2nd tweeter crossover

My vehicle is equipped with a Boss stereo. I find that it's missing a lot of highs so I wanted to add a tweeter. The stereo comes equipped with a 8" woofer and a 2" tweeter. The boss tweeter is crossed over at 1800hz - pretty damn low for a tweeter - its most like a midrange/tweeter hybrid; which is probably why I don't here any nice highs. The boss tweeter is 4ohm and using a 22ufd capacitor to achieve it's 1800 high pass crossover. The tweeter I am installing is a 4ohm tweeter, rated to 3000hz. I will be tapping the pos/neg wires before they run into the factor tweeter/capacitor to send to the new tweeter. I will be looking for a highpass crossover point of about 4000hz for the new tweeter. Question: When I use the capacitor calculator on this site to figure out which size capacitor to add to the new tweeter I get 10ufd, calculated @ 4ohm. But will the overall tweeter(s) impedance change because of the new tweeter? Would I have to calculate for 2ohm load instead? If so, does that mean I would also have to change the capacitor on the boss tweeter to maintain it's stock crossover point? I hope you understand what I am trying to do here and help me with this - been searching around car audio forums for a while and can't seem to get a straight answer. Cheers!

You plan to leave the old tweet and add the new on in parallel with it?  The calculate your high-pass filter for just the impedance of the tweeter you're adding.  Be aware that by doing this you will be placing a 2-ohm load on your amplifier above the second tweet's XO frequency.  This will probably not present a problem for the amp, but you need to be aware of this in case it does.  Also, it is never really a good idea to just add tweeters, as you can create problems with lobing and cancellations.  1800Hz is not low for a tweeter, by the way.  In fact that's fairly normal.  Some of my designs cross as low as 700Hz to the tweet (it has to be a really good tweeter to do that, by the way.)Support the12volt.com

Yes I plan on leaving the original "tweeter" as its more of a midrange. It's huge and heavy; the highs are just not there.    I tested the sound by running the new tweeters, after the boss capacitor and it really makes the stereo sound much better - fills in all of the missing highs nicely. My problem is now protecting the tweeters from receiving too much frequency.

Ok so when you say its 2ohm above the crossover point - does that mean the stock capacitor on the tweeter can stay at 22ufd? And I would just add a 10ufd cap before the new tweeter to get a crossover point of about 4000hz?

DYohn wrote: You plan to leave the old tweet and add the new on in parallel with it?  The calculate your high-pass filter for just the impedance of the tweeter you're adding.  Be aware that by doing this you will be placing a 2-ohm load on your amplifier above the second tweet's XO frequency.  This will probably not present a problem for the amp, but you need to be aware of this in case it does.  Also, it is never really a good idea to just add tweeters, as you can create problems with lobing and cancellations.  1800Hz is not low for a tweeter, by the way.  In fact that's fairly normal.  Some of my designs cross as low as 700Hz to the tweet (it has to be a really good tweeter to do that, by the way.)

Thanks for the help DYohn - I have it sorted now.