6th and 7th rear seat audio controls

Hello all, my disco 2 ES premium has the rear headphone sockets and controls in the back, for the 6th and 7th seats, can anyone tell me if you need Genuine land rover earphones ?, the car did not come with any earphones so i got a cheap set from Asda which when pluged in the sockets the back lights on the controls light up but no sound?? this is the same for both sides, any help would be great................

The children use the rear sockets. They have a mix of headphones none of which are genuine Land Rover and all seem to work.