I agree. For the benefit of the thread, SMPTE 222M (also referred to as modified X curve) has the following spec:
Flat to 2 kHz and then 1.5 dB/octave roll-off above that.
A variant of that makes it flat to 4 kHz and then follows a 3 dB/octave roll off
Yet another (rarely used) variant has a low frequency rolloff below 60 Hz.
The SMPTE curve was derived based on very specific listening room acoustical conditions including requirements for critical distance, volume, etc.
Since these conditions are difficult to match in a typical home listening room, the Audyssey curve is somewhere in between:
Flat to 4 kHz, then -2 dB at 10 kHz, then -6 dB at 20 kHz. Very similar to variant #2 above, but with a key difference being the double knee in the roll-off. That decision was based on very long experiments that looked at several competing variables including speaker directivity, critical distance, and perception of the balance between direct and reverberant sound as a function of speaker directivity.
In the MultEQ Pro software, there are some other presets that the installer can use. And with the 3.0 version out this CEDIA, the installer can customize the target curve at will with a drawing tool or by typing in specific frequency adjustments.
We will be showing this at the Curtis Hotel during CEDIA. It would be great if you had time to stop by.