I don’t think you’re understanding the nature of the underlying software. Even when connected with an Ethernet cable, there is always a 75ms delay, it doesn’t change with different data transmission methods. When you’re playing music from the internet, even on a Sonos speaker connected directly to the router is experiencing that delay. The user doesn’t recognize it, because there is no other signal to compare against.
Sonos chose at its inception to be not a speaker company, but a network music player. The software was written to support that goal. Part of that choice was to have the underlying architecture include the delay in order to be able to sync across all network situations, not merely wifi, but wired networks as well.
There is a single use case in which a signal does not incur that delay. It is on a home theater digital input, and the speakers only contained in that ‘room’s’ logical construct. As soon as the signal leaves that logical ‘room’, it then incurs the 75ms delay, so that it can appropriately sync across all potential 32 devices in the Sonos system.
Perhaps at some point Sonos will decide to go away from network sync’d music. At that point, I’d expect that they would come up with a ‘pass through’ line in with no delay, but it’s hard for me, at least currently, to think that it’s on their list to do in the near future. There are just too many other ‘pass through’ devices out there, it would be unlikely to be a profitable market for them.
I experiment audio delay with my sonos five speakers when watching tv, even with 75ms enabled in settings (the minimum). My audio cable is AUX 3.5mm
I know that because when i turn on my tv sound, they are not sync at all.
I also know that sonos cannot reduce lower than 75ms buffer size to avoid dropouts.
That buffer isn't, as you say at the end in the quote above, to avoid drop outs. It is the time taken to convert analog signals to digital and then buffered to make sure that all speakers chosen to play that signal as a group are in perfect sync. So ethernet wiring isn't going to solve this issue, because that addresses something different - the stable propagation of the synced digital signals where wireless is not able to do that.
It seems to me that you are using the Sonos 5 speakers to improve the sound from the TV. Why then you not want to leave the TV sound muted? That is what I do, and all works fine. The delay does not affect lip sync in a way that intrudes on the experience in my case, as in the case of many others. Which camp of these two types you fall in, I do not know.