# RS SPL meter cal data different on other sites/forums??



## lorkp (May 26, 2010)

Why do other sites have different calibration data for the old analog RS SPL meter?

http://www.avsforum.com/avs-vb/showthread.php?t=505236

The sites linked to from the avsforum agree on:
10Hz -20.5
12.5Hz -16.5
16Hz -11.5 

and so on...but the cal file linked to in the REW forum sticky has:
10Hz -37.2
12.5Hz -27.15
16Hz -20.63

Why is the calibration data posted on the REW forum vastly different?


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## glaufman (Nov 25, 2007)

Not all the sites in that thread have the same cal data. One never even had a correction more than 5dB.
I can't vouche for how they obtained their data, but since a few of them match EXACTLY, it's an easy guess that they all copied the data from one source. Meaning that this data should be treated as one source, not as many different sources agreeing.
Our downloads page has different cal files for different models of RS meters. One of them comes much closer to agreeing with what you see elsewhere. It is my guess that this model is what everyone else used for their values. 

This also shows the inconsistencies of these meters when used as mics over different serial numbers, and reinforces the idea of getting a mic individually calibrated if you're after the utmost in accuracy.

If you prefer the idea of using the generic, it's completely up to you whose data you use to correct it.


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## lsiberian (Mar 24, 2009)

I'd go with what they got listed here.


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## JohnM (Apr 11, 2006)

The cal files were derived by comparing results of various RS meter samples and models against a professionally calibrated mic, more info here.


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## Speedskater (Dec 23, 2007)

The analog meters were manufactured for decades. Probably in different factories using different manufacturing techniques, processes and parts. I'd be amazed if all the response curves were the same.


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## lcaillo (May 2, 2006)

The reason for calibration is that devices vary. As mentioned above, some may be produced very differently over time. All test instruments must be individually calibrated to be reliable. The calibration data that you find in these files are simply estimates based upon comparison of one or more meters to a reference mic, and your meter may be very different than either. The process used to make the comparison will vary considerably as well, making it very hard to rely upon many of these data for offsets for your meter. At best using such data files will get you closer to a reference response, at worst, it could make it worse. The data here are probably some of the best in general, but you still have to understand the limitations of transferring response data offsets across individual meters.


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## lorkp (May 26, 2010)

Thanks for the info, guys


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