Click the arrow on the checklist item to open the FFT response test.
This is an optional item used when the MLP measurement of a speaker shows anomalies from it's near field response.
Follow the procedures for a near field measurement. This time we'll take 6 measurements of the same speaker.
The initial measurement is with the microphone on axis with the drivers.
Subsequent measurements require the speaker to be turned off axis in 15 degrees increments. This should spin the speaker a total of 90 degrees.
For in-wall or mounted speakers, you may need to move the microphone to take measurements at various angles.
Each measurement should be saved by using the "+" control.
The final outcome should shown all measurements overlaid to show the sloping of the response as the speaker turns away from the microphone.
Once you've completed, touch the "Screenshot" icon to save an image of the plot. Touch the return arrow, mark the item complete, and add any comments.

Poor Off Axis Response

The near field test is designed to confirm the speaker is operating properly but it doesn't explore the off axis response.
A poorly engineered speaker can show a flat on axis response, but a good speakers off axis response should correlate reasonably.
It is expected that off axis measurements will show increasingly more high frequency sloping as you increase the angle but the general shape of the curve should be consistent.
If the off-axis plot seems to deviate substantially from the general shape of the on axis response this exposes a problem.
The problem may be with a poorly engineered speaker but it can also be caused by a defective or damaged driver or crossover.
Installation can also be the issue such as in situations where the speaker is partially blocked by some obstruction.
The off axis signal can comprise 50% or more of the signal heard by listeners and this can color the sound quality.