Issue 3

Getting Your Bass Playing The Way You'd Like

Part II

In Part 1 I discussed the importance of the fingerboard as the foundation of the set-up. Now I’d like to get into the other major components of the set-up, and how they affect the bass’ sound and playability.

The Soundpost

A simple softwood dowel held in place between the top and back plates by the tension of the strings, the soundpost is an important structural entity, as it keeps the top from sagging under the treble-side foot of the bridge (the bass bar performs this function under the bass-side bridge foot). But it also performs important roles in a string instrument’s sound and response. Some luthiers believe the post serves to transfer vibrations from the top to the back ; others believe it is simply a stiffening rod, creating a pivot point for the top to vibrate around. I think both these theories have merit, and I also believe that moving the soundpost has an affect on the swinging of the bass bar, the “engine” of the bass’ soundboard. There are several other theories as well, but for the purpose of this article I’ll stick to the practical ramifications of soundpost fitting and positioning.

FIT: The fit of the soundpost where it touches the back, and especially the top, is crucial. This is important for both tonal/response issues, and for the health of the instrument. It is especially important that the post fit securely against the soft top wood, to avoid creating a dent, or worse, a crack in the fragile softwood top plate. Some luthiers (myself included) file a tiny relief bevel around the soundpost ends, to help prevent splitting of the post and abrading of the top when the post is moved around. I have seen several soundposts fitted with a huge bevel which reduces the contact by about half; this can do nothing good for the tone or response, and can actually cause a split in the top table. Any bevel needs to be tiny or the installer cannot tell if the soundpost actually fits. If a soundpost is fitted with no bevel at all, it is important to remove any fuzz or splinters around the ends, because otherwise a nasty buzz may result.

POSITION: In general, the soundpost should be located laterally (east-west) just about opposite the bass bar. So if the bass bar is encountered 65mm in from the bass-side f-hole, the soundpost should be located about 65mm in from the treble-side f-hole. It should be located longitudinally (north-south) about ¾ to 1¼ diameters below the bridge foot (toward the tailpiece). So, if the soundpost is 18mm in diameter, it should sit about 14-22mm or so below the treble-side bridge foot. I usually start a soundpost fit-up by putting the post opposite the bass bar and one diameter below the bridge. I call this the “neutral” position. Keep in mind that the bottom of the soundpost needs to sit squarely under the top, with minimal tilt.

In most cases I do not “adjust” a soundpost until I have first fit it well in the neutral position. This spot works well most of the time. After a little “playing-in”, the bass’ owner and I will determine if adjusting is necessary. The post’s position can be changed if the player wants more or less of a certain type of tone and/or response. Rarely do I adjust a soundpost more than about 5mm in any direction. The effects of soundpost repositioning are usually quite subtle, but sometimes eye-opening. I’d like to state here that soundpost adjusting is a bit of a “black art”, and that sometimes the result makes no sense. I am convinced there is some magic involved.

Here is my take on some basic guidelines to bass soundpost adjusting:

For more bottom: Away from the bass bar.
For more punch: toward the bass bar.
For a more open, resonant sound: Away from the bridge.
For a tighter, more controlled sound: Toward the bridge.

I sometimes encounter a bass that responds differently than is typical to soundpost position changes. Often, the only way to find the “sweet-spot” is via time-consuming trial and error. This can be really frustrating, and I personally can only handle about an hour of this before my ears and patience go bye-bye.

You tinkerers out there, please keep this in mind: most position changes will also require re-fitting. That’s because the surfaces to which a soundpost fits are complex curves, often irregular as well. This is a job for an expert, especially in an old carved bass. Doing the job right requires lots of light, proper tools, mirrors, and huge reserves of patience. I’m not saying a talented and well-equipped do-it-yourself-er should not tackle this job, but there are consequences to doing it poorly. Installing a soundpost with its edge pressing into a grain of the softwood top table can cause a serious crack! And a soundpost should never be moved around with the strings tuned up! If a “luthier” starts knocking your soundpost around without first taking down the string tension, get out of there fast! This practice can tear shreds of wood out of your bass’ top, whether it’s carved or laminated.

TENSION: Ideally, the soundpost should fit just tightly enough to stay in position without strings on the instrument. But seasonal changes and short-term humidity swings can have a major effect on the post’s tension. Round-backed basses are better able to handle these variations, as the back is more flexible than a flat-backed bass with stiffening back cross-bars. Many flat-backed basses require both a summer and a winter soundpost to sound and respond their best.

Response issues are very often related to the tension, or tightness of the post. Violinmakers rely on a simple axiom: A tight post equals a loose fiddle, and vice-versa. This is often true of basses too; however, basses change dimensions so much (because they are so large and their wooden parts vary so much with climatic conditions) that it is impossible to always have the soundpost set with optimal tension. But when a bass is misbehaving, checking the soundpost tension can be the key to improving its response. To complicate this further, some basses sound/respond best with a tight-ish post and others with a loose-ish post. An overly-tight soundpost may manifest in a bright, squashed sound. An overly loose post can make a bass sound flabby, wolf-y, and slow to respond. And then there are the exceptions…

The soundpost must be in place during bridge fitting and adjusting. In my next installment I will delve into the bridge and nut, the other major components in the set-up of the bass.

Meanwhile, I anticipate doing a few Q and A columns in the future, and would appreciate hearing from you folks out there who have problems with your basses, or just want to expand your knowledge regarding our noble instrument. Please send your questions to: ArnoldS@aesbass.com.


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