AHUJA AU-40XT PA DRIVER UNIT durable and weatherproof construction. sharp, piercing sound with a high SPL. Precision winding on an aluminum bobbin provides effective heat dissipation for voice coils. The built-in 100V transformer in the Model AU-40®XT features easily configurable power taps and impedances that may be changed by moving the rotary switch at the back. When placed on a reflex horn, the degree of protection IP 66 offers against foreign particles like dust and water jets makes them perfect for outdoor use.