Legacy Signature SE without dual AMT twitter

Just off the top of my head, my guess is that the dual-tweeter was done to improve vertical dispersion. That is, to get better high frequencies below and above axis.

Any difference from the dual-tweet will probably be there.

Best,

E

The speakers are essentially the same in passive operation (If comparing speakers from different time periods there may be further enhancements to the newer ones; you would have to check with Legacy Audio), but the newer tweeter system is superior. See my reviews of the Focus HD and Focus SE at Dagogo.com for further info. 

With how tall Legacy speakers are, and with their tweeters being located at the top, vertical dispersion is an important consideration.  Especially if you sit 10 feet or less from the speakers.