An air pump includes a housing body containing an electromagnetic drive mechanism for oscillating a pair of diaphragms. The diaphragms define variable volume chambers, the chambers communicating with suction and discharge ports for establishing an air flow in response to diaphragm oscillation. The drive mechanism comprises coils defining an air gap and a permanent magnet type actuator reciprocably mounted in the air gap. The top of the housing body is open to enable the actuator to be visually inspected for proper alignment within the air gap. A cover is installed over the open top of the housing body with the actuator properly installed in the air gap. The cover contains air passages communicating with the suction and discharge ports. The weight of the diaphragm can be altered to achieve a desired resonance frequency tuned to the frequency of the electrical current.