What some speaker builders do (diy) to tame overly bright tweeters is to add a resistor at the positive terminal of the tweeter. The resistor is attached at the end of the positive tweeter wire and then the other end of the resistor is attached to the positive terminal of the tweeter (series). I would start with a 1 ohm x 10 Watt resistor. The resistor values come in .1 ohm increments.
just another option.