# Waterfall graphs too tall



## pgisclair (Mar 9, 2010)

My waterfall graphs appear initially as a solid wall that I then have to cajoule and scale every which kind of way to get something usable. I can't ever see above the waveform.

I've tried lowering the volume, changing the SPL meter setting, and changing every conceivable setting. If I lower settings I get "Input level too low".

I am using a recent Radio Shack SPL meter into a Lynx Aurora.

Any suggestions?


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## Moonfly (Aug 1, 2008)

Can you post the graphs for us to see.


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## pgisclair (Mar 9, 2010)

Here they are.


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## Moonfly (Aug 1, 2008)

WOW, thats a new one on me. Can you put the scale back to normal and post that up, I cant really make head nor tail of that one.


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## laser188139 (Sep 19, 2009)

You would expect the waterfall graph at time slice 0 to be very close to the frequency response curve. So you could post your frequency response curve, and the waterfall at slice zero. How do these compare? 

Do you see the same anomaly when you generate the spectral decay graph? 

One thing that happens is that REW initially displays the frequency response curve that it generated when it measured the data. For the waterfall graph, etc., it has to go back to the raw data and re-analyze the impulse. Did you happen to change computers when generating the waterfall? Sometimes people have weird results because they are using a different soundcard or mic calibration file for the analysis than were used when the measurement was taken. 

Like Dan, I find your graph very peculiar. Have you verified that the Java runtime installed on your system is current? 

Bill


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## JohnM (Apr 11, 2006)

Put the Y axis slider back to 100 and the Z axis slider back to 150.


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## pgisclair (Mar 9, 2010)

I figured out the problem. My monitor is rotated to Portrait mode and I'm running 1200 x 1920. I rotated it back to Landscape and at the good ole' 1024 x 768 it displays the waterfall correctly (after re-generating). I've attached a couple of graphs. I don't know if my room modes are horrible, [only] bad, or OK. How drastic do you think my room modes are based on these graphs? Is this enough info? Any tips on interpreting what I'm seeing? It seems that I have problems at 82 and 142 Hz, and a null around 220. Is fixing this simply a matter of putting more bass traps behind my listening position?

Thank you for all your help, it is really appreciated! 
Perry


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

Welcome to the Forum!

Unfortunately, your waterfall still looks funky. It doesn’t show a smooth signal decay, it “hangs” for a period, then drops like a cliff. Try John’s suggestion of setting the Y axis to 100 and the X axis to 150. It does appear that you have a couple of room modes, though. I assume this is a measurement of your main speakers, not a subwoofer?

Regards,
Wayne


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## JohnM (Apr 11, 2006)

In the Analysis Settings make sure the "Spectral decay Left" window type is set to Hann.


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## pgisclair (Mar 9, 2010)

I'll adjust the Y and X axes tonight, and double-check the Hann setting. I have Yamaha HS50M monitors and HS10W subwoofer. I assumed I had to have both on since that's how I'm mixing. Should I turn the mains off and test only the sub, with the Sub settings?


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

Waterfalls are only valid for the bass, IIR - no higher than ~300 Hz (someone correct me if I have the upper frequency wrong?). So you can run both the subs and mains, but I'd do it with one main only, not both.

Regards,
Wayne


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## glaufman (Nov 25, 2007)

Not sure I agree there... please explain.


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

Sure - which part?

Regards,
Wayne


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## glaufman (Nov 25, 2007)

Um... the part about waterfalls not being valid above some frequency. I can see how they might be difficult to read, or better info could be gleaned from RT60s, but "invalid?":scratch::reading:


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

Just repeating what I’ve seen John state here in the past (although I forget the relevant upper frequency. Waterfalls are best suited for identifying room modes, which are not present in the upper frequencies. Kinda hard to do a search to verify, but I did come up with this:


JohnM said:


> For full range work the Energy-Time curve is useful for showing reflections, which appear as spikes in the response after the initial peak, and the RT60 curves help to show whether the balance of damping in the room is appropriate. The frequency response with 1/3 octave smoothing applied gives an indication of overall balance but for a true representation you would need a calibrated microphone and take care about the orientation of the mic relative to the speaker being measured.
> 
> For low frequency measurements the waterfall and spectral decay plots help show modal resonances and the unsmoothed frequency response shows how even the low end is, peaks in the response are generally due to room resonances. The RTA plot can be very useful when moving things around to see how positioning (of speakers or listener) affect the result.



Regards,
Wayne


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## JohnM (Apr 11, 2006)

The waterfall can be used full range, but that is generally to look at effects of the speaker itself (drive unit resonances, panel resonances) rather than room acoustics. Much shorter windows and much lower time ranges are needed for high frequencies though, V4.11 doesn't allow these parameters to be set low enough for general use at high frequencies.


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## glaufman (Nov 25, 2007)

Interesting. As for the effective frequency, how's the Schroeder frequency for a given room as a cutoff?


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## glaufman (Nov 25, 2007)

I would've thought the shorter windows at higher freqs were more to eliminate reflections for looking at speaker response?

So is it simply a matter of watefalls being to complicated to easily read the room effects at the higher frequencies, where the (generally) simpler looking RT60s give "enough" of the info to draw conclusions?


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## JohnM (Apr 11, 2006)

glaufman said:


> Interesting. As for the effective frequency, how's the Schroeder frequency for a given room as a cutoff?


Good as any 



glaufman said:


> I would've thought the shorter windows at higher freqs were more to eliminate reflections for looking at speaker response?


Yes, but also because the timescale of the effects is much shorter at higher frequencies (when looking at speaker behaviour) 



> So is it simply a matter of watefalls being to complicated to easily read the room effects at the higher frequencies, where the (generally) simpler looking RT60s give "enough" of the info to draw conclusions?


More or less


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