People have been asking for this for 17 years.  At this point, I'd call it an improbable, if not impossible request to fulfill. 

I doubt that ‘many’ people are bothered at all - just a very tiny minority.

It would defeat the major selling point of the Sonos system, i.e. the ability to play all connected speakers in sync. Basically, what Sonos is based on. 

Exactly.  The very first time they did this (if it is even possible to remove the buffering stage at all, a BIG IF), the first posts of the announcement thread would be complaints that it can't be used for multi-room, and "what good is it for DJ'ing if I can only play it on 1 speaker!!??"

Echo also does perfect sync just as well; I don’t see any way of testing to see what kind of delay they run since they don’t offer line in, but it would be interesting to know what is the delay there. But some delay seem inevitable given the feature.

It’s different for streaming sources.  The speed of the download is far greater than the rate of playback, so the buffer builds up very fast behind the data which is playing, meaning the time from selection to play starting is almost instantaneous.  A line-in is real time, it cannot be delivered any faster than it is playing, so you have to delay the start of playback until the buffer is sufficiently filled.

Since Echo does not do line in, then it would appear that the question as to the lag in their case cannot be asked being not applicable; Bluesound does offer line in, I am guessing, so idle curiosity shifts the question to their approach where I suppose the question is how much lag. And if they offer a bypass mode, that is user selectable.

If the lag on a line-in figures in 1% of the purchase decisions between Sonos and competitor XYZ, I’ll eat my shirt.  Sonos said long ago after the release of the Play:3 that the line-in was one of the least used features, and it can only be less used now given the current best selling Sonos units don’t have one.  Also, the thread the OP linked to was 8 pages over 5 years  That’s 200 posts, the majority of which were explanations why the lag was necessary, the rest were a few posters posting multiple times.  It’s a fringe request, and any serious live performance artists have specialty PA systems built for live performance.  I know those facts are anathema to your constant desire since the S1/S2 split to put down Sonos for any apparent reason you can find, but those are the facts. 

Hmm...apart from reading only such posts of mine that allow you to keep saying this, is there anything else you have to say? Grow up, if you can.

Whatever.   Your comments in these types of threads are pretty transparent.  I’m just letting you know that, but go ahead and shoot the messenger. 

OP here.

It would defeat the major selling point of the Sonos system, i.e. the ability to play all connected speakers in sync. Basically, what Sonos is based on. 

Yes I can understand that this is a must-have for all Sonos playback features.

Exactly.  The very first time they did this (if it is even possible to remove the buffering stage at all, a BIG IF), the first posts of the announcement thread would be complaints that it can't be used for multi-room, and "what good is it for DJ'ing if I can only play it on 1speaker!!??"

Fair enough. This would be very probable indeed.
 

I doubt that ‘many’ people are bothered at all - just a very tiny minority.

I also don’t have exact numbers. In the forum-threads about this topic they are not the tiny minority.

So the above comments come down to

1. Multi-speaker over-the-air functionality is a very important feature.
2. Line-in audio-video and creative-production is a minor use-case.

But now I am still wondering if it is possible to greatly reduce, or manual override, latency and leave it up to the user, instead of the current perceivable lag of 75ms.

My situation is that we bought an expensive speaker that sounds amazing for most daily use. Really happy with it. But then we hooked up a little dj set for a newyear party and we got surprised it does not work due to the latency.

A majority of a tiny minority is still a minuscule proportion of the user base. 

In ideal network conditions that buffer could no doubt be reduced somewhat. Witness the fact that home theatre setups can manage 30ms, in large part because the links to the surrounds/Sub are over a dedicated 5GHz connection.

Sonos cannot, however, design a product around a ‘ideal’ network; the tech support phones would be ringing off the hook. They have, after many years of experience, settled on the current buffer size based on the environment found on the ‘typical’ home network at 2.4GHz.

One could actually argue that given the RF pollution that now floods the 2.4GHz band the 75ms figure has become a bit optimistic. This perhaps explains why Sonos now provide the option to increase the Line-In buffer as the user sees fit, without having to change the system-wide compression setting. 

I don’t know if this is simple or not, and of course it may not be possible just via software: a option to use the Sonos unit as a pass-through speaker, that also bypasses the ADC/DAC processes, with no lag, and no grouping possible in this mode. 

Whether there is enough of a market/need for such, I don’t know. But this will also appeal to the vinyl/analog only crowd. Or even to the ones that use it for video and are troubled by lip sync issues perceived by even the 70 ms lag. 

I do see this request is probably technically impossible, or maybe Sonos deems giving people the choice between buffering for multiroom or not buffering for stand alone use would introduce an extra degree of unwanted complication. I’ve described most Sonos users as “ have money, but no technical interest and not wanting to get it”, so ease of use is very important to Sonos.

I do think the line in feature may see more use now than it did in the past because of the renewed interest for turntables though.

That implies a physical analog bypass. There isn’t one. Besides, the volume control and EQ are all in the digital domain. 

Vinyl starts out loaded with distortion/noise/etc. The effect of the ADC/DAC in the Sonos pipeline would be negligible in absolute terms, and certainly in comparison to the damage already inflicted.

As for TV, Sonos has never recommended Line-In. There are HT products designed for such purposes. 

Yes, but if you see the options available to line in play, there is already some complexity there. But if the pass through option rules out grouped play, it also rules out stereo pairing, so vinyl users will have to choose between their cherished pure analog over that loss, or any other kind of grouped play. Perhaps it may make sense only for the Port/Amp, where at least stereo pairing will not be an issue.

All this bother and the niche case for it means it won’t get done, I agree.

Does Bluesound handle this issue differently?

That rules out any kind of physical bypass, for sure.

Digressing a little from the topic - I have found Line In to work brilliantly for my TV uses, one via Connect and the other via Connect Amp. With quality speaker pairs placed to yield a good soundstage, I am pretty sure the sound effect is better than just a HT bar solution, with a very effective phantom centre effect taking care of dialogue. With good speakers, even a Sub isn’t missed and I don’t much feel the lack of surround sound. I have also never been able to find any lip sync issues, even if I look for them. Perhaps the 70 ms is gap is less in my case because of a delay in the video as well? - no idea if that is the case, but I for one don’t need any change to the line in feature. 

Where I faced problems, it was in grouped play of the TV sound, but I solved that by ethernet wiring those Sonos units I needed to be in the TV groups, and this too works flawlessly now. 

An analog bypass for the Port?! It’s called an interconnect cable, leaving Port completely out of the equation.

I know! But then the music in that zone cannot ever be played on other Sonos units in grouped mode, when the buffer delay is not an issue.

If someone was sufficiently obsessed about such matters they’d add a splitter, with one signal going to the Port and the other bypassing it straight into the third party amp. And if even a splitter offended, owing to two parallel input impedances, they’d use a passive switch up front. 

Fair enough! Just the Sonos amp then, with a line in bypass mode?

Too much effort for too little return, I suppose.

At 100% volume from input to output, all the time? 

No, because it would need to be a physical bypass with volume control and EQ, if the bypass cannot be done via software.