Vector, if that's your goal, I'd dig up 2 pots (potentiometers) of relatively low value (say, NMT 1000 Ohms) and wire one in series with the tweeter BEFORE the high-pass section of the crossover. Adjust it to be wide open (= no resistance), play some white noise (FM-tuner noise works very well) and adjust the pot so that the treble output is down just audibly. Live with that setting for a while to see if it's too much or not enough. Adjust the resistor higher or lower as desired for the sound you want. When you're satisfied, lift one wire from the pots, measure them and average those numbers, and order the resistor values you really need, then solder them in permanently. (I use the Mills noninductive wirewounds from Michael Persy.)
Remember, if you install these resistors AFTER the crossover caps, etc., you'll change the filter point of the crossover.
BTW, if your speaker is ported, you can run the pot's wires outside the box so you can adjust them without opening the boxes.
I've done this very thing to my car's system and also to my main home speakers; it works very well. In fact, I'm about to remove a couple pots from my car system so e-mail me if you want them for the cost of postage.