Can't specify Jack output ports

[to7m]

There isn't currently a way to specify which Jack output ports SMPlayer should send audio to, or if there is I can't find it.
This is a problem because it means I have to disconnect SMPlayer's 'mpv' Jack client from 'system' each time I start SMPlayer, and reconnect it with the designated pre-speaker processing client.
For this reason I currently use an ALSA loopback device, which isn't ideal, so my suggestion is to make SMPlayer Jack-aware enough to specify output ports.

[rvm]

What option do you use with mplayer or mpv to select the jack output port?