The Backbore is the expanding, tapered, interior section of the mouthpiece that begins after the cylindrical throat or bore, and extends until it exits the mouthpiece. It can be made up of one, or many small tapers.
The total length of the Backbore has a taper. The length and the distance that it expands generates a number called the average taper. If the Backbore begins at a diameter of .144" and ends at a diameter of .344" the change is .200" . If the Backbore is 2.5" long we can calculate the average taper. Take .200" and divide it by 2.5, we find an average taper of .080" per inch. This would be a straight or linear line shown below with the heavy Black line.
If the initial taper is greater (Shown in Blue) the Backbore will have a greater volume, less blow resistance, and less upper partials in the sound than the linear taper, although, the average taper will be the same.
A Backbore with a smaller initial taper (Shown in Red) will have less volume, more blow resistance, and more upper partial in the sound than the linear taper, although, the average taper will be the same.
- In general terms, a tighter Backbore may be more resistant, aid projection, and produce a sound that emphasizes the upper partials of the harmonic series.
- A more open Backbore may be less resistant, produces a sound that emphasizes the lower partials of the harmonic series, as well as, spreading the sound throughout the room.
The Backbore can have a great effect on intonation.
This can vary between players. A Backbore that is too large will cause the pitch to go sharp in the upper register. A Backbore that is too tight will cause the pitch to go flat in the upper register. A balanced mouthpiece with proper cup, throat, and Backbore that matches the player and equipment will always play best.
The Backbore can have a detrimental effect on sound and resistance.
Unfortunately, manufacturers and players alike often overlook the importance of the Backbore.
At GR Technologies, we incorporate our own backbore designs into every mouthpiece.
As with all components of a GR Mouthpiece, mathematics plays a major role in the Backbore design. Blow resistance and tapers are scientifically manipulated to produce the desired sound and blow resistance.
Our Backbore designs are free from discontinuities and are critically balanced and blended with all other aspects of the mouthpiece. The result is a beautifully centered sound, rich in overtones, with incredible response, intonation, and projection.