OK.  First, you can stop trying to tell Sonos to connect to 2.4GHz - it will sort that out by itself.  

You absolutely have to have a wired Sonos device with that many speakers and with those extenders.  It can be the Boost or a speaker located close to the router.  Do you currently have anything wired?  

What 2.4GHz wireless channel is your router using?  What about the extenders?  And, importantly, are the extenders set up in ‘bridge’ aka ‘access point’ mode?  If you aren’t sure, consult the manual and make sure that they are.

If we get that much clarified, we can work from there.

Thanks for the quick response.

I had a Boost wired to my router and the performance and reliability of the Sonos improved after I removed it and during one of the Sonos support calls I was advised to wire my Sonos 3 to the router and again it did nothing to improve the system. 

The 2.4Ghz channel is 13 but I have to change this almost on a daily basis and when I do it normally helps improve Sonos but only for the day and then then issues resurface and I have also tried the Auto select channel but no difference.

I will have to dig out the extender settings as I’m not a network expert so learning as I go. To be honest one of the key reasons I was attracted to Sonos was the ‘simplicity’ of the platform. 

Hi.  I am only willing to try to help if you have a wired Sonos device.  Sorry - it may not have helped when there are other issues but it is an essential part of finding a solution in my view.  Your router should be on one of channels 1, 6 or 11, with channel width set to 20MHx, not 40 or Auto.  SonosNet should be on a different channel (you only have 1, 6 or 11 to choose from).  You should not be changing the router’s wireless channel  daily, in fact, hardly ever. There is something fundamentally wrong here.

You could try the extenders on the same channel as the main router, or on the remaining option out of 1, 6 and 11. 

Any wired Sonos device should be at least a couple of feet from the router.

Sonos depends on a correctly configured network.  It can cope with less than perfect conditions, but it cannot uninvent the laws of physics.

Btw, the extender manual may refer to ‘disabling DHCP’.  This is the same as putting it into access point or bridge mode, which is where you want to be (and may be already - but we need to be sure).

Thanks John I have changed the router channel to 11 which is the same as the SonosNET channel.

Should I re-combine/syncronise the 2.4 and 5Ghz router bandwidths or is there an advantage to separating them for Sonos?

I will wire the Boost again and in my router setup i don’t have the option to change the mode which i believe is the same as the channel width you refer to, it is greyed out and set to auto.

Hi.  The SonosNet channel must be different from the router channel.  If you have the ability to change the SonosNet channel you must already have a wired device.  (If you don’t have a device wired at the moment I would expect the SonosNet channel to be greyed out, and to become active when a device is wired.)

I doubt that mode is the same as channel width.  Is that a Sky Q router?

Edit - my Sky router has no means I can find to set channel width!  I’ll assume that it defaults to 20 MHz as anything else wuld be foolish on Sky’s part - so let’s not worry about that.

No need to recombine bands.  Mine are separate and give me no issues

If you want to check channel widths on Android I recommend https://play.google.com/store/apps/details?id=com.vrem.wifianalyzer

Thanks guys and the Sonos channel is greyed out hence no wired device yet (v busy weekend)

Yes it is a Sky Q hub and I see you have the same challenge with the channel width.

I have also changed the router channel to 1 and I have been looking into the extenders via their utility app and PC SW but struggling to see anything relating to DHCP but will keep digging.