Making speakers sound tonally similar with an equalizer

In an anechoic space you can equalize and correct the phase of speakers by using FIR filters and make them sound more similar on axis than I think most people would admit, at least up to the volume where the speaker starts to distort audibly. In real listening environments it’s not possible to make speakers with different cabinet shapes and arrangements of drivers to sound indistinguishable because they radiate sound into the room differently and so the combined direct and reflected sound effect is quite noticeably different no matter how you equalize or phase correct. I would bet though that if you took two different reasonably well designed speakers with the same baffle shape, same driver sizes and driver placements on the baffles, let’s say a 5" woofer and 1" dome tweeter on 16" x 7" baffle, they could be equalized and phase corrected to sound similar enough under blind testing that most typical listeners and even a lot of seasoned audiophiles would have a hard time distinguishing them. Any differences that could be heard would most likely be from differences in the specific dispersion characteristics of the different drivers chosen.  

@cd318 

Yes, more similar in frequency response is primarily what the EQ will do. And if distortion is kept low and dispersion is similar the overall presentation will be very similar. Chances are if you like the sound of one you'll like the sound of the other.

I agree tone controls and EQ can be helpful in the less than perfect listening environments most of us have to deal with. I've played around with digital EQ and active crossovers on a number of speakers over the years. My general approach is to get them as flat as I can on axis at 1 meter, and then listen and make measurements at the listening position to try to figure out how to fix the bass issues in the room as much as possible. My front room with lots of glass and hard floor made me realize how much different the same speaker sounded in a different room, and how much the dispersion characteristics of the speaker change the way the room and speaker sound together. I ended up often using a reduced treble curve in that room before I set up some big horns in there. With their narrower dispersion I find the horns don't need any treble reduction slope.

The little Harbeth P3 sounding remarkably similar to the big m40, except missing the bass... I can make sense of that from the perspective of listening to a piccolo solo. They could sound very similar if they have similar dispersion and frequency response in the treble.