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Guitarist in search of practical answers

  1. Jan 19, 2015 #1
    Just signed up to see if I could obtain any guidance on this topic. I'll start with some background.

    As a guitarist, I exist within a set group that, by and large, is in love with 1958 - the Gibson Les Paul, Fender Stratocaster, and some other influential late 50's and 60's instrument designs all but completely speak for the design of the modern instrument, despite massive backlash against this by makers such as auerswald, steinberger, rick toone, etc.

    The argument on tone, sustain, playability, attack, decay, tuning stability, etc, covers a very complex set of variables, but I'm interested in one set of controversies in particular - what, if anything, increases the sustain (length of time of vibration) of a plucked string, in the absence of an outside source of energy to drive the string into further motion? Is the hypothetical perfect sustain as simple as "A string immovably fixed between two infinitely hard, infinitely strong, infinitely heavy objects, will sustain longest?", or are there other elements to consider?

    My laymans understanding is this:

    1 - Once a string is struck with the plectrum, it has a set amount of kinetic and potential energy from being deformed and being in motion. Short of striking it again, subjecting it to electromagnetism, or driving it with high volume feedback, this energy will slowly dissipate into the air and the surrounding structures of the instrument until it is completely gone and the string is silent.

    2 - This being the case, the most effective way of increasing the natural sustain of an instrument would be to limit the ways in which the energy can be lost. This could be done by:

    1. Making the anchor points and contact points stronger, in conjunction with...
    2. Making the mass at the anchor points greater, so that the relatively small amount of energy in the string would be insufficient to start the greater mass into motion
    3. Using a more homogenous material such as steel or tungsten, providing both of the above and also removing points of weakness in the structure that could vibrate and lose energy in a material of variable density like wood.
    4. Making the contact areas of the string with the body smaller, such as using a locking nut[1] with screws instead of using many wraps of string around the tuners[2], using taller, thinner frets[3], and using a simple, strong, locking bridge/saddle[4] arrangement rather than something more involved such as a bigsby[5] or trapeze tailpiece[6]
    5. Minimizing the amount of string that exists outside of the vibrating length, so that there can be less sympathetic vibrations generated outside the useful area.

    So taking my current understanding into account - What would be the ideal scenario here?

    [1] https://altguitars.files.wordpress.com/2011/09/locking-nut.jpg
    [2] http://www.stewmac.com/tradesecrets/newsletter/ts0061/ts0061e.jpg
    [3] http://www.lutherie.net/fret.samples..jpg
    [4] http://www.glguitars.com/features/images/saddle-lock-bridge-large.gif
    [5] http://www.stewmac.com/product/imag...gsby_B70_Vibrato_Chrome_Polished_aluminum.jpg
    [6] http://www.guitarplayersanonymous.org/images/customer-images//81EpiphoneSheratonAngle014.jpg
     
  2. jcsd
  3. Jan 19, 2015 #2

    Quantum Defect

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    I think that you have a pretty good understanding of the basics here. There is a very good book by Benade on musical acoustics -- undergraduate level -- that talks about the decay of a musical tone and the factors that influence it. The book is inexpensive, available as a Dover paperback: Arthur Benade, "Fundamentals of Musical Acoustics."

    I have also found the sources by Bart Hopkin to be interesting to read. Bart has a website on "Experimental Musical Instruments," and has a number of books out on building electric-guitat-like instruments.

    Here is Bart's website: http://windworld.com/

    There is a brief soundclip from an unusual "Wobble Steel Guitar" here: http://windworld.com/features/gallery/wobble-steel-guitar/ [Broken]

    ... and a truly odd-sounding instrument is here: http://windworld.com/features/gallery/savarts-wheel/ [Broken]
     
    Last edited by a moderator: May 7, 2017
  4. Jan 19, 2015 #3

    Bystander

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    Limit the "damping constant." That however means reducing the rate the instrument transmits acoustic energy to the air. This "sounds" like one of those artistic compromises/compositions of physical phenomena.
     
  5. Jan 19, 2015 #4
    In an electric instrument that would be of no concern - in fact it's probably preferable since the amplified sound can then be heard by the player clearly at any volume level - I record at home and often find myself adjusting mixes totally differently during playback versus recording, because the live sound in the room though small, is significant.

    Normal guitar pickups operate via inducing current in a coil+magnet arrangement - this means magnetic pull, so another method could be to use an optical pickup system. I've seen such systems adopted in basses before however have no idea how relevant to guitars they would be. I do know that high output pickups often have enough magnet pull to affect tuning, so it stands to reason that energy is lost there also. This was a primary motivator in "active" pickup systems in fact, which use very weak, low power magnetic coils, in conjunction with a preamplifier that provides decreased noise via differential summing of the coils, and then boosts the output to normal levels via 9v circuits.
     
  6. Jan 19, 2015 #5

    Quantum Defect

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    Electric guitars do not really efficiently transmit acoustic energy to the surroundings. Pick-ups are used that detect the oscillation of the strings.
    The Benade book discusses the perception of sound in the environment. You might find this interesting.
     
  7. Jan 19, 2015 #6

    Bystander

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    Might want to talk to the "sound engineer" regarding how much "feedback" the sound system can handle before it blows out amplifiers, goes into the uncontrollable squeal, other undesirable effects. Do a little reading on "damping" in terms of underdamped, overdamped, critically damped systems. A little creative electronics might give you an "adjustable underdamping" or "artificially enhanced" sustain.
     
  8. Jan 19, 2015 #7
    There are several products which provide infinite sustain - the E-bow, Fernandes sustainer, sustaniac, etc. Are you referring to systems like those, which provide infinite sustain by physically/magnetically maintaining the motion of the string? I'd be more interested in simply maintaining the string's existing motion as long as possible without outside interference - simply because from a practical standpoint, all existing e-bow like solutions only operate on one string or pitch at a time, and thus cannot be used to sustain chords.
     
  9. Jan 19, 2015 #8

    Quantum Defect

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    I don't think that bystander was talking about injecting energy into the string, which is what it sounds like these products do.

    Practically speaking, you will lose energy to dissipative forces (friction in the guitar-string interface) as well as dissipative forces from the pick-up and dissipative forces due to the air (friction of the string in the air). You may be able to experimentally tweak things more easily with the unamplified guitar, by listening to the volume of sound that you produce (minimize this) while maintaining the vibration of the string (visually observing this). Once you think that you have improved the sustain, turn on the electronics to observe the result. The different normal modes of the string will dissipate their energies at different rates -- higher harmonics decay faster -- so you may have to fiddle with things to maintain the quality of sound that you want.
     
  10. Jan 19, 2015 #9

    CWatters

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    How about increasing the density of the material used for the string so that it has a smaller diameter for the same mass. That way reducing air resistance losses?

    Edit: But I suspect that would that reduce the acoustic volume. Perhaps not important?
     
    Last edited: Jan 19, 2015
  11. Jan 19, 2015 #10

    Quantum Defect

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    Tungsten strings :)
     
  12. Jan 20, 2015 #11
    It's been done with the wraps on bass strings... http://thinkns.com/instruments/strings.php [Broken]

    I think the practical issue is that Tungsten is not as magnetic as steel, so current production pickups would suffer from a massive loss in output. With our mooted optical pickup system though, this would be a non issue. (That said, finding a company willing to make tungsten strings would be more difficult, and the replacement sets would be very expensive, and being in contact with sweat already makes steel or nickel plated strings corrode quite quickly, so this may be a concern. (Bass strings have much larger wraps, and have much more inertia because of weight, so have a larger ferromagnetic core and are affected less by debris in the windings, reducing both of these issues)
     
    Last edited by a moderator: May 7, 2017
  13. Jan 20, 2015 #12

    CWatters

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    I'm not a guitar player but..

    If you could eliminate all sources of energy loss then it should sustain forever (but you wouldn't hear anything either). So maximising initial energy and reducing losses would be the way to go. I wonder if lubricating a steel wound string would help? Increase the mass and reduce losses? Impossible to keep tuned I suspect.

    Is sustain longer or shorter on an acoustic guitar? If the string is causing resonance in the body of an acoustic guitar I would expect that to amplify sound at the expense of sustain. (Resonating systems absorb maximum power from the driver at resonance). So I would expect a solid body guitar that doesn't resonate with the string to have a longer sustain.

    Is sustain longer at altitude? I suspect playing in a barometric chamber wouldn't be very appealing - I dare say the acoustics are bad.
     
  14. Jan 20, 2015 #13
    1 - For various reasons, lubrication of the string would achieve nothing - The string once tuned is effectively immobile, and the force applied by picking chances that in the most inconsequential of ways - if the string did move (rather than simply stretch between the two anchor points of nut/bridge) under playing forces it would go immediately out of tune. In any case, the movement of the string outside of those two points is a damping effect and thus exactly what we are trying to minimise with our locking nut and bridge arrangement.

    2 - Sustain is shorter on an acoustic, as you suspect.
    3 - Yes, although doubtful as to whether this effect is significant.

    I would suspect a .052-.09" piece of nickel-plated steel moving over a ~10mm distance is not significantly affected by atmospheric pressure or the air around it. Air temperature and humidity do both affect the sound, although my understanding is that they affect the propagation of that sound, not necessarily the equipment that produces it.

    That said, it is possible to "play a guitar sharp" from picking it up - the heat of your hands going into the body and components causes them to expand while the string stays relatively unchanged. But, once again, using a homogenous and more dense material would solve this issue as it would be less likely to expand from the heat of hands/stagelights/an audience full of adoring, but sweaty, fans.
     
  15. Jan 20, 2015 #14

    Quantum Defect

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    I like this thread!

    Tungsten is used in manufacturing filaments, so you may be able to find it "off the shelf". You would need to find a thickness that would give you the same linear density as your normal strings. I have used thoriated tungsten wire in the past. I don't know if it would wrap well around the tuning pegs in the guitar. As you note, it may not behave the same way with the pick-ups. It may be "fun" to buy some and try.

    The only significant energy losses in the string that you will have (reducing the sustain) are loss of energy to the guitar body, loss of energy to the air, and loss of energy to the pick-ups. I suspect that the energy lost to the air is the one that is most significant -- in which case the denser strings should help, by reducing the aerodynamic cross section.

    Air is a tricky thing -- we often underestimate its effect on things. Thinking about the effect in reverse, there is something called an Aeolian harp that uses wind to get a string vibrating.
     
  16. Jan 20, 2015 #15
    Hmm. Interesting. Lets make things a little more complicated. Would you say the following scenarios still suggest that air resistance is the primary loss in this system?

    Many guitar's have "tremolo" systems (Actually vibrato systems) on which allow the bridge to be moved under the strings, in so doing changing the tension and length of the strings, such that the pitch of the note changes. These are typically "fulcrum" systems, where springs in the back of the guitar counterbalance the pull of the strings on the top while the unit is not in use. The guitarist uses a lever to unbalance the tension around a fulcrum point (Typically two studs in the guitar body), and when the guitarist stops doing this, the system returns to rest, back in tune (ideally).

    These systems, particularly the vibrato, are prone to sympathetic vibrations of the rear springs, etc. I have personally experienced improvements in sustain by such modifications as increasing the mass of the tremolo assembly at a point before the string can transfer energy into the springs. My thinking is that if the assembly has greater mass and inertia, there is less loss of energy after that point.

    Floyd Rose Vibrato/Tremolo system (This pictured unit is actually made by Vigier, and uses ball bearings in those little black blocks, rather than the more common arrangement of a knife edge in a v shaped pivot groove)

    Front: http://www.jerrock.com/66/system/fi..._floyd_rose_roulement_a_billes_vigier_big.jpg
    Rear: http://www.thewindtunnel.com/Floyd/Springs.jpg

    Hardtail bridge - This screws a baseplate to the body, but leaves the saddles loose, held by screws and springs so that intonation (Speaking string length) can be adjusted easily.

    http://www.guitarpartsresource.com/images/large/006-0068-000.jpg

    Babicz Full Contact Hardtail bridge - The same as the previous, but built with as much solid material as possible, providing the greatest possible mating surface between the bridge and the rest of the body, in theory improving sustain by making the bridge more solid.

    http://cdn.snappages.com/kug2i3/assets/217970_1714930_1378309711.jpg

    The babicz marketing material is hugely flawed of course - you cannot "conduct" tone or sustain. What it's doing is providing a much more stable platform that will lose less energy within itself. Any energy lost through this bridge is lost into the body wood. Since the body wood has much greater mass and is a much more stable structure, there is greater inertia than the string's energy can overcome and thus that energy cannot be lost - it remains in the string.
     
  17. Jan 20, 2015 #16

    Quantum Defect

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    Your thinking is correct.

    What you have in many of these cases are coupled oscillators. If the modes of one oscillator (guitar body, tremolo system, etc.) are closer in frequency to the strings, you will lose energy from the string to the other system. Both oscillators have dissipative elements. Your tweaking of the mass of the tremole system effectively weakened the coupling from the string to the spring; the spring probably has modes of vibration close to the string.

    In acoustic stringed instruments, you are trying to find ways to couple the string vibrations to the body of the instrument ( a hollow wooden resonator). Violins have a sound post that couples the vibration of the front plate to the back plate. Acoustic guitars couple the vibration of the strings to the front plate through the bridge (I think that this is the right term).

    If you give the electric guitar body an impulse, you do not hear a sustained tone -- the damping is high. If you give the string an impulse, you will hear a sustained tone -- the damping is small. You need to minimize the loss of energy from the string to the body to help sustain the tone. Tweaking things the way that you did for the tremolo system may give you a longer sustain, but I suspect that most of what is left is loss of energy by the string to air.
     
  18. Jan 20, 2015 #17

    CWatters

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    Do the strings normally vibrate in just the one plane or does the plane change? Could you change the cross section of the string so that it's not round but more streamlined and reduce air resistance that way? Too hard to keep it orientated correctly?
     
  19. Jan 20, 2015 #18
    Nah, the strings vibrate totally different depending on how they're hit. There are also plenty of playing techniques that make the string vibrate around harmonic nodes instead of along the fundamental length. Interesting idea, but I think strings are about as aerodynamic as they're going to get unless we find a way of making them smaller. (And even then, there's a point where you're playing knife edges, even if you have unobtanium strings. Painful...)
     
  20. Jan 21, 2015 #19

    Quantum Defect

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    "I got blistahs on my fingahs!"
     
  21. Jan 21, 2015 #20
    Curiously enough, that's actually Ringo's voice on that recording... They had to do a pretty horrendous number of takes to get the drum track you hear on the record, and it's not exactly the simplest of rock beats. He wasn't joking...
     
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