Out of curiosity I’ve checked the values of my recent song (again). Therefore I’ve used two instances of the same loudness meter at the same time, on one hand as an internal plugin and on the other hand as an external standalone version. And the results differ. On the left you can see the results of the plugin and on the right you can see the results of the external standalone version.
Headroom -6 dB:
Headroom 0 db:
As you can see there’s no difference in terms of TP, but LUFS, loudness range etc. are different when using 0 dB headroom instead of -6 dB headroom. And I also noticed a slight “wind sound” in the back when headroom is set to 0 dB. Pretty strange (ok, I didn’t change anything but the headroom value at this point). I wonder what cause the differences between internal and external measurement, especially in terms of TP (it’s always above 0 when measuring external, but it should be -1). And I also wonder why there’s a difference in terms of LUFS of round about 2 dB when you set headroom from -6 dB to 0 dB. If there’s a difference, the difference should be 6 dB and not 2 dB, right? Damn, I have to think about how to master in future. I’ll probably try going with 0 dB headroom and look what happens.