How are you connecting the Sub to the Port when they are not compatible?

From the Sonos site:

Which Sonos products can be paired with Sub?

Sub can only be paired with any amplified, non-portable Sonos products, including soundbars, amplifiers, and speakers. Sub will not pair with Move, Roam, Port, or Connect.

https://www.sonos.com/en-us/shop/sub

Look in the FAQ.

The only time there is any latency between Sonos rooms is when the first room is playing the input from a TV. In all other cases, there should be no latency between rooms. 

However, ​@Pools-3015 is correct, there is no way to connect a Sonos Sub to a Sonos Port. 

Thanks for the answers. Since I’m not currently a Sonos user, I probably used the wrong terminology in my question. I’ll try again:

If I use a port to connect my 3rd party amp and passive speakers to the Sonos system, can I then group them with a Sonos sub in the same room without a delay issue between the passive speakers and the active sub?

No. The Sonos Sub needs to be ‘bonded’ to a Sonos speaker. It isn’t a traditional ‘Sub’ with an input.

And I appreciate the clarification. ;)

Thanks, I get it now.