TV sound through a port

Hi. I have the following set up in my living room (part of a larger multiroom sonos system):

Sonos Port connected to my 2 active meridian speakers. 

I simply (!!) want to connect my TV to that set up so I have better sound quality through the Meridians than the TV speakers. I am NOT bothered about surround sound.

I did this before in an old house with an old TV which had RCA audio outputs…. plugged those into the port (actually a Connect in those days) and hey presto.

However I now have a newer TV which only has an optical digital output. I tried connecting it to a DAC and then old fashioned audio cables into the port. This lead to a MASSIVE audio delay…. completely useless I’m afraid.

So anything I can do to get the audio synced apart from by an old TV with RCA audio out??

Thanks