Feedback, usually of a verbal nature, is important for speech therapy sessions. Some disadvantages exist however with traditional methods of speech therapy, and visual feedback of acoustic data is a useful alternative that can be used to complement typical clinical sessions. Visual feedback has been investigated before, and in this paper we propose several new prototypes. From these prototypes we develop an iterative model of analysing the design of feedback systems by examining the feedback process. From this iterative model, we then extract methods to inform design of visual feedback systems for speech therapy.