In order to provide a way of changing the shape of the backbore, several controls are provided, the Backbore Width Setting being one of these. Changes to the width of the backbore take place at point on this which we have called the Backbore Nodal point. This may seem like a fancy name but the point is needed both to bring about changes such as the Backbore Width and Backbore Height and also to enable the process of backbore manipulation to be described. The Backbore Nodal Point is indicated by the orange circles on the diagram below, as well as the purple arrows. In this diagram, (a) shows the Nodal Point at its default setting while, on (b), (c) and (d), the position of the Nodal Point has been adjusted using the Backbore Height Setting.
When used on its own, the Backbore Depth Setting produces mouthpieces which are indistinguishable from thos with an extended throat. These are shown below in the diagram. In the rigththand mouthpiece in this diagram, the Backbore Nodal Point has been moved downstream on the mouthpiece by means of the Backbore Depth Setting Slider, its position being marked by the circle and the purple arrow.
As the diagram shows, when the Backbore Height Slider is moved in the positive direction, the Backbore Nodal Point is slid downstrem in the backbore. It is only when the Backbore Width Slider is moved in conjunction with the height slider that conventionally-recognisable backbore are produced. Thus, when the width setting is made positive and the height setting then increased, backbores similar to that shown in the top figure on this page, at (b) are produced. similarly, when the width setting is made negative and the height setting increased, backbores similar to that shown in the top figure on this page, at (c) are produced.
Backbores such as that one shown at (d) in the above diagram are obtained by setting the Backbore and Backbore settings.