but I can't find information on how to calculate the constants. I've searched both the 7705 datasheet and user guide but it doesn't seem to have these. I can kind of figure out how to stuff the freq, Q, and gain into word1 and word2 but I don't know how to calculate the actual constants.
Yeah. IIRC, the 7705 came with a piece of software so that you could calculate preset EQs, and then your software would just push the constants into the chip. I think we reverse-engineered the algorithm (or found a private data sheet) so that we could implement the configurable EQ in the empeg.