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THE ADVANTAGES OF LOW TENSION
Low tension leads to two important advantages - easier play, and less stress on your musical instrument. From a guitar player's perspective, low tension makes it easier to fret the string. Because the titanium core is less dense and less stiff than steel (half the modulus), the pressure required to fret our low tension strings is less than the pressure required for conventional "light" acoustic guitar strings, even at nearly equivalent string diameters! Interestingly, our high-E string has an unusually large diameter (0.0145"). However, its low density actually makes it easier to play when compared to a typical 0.012" steel string! How is this true? In order to see, let's delve into the physics...
It is well known that strings under tension will vibrate when plucked, struck, or bowed to yield a fundamental frequency f1, and a spectrum of n harmonic frequencies, all proportional to the tension and inversely proportional to the mass per unit length of the string (Jeans, Sir James, Science And Music, Dover Publications, Inc., New York, 1937, reprinted 1968). This relationship can be expressed for an ideal string of zero stiffness by
where fn is the frequency of the nth harmonic, L is the speaking length of the string, T is the tension, and m is the mass per unit length.
In simple English, this means that for a fixed fundamental tone (like your high E string which vibrates at 330 Hz), and for a string of fixed length (typically 25.5" on most acoustic guitars), one can reduce the mass of the string by some percentage, and the tension will go down by that same percentage. In fact, this is what we have done. Thanks to our special, low density, titanium alloy core, RohrbacherTM strings have reduced tension at equivalent pitch. This equates to easier playability.
The second advantage of low tension may not be immediately apparent to you, but your guitar truly appreciates it. In addition to easier playability, lower tension equates to less instrument stress, and longer instrument life.
IF YOU WANT MORE TECHNICAL DETAIL...
In order to control the mass and hence the tension & frequency of a string, the above equation dictates that you must change either the materials, the physical dimensions of the string, or both. Unfortunately, material choices have been limited, so most string manufacturers have focused their efforts around changing the physical dimensions. We've approached the problem in a different way - we've made a material change. It really boils down to this: if you want to make a truly better instrument string, you can't use the same materials that people have used for the last 100 years.
With these thoughts in mind, let's get out the slide rule and pocket protector, and put on our engineering hats [Dr. Buzz sometimes sports this hat when he isn't in the studio]. The mass of a string is proportional to the square of its diameter, and the stress on a string is equal to the tension divided by the cross sectional area (which is proportional to the square of its diameter). Thus, the strength of the material required for a simple unwound string is only a function of the material's density - not it's diameter! This may seem counterintuitive, but it's true - i.e. you can't make the string stronger by making it larger because the increase in tension required to maintain pitch gets you right back where you started. In other words, the strength required is the same regardless of the string's diameter (for any given material). Therefore, a string material must have a specific minimum ratio of strength to weight, which severely limits the choice of materials that can be used for guitar string design.
For the past century, the only recognized metallic material with the requisite properties has been steel. We have developed a new, patent-pending, non-ferrous, metallic core which may become the core of choice for the next 100 years - a titanium alloy. In fact, our special titanium alloy is unique in the metals family in that it has the required ratio of properties. While titanium and its alloys are much more difficult to fabricate (and therefore much more expensive), these metals provide other benefits which make them better choices than conventional tin coated steel cores (see chemistry section).
THE ADVANTAGES OF LOW STIFFNESS
While the engineering hat is still on, we should revisit our fundamental equation for a vibrating string. Physicists define idealized systems to keep the science clean, but unfortunately, "Mother Nature's" reality appears to be more complex. Remember when we said that the above equation applies to "an ideal string of zero stiffness"? Well, simply stated, there is no such thing! In the real world, strings have stiffness, and the stiffness contributes its own force to the "restoration" of a vibrating string (i.e. the string's return to rest from the displaced state). This force (due to stiffness) is additive with the force imparted by string tension, but it is not linear with frequency. The stiffness of a string can contribute to the occurrence of dissonant tones (subtle intonation differences amongst the harmonics that can be perceived as not matching the fundamental tone). A string's stiffness also contributes to the dampening of the higher harmonics (the harmonics give the string its perceived "brightness"). It is therefore advantageous to design a string with as low a stiffness as possible.
One of the major advantages of our core is that its stiffness is significantly less than steel (about half). We have made every effort to keep the stiffness of RohrbacherTM stings at the absolute minimum to produce the cleanest, and brightest sound possible.
THE ADVANTAGES OF HIGH TEMPER (HARD) WINDINGS
In addition to zero stiffness, the equation for an ideal string also assumes that a string is comprised of a single, homogeneous "line" in the Euclidean sense. Again, this equation is ideal, and is not entirely applicable to the real world. However, in order to at least approximate this condition, it is necessary for the windings on a wound string to be as tight as possible, so that the entire construction vibrates as a unit - as if they were actually inseparable from one another. Any looseness will result in objectionable damping of the string, which especially affects the higher harmonics (these harmonics give the string its "brightness"). In order to minimize this possibility, we use winding materials that are "harder" than those of most manufacturers. However, because of their hardness, these materials are more difficult to process. That's why we developed the patent pending sheathed-ends - to prevent the windings from unraveling. In combination, these innovations have enabled us to use higher temper windings, which result in strings with longer-lasting, and more consistent tonal characteristics over time.
THE ADVANTAGE OF SHEATHED ENDS
Let's begin with some background trivia. First, as we've already stated, musical instrument strings have been constructed from essentially the same materials for more than 100 years. For example, U.S. Patent 210,172 was issued to Watson and Bauer in 1878, disclosing the first use of polygonal shaped core wires that help to prevent winding recoil both during manufacture and in end use. This technology is still commonly used today. In addition, the core wire is often coated with a ductile layer of another metal like tin, which helps to keep windings tight, and also helps to minimize the corrosion (it's a hopeless endeavor as you'll see in the chemistry section).
Windings for conventional strings are typically made of softer, more ductile metals having various degrees of hardness or temper. The windings are chosen in such a way so as to control mass per unit length, to deliver appropriate ductility and yield characteristics for ease of manufacturing, and to minimize recoil during manufacture and during end use. Ironically, the measures that are taken to minimize recoil in conventional manufacturing processes (ductile coatings and soft windings) are also contributors to shorter string life. For example, the ductile tin coating can easily yield over time; and the softer, lower temper windings can relax more easily than higher temper windings. Both of these problems are compounded by corrosion. When all of these problems occur in combination, the results include loose windings, increased frictional losses, subsequent vibrational dampening, and ultimate deterioration in tonal quality (the higher harmonics are most particularly affected). This leads to a loss in "liveliness" or "brilliance", and ultimately to a "dead" string.
We've eliminated the ductile coating, and hence we've eliminated the potential for both ductile yield, and frictional losses. We've also increased the winding temper and hardness to minimize relaxation and yield. In order to achieve these benefits, we had to invent another means of preventing winding recoil during manufacturing and during end-use - hence the sheathed-ends were born. The sheathed ends serve to tightly grip the windings and to prevent them from unraveling along the entire string. Without this innovation, the use of high temper windings would not be possible.
CONCLUSION
These innovations have culminated in a string with improved longevity (see The Meaning of Longevity to the Musician section for a more complete definition), as well as easier playability. Although we have not eliminated every possible source of mechanical wear, we've minimized several of the historic problems by developing one of the newest string innovations in 100 years - RohrbacherTM Titanium Acoustic Guitar Strings. Enjoy your strings!
Yours Truly,
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