There are many ways to measure your speakers at several price points from virtually free to spending thousands on dedicated equipment. To gather accurate measurements takes a bit of study as well as having the gear.
To make simple comparative measurements between two speakers, you can use an iPhone or iPad with the built in mic and a $10 app from Studio Six Digital.
https://www.studiosixdigital.com
On a separate topic, have you exchanged the two tweeters, moving the left tweeter to the right tweeter location and vice versa to see if the changes follows the tweeter?
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