We get this question a lot. You can’t just willy-nilly replace one tweeter with another. They each have different impedances and other parameters, and a speaker’s crossover is carefully designed to enhance, compensate etc. for those parameters and properly blend with the other drivers in the system.
Changing out the tweeter (or woofer for that matter) with something “off the shelf” – sure, you’ll get sound out of it, but it won’t sound the same.
If it were that easy there would be no speaker manufacturers as we know them. You’d just go into a “speaker store” and pick your cabinet, woofers, tweeters etc., cafeteria style (just as with all the other components in your system), and it would automatically sound great.
Like rojo said, contact Ascend and see if you can get a service replacement. They still make the CBM-170, so there’s a good chance you can. Failing that, another option is ebay where you can get a used one for parts.
Regards,
Wayne A. Pflughaupt