You're not going to get much of a Hi-Fi sound out of that amp, open back and loaded with an "instrument" speaker. Is the Bandit a solid state? If you have an old 8 ohm stereo speaker you could just hook that up to the speaker output and disconnect the internal guitar speaker. If you want to try the tweeter thing, if you buy one from Rad Shack or wherever, they usually come with a crossover capacitor(it will tell you on the box). You would just wire the tweeter in parallel to the speaker in the Bandit. Don't listen if anyone tells you this will screw with the impedance (ohms) of the amp, it won't; the high frequencies that will pass thru to the tweeter won't put any significant extra load on the amp. Considering that a 12" guitar speaker frquency response typically starts dropping off at around 5000hz, I would recommend getting a tweeter/capacitor combo that is rated at 5000-20000hz or so (5000hz crossover frequency).Probably anything rated over 10 watts will work. Look at the efficiency rating too, guitar speakers are pretty effecient, a lot of Hi-Fi stuff is not(might not be loud enough to match). Or you could buy a cheap piezo tweeter or 2, they require no crossover and have a very high impedance. If one is not loud enough, add another, annd another... They are'nt the best sounding but in this application I think it might be a good way to go. Yes there are formulas and tables to choose the right crossover values, you could probably find one pretty easily on the web. Good luck.
