Depending on the system, they could have incorporated them into the cabinetry e.g. Bose or maybe in the walls out of sight like the B&O systems. My guess is probably in the cabinets below the TV.

Thanks for trying to help. I do understand that they could have been incorporated in the cabinets, but there's no sign that this is the case here, which is why I asked. The square box on the ceiling looks to be a heat vent, not a speaker, and the black doors in the center are probably glass, and couldn't conceal a speaker system that would provide reasonably good sound. I suppose that the L&R could be concealed behind the art work on the side walls, but then where is the center? This is a beautifully designed media wall, however an important element seems to be missing. If not, then I'd really like to know the secret.

Hi! Some of the speakers are located in the lower cabinets that have the black centers. This is fabric. Hope this helps!!!