Assuming you have a test signal generator, like pink noise, sure. Most accurate is to use a calibrated mid and phone instead of cheap SPL meters.
You’ll need to use it with an app like Audio Tools which will accept the calibration file.
Measure before passive biamping to get the right original signal.
The problem with making an acoustic measurement is that it is so sensitively variable with the position and orientation of the microphone. OTOH, if the speaker is still endowed with its original crossover to insure that the upper and lower bands are balanced, an electrical measurement of the input signal is simply more precise.
I actively bi-amp with two Wilson Benesch Torus Infrasonic Generators which have their own outboard, free-standing amplifier/crossovers.
I use a Stereophile test CD with the appropriate low frequency tracks to match the level of the main loudspeakers.
I do this using the following instrument:
You can also use this method to determine the proper subwoofer placement within the room.
This is not rocket science. There is no need to make this any more complicated than it is.
I hope this helps!
I purchased a pair of bi-amp wired Tekton Double Impact Special Edition. I want to quad-amp power steer them with four Carver M1.0t mkII 002. Tekton recommended an active crossover to protect the mid-highs. I've been trying to purchase a Pioneer Series-20 D-23 or an SF-850 but they are getting up there in age and no one seems to want to work on them.
Would the SPL Crossover be a good device for what I'm trying to do?