Bluetooth speaker: visible, but no sound

["W. Martin Borgert" <debacle@debian.org>]

Hi,

I'm trying to use a bluetooth speaker, but don't get any sound.

bluetoothctl shows the device as paired, trusted, and connected and
lists it as "serial port", "headset", "audio sink", and some others.

pavucontrol shows the speaker as "Output Device". But xfce4-mixer,
while showing the speaker in the "Sound card" dropdown, does not
allow me to actually select the device. Also, I wonder what device
string I have to put into my .quodlibet/config to use the speaker
(gst_pipeline = pulsesink device=???).

Any ideas?

TIA!