quest_for_tone[1].pdf

The Quest for Tone

Michael Tobias

The Quest for Tone

From Alembic to Zon

Introduction

If this doesn't seem to relate to electric basses,

consider that the electric bass is first and

foremost an acoustic instrument. If you amplify a

2x4, it will sound like an amplified 2x4. That in

itself may not be bad, but it may not be what you

need to get the job done. What you need is an

instrument that sounds good acoustically; if a

bass sounds good without amplification, then it

usually sounds good with amplification.

(Sometimes not, since many other factors are

involved, including the strings, the pickup, the

electronics, the rig, the venue, and the player.)

For the past 20 years, many players and luthiers

(including me) have been engaged in the

musical equivalent of the search for the Holy

Grail. The goal, in our case, is not a physical

object but a sound that might be called "Ultimate

Tone." There are many ways to approach this

quest. There are many paths that lead to tone.

For each of us, the path is different. There are

many subtleties and nuances that characterize

the sound of one player but are very different (or

absent) in the tone of another, even though both

are using similar equipment. Like snowflakes, no

two of us are alike--we don't have the same

ears, the same fingers, the same muscles in our

hands and arms. And we may not share the

same idea of what constitutes good tone.

The Elements

The tone of wood comprises many components,

and it can be analyzed and described in a

variety of ways. I'll try to do it here in non-

scientific terms that will be meaningful to

players. One way to explain the different tone

qualities of different types of wood is to rate

them in terms of hardness. Simply put, hard

woods have a sound that is brighter, clearer,

more articulate, and more conducive to a sharp

attack than soft woods. If a bass is made entirely

of hard woods, what you hear predominantly is

the attack and the fundamental. Soft woods are

more sensitive, allowing you to hear the swelling

of the overtones as a note sustains. By

combining hard and soft woods, a builder can

take advantage of both qualities--if the recipe is

right.

The path I have chosen, as a luthier, is based on

my early interest in acoustic instruments. When I

started building guitars, I was struck by the tone

qualities of different woods. One way luthiers

check for this is with "tap tones," which are used

to judge the resonant qualities of different pieces

of wood. (For an accurate comparison, it's best

to use samples that are the same size.) Tap

tones are generated by holding a piece of wood

firmly, but with as little contact as possible, and

then striking the wood sharply. You can use a

fingertip, knuckle, or something else; the most

neutral tapper is a piano hammer--the doubled

felt does not add any coloration to the tap tones,

allowing you to hear a more natural sound.

A second, even more simplistic, way to rank

woods is by color: light woods are generally

brighter than dark woods. Sound silly? Think

about it--light -colored woods such as maple,

alder, ash, and poplar are all brighter sounding

than dark woods such as walnut, koa,

zebrawood, and rosewood. A third factor in tone

is weight/density. Lightweight wood is brighter

than heavy wood. The perfect example is

swamp ash (also called light ash or southern

ash). Lighter pieces of swamp ash have sweet

treble response and punchy midrange--but if the

wood is too light, the bass response is weak.

Heavier pieces lack the sweetness in the treble

and that nice midrange, but they have a fuller,

rounder low end.

I used to buy acoustic guitar backs, tops, and

sides that were rough-milled to approximately

the same size. While tapping the pieces, I

noticed there were differences from piece to

piece within the same species. Pieces that were

cut from the same log or flitch (a longitudinal

section of a tree trunk) had similar, but not

identical, characteristics.

I found that stiffer woods yielded bright-sounding

guitars. Instruments with thick tops and heavy

braces were darker and less resonant.

Mahogany and maple backs and sides yielded

guitars that were brighter and sometimes

sweeter than ones made with rosewood, walnut,

or koa--they did not, however, have the warm,

rich bass response of the darker woods. To

investigate further, at one point I built a batch of

guitars that were essentially the same except for

one component, so I could observe the

difference made by each modification.

The tone of a piece of wood is a combination of

these elements. For instance: Bubinga is an

extremely hard wood, even harder than Eastern

rock maple. It does not have a brighter sound

than maple, though, because it is much heavier.

Bubinga and such other hardwood as rosewood

and goncalo alves contain large amount of oil,

wax, or resin; this tends to darken their tone,

even though they are hard.

The ear (or, more precisely, the brain) has the

ability to "fill in" the missing components of the

sound spectrum. Without the actual fundamental

in place to muddy the sound, the ear is able to

"extrapolate" the fundamental from the upper

partials. The telephone is an example of this

principle in action: When you talk on the

telephone, the mechanism (which is really a

miniature bass-reflex cabinet) is not capable of

transmitting the fundamental, especially if you're

a man with a fairly deep voice. Yet the person

the the other end hears it just fine.

Lamination

Should we make "hippie sandwich" basses out

of exotic plywood? If so, what is the purpose,

other than aesthetics? Laminating different

woods certainly can make instruments more

beautiful, but it's possible to overdo it. Too many

pieces means too many glue joints--and glue

does not have desirable resonant

characteristics!

Composites

By carefully combining woods, it's possible to

focus on particular tone qualities. Different

configurations yield different results: a maple

neck with a maple fingerboard is generally

brighter than a maple neck with a rosewood

fingerboard. When making a body, if you put a

hard top on a soft back, you can make the low

end clearer and more articulate but still retain

the desired qualities of the softer wood for the

high end and midrange.

High-quality, properly seasoned wood is

becoming increasingly scarce. Some sources

have disappeared altogether, and the rape of

the rainforests has raised not only prices but

also the consciousness of many people around

the world. Consequently, many builders are

buying wood from suppliers who harvest from

sustained-yield forests or who recycle wood

previously used for some other purpose.

A laminated neck has more structural stability, if

it's made properly--that is, by correctly matching

the grain and the moisture content and correctly

clamping it in assembly. Lamination also

changes the Q (quality factor) of the neck.

Here's what that means: Each piece of wood

has a resonant peak. When you laminate

several pieces, you create a system with

multiple resonant peaks at different frequencies.

The laminated piece should have the average of

these resonances as its peak, and (in theory,

anyway) this average Q should make the neck

less prone to accentuate one peak, and thus

respond more evenly.

Other builders have taken a high-tech approach

to materials. Graphite and composite materials

have made a great contribution to the music

industry in recent years. Whether used for light,

super-stiff reinforcements, for parts, or for

complete instruments, these new materials are

making quite an impact. They offer increased

sustain (thanks to greater rigidity) and more

stability (due to being less susceptible to

atmospheric conditions).

If they're so superior, you ask, why doesn't

everyone use them? (I'm sure the people who

sell fiber and resin would like to know, too!) Well,

you know what they say about opinions being

like belly buttons: everyone has one, and they're

all different. Not everybody wants to use the

same materials, and the different choices made

by luthiers offer many different tones to players.

Diversity is good, no?

Laminating creates an interaction between the

pieces, and it generally makes the neck stiffer.

Greater stiffness raises the resonant frequency--

hopefully, to a point where the peaks do not

match the notes on the neck, thus diminishing

dead spots.

Other Factors

Neck-Through Vs. Bolt-On

Neck-through basses respond differently than

bolt-ons. Neck-throughs have more sustain and

a higher fundamental content in their notes,

especially in the low end. This can be adjusted

by using different body woods--lighter woods, for

instance, reduce the accentuation of the low

end. Bolt-ons seem to lack this fundamental

response in the low end, especially with the low

B on a 5-string. (I believe the mechanical neck

joint contributes to this.) This characteristic of

bolt-ons is often perceived as a "tighter" sound,

thanks to a trick of the human ear.

Aside from wood and its composite cousins,

there are many other things that influence the

tone of an instrument, including the hardware

and the finish. Pickups and electronics are also

very important--so much so, it would take

another article as long as this one just to touch

on the important points.

There are many approaches to building

hardware for a bass, and many different

materials are used. The bridge might be made of

brass, aluminum, or steel--or a combination--and

each of these metals has a different effect on

the tone. The mass of the bridge also affects

sustain and attack. In general, brass is

considered to be favorable to sustain while steel

and aluminum are brighter-sounding. The most

important aspects of bridge construction area:

(1) good contact between the parts, (2) a well-

defined "witness point" for the string, and (3)

sufficient saddle movement to allow for proper

intonation.

Coda

I hope you've found this collection of information

and opinions helpful. Hopefully, it will generate

enough interest to help you form your own idea

of "Ultimate Tone" (or at least get you thinking

about it). Nothing in this article is meant to imply

that one builder's opinions are "right" or "wrong"-

-we're all different, and vive la difference. As I

see it, the only hard-and-fast rules are that the

instrument must play in tune and it must be able

to satisfy the creative and emotional needs of its

owner. Play on!

Finish--the bane of the guitar maker's existence-

-also plays an important part in determining the

tone of an instrument. I believe there must be a

compromise when choosing a finish: you have to

balance the need for protecting the instrument

with the sound-dampening effect of the finish. A

finish that's too thick kills the resonance of an

instrument; one that's too thin does not offer

enough protection.

View terms and definitions related to this article.

Modern materials technology now offers finishes

that provide good protection from rock & roll

sweat, even when the finish is applied in very

thin coats. As long as the buildup is not too

thick, the resulting tone can be outstanding.

There are also new blends of tung oil and

urethane that offer the traditional look and feel of

a a hand-rubbed finish with much greater

resistance to moisture and skin oils. The don't,

however, offer much protection from scratching

and denting. These new oil finishes require

greater care than lacquer or urethane sprays--

but I'm really fond of the way they sound.

There are cases when a piece of wood sounds

significantly better with a certain type of finish. I

remember building a bass that had a body made

of very light swamp ash that received an oil

finish. The instrument's tone was okay but a bit

mushy and lacking crispness. For some reason,

which I can't recall, we had to refinish the bass;

the oil was cleaned off and the bass was shot

with polyester. When we plugged it in, lo and

behold--it had gained brightness and clarity.

Luthiers' Forum

As I said at the beginning, there are many paths

in the quest for tone. Because there are quite a

few great bass builders, I thought it would be

interesting to hear what some of them had to

say on the subject. So, over the past few

months, I have interviewed many of my peers. (If

your favorite is not here, I apologize; there

simply wasn't time to get to everybody.)

Because many of the luthiers offered similar

responses to my questions, I have tried to weed

out the redundancies and focus on what gives

each of them--and their instruments--a unique

personality.

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