The ESS Professional 6 series was a large loudspeaker made by ESS (ElectroStatic Sound) of Sacramento, California.
The speaker was very large. Some referred to it as refrigerator-sized. It was made of 2 layers of ¾" thick low-density particle board, which added considerably to its weight. This design was different from previous variations of ESS speakers such as the amt1 series in that instead of one subwoofer there were two 12" woofers. These were not intended for ongoing household playback, but instead medium venue outdoor arrays. There were four air-motion transformers of the mid-sized upward firing variety in a 180-degree format, instead of the traditional horizontal dispersion amt common with all of the "home" type loudspeakers ESS built.