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Steve Rodriguez

Bridge Carving Question

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I have a concern with the bridge I carved on my violin.

I have noticed that the E string sounds very clear, but is a bit bright, and either the amplitude is too great, or perhaps it is harmonics.  The G and D strings sound very good to me; the A sounds good.

The sound post is in a good position I think; not too far to the treble side, but is centered under the foot and about 2.5 mm back and vertical.   

I wonder if the overall mass of the bridge has been reduced too much.  Here are some pictures and some measurements taken under the E string on the bridge. 

If you have any suggestions, I would be most appreciative.

Thank you,

Steve

 

bridge data.pdf

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How high is the E? It seems to go through the bridge and not over it like the other strings. I usually make my bridges thinner than your specs although I don't think that's the problem.

Edited by Torbjörn Zethelius

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Torbjorn,  the E string definitely is going thru the bridge; seems to be under the top surface at the front of the bridge when I looked at it closely.  I think it started out higher.

Nick, I cut the bridge unfortunately.  I think you are talking about the ankles being chunky?

Thanks,

Steve

 

 

 

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Although it probably isn't causing your problem I would free the E string from being pinched. That could make a difference. While you have the bridge out you can lightend it up if you want to before you put it back.

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Okay, I will free that E string.  I think some folks use a parchment material I was reading about; I will try that. 

Melvin, the only way I see to move the force forward is to carve the ankle above that foot at the back side of the bridge at that position if I'm guessing right. 

Thanks

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2 hours ago, Steve Rodriguez said:

Okay, I will free that E string.  I think some folks use a parchment material I was reading about; I will try that. 

 

Or you can cut the bridge down around the E string groove until there's just a nick, unless you want to raise the E string anyway for some reason.

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12 hours ago, Steve Rodriguez said:

Ahhh...that makes sense to me; is easier!

Thank you.

I would still use parchment and get rid of that useless bit of rubber sleeve.  Otherwise, over time that E string is going to cut into the wood and you will be back (near) where you started.  Melvin can speak for himself, but it appears to me that the E string groove -- whether originally cut this way or not -- is deeper on the tailpiece side.  Whether the parchment will take care of this or the problem lies deeper Melvin I hope will answer.

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Most of the performance of a bridge comes from the upper 2/3rds. Fat feet should not cause problems unless they are ill-fitted to the top.

Vibrating strings also twist and stretch slightly. These motions are affected by the fit of the string as it rests on the bridge.

If you do not want to deal with parchment, then try a drop of CA glue (super-glue). Basically, move the E string out of the way. Cover the violin top to protect it against any accidental glue spillage. Put a small drop of CA glue in the E string glue. Wait until it hardens. I would do a second drop to build it up slightly. Gently reform the groove.

Bridge's act has low-pass filters. A rule-of-thumb is that the first natural mode of vibration should be in the 2500hz to 3500hz range. Get a frequency spectrum app for your smart phone. They are free. Place the bridge on its side at the edge of a table. Place a piece of wood across the feet and hold it down by hand. Now take a bow and draw it an an angle across an outer edge near the top. The spectrum app will show the frequency of the modes.

Be aware that the basic frequency of the bridge is largely dictated by the quality of the wood. You might be able to adjust the frequencies by a few 100hz by selective carving. 

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It doesn't appear that the fine tuner is seated under the tailpiece.  In the second picture, it looks like there is a large gap between the tailpiece and tuner.  Check that it is making good contact and seated well.  

 

I agree with thinning the bridge and narrowing the ankles. (But don't narrow the waist!)

It appears that the thickest point is at the knees.  I would move that up a bit to the lower waist (Inline with the kidneys.) I like 3.5 just under the heart and 4.4 at the feet.  I may be wrong but it looks like it get's thicker just above the feet. 

 

Thin the ankles from the inside out.  This will give more leverage to the vibration of the top.  

 

If the E string is bright, I would move the post south away from the bridge 0.5-1mm.

 

Good luck!

Dorian

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4 hours ago, ctanzio said:

Be aware that the basic frequency of the bridge is largely dictated by the quality of the wood. You might be able to adjust the frequencies by a few 100hz by selective carving. 

Selective carving can influence the basic frequency of the bridge much more than a few 100 hz.

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Thanks very much Guys.

I’m going to try out the smartphone app as I’m real curious.  The fine tuner is a bogaro clemente.  I have too much screw travel there; I have to watch that more.  The f hole nicks I put there per the method in my book; I settled on a string length of 329mm in the end.

I realize more and more how important setup is to the sound. 

Thank you all for this information and for your help.

This forum is just plain awesome.

Regards,

Steve

 

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On 9/2/2018 at 3:25 PM, David Burgess said:

Selective carving can influence the basic frequency of the bridge much more than a few 100 hz.

Are you referring to a blank taken to a basic setup (feet snug, string clearance and spacings set), or a bridge that is already setup and trying to "fine tune" the basic frequency?

 

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Yes, and that was my original goal, and to fine tune, and then it was pointed out certain discrepancies which I have corrected.  I have super-glued the E string notch, applied some bridge velum, shaved off some mass per the observations, and then moved the soundpost some.  The sound has improved (less bright), though I would like it to be a little less bright still.  Maybe on the second violin I could study arching more; maybe there is something I can do there to affect this parameter. 

Thank you,

Steve

 

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Bridge carving is a complicated area, with lots of variables, subtleties, and some "rule-of-thumb" principles that various luthiers don't exactly agree about.  I'll leave it to the experts to guide you in how to improve this bridge/violin. 

However, I can strongly recommend the site https://www.violinbridges.co.uk/ which gives you access to pictures of and detailed measurements of thousands of bridges, many from highly esteemed luthiers/shops.  I think that you have to pay a small subscription fee to see all of the measurements, but it is well worth it.  You get more than a dozen accurate thickness/width measurements per bridge (shown on a diagram, so you can see where each measurement was taken), plus the weight and, of course, the maker's mark.  You can learn a lot from that site.

Those measurements above will give you lots of valuable info.  However, you'll need to supplement the measurements with information about where and how to thickness things, the proper curved surfaces on the front (and back) of the bridge, and how to fit accurately, etc.  To get you started with all of that, here are a few Maestronet threads that can help you:

 

 

 

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Thanks for taking the time to help me Joe.  I appreciate the info.  My bridge certainly doesn't look as refined as those on the violinbridges website.  I have my work cut out for me. 

Sometimes I wonder how in the world they came up with the design of the bridge in the first place; both artwork, and functionality too. 

Regards,

Steve

 

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