YIKES!

OK - you are running your Altec amp at the 1/3 point. That does NOT mean you are putting 100 watts into the amp.

You really need to learn some of the basics of audio. Little steps for little feet:

a) Audio Taper Controls: https://i.stack.imgur.com/f5P1V.png

At the 1/3 point you are, perhaps, putting 10% of the amp power into the speakers - and that ONLY IF the signal is driving the amp to that level of power. So, maybe 30 watts at the absolutely loudest passage.

b) Amp output vs. signal input: Amps are rated in WPC/RMS (watts-per-channel/root-mean-square), and at a specified voltage input. Typically around 2V or so, typically at a specified frequency or group of frequencies. A preamp varies the level of input into the amp, from 0V up to as much as 13-or-more V. Consider on that and consider why.

c) I do not know what you listen to, in general. Whether it is classical (as in orchestral or 'high-brow' stuff), rock, country, Polka, or whatever. But, *most* music as recorded these days has a Peak-to-Average of 20dB at the high end, to under 10dB at the low end. Very, very few recordings even approach 30dB. So, if you are listening to well-recorded "classical" music, your P/A is 20dB AT BEST.

d) Not knowing what volume you prefer, but assume that you are averaging 1 watt into reasonably efficient speakers (those Fishers are that, at least). So, you will need no more than 100 watts of output for the very few peaks.

I doubt you have the XP10, or you would not have any issues with replacing the tweeter as that is a 2" soft dome, any decent one will do. But, as these go back to the days of Avery Fisher (1965 or so), you will be having surround-rot issues and more, which you are not reporting. So, I suspect you have one of their latter-day speakers that traded on the Fisher name, but without the quality.

Peter Wieck
Melrose Park, PA