There is a huge comb effect with those 3.5 inch drivers, and no transition to at least a single high SPL tweeter(thought preferably a line).
When I first hooked up my Three way Tri-amp system, with the 3 inch 3mm xmax Sammi's, it was using only them and not the two 12 inch 15 xmax DVC woofers, or the 60 ND20A tweeters.
I thought the sound was great. I used a 1/3 octace equalizer, and i was impressed. But when I hooked up the tweeters, and the woofers, I discovered the missing sound. I disconnected the equalizer, and haven't used it since.
My recommendation is that at least one very high efficiency tweeter should be used. You will notice the difference immediately.