It won't hurt anything. The current capability is far short of what a speaker wants; an output transformer would help a lot. I'd try a line transformer and experiment with the primary taps. Radio Shack has one, catalog 55013095 - it's $10; not the cheapest around, but probably the easiest to find. If it's the same as the version I tested several years ago, it's pretty good - similar to the SPECO we used for some years in Paramour and SEX. You might get conversational-level sound; not loud but audible. Sounds like a fun experiment.