If you're asking about the big black square things above the door, no they are not heaters. Those are speakers. I have another set on the other end of the shop and a pair of subwoofers also. Makes for a fine audio system when out there puttering on the car!
The shop is so well insulated I heat with a 30,000 BTU propane heater. In 15 minutes I can get it warm enough I can work in an insulated sweatshirt with outdoor temps in the 30's.