Resistor to tone down tweeter?

I have a pair of Focal 918s. I was curious about trying to tone down the tweeters a bit.
What options are there?
Can I wire a resistor in front of the tweeter? If so what size/rating would it be.
I would like to get a little more volume without the excessive treble.
Thanks Jayson
Yes it was. The whole tweeter housing has to be changed on the Focal 918 because they are so custom mounted. Wish they would have spent more on the tweeter than the custom mount.:)
They are the same model # also.
Im quite happy with the difference the new tweeter made. I dont notice a huge difference but I think because the old one was in such bad shape I was used to hearing that sharp metallic sound from my right the brightness has shifted more to the left. (much less than before though).
BUT my room has two windows with wood blinds on the left side and not much as far as covering the walls. The right side has wrap around sectional-couch and is open to another area. (no corner/wall)
With that being said I would think the left side would produce more echo/brightness right?
Im thinking I should focus on the back wall/reflection point and the left corner/windows.??
I would think before you go invest in Soft material like curtains and or Carpets need to get both tweeters running the same..My first action would be to make sure both tweeters exactly the same then deal with room next.....
First of all, make sure the tweeter is OK. Both channels should sound the same. A damaged voice coil, or something else in the tweeter can cause this.

If you find both tweeters to sound the same, maybe your sensitive to their resonance (usually right over 20 kHz) like a lot of people are, or just the speakers design.

You can try adding a non-inductive 1-4 ohm wire wound resistor in series between the plus wire and the tweeters input plus (+) terminal. The larger the ohm number you use, will result in less output from the tweeter. Maybe try a 2 ohm to start. This will tame the tweeter down. You may, or may not like the results. I have done this myself with good results. Here is a link to give you an idea about the resistor. Link.[]
Thanks for the input. I will probably go ahead and replace the other tweeter. At least then I have two new tweeters to make a better decision. A little room treatment may help my cause also.
I will take a look at the link you provided.
Stupid question for you electronics boffins. on a guitar if you want to roll off the highs you use your tone knob which uses a capacitor fromt he tone pot to ground (I think). Why would this not work in this case. Suspect I'm missing something but its not my field.