Hi @Nicky Branagh,
Thank you for your question. I'm assuming you're monitoring with your headphones plugged directly into the H8?
When connecting the FS to the Zoom H8, you have several options.
With a 3.5mm-3.5mm TRS cable, you can connect the mic to the Zoom H8 using the stereo mic connection on the side of X/Y microphone attachment that comes with the H8.
With a 3.5mm TRS to dual 1/4" splitter cable, you can connect the mic to the Zoom H8 using the two 1/4"-XLR combo inputs (A & B).
Connecting via the 3.5mm-3.5mm connection, the signal should automatically be stereo with the left and right ears panned.
Connecting via the 3.5mm TRS to dual 1/4" splitter cable, you'll need to full pan tracks A & B so the left ear is full panned 100% left and right ear 100% right.
On page 39 of the H8 product manual, you can find instructions for pan settings: https://zoomcorp.com/media/documents/E_H8_v2.pdf
I hope this info helps. Let me know if you have any other questions.
3Dio Customer Care