# How to create the waterfall plot



## Guest (Jun 9, 2008)

I was wondering if it is possible to create the waterfall plot uisng REW
from the FR plot. i.e I have the FR plot (db vs Hz) and from that
can I create the decay plot. I read that it is possible to convert the waterfall
plot to FR plot uisng fourier transformation (which is built into those free softwares). But I dont know if the inverse is true. i.e can I create the waterfall plot from the FR plot. If not, is there an easy way to create the waterfall plot and what kind of measurements I need. Looking at the REW, it seems like I need to measure the response due to an impulse but I dont know how to do that. All I have right now is the Radio Shack SPL meter.
Are there test tones that I can download to create the waterfall plot?


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## JohnM (Apr 11, 2006)

Waterfall plots cannot be generated from imported frequency response measurements. To generate a waterfall you need to use REW to make the measurement. The help files in REW and the posts on this forum explain how to do that.


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## Guest (Jun 14, 2008)

JohnM said:


> Waterfall plots cannot be generated from imported frequency response measurements. To generate a waterfall you need to use REW to make the measurement. The help files in REW and the posts on this forum explain how to do that.


could you point me to the posts that explain how to get the measurements to make the waterfall plots.

I see an option to import the impulse response in REW so I presume that the impulse response can be measured outside REW and then imported just like I did for the FR.


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## Guest (Jun 14, 2008)

like I said there is an option to import impulse response in REW just like importing measurements. So there has to be a way to separately measure the impulse response (outside REW) and import it into REW. This is the information I am looking for as I cant bring the PC to my living room to do any measurements using REW.


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## brucek (Apr 11, 2006)

> could you point me to the posts that explain how to get the measurements to make the waterfall plots.


The REW HELP FILES explain how to measure with REW.



> This is the information I am looking for as I cant bring the PC to my living room to do any measurements using REW.


How far away is it? Maybe you can simply run cables. 

brucek


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## Guest (Jun 14, 2008)

brucek said:


> The REW HELP FILES explain how to measure with REW.
> 
> 
> How far away is it? Maybe you can simply run cables.
> ...


well it is not the distance. When I hook up the PC there is this hum so I 
could not do any measurement. 

To make the impulse measurement do I still have to connect the BFD and go through all the
loopback measurement etc. I went through the help in REW and it does not clearly explain how to make the impulse response measurement. 

In my opinion REW is written for experts who have PhD in acoustics but not for an average audio enthusiast


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## brucek (Apr 11, 2006)

> When I hook up the PC there is this hum so I could not do any measurement.


Yeah, computers are notorious for producing hum when connected to a system. Usually a cheater plug will cure that problem, even though it certainly is not recommended for permanent use, it is sometimes needed for REW sessions only.



> do I still have to connect the BFD


Certainly not.... although you have to calibrate the soundcard with a loopback (which is then removed, once calibrated). You can do that part before moving the PC.



> I went through the help in REW and it does not clearly explain how to make the impulse response measurement.


When you take a measurement, the impulse is produced.

brucek


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## Guest (Jun 15, 2008)

brucek said:


> Yeah, computers are notorious for producing hum when connected to a system. Usually a cheater plug will cure that problem, even though it certainly is not recommended for permanent use, it is sometimes needed for REW sessions only.
> 
> 
> Certainly not.... although you have to calibrate the soundcard with a loopback (which is then removed, once calibrated). You can do that part before moving the PC.
> ...


so I do the regular measurement like the
frequency sweep and then REW produces the impulse?


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## brucek (Apr 11, 2006)

> so I do the regular measurement like the frequency sweep and then REW produces the impulse?


You take a measurement with REW and that measurement results in the impulse response, that in turn automatically produces the frequency response (and all the other types of responses including Spectral Decay, RT60, Energy Time).

To hookup all the cabling etc, use this Guide.

brucek


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## Guest (Jun 15, 2008)

brucek said:


> You take a measurement with REW and that measurement results in the impulse response, that in turn automatically produces the frequency response (and all the other types of responses including Spectral Decay, RT60, Energy Time).
> 
> To hookup all the cabling etc, use this Guide.
> 
> brucek


but what measurement. Measure what?


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## brucek (Apr 11, 2006)

> but what measurement. Measure what?


I'm having a bit of trouble understanding your question. 

Let's start over. What is it you're attempting to do?

brucek


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## Guest (Jun 15, 2008)

brucek said:


> I'm having a bit of trouble understanding your question.
> 
> Let's start over. What is it you're attempting to do?
> 
> brucek


ok. I have created the FR plot from the measurements I manually made using SPL. I used the test tones from this web site and to get the FR from 25 to 200Hz. I put the bass traps in 3 corners and made the measurements again. I didnt see much difference. People told me that even though the peaks/nulls have not changed much, the reverberations would have reduced thus improving the bass response. I do hear less boominess but it is not gone completely. See the FR before and after bass traps.

So to see how bad the reverberations are I would like to create the waterfall plots.
I am not using BFD at all. I just need to create the waterfall plot. This is what I have been asking in so many threads here and at AVS forum and so far I have no clue as to how to get this waterfall plot. 

No I am not asking how to make the waterfall plot from the FR data.

Also, I see in REW an option to import the impulse response. So I understand that
it is possible to measure the impulse response and can import that into REW.
Like I said the main problem with using REW hooked up to a PC and AVR is the hum and
I just cant use it like that. I dont like to risk using the cheater plug. 

I dont care much about the soundcard calibration as I know its response is flat. I did the soundcard measurement inside REW and it is flat. I am also not a purist. So if the soundcard adds a few db's no problem. I just need some idea what the waterfall looks like for my room.


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## brucek (Apr 11, 2006)

> This is what I have been asking in so many threads here and at AVS forum and so far I have no clue as to how to get this waterfall plot.


OK.

I'll talk about REW for a second.

Once you have connected your soundcard to your receiver and have the SPL meter plugged in properly (and its calibration file loaded) and have gone through the Check Levels routine on the REW Settings page, and the Calibrate SPL routine, you are ready to take a measurement of your system.

Pressing the Measure icon in REW will go through a routine that sweeps a signal through your system that the SPL meter reads and produces an impulse response. You can look at that response on the Impulse response tab. REW automatically creates a frequency response graph on the Filter adjust tab. You aren't interested in these. You want Waterfall, but you had to go through the measurement routine as I described to get to this point.

Click the Waterfall tab. Click the icon at the top right hand corner of REW called FreqAxis, so that the axis is changed from LIN (linear) to LOG (logarithmic). Click the icon at the top right hand corner of REW called Graph limits and change the bottom/top formfill to 45dB and 105dB, and change the left/right formfill to 15Hz and 200Hz.

Press the button at the bottom of the Waterfall tab page called *Create Waterfall*. You now have a waterfall.

You may now play around with the controls on that page to get the look you want.

Clear? 

brucek


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## Guest (Jun 15, 2008)

brucek said:


> OK.
> 
> I'll talk about REW for a second.
> 
> ...


yep. Thanks a lot. now if could only get rid of the hum I can get the
waterfall plot


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