How, exactly, do you “play music through spotify via phone or ipad”? Using Bluetooth? Instigating a stream from Spotify? Or what?

Yeah via Bluetooth, either thru selecting the speaker thru Spotify app, or I've also tried using spotify through the sonos app, no change in results

The system you own does not do Bluetooth. So are you using the Sonos app or Spotify Connect. Both are WiFi connections.

About your problem:  does the Sonos app say it is playing in each instance?

Thank you for the clarification, and yes it does say it is playing 

​@Cuziamindian 

When playing via the Spotify app to the Sonos speakers, the sound you hear is impacted by the EQ in your Spotify app. 
On Spotify, go to your avatar/name, then Settings and Privacy, then Playback, then Equaliser, and if you see a tick/check next to one of the EQ settings, tap that setting to stop using it, and just ensure Equaliser is On but showing a flat EQ line. 
Or adjust to the EQ you find the most pleasing when playing via Spotify to the speakers. (Note: it takes about three seconds for any EQ change to be heard on the speaker, it’s not instant.)

Also make sure the Spotify ‘Volume Level’ in its settings isn’t set to ‘Loud’ as that can impact quality. Stick to ‘Normal’.

I did have it set to a flat eq and normal volume level, but maybe I'll try a bass boost setting and see if that is better. Appreciate the response, thank you

Try a number of them. Bass Boost can make things a bit muddy and lose some dynamics. But just tap them and see what you like best. But don’t forget to leave it a few seconds for the sound to take effect!

BUT as you rightly said earlier, the best and unbeatable sound is via the Sonos app, not via Spotify Connect… 

(You do know you don’t have to play your music through the TV and that you can select the Home Theatre ‘room’ for music playback via the app, right? You add Spotify as a Service on the Sonos app, allowing you to play Full or Ambient as you wish.)

​@Cuziamindian 

I added an edit above.

Hey, thanks, yes I do normally play music through app, not tv. I Just noticed the bass was significantly better via the TV route, was hoping to get the same quality via app

And by “via the app” I mean the Sonos app - ie select music on the Sonos app (from the Spotify account), choose the home theatre room as the speaker, and play the music.
Just checking that’s all! :)

Note that ‘most’ stuff coming from the TV is in some sort of 5.1 format, where the .1 part is just for the sub to play. Most music streamed is in stereo format, where there isn’t a distinct .1 for the Sub to play, so the ‘other system’ kicks in, where data lower than X (and X is usually determined by the Sonos speaker that the Sub is bonded to) is sent to the Sub, rather than the speaker for reproduction. This is how/why there are disparate settings in the controller for streamed content, rather that digital (optical or HDMI) input. 

Thank you, that makes pretty good sense

I meant to type “what” is playing. This is what ​@Airgetlam also alludes to. The app shows if you are getting stereo or 5.1.