I’m puzzled about how your speakers are currently configured and what you want to achieve. 

If you’re creating a home cinema system, you can bond two of your Fives to your Arc as rear effects speakers, plus have the Subs. That’s it for the home theatre setup. If you are using the other Fives, grouped with the other speakers, you’ll have a 70msec or so delay to those Fives. That will muddle the sound in the room space. Adding another pair of Fives will not help this. 
 

So: what is your current setup?

It sounds like you have a single home theatre setup, is that corect?  Arc in the front, 2 fives playing the surround sound channels in the back? Going to assume that’s the case with my answers.

You cannot add 2 more speakers to this home theatre setup.  It’s not supported by Sonos  You can add a separate Sonos room to this same physical room, but you won’t be able to use it for TV sources without creating an echo.  For music, you’re not going to have a clear stereo image, since you have left and right channels coming from many different places.

Your rear surround channels should be placed behind the seating area, which sounds like the middle of the room.  They shouldn’t be 15 ft behind you in the back of the room.

I think you may find that your current setup fills the room up better than you think.  I would try that before purchasing anything.  If it does not, I would get a speaker pair that focuses on the back area of the room, that is only used for music.  Maybe get some Era 100s or 300s and use them for surround, use the Fives for music only.  Another alternative is to use Fives in the front of the room as there own Sonos room for music only, without using the home theatre setup.  It’s not a ‘fill up the room’ setup so much as a great front stage for music.

My space is probably 20’ by 20’ and have an Arc/Ones/Sub setup for tV, and then Fives+sub in the front for music. I’ve never felt that the Fives didn’t cover the space well enough, and think you might be good with that for your space as well.

Thank you to both of you for sharing your perspectives and advice. Yes I do have the rear pair of Fives bonded as surrounds to my Arc. It isn’t for using with TV or movies though, my primary use is for music listening.

Prior to having the Sonos I had large floorstanders supported by two big and capable SVS subs. I decided to go lifestyle system approach and I am happy with it, very happy, but I do find that currently, with four Fives, 2 Subs and an Arc in a midfield listening (not quite nearfield) that I often have the system volume at close to 80. So I was imagining that once I am in an even larger space, that the SPL (sound pressure level) will be lower. Hence the thought that in order to get it back to where it is now in a smaller room, physics suggests that I have to add more drivers to move air, because there will be more air to move.

I am on the fence about this for sure. Thanks for being my sober second thought.

Sonos do offer generous home trial periods. You could buy-and-try the extra pair of Fives. 

I’d also be tempted to try them all as single speakers in multiple rooms rather than stereo pairs. And bond Subs with Fives rather than the Arc. 

I do have many recordings where the stereo effect is extremely important to the perception of the material as cohesive so I am unsure if not having actual stereo pairs would be enjoyable. Although this did make me think that if I went with a third pair of Fives that the third pair could just be added as mono units, potentially. Not clear though if that would be beneficial.

What would be amazing is if Sonos developed a processing unit that would work as a surround sound processing control centre. That would really be amazing.

It would not be beneficial.  More speakers is not better.  Of course, people can have whatever subjective opinion they want, but the idea of stereo is to best represent a stage in the front as if you were hearing an actual live perforamce.  Hearing the same audio coming from different directions cannot improve the stereo effect.  Generally, mono is the preferred option where there is no desire for a front stage, no distinct target area for listening, or perhaps too many people at different tasks to make a front stage make sense.  A large outdoor space where there are multiple seating areas is a good example where mono might be the best option.

For what purpose?  The Arc essentially doesn’t this already in that it distributes different audio channels to the correct speakers for a suurround setup.  Are you wanting this function to be a device without speakers?  Or is more a matter of having more flexibility so that users can place various numbers of speakers around the room and Sonos would be able to use spatial audio tech to send audio to the right speakers, depending on where you happen to be in the room at that time?  That would be spectacular, but well beyond scope of current technology.

Hi @MG1214 

I’ve been following this thread and frankly I’m a bit confused as to your objective. You talk about SPL which in simple terms is about “volume”. I see your point if you are trying to fill a large room from end to end.

However in your last post you reference “stereo imaging”. In strict terms of  “stereo imaging” that only involves two (2) matching speakers properly placed with the listener seated in the “sweet spot” (typically 6 - 10 feet from the front) where the audio frequencies from both speakers converge. Speakers with larger drivers allow you to adjust the seating accordingly. Conversely, in a large room after a certain distance the sound will be mono as the reflections diminish.

Having multiple speakers (beyond two) in the same room placed at different points effectively removes “true” stereo imaging. However that scheme will accomplish your goal for increased SPL.

If increased SPL is your goal you might a submit a diagram of the room showing furniture placement, doors, windows and built-ins. That will provide community members a blueprint of where suggested Sonos speakers of a particular model and size might be placed.

Note:

@melvimbe response and mine crossed. He is a faster typer

I will once it is appropriate provide more details for the room, and I do appreciate that the community can better help with more information. I do understand that stereo imaging is best communicated as you say sitting in an appropriate sweet spot, between two mains. However, I currently have two Fives that I face, and two Fives behind me, and I still perceive stereo imaging. If anything, it feels for lack of a better term, more immersive.

And while I am no expert by any stretch of the imagination, I have been using better quality audio gear since 1980. I realize my questions have been a little incoherent in terms of what I am really trying to achieve, but in a nutshell:

1. I wish to first and foremost increase my SPL, and for that I know I have to add more drivers
2. Secondly, when using a third set of speakers (probably located in the middle of the listening area) how to best integrate them so that they do not obscure the clarity

Based on the feedback, and my limited knowledge, it feels that if I do wish to go this route, perhaps the best way to satisfy item 2 is to leave the two new Fives in the center area as mono.

While I do have the stereo pair of Fives located behind me as surrounds bound to the Arc, I almost never use them that way. 98% of my current use of the Sonos system is with music that I stream from my phone, either local Flac files or streaming from Tidal. Neither of those streams will of course be able to take advantage of any surround processing. 

Hopefully it would be possible to add a third pair of Fives into a larger room and increase my SPL without audibly blurring the fidelity of the playback. My sincerest apology for being so scattered in my thoughts. I’m sure that doesn’t help people who are so kindly offering me their time and thoughts.

If the room is “live” you’ll have some difficulty with reflections. For example if you are at one end of the room, reflections from a nearby speaker will return at 35x2 or about 70ms later.

Likely, your perception of SPL will be tied to the amount of bass. This implies adding more subwoofers and locating them cleverly.

Unfortunately, we humans have been conditioned to equate distorted with “loud”. Once we perceive some distortion because the equipment is being pushed too far, we declare “loud”. In this respect SONOS will never sound “loud” because it is designed to never enter this distortion mode. In my college apartment we could run at levels that made verbal communication very difficult, but there was very low distortion. We would have constant requests yelled in our ear (with cupped hands) to “turn it up”, because it did not yet seem “loud”.

Thanks buzz, and I agree with your general point, but for me I am pretty confident I know the difference. I would not favour increased volume that is achieved with audible distortion products. Hence why I would add more drivers rather than simply turn it up.

Hi

If you decide to add two more Fives in the center of the space you would essentially have 4 Sonos rooms in the same space. Not saying anything is wrong with that idea just pointing out how they would appear in the Sonos app.

Maybe the ideal solution here (dare I say it!) is to sell your existing Sonos gear and buy an appropriate amp-and stereo-speakers combination that will give you the SPL you want, together with the stereo sweet spot.  

I sold off a large system and moved to the Sonos intentionally. I had a set of wonderful Monitor Audio PL200s supported by a pair of SVS SB 2000 Pro subs driven by a NAD M3 integrated amp with a Gustard X16 DAC. I am attempting to just find a balance between my former music life of big speakers and wanting quality, room filling sound when I want it. Not going back to using amps and DACs. Did that for many years. Happy to move past that.