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Thread: Tonal difference between full contact or two-footed bridge

  1. #26
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    Default Re: Tonal difference between full contact or two-footed bridge

    Quote Originally Posted by CaseyMullen View Post
    I've really enjoyed reading the conversation sparked by my question... thanks for all of the thoughtful response.

    Dave, in your first post you said "So, one big foot or two feet, the normal modes of the mandolin body are not gonna be any different." That was essentially the crux of my question... I was assuming that the bridge is acting somewhat like a brace (at least in one direction), and so changing the "footprint" of the bridge might alter the modes of vibration in the top... e.g. open up more high-frequency modes...

    But it sounds like your careful experiments showed that if the modes are altered, it is not by enough to matter.
    Thanks for sharing your data.
    Actually, a bridge does act like a brace to some extent. Braces don't determine the shapes of plate normal modes. Those mode shapes are determind by the shape of the plate itself. Plate mode shapes are only affected by braces at high frequencies, ca 2 kHz and above. For those upper modes, the wavelengths become short enough that large braces begin to look like obstacles. What braces can do to the lower modes is affect their frequencies somewhat, depending on their orientation. I did an experiment lie that back in 2004, & presented it at the May, 2004 ASA meeting in NYC.

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  2. #27
    Registered User fscotte's Avatar
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    Default Re: Tonal difference between full contact or two-footed bridge

    Obviously Dave's response has sparked some "arms crossed hmmmmmm's" and that's understandable because I think many folks here do in fact hear differences in bridge materials. At least that the first thing one would think after having replaced one bridge with another of difference material.

    Dave, science is observation, but I wonder if there isn't more that is simply not being observed. I'm not real sure if guitar saddles are similar to mandolin bridges in tonal color, but I went through an maniacal phase of trying all sorts of materials for my guitar saddles. Anything from Tusq to various sorts of bone and walrus ivory. There are absolutely differences in tone dependent upon the material, I wouldn't even need science to tell me that. I was so tuned with the tone of my guitar I could tell you if there was a gnat sitting on the D post... Ok maybe not that tuned in but..


    I would definitely like to hear the tone of an aluminum mandolin bridge, or one made from plastic. Maybe I'll fashion one someday.

  3. #28
    Phil Goodson Philphool's Avatar
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    Default Re: Tonal difference between full contact or two-footed bridge

    Quote Originally Posted by Dave Cohen View Post
    ....I don't expect anyone to believe anything I say here. .... you offer me one anecdotal observation which I cannot repeat under any circumstances, since you make no measurements of any kind. There is nothing I can do with that; I can neither verify it, nor falsify it.
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    Dave,
    I'm not expecting you to verify or falsify anything. I merely ask if there might be other factors that you have not measured that might affect what we think we hear.
    I think that I'm as skeptical and demand data to verify our perceptions AT LEAST as much as you do. I'm just having a discussion.

    Do you honestly not hear any difference in an ebony bridge vs an aluminum bridge vs a glass bridge, vs a plastic bridge? And I don't ask whether you have measured a difference in modes, nodes, frequencies, or anything else. There are many experiments not yet done.

    I respect your opinions although, as you suggest, opinions aren't worth much when you're trying to get to the truth.
    Phil

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    Registered User sunburst's Avatar
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    Default Re: Tonal difference between full contact or two-footed bridge

    Quote Originally Posted by fscotte View Post
    ...There are absolutely differences in tone dependent upon the material, I wouldn't even need science to tell me that...
    Maybe not, but you'd need science to tell me that. In other words, I don't trust anyone's ears, not even mine (maybe especially not mine) unless they consistently recognize something blind. In other other words, if someone could change the saddle material in your guitar and hand it to you without you knowing what the material is, and you could consistently tell what the saddle is by sound alone, then you have evidence. If other people could repeat the experiment with similar results, that's more evidence, and at that point the somewhat scientific mind (like mine) starts to believe it.
    I've seen sooooo many examples of people hearing what we want to hear only to be contradicted by evidence to the contrary.

    For example, I'm convinced that a new mandolin sounds different (better) after several hours of being strung up, but I have no measurable evidence of that and no repeatable method of demonstrating it. That means I can't say with any certainty that a mandolin actually does sound better after a few hours (but that doesn't "unconvince" me).

  5. #30
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    Default Re: Tonal difference between full contact or two-footed bridge

    Quote Originally Posted by Philphool View Post
    Dave,
    I'm not expecting you to verify or falsify anything. I merely ask if there might be other factors that you have not measured that might affect what we think we hear.
    I think that I'm as skeptical and demand data to verify our perceptions AT LEAST as much as you do. I'm just having a discussion.

    Do you honestly not hear any difference in an ebony bridge vs an aluminum bridge vs a glass bridge, vs a plastic bridge? And I don't ask whether you have measured a difference in modes, nodes, frequencies, or anything else. There are many experiments not yet done.

    I respect your opinions although, as you suggest, opinions aren't worth much when you're trying to get to the truth.
    You say that you are not asking me to verify or falsify anything. Then in your next sentence, you state that you are skeptical "and demand data to verify our perceptions AT LEAST as much as you (meaning Dave) do." That is the problem for me. You are sure that I must have missed something, , but you offer only a wild (and non-physical) conjecture about whatever it is that I must have missed. If you were to suggest something even remotely physical about whatever it is that I must have missed, I could at least address that. I did my best to address what you did offer, and you did not respond to that. My whole point is that I can't do anything about perceptions. I have offered measurements which you can deal with. If you are skeptical of those measurements, they are repeatable, and you can do them yourself. In return, you offer a single "perception" about which no one can do anything.

    I have never seen, nor made, nor heard a glass bridge saddle. Not sure one could be made unless it was quite heavy, so not interested. I have heard a mandolin with an aluminum saddle. Evan Marshall uses one on his mandolin. I have heard him play many times, and frankly, his mandolin sounds like a mandolin, albeit one played by an amazing player. You can see from my earlier post, picture, and description what I did make bridges and saddles from. I still have those bridges and parts, and I can retrieve the mandolin if necessary (it is on loan). So I can repeat the experiments with the same results, and I can offer a repeat of my own anecdotal observations. I heard no difference between any of the bridges in that experiment. I would be extremely surprised if I heard any differences between the bridges on a revisit to that experiment. If you decide that I must be tone deaf, then so be it. There have been lots of instances when I wanted to hear or see a difference, but it just wasn't there. Fact is, for someone my age, my hearing is quite good, but I don't expect you to trust that.

    Regarding "modes, nodes, frequencies, or anything else": So, can you suggest something else I can do that is repeatable, verifiable, and falsifiable? Scientific measurements may not be your cup of tea, but it would be nice if you made some attempt to understand them before dismissing them as coming up short.

    http://www.Cohenmando.com

  6. #31
    Phil Goodson Philphool's Avatar
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    Default Re: Tonal difference between full contact or two-footed bridge

    Dave,
    I'm sorry that I'm irritating you. I truly don't mean to do that. Actually, I don't think that we would disagree at all if we were talking in person and could clarify what we're saying right away. I don't do research for a living and have lost some of the skills to express myself precisely in that arena. I don't have the extensive physics vocabulary or training that you have and use with ease, so I'm trying to say what I mean as best I can. Let me try again to clarify; not to get you to do anything, but just so you know that I'm not arguing against what you're saying, at least not on purpose.

    I agree that only measureable and reproducible data can be depended on to verify a perception as truth.
    I agree that my own perceptions may well be proven wrong if the appropriate experiment is done.
    I don't know whether we agree on whether everything that determines a mandolin's sound has been discovered and tested to provide enough data to fully decide what changes a mandolin's sound. (I really don't know, but am skeptical.)
    I trust your findings with the bridges that you have tested. I wish I had a way to reliably check my previous perception of the Tusk bridge. It's hard to do a blinded study alone. I might, for interest, try to find the saddle and revisit an unblinded "study" some time.
    I assure you that I do make"some attempt to understand [scientific measurements] before dismissing them as coming up short." and I find your suggestion somewhat condescending.
    But I thank you for your well thought out reply.

    Perhaps we can have a clearer discussion sometime on Helton Creek if we both make it to a Comando gathering.
    Phil

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  7. #32
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    Default Re: Tonal difference between full contact or two-footed bridge

    I don't have any measurements of my trials with bridges which was done some years ago, which is a pity, but in order to try and reduce the "you hear what you want to hear" bias I always use a well known reference mandolin as a comparison. In addition to that I usually get the other half to listen without actually telling her what has changed to make sure it is not just me deluding myself. I also have a good friend who plays two of my mandolins, I have modified his bridge, and he hears the same things as what I do. In the case of drilling two holes in the saddle that is repeatable, I have done that many times on several different mandolins, swapping out the drilled saddle with a solid saddle and back again. We always hear a difference. I was hoping to not hear a difference because it is a PITA to always have to drill those holes. Same with Red Henry style Maple bridges. I don't like them, but I have always attributed the louder, brighter and "harder" sound we can clearly hear to the reduced mass of the Maple. So, I am really surprised that Dave can't hear any difference with the Red Henry Maple bridges because I can, my other half can, and of course Red Henry can, although there is some disagreement about what is "better".

    It is interesting to note that the same sorts of arguments have been going on for many years in the world of Hi Fi. Many years ago the engineers were claiming that certain amplifiers must sound the same because the measurements were exactly the same. But people could hear differences - i.e. the correlation between the measurements and what people could hear was not so good. After much research it was found that the measurements that were used then were not telling the whole story. Today the measurements correlate much better with what people hear, but probably is still not 100%. Not only that, but because the correlation is much better, the amplifiers sound better as well.
    Peter Coombe - mandolins, mandolas and guitars
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  8. #33
    Registered User fscotte's Avatar
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    Default Re: Tonal difference between full contact or two-footed bridge

    Quote Originally Posted by sunburst View Post
    Maybe not, but you'd need science to tell me that. In other words, I don't trust anyone's ears, not even mine (maybe especially not mine) unless they consistently recognize something blind. In other other words, if someone could change the saddle material in your guitar and hand it to you without you knowing what the material is, and you could consistently tell what the saddle is by sound alone, then you have evidence. If other people could repeat the experiment with similar results, that's more evidence, and at that point the somewhat scientific mind (like mine) starts to believe it.
    I've seen sooooo many examples of people hearing what we want to hear only to be contradicted by evidence to the contrary.

    For example, I'm convinced that a new mandolin sounds different (better) after several hours of being strung up, but I have no measurable evidence of that and no repeatable method of demonstrating it. That means I can't say with any certainty that a mandolin actually does sound better after a few hours (but that doesn't "unconvince" me).

    It's quite possible that some folks hear things due to the fact that their hands and picks are touching the strings. Vibrations through the body, etcc.. A microphone for one doesn't touch the mandolin, thus it wouldn't have the luxury of "feeling" the vibrations through a person's body. Sounds dumb, but maybe not. Blind folks seem to sense things, or be in touch with feeling the music moreso than someone who can see, Ray Charles spoke of this. Even using fancy devices that attach to the mandolin do not recreate the touch of a musician's fingers and the feel of the instrument against his gut.

    Our bodies are filled with water, and sound travels quite well in water. It's quite possible the sound of the mandolin moves through our bodies in different ways.

  9. #34
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    Default Re: Tonal difference between full contact or two-footed bridge

    Phil, I found your post #28 to be very condescending. When things are said in anger, one sharp retort seems to beget another. However, I have no interest in carrying that on.

    Peter, Red Henry was very kind to donate those two bridges for my experiment. I really wanted to see and hear a difference - of any kind - for the sake of his generosity and his sincere belief in what he was doing with those bridges. I just couldn't hear any differences between bridges on that mandolin, and neither could Jim Rae. Further The lack of audible differences between the bridges correlated with the lack of any sigificant differences in the accelerance spectra - even the difference spectra. One problem with audition of different bridges on a single mandolin is that there is a time interval of at least several minutes between auditions of the different bridges. I don't care how good one's hearing is, human audial memory is not very good after more than a few minutes at most - probably less than that. Further, the mandolin used was (is) a very good-sounding mandolin, according to several different auditioners. So I don't think that any particularly harsh sound characteristic was masking whatever differences there were (and are) between those bridges.

    Fscotte, if you look at an issue of JASA (Journal of the Acoustical Society of America) you would find entire sections on underwater acoustics. Acoustics, after all, is the study of propagation of vibrations in fluids. You might not want to open up another can of worms without doing some homework on that. The water you speak of in humans and other animals is largely tied up in colloids - pretty inhomogeneous chunks of matter, & not simple fluids at all.

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  10. #35
    Registered User Tavy's Avatar
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    Default Re: Tonal difference between full contact or two-footed bridge

    Quote Originally Posted by avaldes View Post
    OK, not a builder, so please pardon what may appear to be ignorant questions.
    3. Bowl-backs have a wood bridge with a saddle made of (presumably synthetic) bone or ivory. Much less adjustable, but it would seem that it would transmit vibration better. Anyone make an adjustable bridge with the saddle portion of such a material?
    I once set up a DeMeglio bowlback with

    * All ebony bridge.
    * Original shelf style bridge with bone saddle.
    * Original shelf-style bridge with brass saddle.

    And you really couldn't tell the difference. Other things like bridge fit, and particularly cleanness of string contact on the saddle did make much bigger differences.

  11. #36
    Phil Goodson Philphool's Avatar
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    Default Re: Tonal difference between full contact or two-footed bridge

    Dave,
    Sincerely, my apologies. None of my comments were meant to be condescending or adversarial. I really, truly was trying to get some new understanding of things that I don't have a good understanding of.
    Let's just lay it aside.
    Honestly hope to see you again one of these days and do some picking and chatting.
    Have a good summer.
    Phil

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  12. #37
    Registered User Tavy's Avatar
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    Default Re: Tonal difference between full contact or two-footed bridge

    To get back to the original "1 vs 2 foot" bridge debate:

    I do hear a difference: the 2 foot bridge is to my ears more "definite" and less twany, but only at the margins, on a well made instrument it probably makes not a jot of difference. However, on an instrument with insufficient downforce on the bridge it can make all the difference between an acceptable sounding instrument and a weak one. Typical examples would include 'zouks, OM's/'dola's or vintage flattops.

    However, I also have no reason to doubt Dave's investigations in this matter, so one wonders what's going on? Some possible reasons might be:

    1) Human error: one foot bridges are harder to fit. Given the limitted time most folks have to get things right as well, there is virtue in picking a design that is more resilliant to minor errors.
    2) Greater contact pressure: if we remove about a 1/3rd of the bridge contact area in moving from a 1 to 2 foot bridge we necessarily increase the contact pressure between the two. In a low downforce situation I can see this making a noticeable difference with less juddering going on. For a slightly imperfectly fitted bridge there is also a greater likelyhood of the top conforming to the bridge shape (something we always rely on to a degree, otherwise every bridge adjustment would require a refit). It is however a double edged sword, as I suspect we've all seen very badly fitted 2 foot bridges that have distorted the top so much as to do damage.

    Just my 2c worth...

  13. #38
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    Default Re: Tonal difference between full contact or two-footed bridge

    i have thought about this quite a bit and came to the conclusion that the two foot bridge was the best way to go. if you look at the two foot bridge and the relief in the centre it will become obvious that the downward pressure of the saddle would apply pressure on the two feet. with the undercut made to a minimum, you will find that the bridge becomes quite flexible and the two feet more able to achieve full and uniform contact...of course the bridge has to be made accurately for fit...just a thought.

  14. #39
    Registered User David Houchens's Avatar
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    Default Re: Tonal difference between full contact or two-footed bridge

    I haven't done much study 1vs2 foot bridges. Maybe at a later date.
    Some of the spruce I've been using has been really stiff. For my part, I like a full contact bridge on these. I feel it adds, maybe no strength in construction, although it could be considered an outside brace, but may add to the stability of the top.
    As to sounding different, I'll have to say my ears have heard a difference in various saddles on a few mandolins. Maybe my ears were ringing at a different pitch between changes.
    Disclaimer; There have been no scientific studies to verify any of my thoughts.

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