Reconciling the waterfall plots from REW with those published on GR Research (CLIO Analysis)

[Panash]

I'm not sure how easy it is to see the waterfall spectral decay aptured fro the GR Research video is but the "Z" axis is 0ms to 4ms and the REW is 0ms to 300ms. Which one is correct?
My REW is 12th octave smoothed.

 

[John Mulcahy]

They are both correct, but they have different uses. The longer duration REW waterfall view helps view room resonances, the shorter duration CSD plot helps see driver and speaker resonances. To generate a similar CSD view in REW use settings such as these:

 

[Panash]

Wow, what a difference! What is CSD Mode? Is the "ridge" at 200Hz a windowing artifact as I see the chart you puplished also had a similar ridge? Is this response good, bad or indifferent?

 

[Panash]

I've put the cursor on 7.03KHz. Can we print the profile or identify the time & attenuation of any point along the time section? Measuring the time & attenuation at the point at which the ridge juts out would be useful for comparison.

 

[John Mulcahy]

CSD = Cumulative Spectral Decay. With a CSD plot the right hand side of the window stays fixed and the left side moves with each slice, so the window gets narrower and the corresponding minimum frequency gets higher. See the help for more details. The V5.40 builds have a 3D option that provides a more flexible view and shows more information at the cursor position.

 

[Keith_W]

That ridge at 200Hz is an artefact caused by the short duration of your waterfall. Think of it like this: you are displaying the first 4ms. This means that any sound with a period longer than 4ms can not be displayed in full.

Frequency = 1/period (f = 1/T)

Therefore f = 250Hz.

It's the audio equivalent of the Heisenberg Uncertainty Principle. The more time resolution you gain, the more frequency resolution you lose. All because frequency = 1/time.

 

[Panash]

I just can't get over how good this program is. I did make a donation a while ago but I don't know it was enough now.

 

[Panash]

CSD = Cumulative Spectral Decay. With a CSD plot the right hand side of the window stays fixed and the left side moves with each slice, so the window gets narrower and the corresponding minimum frequency gets higher. See the help for more details. The V5.40 builds have a 3D option that provides a more flexible view and shows more information at the cursor position.

View attachment 95759

I'll download it now. I see that the calibration aligns properly with the grid now

 

[DY2]

pentru mai multe detalii. Versiunile V5.40 au o opțiune 3D care oferă o vizualizare mai flexibilă și afișează mai multe informații la poziția cursorului.

Îmi place versiunea 3D a Windows 11, am mai multe perspective de vizualizare.
Pe Linux pot instala doar o versiune primitivă de REW, de ce?

 

[John Mulcahy]

On linux I can only install a primitive version of REW, why?

If you are installing the build without a runtime you will need to install a Java 11 or Java 17 runtime for 5.40.

 

[Panash]

I know I'm guilding the lilly now but I've been stumling around the house this afternoon unable to get over how good this program is.