Connect with selected devices only

[epalosuo]

Hi,

I've used Spotify Connect with my Yamaha amplifier, with big loudspeakers connected with it. Now, I'd like to download Spotify also in my son's mobile phone and let him use my account, when listening to music in his own room, through his own small loudspeaker.

Is there any way to only connect his phone with his own loudspeaker through bluetooth, while he'd still be operating Spotify account through our mutual wi-fi connection? When tested, his phone also showed the Yamaha set as a potential option for listening, and I can only imagine what will happen: with his small loudspeaker, he will set volume very high, and then accidently switch to the Yamaha, with the result of everyone's ears blasting. I really don't want to risk this. How to go about, with him still having a chance to listen to Spotify with his own set?

He is using a Samsung Trend mobile phone.

Thanks for help!