thanksNot much info there. An overlay phase chart has more value when timing the XO, but:
It is likely a anechoic or quasi-anechoic measurement as no room influences are indicated.
It displays a typical phase rotation through the bass range
It hints that:
There may be a high-pass filter applied around 20 Hz or so thus increasing the phase rolloff in the low bass.
There may be an acoustic XO at about 110 Hz with favorable timing selected that minimizes the overall group delay.