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This past weekend Spectralissime to monitor an outdoor concert. I had it set for ISO mode so it was displaying RMS SPL. It worked splendidly. I recorded it's output, overlaying it on a video stream of the stage.

I also used a standard logging SPL meter (3M) to keep track of the simple loudness, expressed as db(A).

The RMS SPL shown by Spectralissime doesn't match the 3M meter, presumably because one is A weighted and the other unweighted. Technically that's known as Z-weighted.

Given that I have a recording of the Spectralissime screen, so I can see levels of the 60 RTA bands, is there any formula by which I could derive an A-weighted SPL measurement?

Would you consider adding weighting to Spectralissime?

thanks for your feedback, we will add A-Weighting soon i guess...
(BTW: for SPL measure, you have to calibrate your microphone - see user manual use case #1)

Feel free to report the SPL difference between our analysis (without weighting ) and normalized tools. we firstly did it for that
because we would like to encourage sound engineers to watch true level and appreciate the sound quality/balance with their ears.

We think that A-weighting is leading sound engineers to setup P.A. system with something around +20dB in bass/sub and +6 to +10db in the range 1k -5kHz...

Yes, I used a MiniDSP UMIK-1 microphone and a calibrator. The calibrator exactly fits the mic head. It generates a 1kHz tone at 114 db and 94 db. I was able to calibrate the software to within 0.1 db.

I appreciate that production work (broadcast, PA, recording) demands unweighted measurement. Actually, the standard is now called "Z-weighted," which specifies flat from 10 Hz - 20 KHz (+/- 1.5 db)

Environmental noise analysis is quite different. A-weighted measure is the norm.

Is it correct to think that the A-weighted filter might be applied to the overall SPL measurement, separate from the RTA measure?

That is, the meter on the extreme right could be set to display A-weighted, independent of multi-band display? If so then perhaps mere adding an optionl a-weighted meter would be an approach?

Having considered it further, both displays should read the same; A, C or Z-weighted. To do otherwise would be silly.

My project is ongoing over the next few months. Leads to the question of when A-weighted measure might be available?

should be done before end of May...

Any news on this? I have another day of monitoring scheduling this coming weekend.

Incidentally, there are three of us with Board Spectralissime licenses engaged in this project. The other two have followed my lead.

i should do this in the next week...
see download link on our facebook/g+