# Secrets of the Double Bass



## Guest

Double basses and all members of the violin family have "secrets" unknown to the layman and even to many players of the instruments. Since I am most versed on double bass, I shall reveal these secrets as they apply to that specific instrument but they also apply to cello, viola and violin as well but the methods for determining them might be very different. Some may be applicable only to be bass.
To start, let's go over the basics of how a violin works. First, let's get familiar with the parts of the violin:


















Like all instruments, the transmission of vibration is fundamental. Since music is sound and sound is produced by vibrations of the air, no transmission of vibration means no sound and hence no music. Violins transmit vibration via resonance chamber (often called a box or, in the case of bassists, a doghouse). But that's not enough! Look at the diagram of the cross-section of a box below:









Referring to the above diagram, the way any member of the violin family produces sound is that the string vibrates and this vibration is transferred through the bridge. The bridge is held against the belly only by string tension. The bridge has an E-foot (on the left) and a G-foot (on the right), named after the strings that pass over them. The bass is tuned opposite of the violin. The violin's thickest string is G then D, A and E. The bass's thickest string is E then A, D and G. So the E-foot on the bass bridge is under the thickest string and the G-foot is under the thinnest. Sometimes the E-foot is called the bass foot and the G-foot is called the treble foot although I find this a bit misleading.

There is a lot of tension put on the belly by the bridge and so two important features prevent the belly from caving in: the sound post (on the right) and the bass bar (on the left seen in cross-section). The sound post is a wooden dowel, usually spruce or pine, that is literally squeezed between the belly and the back. It is held in by string tension. The top of the sound post is situated very close to the G-foot of the bridge. It pushes back against the bridge as it presses against the belly. The bass bar is a slat of wood usually made of the same type of wood as the belly (which may be spruce or maple). It runs parallel to the strings and runs almost the entire length of the belly. The bass bar passes under the E-foot and distributes the downward pressure of the bridge horizontally between upper and lower bout instead of vertically between belly and back plates as with the sound post.









Belly plates showing bass bars.

The bass bar must be carved to exactly fit the contours of the belly, no gaps.

The sound post is also fitted on top and bottom but the best way to fit the sound post to the belly is to carve it like the butt end of a drumstick-no edges or corners to it. That way, when the sound post twists while the bass is being played, it won't wedge a corner against the top which will greatly affect the sound. Rounding it off as described always presents the same amount of surface area of sound post to belly.









Violin cross-section showing sound post.

But the bass bar and sound post serve another important function than just reinforcing the belly against the downward pressure of the bridge caused by the tension of the strings. The bass bar distributes the vibration of the bridge throughout the belly while the sound post transfers that vibration to the back plate. As the strings vibrate, the bridge and belly plate rock back and forth, to and fro in a complex motion.


----------



## Guest

There is another important factor involved in the transmission of vibration-mode-matching. Vibration moving through wood follows the same rules as electricity moving through a circuit. Resistance is opposition to current flow in a DC circuit. In an AC circuit, this opposition is called impedance. Whenever you plug a microphone into a mixing board, you have to match impedances such that a low impedance output from the microphone feeds into the high impedance input of the board or, in other words, a low-impedance source feeds into a high-impedance destination. Otherwise, the signal degrades before reaching its destination and the longer the cables used, the worse the problem becomes.

We should think of the types of woods used in the bass as each having its own impedance. Soft wood has a low impedance (i.e. absorbs rather than transfers vibration) and hard wood has a high impedance (i.e. transfers rather than absorbs vibration). The types of woods used make all the difference. The sound post must be of harder wood than the belly. A softer wood will result in a deadening of the sound because it will absorb the vibration of the belly rather than transmit it to the back plate. The bass bar should not be a harder wood than the belly, however, because it doesn't transmit sound between two separate pieces of the body the way the sound post does. Luthiers usually make the bass bar out of the same wood as the belly plate and sometimes even carve the bass bar out of the belly so that it is all one piece. As the bridge rocks likewise does the belly plate and, with it, the bass bar. If the bass bar is too heavy, then vibratory energy is lost simply trying to move the extra mass around. Too light and the bass bar won't distribute weight and vibration effectively.










Another aspect of mode-matching is the grain of the wood. The vibration travels along the grain. The grain of the bass bar must run parallel to the grain of the top plate because it couldn't accomplish its purpose otherwise. Likewise, the grain of the sound post should run vertically from belly to back. So between the bass bar and the sound post, the vibrations are distributed fore and aft as well as top to bottom to fill the whole box with vibrations in an xyz-axis. You want to get the box vibrating as much as possible and in as complex a way as possible in the three dimensions of length, width and depth. I've even encountered designs calling for two bass bars! The belly also arches and cups along its surface although this can't be seen with the naked eye. The more vibration and the more complex the movement of the top and bottom plates, the louder and richer the sound.

The sound post really brings the bass to life. Without it, the instrument sounds dead. For this reason, the Italians call the sound post the anima or soul. Do we place the sound post directly under the bridgefoot? No, it should be offset a bit. If it were directly under, that would actually suppress the vibration of the top plate. So we offset it. But the further you offset the sound post from the bridgefoot, the darker the sound will be. So you should experiment with the placing but there is a limit to how far and how close you can place the sound post by the bridgefoot.

Besides sound post placement, other things play a role in the quality of the sound include such things as the end pin, tailpiece, the type of wood, the size of the instrument and the size and placement of the f-holes. The idea is to get the entire instrument vibrating and anything that inhibits that vibration should be either eliminated or reduced as much as possible. That area of the top plate where the bridge rests is the most important part because that is where the vibrations of the strings are generated. So this area has to be setup optimally or you're hurting right out of the gate. Think of it as the heart of the bass. From there the vibrations-the blood of the bass-spread out through the entire instrument at about 8800 feet per second or 6000 miles per hour. If this sounds crazy, remember that sound travels through air at 1,120 feet per second which is close to 800 miles per hour. Sound travels more than four times faster through water than air. Through solid diamond, it travels about 8200 miles per hour which is about as fast as it has ever been tracked. On average, sound travels about 6000 miles per hour through a bass.

There are four elements called modes that bass-makers use to get the optimum loudness from a bass. Each of these modes produces a tone and the luthier must determine what note represents each tone. He must get two modes to match notes to unlock the sound of bass. These notes can be a different pitch, e.g. an octave apart, but must still be the same note. These modes are:

·	The tone emitted by the tailpiece.
·	The lowest/loudest tone emitted by the wood (W').
·	The lowest tone emitted by the body (B0).
·	The lowest tone made by the air resonating inside the bass (A0).

A0 and W' (pronounced "W prime") are fixed and cannot be changed. B0 and the tailpiece mode are adjustable (for some reason, the tailpiece mode has no designation as the other three).

Before we set about matching modes, we want to check A0 and W' and see if they might incidentally match. If they do, no further work needs be done. I'll explain that more in a bit. But what if A0 and W' are not matched? There is nothing we can do to make them match because each of these modes are fixed and non-adjustable. We're stuck with them. Experimentation has shown that the best match is B0 and A0. If not, then B0 and the tailpiece mode should be matched and, since both of these are adjustable, this match has a wider latitude.

So how do we adjust them? First, we determine what note they emit. To determine the tailpiece note, we suspend the bass with a thin but strong rope tied around the bottom of the pegboard where the nut is. There is a kind of ledge there where the rope can grip without damaging the bass. We retract the endpin fully. Wrap a towel around the strings at the bridge so that they are completely muted. Now we use a doctor's reflex hammer to tap on the tailpiece right in the center. Tap a few times and let your ear adjust to hearing the ping. Use a tuner to help determine the note and write that note down.









Reflex hammer.

Keeping the bass in the same situation, we are now going to determine B0. The B stands for body and the 0 means it is the lowest tone in the series that the body emits. The next tone in the series is B1, then B2 and so on. Use the reflex hammer to tap on the wide end of the fingerboard about 3 to 4 inches up. Tap a few times while moving the hammer around slightly as you listen for the ping. If you can't pick it up readily, tap on the top of the scroll and try each scroll "ear." Then go back to the fingerboard and you should be able to pick the note out. This is B0. Write it down.

To determine W', we position bass face up (mounting the bass on a varnishing stand would ideal for this). W stands for wood and the prime means it is both the loudest and lowest note the bass is capable of playing. Place one hand on the top plate under the tailpiece near the bottom and place the other under the fingerboard near the top and simply sing out the lowest note you can against the top plate and feel for the vibration then sing a half-step higher and then another half-step higher after that and so on. Wherever the vibration is felt the most is W'. Write it down.

A0 is the hardest mode to measure and requires a sine wave generator. A sine wave in acoustics is a sound wave with no overtones (a.k.a. harmonics, partials, etc.). A0 is the lowest resonant frequency the air within the bass vibrates at. Higher frequencies are designated A1, A2 and so on. Harmonics would make finding A0 very difficult. To find A0, the generator's output signal must be attached to a small speaker/amplifier. Now insert the speaker into the f-hole that is next to the E-string and sweep it around slowly and methodically. Do this as you cover one full octave with the sine wave generator. One note will be noticeably louder than the others and that is likely to be A0. However, you will probably have several notes that sound louder. The loudest will be A0 but it's hard to tell sometimes which is loudest. So, with a long piece of string tied to the speaker, lower it into the f-hole that is next to the E-string. Have the sine wave generator emitting the tone you think is A0. Let the speaker bump the back plate and then you gently but quickly pull the string up until the speaker is about even with the f-hole. A0 is concentrated between the f-holes and does not extend to the edges of the belly plate so the vibration generated by the bump will resonate with the generated tone and be loudest at the f-hole if the generated tone is A0. If the generated tone gets no louder then it is not A0. If you're not sure if it's getting louder, do it again with the other f-hole covered up. There are other more reliable ways of finding A0 but they involve the use of more electronic equipment.

So those are the four modes and how we find them. Two cannot be adjusted but two of them can. This is necessary because two of the modes must be matched, i.e. they must produce the same note or the bass will not reach it's full potential. How do we do that? First, realize that in adjusting the pitch of a mode, we have no more than a half-step or semitone of range either above or below the determined pitch of the mode in question. For example, if B0 is found to be F then it can be tuned down to E or up to F#. So, first, compare A0 and W' because if they are already in tune with one another (pretty rare), nothing needs be done. If they are not tuned the same then compare B0 and the tailpiece mode first to one another and then to the fixed modes. Whichever two are closest, adjust the movable mode to match the fixed.

What if the two movable modes are already in tune? Then, again, there is nothing more to be done but optimally, we would like to have one movable and one fixed mode in tune, preferably A0 and B0. Why? The fixed mode serves as a reference and cannot change no matter what which makes it easier to adjust the movable mode to match it and A0 and B0 seem to work the best. While matching the two movable modes seems the most optimal since both are adjustable, either can drift simply by changing strings, for example. Lowering or raising the bridge can change them or moving the bridge to change the scale length can change them and now everything may have to be readjusted. Any adjustment involving the tailpiece runs this risk. But if the two movable modes are already matched, then there isn't much to do about it. What about matching three modes? That does not work. It is the same as having no modes matched. Why? No one knows. Matching three modes simply does not work. What about four modes? I don't know that anybody has ever matched all four but the problem again is that the tailpiece mode may change if one changes strings leaving only three modes matched which will be detrimental to the sound. Two modes matched, A0-B0 preferably, are optimal.

So how do we change B0 and the tailpiece mode? To lower B0, shave off some wood from the fingerboard or neck. This is tricky, of course, so if the mode does not have to be lowered a great deal, just using heavier tuning machines might do the trick. You can also add fishing weights to the free end of the fingerboard. To raise B0, you can use lighter tuners or you can shave off some wood off the underside of the free end of the fingerboard. If you want to get drastic, you can shorten the fingerboard but that isn't recommended.

To lower the tailpiece mode, you may lengthen the tailpiece wire (or gut as it's called in the diagrams I provided). You can also add fishing weights to the underside of the tailpiece to make it heavier. Some luthiers use special little clamps. Of course, you might simply want to use a heavier tailpiece. To raise the tailpiece mode, you may shorten the tailpiece gut, shave off wood from the underside of the tailpiece or simply use a lighter tailpiece. When lengthening or shortening the gut wire, bear in mind there are limits. If the gut is too long, the tailpiece will be closer to the bridge. If the amount of string from bridge to tailpiece is less than 6 and ¾ inches then the E-string will die. It will be noticeably lower in volume than the other strings. If the gut wire is too short, the tailpiece will not have the proper freedom to vibrate on its saddle (see diagrams provided earlier) which will hurt the volume of the bass.










Next, we'll discuss bows and varnish.


----------



## Guest

Early violin bows were crude things-a curved wooden stick with the hair of a horse's tail tied at both ends. There was neither a head not tail to the bow which was D-shaped. The curve was forced by the hair tied at both ends which held the hair taut.










The violin family is descended from the bowed instruments of the Central Asian nomads. These instruments such as the kylkobyz, morin khuur, kemenche, ravanhatta, er-hu, kokyu etc. were developed by nomadic horsemen. In all cases, the strings are made from horsehair and the bowstrings are also horsehair. So, we know that whoever made these instruments had a very extensive relationship with and knowledge of horses. We know they were hunters simply because these instruments descended from the hunting bow. We still refer to this implement as a bow. The archery terms are still there. On the double bass is attached a leather pouch to hold the bow when it is not in use. It is called a quiver. Even the term "arco" shares the same root as the word "archery." In these Central Asian languages, Eric Halfpenny notes that the word for the bridge of a stringed instrument all relate in some way to the horse due to its appearance. In fact, in the Mongolian fiddle-the morin khuur, the national instrument of that country-the scroll area is always carved into the shape of a horse's head. I've even seen them carved into three horses' heads. The very term morin khuur means "fiddle with a horse's head." The Chinese fiddle-the er-hu-also means "two-stringed instrument of the Hu people" whom Wiki describes as originating "from regions to the north or west of China generally inhabited by nomadic people on the extremities of past Chinese kingdoms."

The bow is an art in and of itself. The modern bow was perfected by a watchmaker named François Tourte (1774-1835) who went into bow-making following in the footsteps of his father and brother. After much experimentation, he decided that bows should be made from Pernambuco wood (a.k.a. Brazil wood). Tourte set the length of the violin bow at 74 to 75 cm. The part of the bow that contacts the string comes from the tail of a horse. For some reason, the horsehair in question must come from a white stallion. The hair must be unbleached. The preferred hair is from Mongolia (although South America and Canada make perfectly good bows). Hair from mares' tails is not used because it is often soaked with urine which makes the hair more prone to snap. The hair is tightened or loosened by turning the screw on the end of the bow either clockwise or counterclockwise as the case may be. The screw, in turn, moves a special rectangular retainer called a frog to which the hair is attached. The frog moves up or down the bow shaft (or stick) thereby increasing or lessening the tension on the hair. Before storing the violin, it is customary to loosen the bow a little before stowing to take the stress off the hair or it will permanently stretch and lose elasticity.



















The hair attaches to the frog and is held spread out to form a ribbon-like appearance with a silver collar or sleeve called a ferrule. Under the ferrule is a little triangular piece of wood called a talon that holds the hair fast. The hair attaches inside the frog to a joint called a slide. The slide is covered with a protective rectangle of mother-of-pearl although cheaper bows use plastic. The frogs used to be made of ivory but are now generally made of fossilized (mammoth) ivory. But authorities are cracking down on using mammoth ivory as well.

The curve of the bow gradually changed from the inefficient, convex D-shape to a long gentle, concave curve with the head sort of angled back. This shape pulls the hair ribbon more efficiently and uniformly. Two types of bows evolved for double bass, the German bow (shown on top in the figure below) and the French bow:










As with the violin, the entire bow must vibrate. The cheap fiberglass bows don't sound particularly good no matter well they may appear to be designed because they don't vibrate the way a good Pernambuco bow does. Generally, the fiberglass bows are heavy and imbalanced. Pernambuco is expensive because it is a knotty wood and only a few feet in a hundred will be any good for a bow. Knots prevent the wood from vibrating and will deaden the sound. A good Pernambuco bow is expensive as a result.

Should the bow produce scratchy sounds and loss of clarity and volume or even no sound at all, it needs to be rosined. Every violin case you buy has a little box of rosin. Rosin is made from pinesap tapped from fir trees. The sap is mixed with pulverized trees and heated until the wood fibers are separated from the oleoresins. The oleoresins are distilled producing turpentine and a product called "black liquor." This is refined into "tall oil" composed of pitch, fatty acids and rosin. This tall oil is prepared for molds by being heated and various substances are mixed with it and these substances vary between manufacturers and are kept secret. A constant flame is maintained to burn off most everything but the rosin and force out bubbles. Rosin must have no bubbles. The rosin is poured into a mold and then the surface of the exposed rosin is torched to remove bubbles and provide a smooth, clear surface. The rosin hardens into a cake that is packaged and sent out. The musician takes this hard cake of rosin and scrapes the surface with a key or the edge of a coin to loosen up particles and then drags the bow through it back and forth. Rosin helps the bow to grip the string and produce an even, clear, strong tone.










There are many types of rosin on the market but not only are there different makes but each member of the violin family gets its own rosin although some brands overlap. One may find violin rosin, viola rosin, cello rosin and bass rosin but some rosins are used for violin and viola, some for violin, viola and cello and some for cello and bass. I would recommend using only bass rosin for the bass. Some cello rosins aren't strong enough for bass strings. Never use violin rosin for a bass, it simply won't work.

Rosins leave residue on the strings so wipe off the strings after each use to prevent build-up. Not only does build-up affect the string vibration but eventually rosin particles will fall to the surface of the bass where it eventually collects in little gobs that adhere to the varnish and will damage it when removed. There are rosin removers on the market but the best solution is to wipe the bass with a clean rag on a frequent basis. To remove rosin from strings one can use rubbing alcohol but be careful not to get any on the varnish or fingerboard or they will be damaged. There are non-alcoholic rosin removers that might be a better way to go. These can be found online at various double bass websites. I recommend Lemur Music or the Kolstein site.


----------

