Warped Top and Low E Sharp Issues

Discussion in 'Acoustic Heaven' started by NiMo, Jun 10, 2021 at 6:08 PM.

  1. NiMo

    NiMo TDPRI Member

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    About two years ago I bought a 2004 Seagull S6 acoustic at a pawn shop for $100. It's a cedar top and has pretty scars that come with age and use. I should have known better but I didn't realize at the time the amount of top warping/dishing/bellying that this guitar had. I never encountered (or was aware of) this issues with other acoustics I've owned and had no prior knowledge how to deal with it. After a few days of research online it seemed the best approach was try to fix it with humidity over a month or two. I put a damp sponge inside a plastic soap box that I drilled holes in the top and sides. The sponge never made contact with the wood inside the guitar. I covered the sound hole tightly to retain moisture and kept it inside a guitar case. Tried this over a period of almost two months but it didn't have much effect.

    Went on to plan B which involved installing a JLD Bridge Doctor. I applied tension slowly over a period of a week to help avoid damaging bracing or lifting the top too high. It definitely helped straighten the top, but at the cost of dulling the tone some. At this point I was satisfied with the warp correction but the low E is definitely sharp during intonation tests. I installed a compensation saddle but it had little to no effect. I did all of these correction attempts about two months after buying the guitar. My son has been using it since I did those repairs and now it's back in my possession. It still has the low E sharp issue so today I tightened the bridge doctor a bit more which lifted the strings higher off the neck and I thought would add length from 12th fret to the saddle for the low E to reduce/eliminate the sharp pitch. However, it didn't help. Would decreasing neck relief help add low E string length while also lowering string height?
     
  2. Boreas

    Boreas Friend of Leo's Silver Supporter

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    Ultimately, you may need to fashion a new compensated saddle to get it to intonate properly. I wouldn't mess with the guitar's basic geometry to try to achieve proper intonation. But you could try a change in string gauge.
     
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  3. Freeman Keller

    Freeman Keller Poster Extraordinaire

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    Without a whole lot more information I cannot answer your question. How much sharp, exactly where is the break point of the string relative to the scale length, action height, relief, and so on.

    The bridge doctor should have provided a slight amount of rotation around the bridge axis. It should be pushing the lower bout down and pulling the area between the soundhole and bridge up, and actually back. That should actually help with your intonation problem.

    Art and Lutherie guitars have a bolted butt neck joint and are relatively easy to reset the neck, however some use epoxy for the fretboard extension which makes them hard to get off. A&L also uses several different thicknesses of bridges to help with geometry issues. Last, but far from least, if you can't get the break point where you need it its possible to fill the slot and route a new one.

    I have pictures of several of these operations if you think it would help.

    ps - get the bridge doctor out of there, its a poor solution to a problem that can be fixed in other ways.
     
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  4. NiMo

    NiMo TDPRI Member

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    Thank you for the reply.
    The original saddle was not a compensated saddle. I installed a compensated saddle that contacts the low E and A closer to the bridge pins compared to the original, but it didn't help. The only way to get the bridge back farther route out the current saddle and fill in the space when the bridge is moved back, or buy a new blank saddle and route out the bridge cavity back more than the current one.

    The other option is to add a small piece of bone in front of the nut to shorten the distance from the nut to 12th fret as shown in the video below. I would be okay with this option as a last resort as this guitar is already beat up a bit anyway.

     
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  5. BB

    BB Poster Extraordinaire

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    I was hoping Freeman would respond o your post. Whatever he say's to do, do! Good luck.
     
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  6. Boreas

    Boreas Friend of Leo's Silver Supporter

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    If the saddle adjustment didn't help, I would say until you get the body and neck of the guitar stable, don't worry about the intonation. It is easy to start chasing one's tail when trying to "work around" fixing the main issue. It is conceivable the bridge/saddle never intonated properly from day one, and may need to be re-positioned after the top and neck are stabilized.

    Keep us posted.
     
  7. NiMo

    NiMo TDPRI Member

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    I haven't measured it.

    That's what I was hoping for but it lifted the string height as well and didn't help the intonation. I've tested intonation often during the several ranges of (guitar top) adjustment with the bridge doctor and it doesn't flatten the sharp pitch.

    It has two bolts that mates the neck to the body. I discovered after purchase one of those bolts were missing and I installed a new one.

    yes, please.

    Willing to do that, but I don't want to put much more money into this guitar.
    Thank you for the reply.[/QUOTE]
     
  8. NiMo

    NiMo TDPRI Member

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    Sounds like a ringing endorsement and good advice.
     
  9. vgallagher

    vgallagher Tele-Meister

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    Maybe the nut slot is too high. That could cause sharpness when fretting
     
  10. NiMo

    NiMo TDPRI Member

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    Might be.
    I put a set of Martin Retro acoustic .52-.011 Monel (nickel/copper) strings on it a couple days ago and the low E doesn't in the nut correctly, it seems to be seated high. I don't know the gauge of strings this guitar was originally fitted with but apparently not the ones I just put on.

    I just FB messaged a guitar tech that has re-fretted one of my electric guitar's and replaced on a nut on 90's Tacoma acoustic guitar to get his advice. I might bring it to him to look at as well. His shop is about a 30 minute drive away but he does great work and is reasonably priced.
     
  11. Freeman Keller

    Freeman Keller Poster Extraordinaire

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    Before we go any farther please measure everything and post the measurements. I want to know how sharp or flat all the strings are when fretted at 12. I want to know the scale length (measure it) and how much the saddle slot has been moved. I want to know exactly where the break points on each string is, I want to know the gauge of strings you are using (I an calculate the theoretical compensation which you can compare with what you actually have). I want to know the relief and action for each string at the 12th fret. I want to see a picture of a straight edge on the frets pointing to the bridge. It is helpful to know the thickness of the bridge. I want to see a picture of your straight edge on the lower bout right behind the bridge (I want to see how "bad" the belly is).

    There are some things that don't make sense in your first post. First of all, a healthy acoustic guitar has a belly, they are built that way. When a guitar dries out the top shrinks and goes flat (and often cracks). Humidifying a guitar is intended to get that dome back into the top.

    The JLD Bridge Doctor works on the principal of creating a lever against the bottom of the bridge structure that attempts to rotate it around its axis by pushing on the tail block of the guitar. The strings and saddle create another lever on top of the guitar applying a torque (and a rocking motion) to the top, the Doc fights the rocking. It can remove the belly (somewhat) but it also counteracts the way an acoustic guitar makes sound. There happens to be a discussion about them right now at one of the lutherie forums

    https://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=54189

    Whether you decide to use the bridge doctor is up to you. I can help you get the geometry correct with it in or out, but I need the measurements above. FWIW I do build guitars and I have worked on guitars made by A&L, they have some of their own idiosyncrasies.

    Edit to add - here is an A&L (parent company of Seagull) showing the expected dome to the top

    IMG_5712.JPG

    The neck angle is bad, so the action is way too high
    IMG_5711.JPG

    After removing the neck and resetting it

    IMG_5739.JPG

    A new saddle was made with better action and acceptable intonation

    IMG_5740.JPG
     
    Last edited: Jun 11, 2021 at 12:46 PM
  12. NiMo

    NiMo TDPRI Member

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    Thank you. I will post the requested info and pics soon.

    The area between the saddle and sound hole definitely had (pre-JLD) a noticeable dip, saddle and bridge tilted too far forward and downward. I did measure the top of the guitar as you linked soon after purchase and there was excessive bellying. I will measure again and attach similar pics to the ones you posted.

    Thank you for the link and appreciate any of your knowledge you're willing to share.

    I read that thread last night during my research.
     
  13. Freeman Keller

    Freeman Keller Poster Extraordinaire

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    The way the forces work on the top of a guitar is to pull up the area behind the bridge and push down between the bridge and sound hole. That's why the X brace is such a brilliant construction - it puts the strongest and stiffest part of the brace where the maximum deformation of the top is, yet still allows the majority of the top to vibrate.

    TORQUE-LOAD-300x160.jpg

    Obviously too much bulge or depression is not good, but a little is natural. The other thing that happen in the above picture is that when the sting is plucked it is first stretched, which pulls even more bulge, then released with lets the top rock around the axis of the bridge. The Bridge Doctor counters that motion which is what is making sound.

    My other objection to the Bridge Doctor is that it weighs 2 ounces, twice as much as a typical Martin bridge

    IMG_6735.JPG

    IMG_6737-1.jpg

    This can't be good if your goal is a light weight responsive top - your observation about "dulling the tone some" is what I experienced when I tried one. I took it back out, had the neck reset on the guitar in question and life has been good.

    Anyway, lets put this on hold until you get some measurements.
     
  14. magicfingers99

    magicfingers99 Friend of Leo's

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    how far off is it?
    you know you can take the low e off like keith richards and still play...
     
  15. schmee

    schmee Doctor of Teleocity Ad Free Member

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    WHERE is the intonation issue? Open E string? 12th fret?

    Your intonation should have nothing to do with the top of the guitar.... it's all about two points and the length in between; the nut and the bridge. In fact, some guitars have no body at all!
    Custom bridge segment or relocate the entire bridge some maybe.
     
  16. NiMo

    NiMo TDPRI Member

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    I play better than Keith Richards..why would I want to go backwards in skill? Lol, That was quite an arrogant statement I just made with a half truth thrown in. I'm an at home hack while old Keith has traveled the world many times over imparting his licks to adoring fans. Though, I will cut heads with him if he ever wants to to do so...lol.
     
  17. Freeman Keller

    Freeman Keller Poster Extraordinaire

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    We customarily "intonate" a guitar at the 12th fret because we have a nice convenient reference (the harmonic). Since the amount that a string goes sharp when fretted depends on the diameter of the core and the amount it is stretched, the action is very important, action frequently is affected by the geometry of the guitar. The low E string frequently has a higher action that the high

    I'm trying to get NiMo to give us some numbers.
     
  18. magicfingers99

    magicfingers99 Friend of Leo's

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    the low e has to have a higher action than the high e, due to the diameter of the string. it will buzz if its too low

    but agree can't fix it, if you don't know how far off it is..
     
  19. schmee

    schmee Doctor of Teleocity Ad Free Member

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    Yes, we have no idea if he means the E string sounds sharp by fret 5 or just 12 or......... how far off is it?
     
  20. Freeman Keller

    Freeman Keller Poster Extraordinaire

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    I think the OP has two issues. The geometry of his guitar and his attempts to compensate ("intonate") one or more of the strings. They are related because geometry affects the setup and intonation is part of setup.
     
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