DJ Monitor using B&C 12HCX76

Measure the raw response of each driver on axis

Measure the raw response off axis to check if there is an area where the attenuation off axis matches

Measure the response of a filter on the DCX - this will be your acoustic target response (HF first your case as filter will be near lower limit of HF driver) Pay attention too phase versus target response.

Use low 'Q' filters to flatten response of HF driver

Overlay target response of DCX filter (eg LR24)

Attempt to use EQ and filters to match the HF response to the target.

If not possible to match to given target then adjust target to make it achievable by iteration.

Follow same process with LF to match ideal HF filter response.

Pay attention to the phase response of the drivers compared to the DCX target response.

Use delay in DCX to get phase response of LF and HF to overlap neatly through crossover region

Remember that it is the combined acoustic response of filters and drivers that matters - not the filters alone.

Your measurements look a bit wiggly, I presume your not using time domain gating.  Try getting the speaker up on a tall pole and away from surrounding objects along with gating to get quasi ancoic results:

This won't cover bass measurements unless you have a very big pole.  The usual way to get those is to perform them on a ground plane or near field and then splice with the gated response.

The best way to see the box tuning frequency is to measure the box impedance minimum frequency which can be done using a power amp, a resistor and a multi-meter. 

if you look at the impedance curve in the above link your aiming to find the minimum between two peaks.

1) connect speaker in series with resistor (8 ohm for example)

2) connect multi meter in AC volts mode across resistor

2) connect to power amplifier output

3) drive amplifier with sine tone generator (EG from pc software)

4) adjust the frequency until you find the first peak in impedance (local maximum volts reading)

5) adjust the frequency until you find the 2nd peak

6) between those two points find the minimum impedance (minimum volts) this is your tuning frequency.

You can confirm this by observing the cone when driven to visible excursion it should stop moving at the tuning frequency.  Be careful not to run at significant power for long in this condition as the coil is not moving so poorly cooled.

Listening test wise no noticeable HF issues, it isn't quite as bright as the Genelec, but then they do have their characteristic sound. The B&C has an impressive amount of clarity and detail for a PA speaker and the coax arrangement works brilliantly for a monitor.