Unusual idea in the Traeger book

Discussion in 'Setup & Repair [DB]' started by Steve Swan, Dec 14, 2013.


  1. Steve Swan

    Steve Swan

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    I just had a conversation with a fellow who owns the Traeger repair book. A home repair kind of guy, he has tried several techniques described in the book. One of them calls for a strip of Teflon to be inserted under the bridge feet for "better sound transmission". Really? What's this all about?
  2. fdeck

    fdeck Supporting Member

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    Teflon creeps under pressure (why it's a PITA to machine). Maybe the Teflon is molding itself to whatever gaps remain due to poor fit, thus improving the contact between bridge and belly.
  3. bssist

    bssist

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    I use the Teflon. The theory is that it allows the top to move more than straight contact of the bridge to the top.

    I have made many small tweaks like that so I can't really say how much of an effect it had. The biggest changes I experienced were with different drumsticks for end pins and the Marvin tailpiece
  4. aaronallen

    aaronallen

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  6. John Sprague

    John Sprague Sam Shen's US Distributor

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    That has been our experience, that it can help get a little more out of poor sounding instruments, but not much impact on a good sounding bass.
  7. robobass

    robobass

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    Possibly, but PTFE is has very high compression resistance. If better mating of the bridge feet to the top were the goal, then lots of other materials would work better.

    The quote from the seller is "Use of this teflon under the bridge feet of a bass will allow the top to vibrate closer to the optimum level by allowing greater freedom of the movement of the top under the bridge feet". I just don't see how this could be so. I'd try cork! On the downside, with PTFE shims under your bridge feet you will be much more likely to drop your bridge with a casual bump. Notice that shoe treads tend not to be made of Teflon:hyper:
  8. Sam Sherry

    Sam Sherry Inadvertent Microtonalist Supporting Member

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    I don't know but you might be able to run a cheap experiment using this.

    $1.37 is cheap in my book and this would be a lifetime supply at that.
  9. Jake deVilliers

    Jake deVilliers Supporting Member

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    That would be interesting: its slippery enough to free up the top but its so thin that it would conform to every grain line...
  10. bssist

    bssist

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    This from pg 18 of "Coda..." - C. Traeger

    Wh thought at the time what had happened was that the pads made the bridge fit the top more accurately. That is why the sound was louder because we were helping the bridge. ________ said she could improve the sound by rounding the underside of the feet slightly in the long direction of the feet. However, she didn't recommend it because cosmetically it looked like badly fitted feet. This is when I first began to suspect that the help-the-bridge theory was flawed because you shouldn't get a better response from poorly fitted feet than perfectly fitted feet.
    ...//...
    If decreasing the bearing area of the sound post against the underside of the heart produced a positive result why shouldn't decreasing the bearing area of the bridge feet against the topside of the heart produce an equally positive result?

    He goes on to explain the motion of the top in three planes as well as thickness and hardness of different teflon products and why he decided the specific product that is now sold by Metropolitan gave the best results. According to Traeger .005 was too thin and .010 was too thick.
  11. robobass

    robobass

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    But why would it free up the top by being slippery? The feet aren't sliding around on the top, they're staying in one place with or without the Teflon.

    "If decreasing the bearing area of the sound post against the underside of the heart produced a positive result why shouldn't decreasing the bearing area of the bridge feet against the topside of the heart produce an equally positive result?"


    So it seems like the Teflon somehow mimics the effect of a smaller bridge footprint. I guess this would be due to compression. Again, I don't really see why you would choose PTFE if you want this effect. Cork, spruce, or even neoprene would have more compressibility, and not cause a safety issue. I've got a terrible scar on my Geiger top from an adjuster wheel when my bridge went down once. I really wouldn't recommend this!
  12. Jake deVilliers

    Jake deVilliers Supporting Member

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    It seems to me that if you wanted a smaller footprint you'd make the feet a little smaller - or am I missing something?

    I notice a big change in sound when I re-shape the bridges that show up on DBs at the store. The place that 'sets them up' for L&M in Toronto has no idea how to cut a bass bridge and they come VERY thick from the waist down, with almost full sized feet.

    I think cork or anything soft like that would be too absorbent of vibration - rather than passing it through, it would consume/dissipate some of the string's transmitted vibrational energy. Very much in the way a soft Chinese bridge does, for example...

    I'm going to have to get some of that material and do some experimenting. Unfortunately, I just received a large order from Metropolitan Music, so it will be a while.
  13. bssist

    bssist

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    That is what Traeger suspected was happening with teflon of .010 thickness. He referred to is as "acting like a blanket between the bridge and the top"
  14. fdeck

    fdeck Supporting Member

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    Good points, and I wouldn't try the PTFE on my bass, which has an extremely well fitted bridge.
  15. Greg Clinkingbeard

    Greg Clinkingbeard

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    My feeling on the subject as well. Mr. Traeger has some interesting ideas, some of which have merit. This doesn't seem to me to be one of them.
  16. arnoldschnitzer

    arnoldschnitzer AES Fine Instruments

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    A client showed up a while back with 3mm thick cork pads under his bass' bridge feet. His strings had gotten too low so he had fitted these pads; also he claimed the bass sounded better with the cork there. Surprisingly, when the cork was removed (and replaced with well-fitted maple) the bass seemed to lose power and tonal complexity. I was dumbfounded, and put the cork pieces back. I can't explain why.
  17. KUNGfuSHERIFF

    KUNGfuSHERIFF

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    That's bizarre. Do you recall anything about the bass and how it was set up?

    In my very limited experience, mostly with hacked-up Kays, the cork risers are a liability for sound and stability. My nicest old German has maple pads underneath the feet and it sounds fine, but looks pretty bad.
  18. Jake deVilliers

    Jake deVilliers Supporting Member

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    I hate when that happens! ;)

    But instruments are teaching me new stuff all the time...
  19. arnoldschnitzer

    arnoldschnitzer AES Fine Instruments

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    The bass is a five-string converted Hawkes. The top is thin and has a fair amount of distortion and sinkage. The owner still has the cork in place. My thinking is that the cork helps the bridge maintain contact while the flexible top table is moving all over the place. The purpose of a bridge after all is to transfer and amplify motion, which the box turns into air movement/sound. Makes sense that good contact might translate into improved sound. Teflon scares me though because it is so slippery.
  20. turf3

    turf3

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    Well, what you have here is a spring-mass-damper system with multiple springs, masses, and dampers, vibrating in all 3 dimensions. (Analysis is basically impossible; measurement is complex as all get out and understanding it very difficult.) Two pieces of cork under the bridge feet are both springs and dampers, inserted in a critical point in the system. Depending on the "spring rate" and "damping rate" - I put these in inverted commas because those terms imply a certain model of behavior as a function of force or velocity, which is probably not accurate in the case of pieces of cork (or PTFE) - the effects on the total system can vary widely.

    I think that in essence no one knows enough to be able to say with certainty the effects of fooling with this bridge-top plate interface, nor - and this may be the most important thing - does anyone know what are all the other factors that affect those effects. (For example, does top plate thickness have an effect on the results of putting pieces or cork, or PTFE? How about mass of the bridge? And different string types, or different string masses, etc., etc., etc.) So in the end I think until someone ponies up a few hundred thousand dollars for high powered measurement and analysis of a statistically significant sample of double basses with multiple variants of the bridge-to-top plate interface, the world will have to proceed on the basis of "this is an interesting idea; this is what it did on the one (or two, or eight) basses I applied it to; the effects on yours might range from duplicating my effects to the exact opposite, based on input parameters which are unidentified and not understood".

    In other words, try it and see what happens.
  21. Heifetzbass

    Heifetzbass

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