Use the point of a spudger to push on alternating sides of the connector to "walk" it out of its socket and disconnect the speaker cable from the I/O board (also known as the daughterboard)..

Don't pull on the cables.

It may take a lot of alternating before the connector comes out.

To reconnect the cable, align the connector and use a spudger or clean fingernail to push it fully into the socket.

Don't push on the cables themselves, or you may damage the connector.