There are two crucial distances in the placement of the spruce sound post.
The first is the relationship of the soundpost to the bass bar. The soundpost and bass bar are usually equidistant from the respective edge of bridge foot. This measurement can be made with a cut business card.
The balance of the strings is affected by this distance.
If the post is moved to the right, the E-string becomes strong. When moved to the left, the G-string becomes strong leaving the E-string weak.
The second measurement is the distance of the soundpost from the backside of the bridge foot.
This distance is usually 1/2 the width of the bridge foot , or, 1/2 the width of the soundpost.
|Distance between edge of foot and bass bar (4/4size)|
|Violin||1.0 - 1.5mm|
|Viola||1.5 - 2.0mm|
|Cello||3.5 - 5.0mm|
This second measurement greatly influences tonal qualities.
When the post is positioned close to the bridge, the sound becomes bright and stiff. When placed further from the bridge, the sound becomes softer and darker.
|Distance of back of bridge to soundpost (4/4 size)|
|Violin||2.0 - 2.5mm|
|Viola||3.0 - 3.5mm|
|Cello||5.0 - 6.0mm|
These measurements are the traditional beginning place for tonal adjustment.
Cutting and Setting the Soundpost
- Humidity, seasonal changes, or a poorly cut soundpost can affect the fit, or tension.
- If the post is too long or tight, the sound will be choked, harsh and stiff.
- If it is too short or loose, the sound will be muffled and shallow.
The angle, contact, fit and grain of the soundpost are critical to the full transference of sound and tonal qualities of the instrument.
The post must stand straight and be cut to have full surface contact with both top and bottom plates.
The soundpost grains must run perpendicular to the grains of the top plate.
At Southwest Strings, all soundposts are professionally carved and correctly placed to maximize sound quality.