Discovery 2 driver's door speaker not working

The large speaker in the driver's door on my 2003 D2 has stopped working. There is no power getting to the speaker - will check the back of the stereo but do I have to fiddle about with the amp under the passenger's seat? All of the other speakers, big and small, work fine and have connected the passenger door large speaker to the driver's side to check it is the lack of power that is the problem. Any suggestions gratefully received!

I'd check the wires in the rubber conduit between the A pillar and door - D2 wires have a tendency to chafe in there.

Check for voltage on the output from the amp to the loudspeaker when in use, no voltage means an iffy amp.

Will check both - thank you. If only one speaker is not working would this tend to suggest a problem with a wire rather than a dodgy amp? I couldn't find any power going to the speaker when I tested it. Will take the head unit out and wiggle the wires there too - or is this a waste of time?!

As Discomania says, the first check must be in the flexible rubber tube between the door and the bodywork, 90% of open circuit faults in any of the door systems; speakers, mirrors and windows will be in there somewhere.

Will check there first - thank you

Two broken wires in the rubber door tube - all fixed now - thank you for the help!