# REW Noob - smooth waterfall, but slow decay?



## Robertsmania (Jan 20, 2013)

I'm trying out REW, and am interested in hearing if you guys have insight into what I'm seeing with my waterfall graph.

I've used other RTA software, but this is my first attempt with REW so apologies up front if I'm making silly mistakes.

Here is the waterfall for my right channel:








I've sifted through the forums and searched around for tips on how to interpret waterfall charts, and am honestly a little confused.

What it looks like to me is that the decay is pretty even across the frequency range, but is very gradual with lots of volume even after 300ms.

The bare frequency response graph looks like this:








Should I be concerned about the decay time, or are there other issues that jump out at you guys?


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## Robertsmania (Jan 20, 2013)

Oh, and the data file is here:
http://robertsmania.com/stereo/130125_01_Side_Subs_Right.mdat (2.7Mb)


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## Robertsmania (Jan 20, 2013)

Figured out how to include the images as attachments in the initial post...:sarcastic:


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## AudiocRaver (Jun 6, 2012)

First of all, welcome to Home Theater Shack.

Looks pretty nice. With one-third octave smoothing, your response is about plus/minus 3 dB between 100 Hz and 10 kHz, very respectable.

The RT 60 (decay time) does seem a bit high. Values around .2 to .3 are good goals to shoot for, this room is closer to .6 to .8 or so, very live.

Have you done any equalization yet? The peaks at 28, 58, 88, and 125 Hz could be tamed a little with some EQ, if they bother you.

Other than that...:T

How does it sound?


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## JohnM (Apr 11, 2006)

There are a few tips on settings for graphs here: http://www.hometheatershack.com/forums/rew-forum/934-please-read-posting-graph.html

Best to set the frequency axis for your waterfall to log rather than linear (use the freq axis button top right of the graph) and focus on the range up to 200Hz or so.


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

Robertsmania said:


> I've sifted through the forums and searched around for tips on how to interpret waterfall charts, and am honestly a little confused.


 For starters, waterfalls are only meaningful up to about 400 Hz or so. IOW, they’re primarily for the lower frequencies,

And as John mentioned, scaling the graph properly would be helpful, except for a waterfall you want the lower limit close to the room’s noise floor. In most rooms that’s ~30-35 dB, not 45 dB.

You might find some useful general info on waterfalls at this post.




> Should I be concerned about the decay time, or are there other issues that jump out at you guys?


Waterfalls are mainly useful for comparing “before and after” to see the effectiveness of low frequency room treatments.

Regards, 
Wayne


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## AudiocRaver (Jun 6, 2012)

I declare an "oops" on my RT60 comment earlier, it is around 0.4 above 150 Hz, quite respectable, not sure what I was looking at before.:huh:


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