# CEA 2010 Subwoofer Measurements



## littlemike (Sep 17, 2008)

Would it be possible to include this in a future REW release? Though I have only glanced at the requirements, the few measurements I have seen convey quite a bit of information in a single plot. It seems like this could be implemented in the Spectrum section of REW without too much additional effort.

As I understand the technique, this would require having something like the 6 CEA signals as a source (6.5 cycle tone-bursts centered at 20, 25, 31, 40, 50, and 63 hz that repeat at one-second intervals), then making a series of spectrum measurements with each of the test tones where the drive level is raised until the distortion threshold is met, then recording the SPL at that point, as well as saving the spectrogram with SPL and distortion data. 

Using instructions I found at Linkwitz's site, I have created similar tones, though I am still working on the proper periodic spacing. REW already "hears" these tones, plots the spectrum, and calculates distortion. I know that I can save a spectrogram, as well as export the raw data as a text file. I can also do the post-processing and plotting in Excel without too much difficulty. The problem I have is that I can not "see" the limits while I am testing - but rather figure out I was over the limit after the fact.

The CEA 2010 distortion threshold is normalized to the input signal. My understanding of the limits are as follows (fo = test frequency, 2nd = 2*fo, and so on):

fo 0 dB
2nd -10 dB
3rd -15 dB
4th -20 dB
5th -20 dB
6th -30 dB
7th -30 dB
8th -30 dB
9th and higher -40 dB

The "steps" in the lines are a little different, and appear to be as follows based on a close look at a few plots:

0 dB from fo to 1.5 fo
-10 dB from 1.5 fo to 2.25 fo
-15 dB from 2.25 fo to 3.33 fo
-20 dB from 3.33 fo to 5.66 fo
-30 dB from 5.66 fo to 8.5 fo
-40 dB thereafter

Anyhow - if this is something that could be integrated into REW without considerable effort, it would be a tool appreciated by many users of this software. Though I am no programmer, if you feel that there is anything I can do to assist, by all means drop me a note.

Finally, thank you very much for your efforts, REW is an exceptional tool.


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## JohnM (Apr 11, 2006)

To display the limits on the RTA graph you could create and import a set of simple SPL vs frequency text files and select the appropriate imported measurement before generating the tone, it will then appear on the RTA plot to act as a reference.

Automating the whole process would be a fairly significant effort, can't see it getting to the top of the list any time soon.


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## littlemike (Sep 17, 2008)

That's how I am approaching it for now. I've calculated appropriate values for each frequency and have them saved as text files ready to be imported before each measurement.

Thanks for the response, and thanks again for the work you've done.


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