I've seen many other threads for this, this is a feature request that in the new app a feature is added to disable the Sonos Arc during music playback.

I have an Arc, Sub Gen 3 and a pair of Fives set up for surround. The sound quality is worse than just using the pair of Fives in stereo with the sub. Turning music on the surrounds to +15 kills the bass from the sub. The music playback experience is just much worse since adding the Arc and this needs to be fixed