There will always be a minimum 75ms delay with the line-in connection. You cannot eliminate it. The best you can do is set the Audio Delay setting under the Line-In settings to Low.

You bought the wrong speaker if you wanted line-in without a delay.

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Thanks for confirming!

Didn’t buy it specifically for the Line-In feature but when it’s not portable I wanted to mix it in with my other gear.  It’s an innocent question. Last post I saw on the forum with regard to latency was 7 years old. Just thought there might be a work around…

The delay is part of the way Sonos works, baked in to the software, not the speaker, in order that Sonos can play in sync in many rooms at the same time. 

The only modification made is the digital inputs on a Home Theater ‘room’, so that the fronts, surrounds, and Sub can be lip synced with the video. As soon as you group a second Sonos ‘room’, the signal gets buffered for the second (and any other) room. 

If you haven’t seen a post about this delay for seven years, you’ve not checked (which is fine). It comes up dozens of time a week, in various threads.