use a 12uF non-polarized capacitor
(just tell them you want to use it for music)http://www.apicsllc.com/apics/Misc/filter2.html
I used this calculator here, they said to use 13.25uF, but 12 is the closest size and it would protect the tweeter a bit more since the new cutoff frequency is 1650Hz.
And hook it up in series with the tweeter like this. Inline with the positive terminal of the tweeter.
You could get it in steve's/sham's/any music store really.
Don't let them chain you up and give you the regular 2.2uF yellow capacitor. Your drivers wont play anything below 9000Hz and it will just sound like nails on a blackboard.
But if you can't get the 12, there's a way to combine capacitors to get the value you want, but I feel like this post is already too long so I'll tell you that if you cant get the 12