I assume you meant Janszen Z-600. If so, the company is again in business and David Janszen is familiar with all of his father's designs. I'd suggest contacting him with your questions.
What do you know about the JENSZEN Z-600 speakers and cross-overs
I have a what looks like a perfect pair of these Z-600 speakers , but they almost sound like the cross-overs are messed up........They seem to be lifeless in sound, light in the bass, no real detail.....Maybe a past engineer could help me sort this out.........THANKS