As I said previously, this is not correct – you’ve misunderstood what Sean Olive meant in his description of LFX. Here it is again from the
full AES paper (scroll down in that link for the paper):
The next two sentences in the paragraph are just
explanations for the choices made above:
He is explaining
why the -6 dB frequency is taken from the sound power curve and not from any of the other curves i.e. why he is using x_SP and not x_LW or x_ON – because it better defines bass output of
all speakers, but
particularly (not only) speakers with rear ports (presumably because bass and sound power are not directional measures, unlike e.g. the on-axis and listening window curves). The listening window however better defines the average level in the range 300 Hz-10 kHz (where we can localize sound), so this is used for the reference level ybar_LW
for all speakers.
I think your misunderstanding comes from the language used in the patent application (which is generally less clear and easy to follow), in which he says ‘may be used’ instead of 'is used' in bold that I've highlighted in the above quote. This is merely because the patent application is describing
techniques that may be used to calculate predicted speaker preference ratings, so he uses 'may be' throughout the paper (Adobe pdf reader says 47 times!
) for
all techniques he
actually used when creating the model. Here's just one example from the end of the paragraph marked [0046] in the patent:
Contrast this with the same sentence from the end of the second paragraph of Section 3.2 of the AES paper:
I suspect this change is just some legal requirement to use very precise language when applying for a patent on a method that
may be used for a particular purpose, nothing more.
So, it is definitely the mean level of the
listening window (and not the sound power curve) between 300 Hz and 10 kHz that should be used for the reference level of the LFX calculation, for
all speakers, including, (but not only) rear-ported speakers.