Wharfedale 9.5 Diamond Front Speaker

you have a poor connection somewhere in your signal path. This sort f problem could be anywhere from inside the speaker box to the output stages of the amp. speaker protection relay in the amp, or even a noisy vol control or dry solder joints in the output stages of the amp. eliminate anything external to the amp by swapping right for left and test, spray the speaker protection relay in the amp with 2-26 or burnish the contacts with a piece of white business card cut to fit into the contacts. You will see deposits on the card that you have cleaned from the contacts. Carefully inspect the soldering about the output stages(heatsink area) and re-solder any poor or cracked solder joints. Good luck... these are the most common problems. I can go further in if the problem remains after you have done this. Good luck