# REW Interpretation



## calmposer (May 31, 2013)

Hi all,

Firstly thank you to the creators and moderators of this forum. I downloaded Room EQ Wizard and ran a test of my (imperfect) room with a Behringer ECM8000.

So far I found information regarding performing the test, but not much about interpreting the graphs. Can anyone point me in the right direction? Should a perfect room yield even SPL and reverberation time across the spectrum?

Can anyone show me graphs of a well treated room? 

Attached is my measurement.

Thanks a lot onder:


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## Wayne A. Pflughaupt (Apr 13, 2006)

calmposer said:


> Should a perfect room yield even SPL and reverberation time across the spectrum?


Theoretically yes, but I guess you know that there is no such thing?

Assuming best-practices measurement equipment and technique (e.g. custom calibrated mic with a 0-degree calibration file and measured pointed at the speaker), looking at the 1/3-octave smoothed graph you have what I’d call “haystacked” response: Lots of midrange with reduced energy in the highs and lows.

All the comb filtering seen in the unsmoothed graph is typical for residential living spaces, yours looks better than some I’ve seen, indicating you’re getting some “free” acoustical treatment from common room furnishings, rugs, etc.
















​

Regards, 
Wayne


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## calmposer (May 31, 2013)

Thank you Wayne! Would you mind sending a graph or a well-treated room so I can compare?

Luckily I'll be moving to a new room - similar size to this one (c 3x4 meters) but much more absorbent.

I'll be calling the GIK acoustics people for advice and products, but would like to educate myself as much as possible at this point.

Neil :whistling:


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## calmposer (May 31, 2013)

*of a well treated room


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## Wayne A. Pflughaupt (Apr 13, 2006)

Here are a couple of graphs of a live and well-dampened room. As you can see, you’re somewhere in between. Before you go hog-wild getting treatments, you might want to review this article and this post.









*Live Room








Well-Dampened Room*​

Regards, 
Wayne


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## calmposer (May 31, 2013)

Thank you Wayne, great article - I read this in detail, as well as his other two about low frequencies and dynamic range.

The SPL range between, say, 1-2khz in my current room is around 25db. Your live room is around 40db, and the well-dampened room is just under 20db. when you say 'you're somewhere in between' is this what you mean?

Amir points out due to computers' over-analysis comb filtering in a pre-smoothed graph is inevitable (it looks like your graph of a well-dampened room has a lot of mini comb teeth too). And even more, that we're unable to hear comb filtering at this resolution. Should we use an unsmoothed graph for analysis in the first place?

It looks as even in a smoothed graph of your treated room there would still be a dip about 3-4Khz. Is this a problem? As this is well over the transition frequencies should this be put down solely to the speaker/amp?

Thanks a lot


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## Wayne A. Pflughaupt (Apr 13, 2006)

calmposer said:


> The SPL range between, say, 1-2khz in my current room is around 25db. Your live room is around 40db, and the well-dampened room is just under 20db. when you say 'you're somewhere in between' is this what you mean?


Not exactly. We’re not looking for the “deepness” of the comb filtering so much as the _amount_ of it (although the two are related). As you can see in the green ("Live Room”) graph, there is so much comb filtering that it all bleeds together and you have the big green “glob” between 2-10kHz. In the teal (“Dampened”) graph you have very little of that, only between ~2.5-4.5 kHz. By contrast your graph shows your room is better dampened than the green graph, but not as well as the teal graph. Make sense?




> Amir points out due to computers' over-analysis comb filtering in a pre-smoothed graph is inevitable (it looks like your graph of a well-dampened room has a lot of mini comb teeth too). And even more, that we're unable to hear comb filtering at this resolution. Should we use an unsmoothed graph for analysis in the first place?


Depends on what you intend to do with the information. For main-channel equalizing you definitely want to smooth, as it would be impossible to EQ from an unsmoothed graph. For gauging the results of new treatments unsmoothed would be better (along with additional acoustics-related measurements such as ETC that REW can generate).




> It looks as even in a smoothed graph of your treated room there would still be a dip about 3-4Khz. Is this a problem? As this is well over the transition frequencies should this be put down solely to the speaker/amp?


Yes to both. Treatments tame reflections but have little effect on frequency response (beyond perhaps an overall attenuation of the highs). 

For example, see the picture below. The top row shows the frequency response of an untreated room, while the bottom row shows the same room treated. As you can see, the bottom row still shows frequency response issues that are severe enough to be audible. That's coming from the speaker itself. (BTW, If smoothing had been applied to the top-row graph it would look like the bottom-row graph.)







​

Regards, 
Wayne


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## calmposer (May 31, 2013)

Thanks Wayne - very clear! Can you share where the last picture came from?

And can you share graphs of other well-treated spaces (or even .mdat files if possible)?

I can probably take it from there (I hope so anyway)

Thanks!

Neil


PS I know there are things posted in forums but it's hard to tell what's reliable and what's not


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## Wayne A. Pflughaupt (Apr 13, 2006)

I got the last picture from a thread a the AVS Forum a few years ago. I don’t have any more graphs; you might try scouring our Acoustics forum for some. You can also get other info there relating to other acoustics-related graphs that REW can generate.

Regards, 
Wayne


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## JohnM (Apr 11, 2006)

If you are willing to spend some time reading I highly recommend The Master Handbook of Acoustics, has everything you need to know and a whole lot more in a digestible format.


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## calmposer (May 31, 2013)

Thank you John I am willing to buy this! Are there alternate books I should consider? I'm essentially after a reliable source for graphs and theory, with emphasis on practicality (I'll be working on my new room later this month). Neil


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## JohnM (Apr 11, 2006)

Another one to consider is Rod Gervais' book Home Recording Studio - Build it like the pros


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## calmposer (May 31, 2013)

Thanks John

The Master Handbook of Acoustics is very thorough but probably too theoretical. 

I'm inclined to get the latter, (my new room won't be a residential space though). Is there anything else along those lines you can additionally recommend?

Neil


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## JohnM (Apr 11, 2006)

I'm sure there are many, but I don't know the titles. Here are a few online guides that may help:
MiniDSP acoustic measurement article using REW and UMIK-1,
Realtraps Room Measuring Series, 
Bass integration guide,
Quickstart guide to bass measurements.


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