I've used them over many years, including the silver face, blackface, and modded silver versions. They are not muddy at all, however like any vintage compressor built before frequency compensation, they can dull out your tone with misuse. Of course one of the cool things about the 1176 is misusing them , especially to squash the bejeebus out of bass. I suggest you tell your school they are way behind the times and need to get whatever the latest PC plugin is. Then they can unload those 1176's to me. As Bongo says, they might be out of spec but I've used some real old 1176's at studios that I know had crap maintennance and they sounded fine. Count yourself fortunate you have 4 of them to play with. Want some fun? Cascade a couple or more of those 1176's and see what it does to the bass.
That said...
Debates about compressors and their sound in the recording world is like debates about 'which bass is best' that often get started here. The final judge should be your ears, if the gear isn't getting what you want, move on. If you get a killer bass tone no one will care if it came from a $20,000 vintage compressor or from a $100 stompbox into a DI. Experiment until you find what works for you.