I suppose that's them:
Code:
Bus 006 Device 005: ID 08bb:2900 Texas Instruments Japan PCM2900 Audio Codec
Open a terminal and give:
and check if you can see them listed in the output of this command.
The next step would be to install the PulseAudio Device Chooser (using Synaptic). You need to run it, left-click on its icon in your system tray and select the Volume Control.
Next, you will need to select the Output Devices tab, right-click on your speaker's entry there and enable the Default option to set them as the default output device in your system.
Or if don't want to set them as the default device, you can just sent the sound of an application to these speakers on-the-fly in the Playback tab.
For more info, check this helpful thread here.