The problem is, grouping doesn’t do the job.  A more complex configuration is required, including the means to handle the crossover.  When you group Sonos rooms, every room plays the same.

I am sorry, but this is a complete non-starter.

I would expect Sonos would still provide the ability in the app to set the crossover and level on the Sub the same as it is when bonded. I understand the crossover also serves as a way to blend the main speakers but that isn’t necessary if you have speakers that can support the low end frequencies. The Move definitely can, and if I want to add a secondary Sub to an existing Speaker/Sub configuration, the crossover on the Speaker is already handled there.

Is there a technical reason why a Sub can’t be treated just like another connected, Sonos speaker?

Yes. Did you ever come across a subwoofer that has not been cabled to a traditionell system? Since it’s not a standalone device it wouldn’t know what’s being played.

Subwoofers are never used alone, as they are intended to augment the low-frequency range of loudspeakers that cover the higher frequency bands.

https://en.wikipedia.org/wiki/Subwoofer

Yes - it’s called a Sonus Sub.  It would know what is being played in the same way any other Sonos speaker does. You stream your content to it. Did you read the use cases in the original post?  Here’s another use case:

Currently, the Sub requires bonding with another supported Sonos device.  My feature request is that Sonos remove this restriction and allow the user to create a room with just the Sub that can then be grouped with another room(s).  In theory, since Sonos is already taking care of the sync via the group functionality, would work famously.

Think about it this way.  When you plug in your new One, Five, etc., you’re prompted to create a room.  What I propose is Sonos allow Sub to either bond to a device or configure as a new room.  You want to group it with a pair of Moves? Done.  As a second Sub in your HT? Done.  As a secondary Sub when you take your Moves out to the garage and you don’t want to be bothered to relocate your first Sub?  Done.

The idea has merit.  The question is whether or not it is technically possible.  What I don’t know is if Sonos streams the content directly to the Sub or is redirected via the master “bonded” device.  If it streams directly to the Sub, should be feasible.

If this config were possible, and the sub wasgrouped to a home theatre system a 70msec delay would exist, making the sub out of sync with the other speakers. 

Why would that be? The delay would not be there if bonded to an Arc or Amp, so what makes it different?

The link below are my ‘first thoughts’ on a standalone ‘grouped sub’ suggestion ...and why I believe it wouldn’t work with the current Sonos hardware. It explains the audio delay too:

https://en.community.sonos.com/controllers-software-228995/feature-request-allow-sonos-move-to-pair-with-sub-6833720?postid=16495379#post16495379

Thanks for the detail in the other post. I’m trying to wrap my head around the delay. For arguments sake, let’s think of the Sub as Five. Would there still be the delay if the Five was grouped with an Amp? Grouped with an Arc? Grouped with a Move?

if the answer is no, which I believe it is, why would it be different with a Sub. Especially if in the same room as the Arc, Move or Amp.

I regularly group a pair of Moves with my Kitchen Amp set up and haven’t noticed any delays.

There would be a delay - that’s why the ‘Amp’ (or any Sonos HT product) has the ‘Group Audio Delay’ feature in the Room Settings. 

See my reply above

It depends on the type of audio you are playing - try TV DD 5.1 audio-out to the Amp & it’s bonded surrounds ... and then put your ‘grouped’ Move Speakers next to your Amp speakers you should then hear the apparent audio-delay.

So does the same delay logic apply when playing just music?  My OP wasn’t pitching this necessarily as solution for HT -  More for these two primary use cases:

The other post you replied to was specifically targeted as solving for bullet #1 but could be applied to situations where the user desires more than one Sub in a location or where the Sub is far from the Amp but the user wants to play only music.  At that point, would there still be a sync/delay issue since the Sub would be operating as just another connected product in the group?

Just a few further thoughts, off the top of my head, on the ‘Sub’ subject…

The Sonos sub obviously needs a known receiver/amp device to bond-with in order to work correctly - that’s why we cannot get a Sonos sub to work with a ‘Port’ or ‘Connect’, for example. So in addition to Home Theatre Products (Amp/Arc/Beam) & the ‘grouping’ issues mentioned earlier  ...there are also issues with the Sonos Port & Connect too - all these devices would need to be excluded from ‘grouping’ with the Sub. 

So bonding (IMHO) to an ‘active’ Sonos product is the best way forward and whilst I can’t currently see any reason why two subs, for example, cannot be bonded to the same Sonos Room (that’s for Sonos to perhaps consider?), I just haven’t seen much call for that type of dual-sub setup from many folk here in the community. So perhaps more demand is needed in this area before Sonos may ever choose to go down this route. 

Obviously two separate Sonos Rooms, something like A Beam, Sub and Surrounds and a stereo pair of Sonos Fives & Sub, in the same physical room, can be ‘grouped’ and will work flawlessly for Music audio playback. Such a group (which contains two subs) can also work in some instances aswell for ‘some’ TV audio codecs and that’s where the HT Tools ‘TV dialog Sync’ and (to a lesser extent) ‘Group Audio Delay’ each have a role to play to help keep the audio in sync across all players. 

The bonding of the sub to a Sonos receiver product is currently mostly done using an ad-hoc (faster) 5ghz connection, or a wired connection back to its main player/receiver. The wireless connection is fast, but limited in terms of both range and penetration. During music audio playback the main player uses a 2.4ghz ‘buffered’ connection, which is where the 75ms audio-delay occurs. It might be possible therefore to ‘group’ the sub over the 5ghz band to some ‘active’ Sonos players for music audio only, but I don’t see much advantage to ‘grouping’ when ‘bonding’ would be a better alternative (particularly when it comes to TV audio playback and lip-sync).

THE SONOS MOVE

Yes, I guess a sub could perhaps ‘technically’ be ‘bonded’ to the ‘active’ Sonos Move and the frequency crossover automatically setup to play the .LFE channel to the Sub, but there are then issues as the Move is really meant to be a ‘portable’/‘movable’ device and ideally you would want to break the bonding ‘properly’ to play the .LFE channel before taking the speaker outdoors etc. It could all be a little ‘messy’ I think when both creating and breaking the ‘bond’ (manually or automatically), taking into account its auto-TruePlay tuning, Wifi/Bluetooth-switching features too ...and in real terms the Move has a pretty good Bass speaker built-in already for what is ‘mostly’ (for many) a portable device.

So I can see why Sonos chose to exclude the Move from bonding with a sub, but please note that the issue with attaching a Sub to a Move is just only a personal point of view.

Leaving aside any interaction with HT setups, which would be distinctly messy, the main issues with having a Sub as a groupable standalone room are not related to networking. It could simply be connected to the Group Coordinator node (in the first room) via direct routing over 2.4GHz.

As a non-HT component, buffering requirements would be no different from a bonded Sub, and channel maps (e.g. L+R) could be applied in the usual way.

The problem is how to manage the actual audio, in terms of crossover from main speakers which could some and go on a whim. And phase. And, by implication, Trueplay.  

Interesting problem, but I doubt there’s much commercial imperative for Sonos to pursue it given that its marginal effect would presumably be to reduce the sales of Subs...

@ratty would the Move though need it’s 2.4ghz band to stream it's music audio over WiFi? I’m thinking of the case where it is perhaps also ‘grouped’ with other Players, like a Play:1 for example - my thoughts were the ‘grouping’ (not bonding) between the Move and Sub would have to switch to the 5ghz band. It appears to be quite messy all round I think and even moreso with HT setups, as you mention.

Adding a Sub to Move would be rather questionable, for well-rehearsed reasons. One is designed to be portable, the other is anything but.

In terms of network communication, if a Move on WiFi can maintain group sync with rooms that are on SonosNet or a different WiFi band then there’d be no reason why it couldn’t do the same with a Sub ‘room’. 

This is precisely where grouping would be a beautiful thing.  No complicated Add/Remove bonding process.  Just group the Sub with your Move(s) when in the same room, ungroup when not.

I assume Sonos would still provide the ability to configure crossover, level, and phase on the Sub, whether in bonded or standalone mode. Again, we’re talking about the ability to add supplemental low-end (likely 80Hz and below).  The crossover on the main(s) isn’t ‘required’ here.  In an ideal world, Sonos would provide the ability to configure low/high crossovers on all of their speakers so you can achieve optimal blending, but isn’t required. The main Sonos speakers all have built-in crossovers that prevent the drivers from overloading. This is where I believe Auto Truplay would actually shine on the Moves.  It would, in theory, detect the extra bass from the grouped Sub and dial back it’s own low frequencies.  I may play around with this a bit.  I can disconnect the wired mains from my Amp but leave the Sub connected and then group with the Moves in Auto Truplay mode and see what happens.

I actually see this as an opportunity for Sonos to sell more Subs (and other speakers), and avoid some returns as well:

• Those with Moves that want a Sub but can’t add it.
• Those that bought a Move (or Moves) along with a Sub at the same time, only to find out they don’t work together.  Ultimately, they’re frustrated and return everything.
• Those that would buy a Move/Sub combo but have done their research and don’t because of this limitation.
• Those that want a second Sub (or more) in a room.  Whether you agree with the principle of multi-sub systems, there is a market here and it isn’t a small one. There are companies out there like REL that only make subs.  And this just covers those that are existing Sonos customers.  Think about the additional market Sonos could capture if they offered multi-sub systems (potential new customers looking specifically for this but going another route because Sonos doesn’t offer this).
• Symfonisk customers that want more bass.  There’s a whole, cult-like group that is hacking Symfonisks just to add a powered, 3rd party sub to their system.  Wouldn’t Sonos rather they just buy a Sub?  I’m sure Sonos would prefer they buy Ones with a Sub instead, but if the alternative is to have more business going to IKEA, might want to re-think this.

Bottom line, Sub is a great product and people want it.  Solve for these limitations and they’ll sell a load more of them, along with other Sonos products. 

Would love to hear more about the Group Coordinator node.  If I understand what you’re saying, perhaps an alternative approach would be to offer a “grouping” device that can bond to a Sub?  It would essentially be a One without speakers.

The crossover frequency is set automatically (except with Amp as it’s usually driving unknown passives). The capabilities of the main Sonos speakers are already known. Level and phase are preconfigured by Trueplay. The former can be adjusted to taste. 

It certainly is. A key point is to relieve the mains of low frequency duties so they can perform better in the mids. In particular Five/Play:5 goes down to below 40Hz on its own, so avoiding overlap with a Sub is important. Multiple LF sources would introduce peaks and nulls.

In an ideal world Sonos optimises everything itself. Which it does rather nicely.

Built-in crossovers? These are active speakers, with per-driver amplification. The crossover would almost certainly occur in the digital domain (DSP).

The GC is the node responsible for fetching the stream and distributing it to the peers (bonded or grouped). It’s in the first room of the group. In a stereo pair it’s typically the left unit of that room. In an HT setup it’s the master player. As such there’s already a “grouping device”.

We’ll have to agree to disagree whether the mains require a crossover.  I concur with you that low-frequency overlap would exist with a Five, but it definitely would not with a Move (or Symfonisk), which are the primary use cases here.  A Five can already bond to a Sub - a Move or Symfonisk can not.  I did run a test with a pair of Moves grouped with an Amp/Sub without the hardwired mains connected.  I dialed in the Sub crossover at 70Hz and it sounds amazing.  It takes the Moves to another level.  That said, would never suggest a consumer spend $649 on an Amp just to have this capability. 

So, there would be a need to add the crossover config, same as an Amp set-up, that allows the user to dial in the crossover of the Sub. Or, alternatively, use Trueplay to set a baseline and then adjust level to taste.

Adding a secondary, grouped Sub to a system would only require the same Sub crossover config.  The main system is already performing the Main/Sub crossover, whether automatic/Trueplay or manually configured.

FWIW - I’m a huge Sonos fan and consumer.  I have over 25k invested in whole-home audio, nearly 9k of that is Sonos.  I have Goldear speakers (HTR700s mostly) with REL Subs (2) and Sonos Subs (2) attached to four different Amps, two pairs of Moves, a Playbar+Sub and a hardwired HT system with Goldenear SuperSat speakers and Forcefield subs. It would be even more if Sonos offered this capability (I’d replace my HT with Sonos Arc/Amp/Subs). While you may not be a fan of what I’m proposing, there are others that would.  I ask that instead of shooting down the idea, suggest something that would solve for this without requiring a hack or cost-prohibitive alternative.  I’d gladly spend another $100 to have a device that gives me the ability to group a Sub (the Sonos Group?) or a Gen 4 Sub that can be bonded or grouped.