I used a sheet of 18mm MDF, used the original shelf as a template, routed it out. put a nice edge on it. grip filled an extra piece of 18mm MDF at the front for strength and to allow me to drill into it for wooden dowels for the pivot points.
Sprayed the underside black and used techserts to allow me to bolt the speakers in and so not ruin the wood if I kept changing speakers about.
Used aluminium mesh to cover the speaker holes then covered with acoustic carpet bought from halfords. Black shoe laces used for the little lifting cords.
Cost me bugger all as I used everything at work, the only cost was the carpet and speakers and I got them half price by badgering the local sony centre.
Cheap as chips as a certain orange man says.
