Hi @SerCaf, welcome to the Sonos Community!

Sorry to hear that the Sonos Ace’s volume is too loud. There isn’t any way to make the Ace quieter than the minimum volume, so if you’re one touch up from the headphones being muted, that’s the lowest they’ll go.

I have seen another user mention that updating helped them, I’d suggest trying that. Our support article for Updating the Sonos Ace has the steps to do so.

I hope this information helps!