This is what I think I’m understanding, or misunderstanding.
Is measuring a rear firing port or PR, and getting its “approximate FR up to 1-2KHz”, at a resolution that’s not high enough, to determine how it contributes, or affects. with it’s out of phase behaviour, to the frontal hemisphere response of the woofer?
I hope I understand you correctly, but I think there is a problem of communication and understanding.
The near-field measurements (directly at the BR ports and as close as possible to the woofer chassis), which have been described more often, have a very high resolution over the whole measuring range.
But if you measure with the microphone 0.2'' away from the dust cap of the woofer chassis, the measurement to high frequencies is less and less in accordance with reality. For example, a surround resonance is only insufficiently imaged in such a near field measurement - I have described further effects in the previous post.
The curves consisting only of the near field measurements have a high resolution and show the effects of the BR-Port resonances on the overall frequency response of the loudspeaker at 1kHz (with the mentioned limitations, therefore "approximated").
After having determined the total frequency response of the near-field measurements of the loudspeaker (red curve), which is shown in the upper diagram, this is combined with a gated frequency response measurement (1m micronphone distance) - and this at the point where both measurement curves match each other as closely as possible.
This gives the quasi anechoic free field frequency response of the loudspeaker. Since the joining of the two curves usually happens in the range around 300Hz, from 300Hz on you only have the resolution of the gated measurement.
This is where the problems begin that
@hardisj has also described, where the effects of the BR-port resonances may not be recognized correctly due to the low resolution, because the FR is too strongly smoothed - especially in the lower frequency range of the gated measurement (300-1000Hz).
But the above near-field measurements have been determined anyway and these show with high resolution approximately the effects of the BR-Port resonances. Thus, a loudspeaker developer should always notice the possible problems.
Hope I could make it a bit more obvious.