HTC One M9 - Manual (Page 247)

Connectivity 234
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Just tap another speaker to stream music to it.
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To group speakers so that music plays through them at the same time, tap the Group button
next to a speaker name, select the other speakers you want to group it with, and then tap
OK.
Rename the Speakers
You can rename your Blackfire compliant speakers in Settings.
1. Make sure the speakers are connected to your Wi-Fi network.
2. Tap > > Settings > HTC Connect.
Your phone then turns Wi-Fi on automatically and scans for media devices on your Wi-Fi
network. You'll then see the available Blackfire speakers listed.
3. Tap next to a speaker name.
4. Enter the new speaker name, and then tap DONE.