My idea was to run my woofers with a separate Pi and implement XO in Roon.
Some days ago I took two Pis running Roon Bridge. Bundled them in one zone. Send a square wave signal to both, attaching my old oscilliscope and was disappointed.
After each start of the track the time offset between the devices was different. Even worth the time offset drifts over time between the two units. This will cause phase and amplitude errors.
My conclusion: Time sync between zones is much too bad in Roon to be used for XO.
What is the solition? Either run RME digiface and attach some DACs to it but Toslink is not my favourite.
I decided to go with RME ADI-2 Pro FS R Black. Ist has a multichannel mode and two separate very good DACs ohne with XLR and one asym. at it‘s headphone outputs. Enough for my Woofers and Horns. If you need more you can connect two additional DACs.
I plan to include an other Roon Extension in https://rooExtend.com this year that creates XOs for the Roon convolution engine.