Unrealistic requirements are often placed on sonar transducers employed in ocean acoustical tests. This is because projectors and hydrophones are often the last components considered when system requirements are established. Acoustical systems for performing these tests are typically designed for one application, but are frequently used for additional tests. This can cause conflicting system requirements and place constraints on the transducer design which result in failure to meet test objectives and redesign of the whole system. This paper provides an approach for first establishing realistic transducer design requirements which, in reality, drive those for the complete system. Experience with important transducer acoustical parameters such as operating frequencies, sensitivity and transmitting response, directivity, dynamic range, self-noise, and flow noise is discussed. Also discussed are experiences with at-sea effects of system deployment while stationary or maintaining a constant velocity, operating depth, cable dynamics, hydrodynamically configured tow bodies, and costs.