I have a question about the advisability of making a change to a DR260 factory setting.
The "program" is for an SRX722 run passive over an SRX728. The speakers are driven from identical Xti4000 amps run stereo with attenuators fully open. The program can be keyed in manually from the JBL published tunings. The same settings can be achieved by using the Wizard on the DR260.
Systune is used to provide a pink noise signal and a dual FFT measurement is made with the DR260 as the Device under test. Prior to testing, a hard wire is used to bypass the DR260 to verify that the measurement setup yields a perfectly flat frequency and phase response. It does so the assumption is that during testing any frequency and phase response changes are due only to the DR260.
The question relates to the phase response and whether a delay should be added to the sub channel output. Note that the measurements here are purely the electrical output of the DR260, not acoustic measurements. I am just looking at a "baseline" response from the DR260 and so will also assume that the speakers would be set up with the 722's directly over the 728's with the front grills aligned. That is- the physical spacing of the speakers is not a factor of itself that would affect phase alignment.
The screen shot below shows:
Mid-High output RED
Subs - No Delay Dark Grey
Subs - 3ms Delay Light Blue
The factory settings show the sub and mid-high outputs tracking along with each other very nicely for an extended range of frequencies on both sides of the crossover point (about 78Hz). But there is also a consistent 75 degrees of phase shift throughout the crossover area. It seems to me that right around the crossover area a better alignment is achieved by adding the 3ms of delay to the sub bandpass. Yet I am reluctant to second guess the Harmon engineers and there vastly superior experience.
Would you add the 3ms delay and expect to have better phase alignment at the crossover (at least electrically)?
Or is there some other factor I am not considering that make the factory tuning superior?