Hi,
The CS80s filters for each synth line work in series. As such combination the two filters give you something like a Bandpass filter. I believe the HPF is before the LPF, but as they work from opposite ends of the spectrum so to speak, then i think it just as well could be the LPF before the HPF.
In the original Yamaha CS80 manual, then the HPF is set before the LPF in the availble diagram.