Not a GIANT VIOLIN

Compared to a violin, the double bass is enormous, heavy, ergonomically challenging and prone to mishap. Its size and mass make it difficult to carry, store and transport. The amount of tension pulling on the instrument (commonly around 100kg or 220 pounds) makes its construction parameters critical. Build it too lightly and it will self-destruct; too heavily and it will sound and respond poorly. The set-up is noticeably different in many ways from that of the violin, viola and cello, and is crucial to a good, healthy playing experience. The double bass is played in more varied types of music than any of the other stringed instruments, requiring various set-up details. There are no real standards for string length, body size or shape.

My intention in this article is to provide some important set-up and playability details to aspiring bass luthiers and handy double bass owners. With that in mind, here are a number of considerations for getting and keeping a double bass in good playable condition.

CLIMATE CONSIDERATIONS

Being so wide (wood expands and contracts mainly across its width), a double bass reacts more severely to rapid changes in relative humidity (RH) than other instruments. Most problematic is the change from humid to dry conditions, when cracks and seam openings tend to occur. Top plate-to-rib seams should therefore be closed with very weak hide glue, so that seams will tend to open before cracks form in the fragile softwood. RH should be monitored regularly; of course 50 per cent would be ideal. But that is rarely attainable in the real world (of central heating and rapid travel between different climate zones). Basses that reside in temperate areas should in most cases be humidified in the dry months. Gradually weaning the RH into the 30–40 per cent range will avoid most problems. Room humidifiers are most effective, but internal humidification is sometimes the only available solution. This is most effective when the instrument is kept in its case. Care must be taken to avoid damage caused by dripping from internal humidification devices.

Flat-backed basses are more prone to dryness-related problems, because the back braces are mounted at acute angles to the wood of the back plate. Violins, violas and cellos do not encounter this issue as they do not have braced flat backs. Flat-backed basses are also more likely to need seasonal soundpost changes and/or adjustments.

Warning: Over-humidifying a bass in the dry season can cause open seams and cracks when the instrument leaves its humid environs for very dry venues.

SET-UP PARAMETERS

Unlike the other bowed stringed instruments, a majority of bass music is played in the lower positions of the neck. It is important for the fingerboard camber to be even throughout, and not sloped noticeably up towards the nut. The camber on the E-string side should be 1.5–2.5mm, and 1–1.5mm on the G-string side. In both cases, the nadir occurs around the exit of the fingerboard from the neck wood.

Under the centre strings, the camber should get progressively lower from the E to the G side. Camber is best measured under string tension. Because bass necks are under considerable tension, there is a tendency for them to bend a bit. Many bass luthiers (myself included) utilise carbon-fibre stiffeners in bass necks to counter this. The stiffener seems to have a secondary benefit of improving the instrument’s response, as little energy is wasted in making the neck wobble and vibrate, instead promoting more energy transfer to the corpus.

Keep in mind that aggressive players generally need more camber than finesse players. This is especially true of jazz and bluegrass bassists, who tend to play mainly pizzicato. Luthiers setting up a bass would be wise to observe the playing style of the bassist before tackling their set-up. Pizzicato players who fire the string towards the fingerboard cause considerably more rattling than those who fire across the string. Arco players who tend to play near the fingerboard will cause more rattling than those who play close to the bridge. Regardless of the fingerboard layout, any bass can be made to rattle if played super-aggressively. Dressing a bass fingerboard must be considered a compromise between easy playability and attaining the cleanest possible sound. Perfection is unattainable.

FINGERBOARD ARCH SPECS

Based on a standard fingerboard length of 860–870mm:

For general all-around playability End 68mm radius; nut 53mm radius.

Easy jazz set-up End 72mm radius; nut 60mm radius Soloist set-up End 64mm radius; nut 50mm radius.

A slight inverted ‘V’ shape towards the upper (thumb) positions can be helpful to players who often venture into that zone. That shape can help prevent the string from sliding sideways when pressed down in the thumb positions.

FLAT-BACKED BA SSES ARE MOR E LIKELY TO NEED SE ASONA L SOUNDPOST CH A NGES AND/OR A DJUSTMENTS

All these specs are for a rounded fingerboard, not one with a Romberg shelf (see figure 1). Those will generally have less arch under the middle strings, and will therefore require extra height above the fingerboard on those strings. Keep in mind that the wider the strings are set at the bridge, the less arch is needed to facilitate clean string-crossings. Also bear in mind that not all fingerboards are thick enough to be dressed for a tight-radius arch while still maintaining adequate edge thickness of over 9mm. At the nut, the average distance between string centres should be 10mm for average spacing, 11mm for wide spacing and 9mm for narrow spacing. All strings should be set approximately 0.4mm above the fingerboard surface (about the thickness of an average business card). This will probably seem low to violin luthiers, but keep two things in mind: firstly, a lot of bass playing occurs near the nut; and secondly, the thick bass strings resist bending somewhat, and form a slight arch shape leaving the nut, so buzzing rarely happens there. The nut grooves should be formed accurately, just slightly wider than the string’s diameter. Groove depths should be about two thirds of the string’s diameter. Widening the grooves slightly as they enter the pegbox eases tuning, as does lubricating with soft pencil graphite. At the bridge, the average distance between string centres should be 26–27mm. Wide spacing would be 28–29mm while narrow would be 24–25mm.

FIGURE 1 Double bass fingerboard styles (at the end towards the bridge)

Checking the distance between string centres at the bridge. Dividers are also useful for this task.

STRING HEIGHTS AT THE END OF THE FINGERBOARD

Measured to the underside of the string:

Average G: 5–6mm; E: 8–9mm

L ow G: 3.5–4.5mm; E: 6–7mm

High G: 7–9mm; E: 10–12mm

These measurements are for steel and hybrid strings. Gut strings will generally need more height and more fingerboard camber (especially for players of the ‘slap’ style, who often like to be able to get their entire plucking finger between the string and fingerboard). Ideally, each string from G to E will sit 1mm higher above the fingerboard, i.e. G: 6mm, D: 7mm, A: 8mm, E: 9mm. As you can deduce, string heights and bridge arch are dependent on the shape of the fingerboard. There is no universal template for bass bridge shape/arch. Again, Romberg-shelved fingerboards will require higher middle strings to be bowable.

Bridge adjuster wheels are a valuable tool with which to assess the best bridge height for player comfort and sound quality. There is still some controversy concerning the effect of adjuster wheels on sound quality; truthfully, I and most of my colleagues cannot hear a significant difference between solid bridges and those with adjuster wheels (when they are properly installed). Different types are available, made of materials such as aluminium, Delrin and wood. The tonal differences between them are subtle.

Checking string height using a home-made gauge crafted from an old credit card

ALL PHOTOS AND DIAGRAMS ARNOLD E. SCHNITZER