Issue 8

FLAT BACK vs. ROUND BACK
What's the difference? Which is better?

Part I

Early Double Basses were most likely built by artisans experienced in the making of Viols, and by others experienced in the making of Violins. The Viol family of instruments were built with flat backs; the Violin family with round, or carved backs. There is some disagreement amongst musical historians about the actual lineage of the double bass. Unlike most other stringed instruments, the bass has never become truly standardized in its 400-plus-year history. There are abundant flat-backed, round-backed, violin-cornered, gamba-cornered, busetto-cornered, corner-less, high-shouldered, sloped-shouldered, wide-ribbed, narrow-ribbed, chunky and svelte basses around to this day. Basses usually have a break or bend in the midst of the back in the upper bout, tapering into the neck block, which allows the instrument to nestle closer to the player. This feature is unique within the violin family.

Flat-backed basses are more economical to make, for two reasons: 1) The back requires about 1/4 the thickness of rough-cut wood, and: 2) A lot of labor is saved in the making because the back is not carved out. (Some makers prefer to build flat backs because it conserves a dwindling resource; fine tonewood. Nowadays, lots of beautiful tonewood is being wasted on the building of mediocre (and worse) instruments, putting pressure on a tight, shrinking supply.) So, if a flat-backed bass requires less wood and less labor to build, should it be priced lower than a round-backed one? The answer is yes, and no. A bass maker who does the work by hand should be able to pass along some savings (in the case of a flat- backed bass) to the buyer. A commercial shop that primarily machines its work probably considers the difference a wash, as they'll need to make and install bracing in a flat back, while they would need more material for the carved round back. In the case of older basses it's mostly a non-issue, as they are marketed and priced mainly based on their tone, playability and area of origin (and sometimes based on the particular maker).

There is some argument in the bass community over which type of back sounds "better." Some players and makers believe that flat-backed basses sound "punchier" and have a more immediate response. They also tend to feel that round-backed basses sound deeper, darker and perhaps project more, because of their larger interior air volume. And I'm pretty sure there are folks who believe the opposite of both of these statements. I'm personally of the opinion that in a darkened room, most listeners could not tell a flat-backed bass from a round-backed one. It would be nearly impossible, however, to prove any of this, unless one had access to two identical basses, both made from the same wood, at the same time, with the same exact measurements, weights, thicknesses of parts, varnish, etc, set-up in an identical manner, but with a flat back on one and a round back on the other. (Stay tuned, as a colleague of mine has recently built a pair of basses exactly as I've just described. I'm anxious to hear about the results, and will pass on what I learn, pending his permission).

Disregard for a moment the statement I just made about the darkened room. There is, in my opinion, a difference in the way flat-backed and round-backed basses respond to bow or pizzicato input. I hold that this is not really because of the contour of the back, but because of the bracing which is attached to a flat back. Because round backs are thicker and arched, they generally do not need to be beefed up in the area of the soundpost. Flat backs, on the other hand, are made of thin wood, usually 4 to 6 millimeters or so, and require braces to help them keep their shape under the pressure of the soundpost and the torsion of the strings. The braces, traditionally glued-on across the back, are made of spruce, or a similar softwood. Spruce is extremely stiff and springy, and when pushed in one direction, it springs back quickly in the other direction. This imparts a certain feedback to the player which can be perceived as quickness under the bow, or punchiness when plucked. Think of the spruce brace as a spring; the bridge rocks from string input, propelling the soundpost down into the brace, which springs back upward, amplifying the input. This is a gross oversimplification of the modality that actually happens when a bass is played, but I think it serves to clarify my idea. Some players describe this effect as a "strong front of the note." A recording engineer would call it "fast attack."

Another controversy among makers concerns whether the back of a bass should be heavy and solid, and resist vibrating, or be light and resilient, and vibrate freely. Those in the first camp assert that a stiff, unyielding back allows more of the energy to be focused on the top table, where it will better project to the listener. Those in the second camp assert that a bass back is like a secondary sound board, and should be allowed to vibrate freely, and since bass frequencies are mostly omnidirectional, it makes no difference where the sound is emanating from. I have worked on basses with heavy, stiff backs, and also on those with lighter, more vibrational ones. Both can sound good, but I personally prefer the tone and response of a bass that is built on the lighter side. It is also worth noting that most every bass player can tell the difference between the way his bass sounds and responds when standing (without leaning into the back), and when sitting, with one's leg and knee damping the back of the instrument. This damping seems to affect flat-backed basses more than their round-backed cousins. If you have ever played classical guitar, or closely observed one being played, you will know that it is important for the back of the guitar to be free of the player's body, so that the full resonance of the instrument can be heard. Ideally, a bass should be played in the same manner, though sitting on a stool during a long orchestral or operatic performance is just about a necessity. (Wagner be damned.)

In Part 2 of this article, I will discuss the pros and cons of the flat back vs. the round back from the standpoint of the health and longevity of the bass. Kindly refer any questions you may have to ArnoldS@aesbass.com. I look forward to answering them in future issues.

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