Why do you want to do this? How did you come up with the 1 amp rating? As for the voltage it makes no difference in a loudspeaker, but you might as well use the 250 volt fuse. The main issue is the amp rating. I would check with B+W and find out how many watts the tweeter is rated for then you can do the math and come up with a figure.

Hello, I have a few sets of B&W 800 series speakers and I'd like to install an inline fuse to protect my tweeters. My question is; should I go with 125v or 250v 1 amp fuse? Open to suggestions.Thanks