Lower Loudspeaker doesn't work

Hi there, after the LCD replacement the lower loudspeaker seems not working anymore (also if replaced, so I think the problem is not the speaker itself but maybe is missing the connection between it and the MOBO). How is it connected to the MOBO? Maybe trough the black plastic bezel which contains the screws? It is broken in the left side, it fits good but maybe this is the problem that cause the malfunction?

Waiting 4 your kind reply