An important consideration in the use of ultrasound in biomedical applications is controlling the range and spatial resolution. In this study, the feasibility of using a mechanical waveguide to control the axial range of a flat disk transducer is considered. The waveguide is a water‐filled, circular glass cone fixed to the transducer. Experimental beam measurements are compared to theoretical predictions for transducers with and without waveguides. The results confirm that mechanical waveguides may be used to control the axial location of the natural focus and reduce the beamwidth at the focus and beyond. They provide a relatively inexpensive alternative to phased arrays and more flexibility than single‐element transducers, as different sized waveguides would allow a single transducer to operate at a variety of axial ranges and spatial resolutions.