The "best" ones are the ones that sound best to ..... wait for it ..... YOU!.
For communications, don't go for super low or super high responses; anything lower than about 300 Hz or above 3KHz will be wasted, IMO.
Try a bunch of different commercial speakers. If you still don't hear what you like, put "a" speaker in a box and experiment with baffles, vents and so forth.