Hi, sorry for the slow response. What tilt basically does is, it tries to de-tilt the audio before detecting clipping. As you can see in many files, if a tilt has been introduced after clipping, then detecting clipped audio is no longer a matter of just finding samples at the same (and highest) level, but instead you need to tilt the audio first to make those peaks flat.
It's a bit hard to explain, the default settings were created based on some worst-case recordings. But there may be even worse out there that we haven't seen.
To get an idea what tilt does, you can use the RC slider for the FM output and check what it looks like on clipped audio or on square waves. The de-tilt filter basically tries to find the best RC value match for every piece (a few dozen ms) of audio.
Hey Hans, in the Metallica Album Death Magnetic, if you zoom in on the waveform, the signal is not only heavily clipped, but you can also see a very clear tilt downward of around 15 degrees in the flat peaks across say 100 samples. Is this what you are talking about? If so, when I get back home I can upload an image of it. BTW, What the heck plugin would have caused that in the mastering stage when they made that fatiguing album?
Yes that's exactly what it is, and in fact I tweaked the settings on that album. No idea what caused this, it looks like they first clipped it and then highpass-filtered it. But it's a mystery why anyone would do that, for one, it would have been both louder and with less distortion if they had done it in the opposite order.