what self-resonance of a body/neck means?

Discussion in 'Luthier's Guitar & Bass Technical Discussion' started by turntable_blues, Jan 11, 2019 at 9:46 AM.

  1. turntable_blues

    turntable_blues Member

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    So I saw that on one builder's website:

    what does self-resonance (to the note) in that context mean? what effect does it suppose to have (more overtones, biggest possible resonance per description above - but why?)

    source: https://www.tonfuchs-guitars.com/gitarren/
     
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  2. Terry McInturff

    Terry McInturff 40th Anniversary of guitar building! Gold Supporting Member

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    Ive written quite a bit here on TGP regarding the importance that the acoustical response of the electric guitar plays in the amplified possibilities, regardless of the pickups or the amplifier.

    If the goal is to build a sound, one which is a rather specific variation of, say, a certain breed of LP Standard, the best method is always to build the acoustical chassis which will be appropriate. This means in part choosing the correct examples of a the appropriate species of wood; it also means using that wood correctly and mating it with the appropriate hardware. All of which adds-up to the appropriate acoustical sound, which in turn provides the key to success.

    The resonant nature of the unplugged "chassis" answers the age-old question of why two seemingly identical guitars can sound so different amplified. At this time I am surprised that this continues to be a matter of debate.

    The resonant characteristics have a massive effect upon how the strings vibrate in a number of ways; the pickups sense these things of course and send them to the amp.

    And so if a builder makes a point of mentioning resonant characteristics, it may be a very good sign regarding the builder, provided there's a real strong body of experience and knowledge backing-up the effort. It is NOT easy. It took me at least 20 years full-time and hands-on with many thousands of guitars to begin to really grasp the topic....and here in my 42nd year of doing this, I still learn continually!!!
     
  3. EdFarmer

    EdFarmer Silver Supporting Member

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    Forty-five years ago, when I started playing and my father was working in a music store, he taught me that a guitar that doesn't sound good with the amp turned off, will not sound better when you turn the amp on.
     
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  4. Timtam

    Timtam Member

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    The science of solid body electric guitars is frustrating. The evidence from objective experiments, or even physical theory, is just not there yet to make totally conclusive starements regarding the relative magnitude of different elements on the amplified performance of solid body electric guitars. With that proviso I offer the following ....

    The theoretical problem with acoustic resonance of a solid-body electric guitar's body is that once you allow vibrations to reach the guitar body/neck via admittance of the bridge and nut - interacting with the tendency of the type of wood to vibrate (or not) - you have no way to control whether such vibrations might add to string vibration at the same frequency detected by the pickups (if in-phase with string vibrations) or cancel it (if out-of-phase with the string vibration). So the effect on the amplified sound, if there is a mechanism of body vibration transfer back to the strings of sufficient magnitude, could be positive (pleasing) ... or not.

    Long-term building experience can obviously lead to the choice of hardware / woods / pickups / construction techniques that produce a pleasing-sounding, acoustically-resonant, amplified solid body electric guitar sound. ie trial-and-error would lead one to dismiss bad-sounding combinations, that may be concluded by the builder to be related to resonance.

    But even when the overall amplified tone of an acoustically resonant solid body is pleasing, physics says that vibration of the body is, on face value, evidence of lost sustain of the strings ...
    https://www.researchgate.net/public...r_T_Mechanical_vibrations_of_electric_guitars

    But where does that leave the builder without years of trial-and-error experience and/or a PhD in physics ? One school of thought is that because of the uncertainty on how acoustic resonance might affect amplified sound (positively or negatively), you are better off preventing body vibrations as much as possible .. ie aiming to build a amplified-pleasing-sounding, non-acoustically-resonant, solid body electric guitar.

    Regarding the uncertainty, we currently have only limited objective data to suggest that the magnitude of any body / neck resonance has a significant, predictable, measurable effect on solid body electric guitar sound. Certainly neck resonance is an explanation for dead spots (ie a negative effect) ..
    http://acoustics.org/pressroom/httpdocs/137th/fleischer.html
    But small-scale experiments have shown even when you add significant resonance to a solid body electric guitar - that you can easily hear acoustically - an effect on the amplified sound from the pickups is not apparent (see Zollner's experiment referred to here ...)
    https://www.thegearpage.net/board/index.php?posts/27774095/

    In any case, an experienced guitar builder who happens to be a PhD-trained physicist (and indeed a rocket scientist), who builds his guitars based on his understanding of the physics, and generally cites relevant scientific evidence in his writings, has concluded on the overall significance of body vibration ..
    "But for a solidbody electric, the whole notion of increasing sustain with resonant tonewoods or letting a string send its vibrations into the body to resonate before returning to the string is pretty much nonsense."
    https://www.premierguitar.com/articles/24287-bass-bench-searching-for-resonance

    As I said at the start, guitar science is frustrating because of the lack of objective certainty. Until it is less so, 'question everything' is a good mantra. ;)
     
    Last edited: Jan 11, 2019 at 10:09 PM
  5. turntable_blues

    turntable_blues Member

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    @Timtam - thanks a lot for that post! maybe doesn't directly answer my question, but certainly scratches my "guitar science" itch :)
     
  6. Tone Meister

    Tone Meister Member

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    I wasn't taught this, but it is a rule I have used to buy guitars since 1974. It just always made sense to me, and it's the reason every guitar I have sounds great with excellent reasonance and sustain.
     
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  7. Tone_Terrific

    Tone_Terrific Member

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    I have a guitar that tends to be resonant at E.
    This does not hamper its sustain at all at that note rather it tends to 'take off' far too easily.

    Other points of resonance seem to boost tonal balance at resonant freqs too.
    This seems to go against the notion that a resonant freq burns up energy, at least at that freq.
    It MAY suck up the energy from other points and focus it excessively on resonant notes. How? :dunno

    What we maybe should look for more carefully are the weak/dead notes that fail to create adequate resonance or are somehow filtered out of the mix.
    I prefer low levels of resonance with balanced response at all fret positions but am definitely not as fussy as some.
     
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  8. KGWagner

    KGWagner Member

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    The fact that it wants to "take off" at that frequency tells you that it is indeed resonant there, but in the case of an amplified electric, rather than the body/neck "eating" that frequency and causing loss of sustain, it's vibrating at its resonant frequency in sympathy with an environment that's vibrating at that frequency. In other words, the body is driving the string. It's feedback. The string doesn't continue to vibrate on its own, it's driven. If you were to play the guitar acoustically, you'd hear a loss of sustain as the wood absorbed the energy from the string.
     
  9. Terry McInturff

    Terry McInturff 40th Anniversary of guitar building! Gold Supporting Member

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    Let's look at some common examples of guitars that share the same scale length, pickups, and hardware.

    Les Paul Standard and ES335. To my ears these sound distinctly different amplified, and of course acoustically they are quite different. To me that is no coincidence. They do share "family similarities".

    SG Special and ES 330. To be fair, the ES330 sports a trapeze tailpiece whilst the SG Special has either a wraparound, a wraparound+vibrola, or TOM+stop tailpiece. Regardless, these two have distinctly different amplified sounds, and of course very different acoustic sounds.

    The resonant characteristics of the guitar influences the amplified sound.

    I would imagine that a Stratocaster with a solid marble body would sound different than it's alder-bodied twin, wouldn't you all? No data available though!
     
  10. Raimonds

    Raimonds Member

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    Yeah, its a pitty that there are no marble strats around, it is quite empty business niche :)
     
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  11. Tone_Terrific

    Tone_Terrific Member

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    Not so much. The problem is more that the resonance triggered by the E gets the body/neck excited and the other strings chime in through mechanical coupling.
    This type of thing makes me skeptical about the claims of how great a resonant guitar can be.
    Hot spots are not cool.
     
  12. KGWagner

    KGWagner Member

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    Certainly other frequencies get coupled. There are several orders of harmonics the string is vibrating at, so other strings may chime in. It's why I'm skeptical of the value of a resonant guitar. All that energy-diminishing vibration is subtractive. Of course, it also determines the character of the instrument, so it's not always a Bad Thing.
     
  13. Killed_by_Death

    Killed_by_Death Member

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    Wondering how much the materials would cost to build a stringed-instrument out of carbon fiber.
     
  14. KGWagner

    KGWagner Member

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    I don't know, but I suspect it's not an issue of materials cost as much as fabrication/labor cost. You can throw a hunk of wood in a CNC machine and get a good ways along toward a neck/body in 15 minutes or so, but carbon fiber? No.
     
  15. EdFarmer

    EdFarmer Silver Supporting Member

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    How about this?

     
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  16. Timtam

    Timtam Member

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  17. macatt

    macatt Member

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    ^THIS^
    The entire post is right on the money and I've been trying to get this point across forever.
    This was stated most clearly and accurately.

    S Mac
     
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  18. Timtam

    Timtam Member

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    What about this then ? Also from an experienced guitar builder of 6-strings and basses (and a physicist). Clear and accurate ? Not wishing to criticize anyone, but how do we decide ? ;)
    "But for a solidbody electric, the whole notion of increasing sustain with resonant tonewoods or letting a string send its vibrations into the body to resonate before returning to the string is pretty much nonsense."
    https://www.premierguitar.com/articles/24287-bass-bench-searching-for-resonance
     
  19. Tone_Terrific

    Tone_Terrific Member

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    But this is what happens. All things resonate.
    The impact of the resonance will be reflected by the pattern of string vibrations.
    I'd like to know how a physicist explains that away.
    I think you just have to deal with it by making good choices, compromise and compensations.
     
  20. Timtam

    Timtam Member

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    I wouldn't like to speak for Heiko Hoepfinger, the physicist and guitar maker who made the statement using the term 'nonsense'. But if I was to suggest where that position comes from, I would think it is a combination of his company's experience of making solid and hollow electric guitars of various materials - ie empirical experiments - and his knowledge of the likely physical theory involved, as well as the limited number of scientific studies that bear on the question (he cites studies when available, in his Premier Guitar column). But there is no large body of objective evidence that definitively proves anything in relation to the structural physics of solid body electric guitars, or he would be citing it.

    So I would expect that he is mainly sceptical of the magnitude of any effect. So while all things resonate, the question is whether solid body electric guitar bodies resonate enough to influence string movement in any meaningful way. German work shows that the transfer of string vibration to/from the body is very small compared to an acoustic ... eg Fig 3 here for a strat vs an acoustic ...
    https://www.researchgate.net/public...anical_vibrations_of_electric_guitars/figures

    Transfer to the neck at the nut or at fretted notes is larger, and explains the loss of sustain associated with dead notes ... eg Fig 4 above for a Les Paul body vs neck.

    Also for example is Zollner's test where a large resonance was added to a strat body and also the neck, where one could clearly hear the difference acoustically, and see it in the measured microphone response, but there was no difference in the output of the pickups ....
    https://www.thegearpage.net/board/i...ck-wood-for-tone.1988966/page-4#post-27774095

    So yes, there is some resonance in electric solid body guitar bodies. You can often feel it and hear it. But existing evidence would have to make one sceptical of any real influence on pickup output. Whether one should assert that any influence is 'nonsense' - as Hoepfinger does - possibly depends on one's experience, perceptions, and understanding of the relevant physics. But your assertion that "The impact of the resonance will be reflected by the pattern of string vibrations" does not appear to be well supported for solid body electric guitars.

    By the way, measurements like in the Zollner strat resonance test are easy to make. Digital interfaces for guitar / microphone are cheap and readily available, as is recording and frequency analysis software*. Objective recordings / analyses from multiple exemplar guitars are thus well within the capabilities of any commercial builder. As far as our hearing of any differences is concerned, blinded sound files can be easily provided. So anyone asserting a difference in pickup output due to body acoustic resonance should now be willing to come armed with evidence which we can judge.

    * eg https://www.sonicvisualiser.org/index.html
     
    Last edited: Jan 16, 2019 at 12:41 AM
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