Making speakers sound tonally similar with an equalizer

I’ve owned many speakers and they all sound different. I would say very difficult or impossible. Maybe if the speakers are in the same line- cabinet materials, driver materials, crossover components, etc. otherwise too many variables. I suppose frequency is frequency so there is an argument for it, but I say no way.

Roon has an eq feature. I tried to remove a frequency in the 2-4k range that drove me crazy with a pair of speakers. I found it actually ended up being a resonance or property of too much being expected of a bass driver playing this frequency. I also tried the Fozgate tube buffer on another speaker, but it took away from the transparency of the system- added more connections, wires, outlets, etc. 

Roon does have an EQ headphone catalog where they've tried to match the sound of various headphones. Interesting feature- anyone payed with that?

It would be great if we could buy a $5,000 speaker and add the Alexia EQ, or change that EQ to the Rockport Lyra for the day. I'd like an 8 foot pair of horn please.