TBProAudio releases dpMeter II - Free Digital Precision Meter Plugin including Loudness Matching

[TB-ProAudio]

I noticed the A curve is 3 dB up from the B and C curves at 1 kHz, though?

The spec I linked before has them all the same at 1 kHz (Table IV), same as Wikipedia's graph. Whether that should be 0 dB or -3 dB in your software, I don't know. Probably A should be dropped -3 dB to make it consistent with unweighted/B/C, and "RMS Averaged + 3dB" setting can be used to normalize any of them back up? I've always been confused about the conflicting definitions of dBFS/dBov.

Right, A-Weighting is calibrated to 0dBFS at 1kHz, but leq(a) is A-Weighting + 3dB, leq(B/C) use B/C-Weigting without offset. No matter if RMS Sum or AVG is used.

[Endolith]

I mean that Leq(A) is 3 dB higher than the other filters:

level comparison.png

but they should all be the same at 1 kHz:

ansi.s1.4.1983.png

[TB-ProAudio]

I mean that Leq(A) is 3 dB higher than the other filters:

Well, reference of A-Weighting is 1kHz 0 dB, right.
But we shifted it by 3dB to be compatible with Nugen and Waves.

[Endolith]

Probably A should be dropped -3 dB to make it consistent with unweighted/B/C

I've since researched this more in-depth and found that it's incorrect: All the official standards agree that the rms of a full-scale sine wave is 0 dBFS.

So Leq(B) and Leq(C) should have been changed to 0 dB instead of changing A to -3 dB.

Well, reference of A-Weighting is 1kHz 0 dB, right.
But we shifted it by 3dB to be compatible with Nugen and Waves.

There is another standard that you could use for this: The rms of a full-scale sine wave can also be measured as -3 dBov.

dBFS and dBov are essentially the same concept, except with a 3 dB offset. So maybe instead of "Leq(A)+3", you could have a dBFS vs dBov switch? Then the ---/A/B/C are consistent, the 3 dB offset can be set to match levels shown in other software, and the units are unambiguous and follow the standards.