo 5509 has a phase 0 / 180 degree setting, if that is what is meant. It's useless of course ;)

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post #2795 of 10862 Old 05-08-2013, 09:50 PM
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Originally Posted by Pres2play View Post

Jerry, here are the results. I did not have time to run a test with the sub on the floor.

The red line is with no room correction. The blue line shows Audyssey and Anti-Mode enabled. The difference with the stand is amazing, but what really worked was using the crossover settings established by Audyssey. Actually, the ones that worked for me are the fronts and center at 50 Hz and the surrounds set to 80. Will this ruin my amps???

I will post more tonight. Must leave for work.

Edit: I take back what I said about the stands making a difference. After a week moving subs around, calibrating and measuring, the sub response shows little change. In the image, the red line is with the sub on a stand; the black line is the sub on the floor.

What I have learned is that I have dip at 30, 60 and 125 Hz that's in every graph. Will have to figure this out.

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post #2796 of 10862 Old 05-08-2013, 11:00 PM
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Quote:
Originally Posted by Pres2play View Post

I have dip at 30, 60 and 125 Hz that's in every graph.
Divide the speed of sound by the second mode in your graph:

1130 ÷ 61 = 18.5

Remind me again, is one of your room dimensions anywhere near 18.5 feet?

Sanjay
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post #2797 of 10862 Old 05-09-2013, 02:19 AM
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Quote:
Originally Posted by sdurani View Post

Quote:
Originally Posted by Pres2play View Post

What I have learned is that I have dip at 30, 60 and 125 Hz that's in every graph. Will have to figure this out.

Divide the speed of sound by the second mode in your graph:

1130 ÷ 61 = 18.5

Remind me again, is one of your room dimensions anywhere near 18.5 feet?

Thanks, sdurani. That's right, the room is 18.5 x 10.5 x 9. The lenght side is also my front wall. One sub is located midway on the sidewall and the other is beneath the left speaker (see pic). The one beneath the front left speaker is 6.5 feet from the side wall, or ~1/3 of the way in.



The room is not that empty, BTW. There's a wall-size book case behind the couch on the right side of the room, and a small CRT stand beside the main couch on the other side. There are other placement constraints, as well, like the radiator and windows that you see on the bottom right corner of the picture

I took another look at the mode cal chart of my room, and the dips I mentioned (30, 60, 125) show they are directly related to modes. I think I'm screwed!

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post #2798 of 10862 Old 05-09-2013, 04:59 AM
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The 61Hz mode suggests placing a sub at the 1/4 spot might be better than the 1/3 spot.  Have you placed and measured a sub in that spot, perhaps next to the right front speaker?  The 59Hz mode associated with the room height could be exacerbating that dip as well, but it's pretty difficult to place a sub 4.75' off the ground.

 

Perhaps Sanjay will have some more useful suggestions.

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post #2799 of 10862 Old 05-09-2013, 07:51 AM
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You have three dimension all nearly multiples of each other. That makes for a tough room... Can you re-arrange the room?

"After silence, that which best expresses the inexpressible, is music" - Aldous Huxley
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post #2800 of 10862 Old 05-09-2013, 08:39 AM
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I haven't given 1/4 placement much consideration. I have that darn radiator blocking one corner of the front wall and on the other side there's a worm hole - no sub works there. That's where I had the twin ULS and the reason I decided to send it back. The equipment rack is there now. I'll try placing the sub in front of the radiator temporarily and see what kind of response I get.

Placing the sub higher is worth trying.

I have a question regarding DEQ. In the Onkyo 818, it seems to be on during calibration. If I turn it off, the new measurements show a drop in the low end. I'll put this question in the 818 thread.
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post #2801 of 10862 Old 05-09-2013, 08:47 AM
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Quote:
Originally Posted by Pres2play View Post

I took another look at the mode cal chart of my room, and the dips I mentioned (30, 60, 125) show they are directly related to modes. I think I'm screwed!
Why screwed? Just follow Jerry's suggestion and place your subs at the quarter points of room width (either on the front wall or back wall). That should take care of the modes below the crossover point (80Hz?). Above that point, your mode cal chart shows that placing your L/R speakers 3' in from the side walls should address the next two modes.

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post #2802 of 10862 Old 05-09-2013, 09:23 AM
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Quote:
Originally Posted by Pres2play View Post

I haven't given 1/4 placement much consideration. I have that darn radiator blocking one corner of the front wall and on the other side there's a worm hole - no sub works there. That's where I had the twin ULS and the reason I decided to send it back. The equipment rack is there now. I'll try placing the sub in front of the radiator temporarily and see what kind of response I get.

Placing the sub higher is worth trying.

I have a question regarding DEQ. In the Onkyo 818, it seems to be on during calibration. If I turn it off, the new measurements show a drop in the low end. I'll put this question in the 818 thread.

 

On every AVR with Audyssey I have owned, all internal settings are disabled when the calibration is running.  There is no reason to expect the 818 operates any differently.  Are you sure this isn't just slight variations between measurements?  How big a drop?

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post #2803 of 10862 Old 05-09-2013, 09:44 AM
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Originally Posted by DonH50 View Post

You have three dimension all nearly multiples of each other. That makes for a tough room... Can you re-arrange the room?

Thanks, Don. Rearranging the room is possible, I'm aware the MLP is far from ideal. I am resisting that for now, though, as rest of the family don't agree.
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post #2804 of 10862 Old 05-09-2013, 09:51 AM
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Originally Posted by sdurani View Post

Why screwed? Just follow Jerry's suggestion and place your subs at the quarter points of room width (either on the front wall or back wall). That should take care of the modes below the crossover point (80Hz?). Above that point, your mode cal chart shows that placing your L/R speakers 3' in from the side walls should address the next two modes.

Thanks. Will try.
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post #2805 of 10862 Old 05-09-2013, 10:11 AM
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Quote:
Originally Posted by AustinJerry View Post

On every AVR with Audyssey I have owned, all internal settings are disabled when the calibration is running.  There is no reason to expect the 818 operates any differently.  Are you sure this isn't just slight variations between measurements?  How big a drop?

Looks like I've been measuring with Dynamic EQ on all this time without realizing the low-end boost it provides. I guess that accounts for the somewhat flat response I got last week with the sub on the stand. With DEQ off, the true curve would have dropped off.
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post #2806 of 10862 Old 05-09-2013, 10:12 AM
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Quote:
Originally Posted by Pres2play View Post

I have a question regarding DEQ. In the Onkyo 818, it seems to be on during calibration. If I turn it off, the new measurements show a drop in the low end. I'll put this question in the 818 thread.

 

The 818, in common with all other Audyssey-equipped units, disables all forms of processing during the calibration. It would make no sense for DEQ to be enabled during a calibration and nobody in the 818 thread has ever reported such a thing - not even Markus or Igor who investigate everything very deeply. If you are seeing variations, it has to be something else that is responsible. As Jerry says, possibly different mic placements - even an inch or so will give different results on the graphs IME. 

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post #2807 of 10862 Old 05-09-2013, 10:13 AM
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Quote:
Originally Posted by Pres2play View Post

Quote:
Originally Posted by AustinJerry View Post

On every AVR with Audyssey I have owned, all internal settings are disabled when the calibration is running.  There is no reason to expect the 818 operates any differently.  Are you sure this isn't just slight variations between measurements?  How big a drop?

Looks like I've been measuring with Dynamic EQ on all this time without realizing the low-end boost it provides. I guess that accounts for the somewhat flat response I got last week with the sub on the stand. With DEQ off, the true curve would have dropped off.

 

Ah yes - a different thing entirely. You can easily, using REW,  measure with DEQ on by mistake - but you cannot do an Audyssey calibration with DEQ on.

 

It can be instructive to make a set of graphs with DEQ off (the usual way) and then a set with DEQ on so you can observe exactly what DEQ is doing. If you vary the level of the MV you can see how DEQ behaves as the SPL goes up and down (although strictly speaking this should be done via the preouts). 

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post #2808 of 10862 Old 05-09-2013, 10:28 AM
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Quote:
Originally Posted by Pres2play View Post

Looks like I've been measuring with Dynamic EQ on all this time without realizing the low-end boost it provides. I guess that accounts for the somewhat flat response I got last week with the sub on the stand. With DEQ off, the true curve would have dropped off.

Yes, having DEQ engaged during measurements, as Keith says, would make a difference. On my system, I see ~5dB gain in the bass frequencies with DEQ engaged.
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post #2809 of 10862 Old 05-12-2013, 05:19 PM
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Originally Posted by Pres2play View Post



Thanks, sdurani. That's right, the room is 18.5 x 10.5 x 9. The lenght side is also my front wall. One sub is located midway on the sidewall and the other is beneath the left speaker (see pic). The one beneath the front left speaker is 6.5 feet from the side wall, or ~1/3 of the way in.



The room is not that empty, BTW. There's a wall-size book case behind the couch on the right side of the room, and a small CRT stand beside the main couch on the other side. There are other placement constraints, as well, like the radiator and windows that you see on the bottom right corner of the picture

I took another look at the mode cal chart of my room, and the dips I mentioned (30, 60, 125) show they are directly related to modes. I think I'm screwed!


What software did you use for the mode cal?
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post #2810 of 10862 Old 05-12-2013, 07:37 PM
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What software did you use for the mode cal?

 

Hi Mark, nice to see you post here.

 

The Room Mode Calculator can be downloaded from the Harmon web site here.

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post #2811 of 10862 Old 05-13-2013, 05:40 AM
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Originally Posted by AustinJerry View Post

Hi Mark, nice to see you post here.

The Room Mode Calculator can be downloaded from the Harmon web site here.

Thanks Jerry. Good job on the guide by the way

FYI, ASIO4All didn;t work for me. I got the option to select individual channels, but no sound. I also managed to "solve" the problem of getting the play icon to appear on the appropriate device (your guide said there were no suggestions on trobleshhoting other than clicking on the device): I simply disabled all other playback and recording devices and REBOOTED, then I had the play icon on the device I wanted to use for input and output

Regards

mark
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post #2812 of 10862 Old 05-13-2013, 07:19 AM
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Quote:
Originally Posted by mark_anderson_u View Post


Thanks Jerry. Good job on the guide by the way

FYI, ASIO4All didn;t work for me. I got the option to select individual channels, but no sound. I also managed to "solve" the problem of getting the play icon to appear on the appropriate device (your guide said there were no suggestions on trobleshhoting other than clicking on the device): I simply disabled all other playback and recording devices and REBOOTED, then I had the play icon on the device I wanted to use for input and output

Regards

mark

 

Yes, the Guide should mention that re-booting sometimes clears issues immediately after an install.  However, since it is a beta product, it seems a bit unpredictable.  eek.gif

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post #2813 of 10862 Old 05-13-2013, 07:30 AM
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My latest mini-project is trying to understand and address room reflections that I am seeing in the ETC graphs.  Bryan Pape at GIK Acoustics suggested that I look at the Filtered IR tab, to which TBH I have not really paid much attention.  The REW Help on the tab is perfectly descriptive--unfortunately I don't completely understand it.  IIUC, the Filtered IR graphs allow us to see which frequency bands are causing the reflections, and thus assist us in selecting the appropriate type of treatment to address the issue.

 

 

 

 

 

 

Filtered IR.pdf 653k .pdf file

 

 

 

The above attachment shows several filtered IR graphs for my listening room.  The underlying REW measurements are for the left, right, and center speakers, taken individually (Audyssey off, although I don't think Audyssey affects reflections significantly).  There are four graphs for each speaker (identified by the legend at the bottom).  The graphs show filters at 250, 500, 1000, and 2000Hz.

 

While I am no expert in analyzing the filtered IR data, the graphs seem to show that reflections are clearly an issue at 250Hz, and get progressively less of an issue up to 2000Hz, where they don't seem to be an issue any more.  If any thread participants have additional insights on how to interpret the filtered IR data, or how to apply the data to fix the reflections issues, your feedback would be appreciated.  I have asked Bryan for feedback as well, and I'll share his response if appropriate.

 

Edit:  Initial feedback from Bryan is that the graphs are much too course.  I have generated new graphs and am waiting for his reply.

Attached Files
File Type: pdf Filtered IR.pdf (653.1 KB, 16 views)
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post #2814 of 10862 Old 05-13-2013, 08:33 AM
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Originally Posted by AustinJerry View Post

Yes, the Guide should mention that re-booting sometimes clears issues immediately after an install.  However, since it is a beta product, it seems a bit unpredictable.  eek.gif

The thing that did it for me was disabliong all other devices first. Wasted about an hour trying all sorts. Seems there should be a better way. Is ASI4ALL dead? been no updates for some time
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post #2815 of 10862 Old 05-13-2013, 08:38 AM
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Originally Posted by mark_anderson_u View Post


The thing that did it for me was disabliong all other devices first. Wasted about an hour trying all sorts. Seems there should be a better way. Is ASI4ALL dead? been no updates for some time

 

If you check the web page, I think the driver was developed as a hobby by someone in Germany.  What incentive the developer has to issue new releases or bug fixes is unclear to me.

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post #2816 of 10862 Old 05-13-2013, 08:48 AM
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Quote:
Originally Posted by AustinJerry View Post

My latest mini-project is trying to understand and address room reflections that I am seeing in the ETC graphs.  Bryan Pape at GIK Acoustics suggested that I look at the Filtered IR tab, to which TBH I have not really paid much attention.  The REW Help on the tab is perfectly descriptive--unfortunately I don't completely understand it.  IIUC, the Filtered IR graphs allow us to see which frequency bands are causing the reflections, and thus assist us in selecting the appropriate type of treatment to address the issue.






Filtered IR.pdf 653k .pdf file



The above attachment shows several filtered IR graphs for my listening room.  The underlying REW measurements are for the left, right, and center speakers, taken individually (Audyssey off, although I don't think Audyssey affects reflections significantly).  There are four graphs for each speaker (identified by the legend at the bottom).  The graphs show filters at 250, 500, 1000, and 2000Hz.

While I am no expert in analyzing the filtered IR data, the graphs seem to show that reflections are clearly an issue at 250Hz, and get progressively less of an issue up to 2000Hz, where they don't seem to be an issue any more.  If any thread participants have additional insights on how to interpret the filtered IR data, or how to apply the data to fix the reflections issues, your feedback would be appreciated.  I have asked Bryan for feedback as well, and I'll share his response if appropriate.

Edit:  Initial feedback from Bryan is that the graphs are much too course.  I have generated new graphs and am waiting for his reply.

How exactly did Bryan suggest your graphs could be improved? Is it just the presentation, or did you have to take fresh measurements? Does the measurement length help (128, 256, 512 or 1M)?
Regards, Mike.
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post #2817 of 10862 Old 05-13-2013, 09:06 AM
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I'm sure one thing is that the time reference is much to long to be able to see any granularity in the area that is most useful (0-40ms). The x-axis for time should normally be windowed to around 40ms, not 750ms as shown.
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post #2818 of 10862 Old 05-13-2013, 09:07 AM
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Originally Posted by AV_mike View Post


How exactly did Bryan suggest your graphs could be improved? Is it just the presentation, or did you have to take fresh measurements? Does the measurement length help (128, 256, 512 or 1M)?
Regards, Mike.

 

I didn't need to re-measure, just change the horizontal scale on the graphs to show a shorter time interval.  I am unaware that measurement length affects the results of this particular graph.

 

Edit:  Exactly, Fotto.

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post #2819 of 10862 Old 05-13-2013, 10:11 AM
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Quote:
Originally Posted by AustinJerry View Post

My latest mini-project is trying to understand and address room reflections that I am seeing in the ETC graphs.  Bryan Pape at GIK Acoustics suggested that I look at the Filtered IR tab, to which TBH I have not really paid much attention.  The REW Help on the tab is perfectly descriptive--unfortunately I don't completely understand it.  IIUC, the Filtered IR graphs allow us to see which frequency bands are causing the reflections, and thus assist us in selecting the appropriate type of treatment to address the issue.

The above attachment shows several filtered IR graphs for my listening room.  The underlying REW measurements are for the left, right, and center speakers, taken individually (Audyssey off, although I don't think Audyssey affects reflections significantly).  There are four graphs for each speaker (identified by the legend at the bottom).  The graphs show filters at 250, 500, 1000, and 2000Hz.

While I am no expert in analyzing the filtered IR data, the graphs seem to show that reflections are clearly an issue at 250Hz, and get progressively less of an issue up to 2000Hz, where they don't seem to be an issue any more.  If any thread participants have additional insights on how to interpret the filtered IR data, or how to apply the data to fix the reflections issues, your feedback would be appreciated.  I have asked Bryan for feedback as well, and I'll share his response if appropriate.

Edit:  Initial feedback from Bryan is that the graphs are much too course.  I have generated new graphs and am waiting for his reply.

Jerry,

Have you had a look at Nyal's article (first post below) and the full paper it is drawn from (second post below)?

It seems to me his methodology will help with your analysis.

Mark
Quote:
Originally Posted by Nyal Mellor View Post

I prefer looking at octave smoothed ETCs as per this article: listening room reflections and the energy time curve as it gives more data.

Quote:
Originally Posted by amirm View Post

The shorthand version quoted there can be quite misleading. I suggest reading Nyal and Jeff's paper instead: http://www.acousticfrontiers.com/static/513e1e34e4b00efcff5b05fd/51523db2e4b05218a1268532/51523db3e4b05218a126876f/1340681100537/acoustic_measurement_standards.pdf. Go to page 5 and notice this:

"Be downto *10dBby 40ms to prevent breakdown of the precedence effect"

Note the 40 msec criteria. In other words, he is saying make sure you don't hear reflections as distinct echos. This is not a criteria meant for suppression of reflections for the sake of it.

He also makes the important point which was mentioned earlier in this thread that you cannot trust ETC measurements to provide reliable data for this purpose:

"A popular approach issimply to analyze the level ofreflections on an ETC and compare these to the
direct sound,setting a target for the reflections to be 10dB or more less than the direct sound. This
analysis is not sufficient since ETCs are spectrally blind (i.e.they contain no information as to the
spectral content ofthe reflected sound) and the auditory system is very discerning in its requirements
for spectral balance between the direct and reflected sounds in a room."
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post #2820 of 10862 Old 05-13-2013, 11:39 AM
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Originally Posted by AustinJerry View Post

My latest mini-project is trying to understand and address room reflections that I am seeing in the ETC graphs.  Bryan Pape at GIK Acoustics suggested that I look at the Filtered IR tab, to which TBH I have not really paid much attention.  The REW Help on the tab is perfectly descriptive--unfortunately I don't completely understand it.  IIUC, the Filtered IR graphs allow us to see which frequency bands are causing the reflections, and thus assist us in selecting the appropriate type of treatment to address the issue.






Filtered IR.pdf 653k .pdf file



The above attachment shows several filtered IR graphs for my listening room.  The underlying REW measurements are for the left, right, and center speakers, taken individually (Audyssey off, although I don't think Audyssey affects reflections significantly).  There are four graphs for each speaker (identified by the legend at the bottom).  The graphs show filters at 250, 500, 1000, and 2000Hz.

While I am no expert in analyzing the filtered IR data, the graphs seem to show that reflections are clearly an issue at 250Hz, and get progressively less of an issue up to 2000Hz, where they don't seem to be an issue any more.  If any thread participants have additional insights on how to interpret the filtered IR data, or how to apply the data to fix the reflections issues, your feedback would be appreciated.  I have asked Bryan for feedback as well, and I'll share his response if appropriate.

Edit:  Initial feedback from Bryan is that the graphs are much too course.  I have generated new graphs and am waiting for his reply.

I wouldnt worry about the 250hz response in that your down in the modal area and what you are seeing is partly/mostly that.

Even at 500hz, with 1 oct bandwidth, a bit of modal data is present.

In a nutshell, having them all run together is nice in a perfect world. But in the world we live, its basically routine for the lower slices to have higher early data.

Now, modal issues are certainly relevant, but a different animal entirely. The ETC isnt the best tool for assessing them.

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