You can spend your entire life learning about taking and interpreting acoustic measurements.
To do it well is not easy, especially “at home” even if you have a studio. That does not mean it can’t be done, just that you need to know some of how your results may deviate from those at a legit test lab.
It is difficult to separate the effects of the room (reflections) you are in, from the direct test signal hitting the capsule. This is especially bad at low freq since you need to have the signal source a fair distance away to develop enough of a wave to measure. It will quickly become apparent, that to eliminate any room reflections, and to get accurate low freq results, you need a gigantic anechoic chamber or a very tall platform outdoors above ground. Most people don’t have those.
. There are other “nearfield” techniques to get around this for loudspeaker response measurements you will find.
At the other end of the spectrum you run into issues too. Even small changes in the positioning of the capsule in relationship to the sound source (tweeter is usually getting very directional itself at these frequencies too) make a difference, along with the mechanical contraption you are using to hold the capsule causing reflections at these freqs. Don’t expect to be able to easily “match” the responses here. Your measurements may not be accurate enough to make valid comparisons.
Obviously, legit mic manufacturers have developed better tools for doing this, like dedicated test mic couplers and other specialized techniques that eliminate a lot of these issues, but again, most people won’t have access to those.
Luckily for you, you are starting with great mics (DPA) and can get really good results as others have mentioned just matching the sensitivities. Their freq responses will likely be very close.
Free acoustic software for room correction like REW will work fine for what you want to do. If you look at the time response of a sweep you take, look for the first reflection’s arrival time. Anything arriving after that will be corrupted by room response and will limit your LF measurement capabilities. Gate the measurement here and ignore the response below the LF freq point this corresponds to. It will be determined by the distance between your sound source - the capsule you are measuring - and the closest reflective surface. Check out Fig 6 in this fundamental paper by Struck and Tempe.
https://pdfs.semanticscholar.org/95cc/acd898f6b30fd2dbad3bbb4ba2a12ab53744.pdf They have a much better handle on this than me.
Keep in mind, your sound source (monitor speaker) will not have a perfectly flat response and the “reference” mic you use to compare the capsules to will not be perfect either.
Taking sensitivity measurements using full bandwidth pink noise should be pretty easy. If you position the mics the same way each time, close to the front of the speaker and in line with the tweeter, you should get pretty repeatable measurements. Try positioning a capsule, taking a sensitivity measurement. Remove the mic from your test set up and then reposition it in the same spot again. Take a second measurement of the same mic. Are these two measurements the same?? Should be pretty close if you are in the same spot. This should give you some idea how varied the responses will look at HF.
There are other threads, from many years ago here, where people discussed doing these kinds of measurements and even attached some pics and graphs. Might try searching for more info here and on the web. There’s lots out there....
Miq