Bridge again

wolftone

Josh, great article. This bridge I got is virtually symmetical insofar as the top is angled from one end to the other, so I pesume there is no particular "bass side". How much can one remove from the top before the top becomes too flat - or does that matter?

Josh Hegg

As you take the top down it will get too wide. You will then need to take a file and sand paper to bring it back to a nice width. Not more then about 1.5 or 2 mm. On a Dupont I think the side that has the number stamped on the foot is the bass side. I could be wrong about that. One way to tell it set the bridge on a table an put a ruler behind it. Get eye level with the bridge and sight the high and low sides. The higher side is the bass or low E string side.

Chers,
Josh

wolftone

WEll, the birdge is finsished and I think it went quite smoothly for a first effort. I ended up a exactly 4mm clearance. The bridge is positioned slightly offset between the whiskers to accomodate the B string. The A string intonation is a bit off (sharp) although the D and low E are OK, so thats a bit of a suprise. I tried to get the string slots just right using a tiny tapered rifling file, but the G string bust during tuning!

Josh Hegg

Intonation is hard. At 4mm it is going to be even a bit harder. Down low it will be fin but at you move up towards the bridge the tension will cause the tone to go sharp. It takes some real tweaking to get the intonation correct on a high action set up but it can be done if the time is taken.

Cheers,
Josh

Chiefbigeasy

Hey Josh, if you're still around looking at these posts, I'd like to resurrect this one for a moment to ask a related question:

Is it better to have a flatter radius for the bridge and consequently the string placement over the fretboard, irrespective of what is a more pronounced radius on the fretboard? Or, is it better to match the radius of the fretboard with the position of the strings over it?

Am fine tuning my setup on the beautiful Dupont MDC50 I picked up recently. The previous owner had the action adjusted by a luthier who cut string slots a little deeper into the Dupont bridge rather than sanding the feet. I know enough to realize that the bridge can't exactly match the fretboard radius because the fatter strings need more room to vibrate. But, I'm also wondering if the bridge radius should be decidedly flatter.

Haven't seen too much discussion of this particular topic on the forum, so I thought I'd bring it up again to see if you or others wished to comment.

Bones

El Jefe, the little notches in the bridge are what is important. You need to have the proper 'action'. The top of the bridge does nothing so the radius doesn't matter other than the 'notches' need to not be very deep at all, really more like indentations. Just enough so that the strings don't pop out but if you have enough angle over the bridge there should be enough force down on the bridge to keep the strings in shallow indentations no problem. It sounds like the wrong height bridge was used and I think Dupont sells them in different heights so it might be better to just start with a new one the proper height and then set ur action from there.

Jeff Moore

Cheifbigeasy: Not sure if I should answer but I've made a lot of bridges (but I'm nothing close to a luthier) so have some idea of an answer.
The top of the bridge and of course the notches themselves (the arc) will be less, to a lot less, of an arc than your fretboard. (It seems all my GJ fretboards are a 20" arc). This bridge top (notch) arc will define your string height of course but is a choice for how much room (and fret buzz) is the right compromise for you personally.
My bridges wind up being almost a arcless, not that that is the "right" way, but is rather, my choice. Obviously, the low strings get farther and farther from the fretboard because they swing farther as thickness (and weight) increases. How much? - Your choice.
The further you go toward a buzzless sound, the closer your getting to 0 arc (a straight line), and as Josh said, a more difficult arrangement of the settings for intonation.
If you buy a bridge, your intonation is virtually fixed. You can only move the whole bridge out of position relative to the mustaches. That's why I make my own. I've made a lot of mistakes, but mostly on a much easier design of bridge that I could bang out fast, but is not a very good bridge overall. Now I can make a good bridge first time (usually) with all my favorite compromises pre-chosen. I quit making the simple bridges long ago, but from them I learned to control the three dimensions required to get it all where I want it.
I also learned that picking a straight line or a mildly arced bridge is easier than an arc close to the arc of the fretboard, and that a bridge top (and notches) that is a compound curve (that completely minimized string heights) is horrible when cross picking. The finished bridge should put the tops of the strings in a smooth arc regardless of what arc you choose. This factor alone is then 6 compromises in string height - one per string.
So the answer to your question is likely - "decidedly flatter".
I don't even own a luthier or factory made bridge so maybe someone with arc gauges can tell us what Dupont or Gitane are using for top arc on their bridges.
Hope that helps.

Chiefbigeasy

Thanks for the feedback so far, guys.

Because I hadn't gotten much feedback the first time I wrote about this, I wrote directly to Obi Wan himself--Bob--for his thoughts. He wrote the following:


This is very much a personal thing. Typically, people match the radius of the top of the bridge to the fretboard, particularly with GJ instruments. Selmers had very slightly crowned bridges and flat fingerboards, so they had overly crowned bridges. It's rare to have a crowned fretboard and flat topped bridge - typically they either match in radius or the bridge is a little more crowned.


So, while I appreciate the opposite point of view, I'm glad to hear the other side as well.

Additionally, I posted earlier about this unconventional action-lowering method--deeper slots--and was advised that if there was no pinching, it would be fine. So far, it has been; the tone and timber are top notch.

Finally, this is a nice Dupont bridge that looks and sounds great, and I've carefully sanded it to contact the guitar surface completely, except for the flared-off edges. (Thanks, Josh, for the clear instructions on how to do this.) Also, intonation has not been an issue.

I'm not far from where I want to be, but I'm willing to experiment a little, even if I have to get another bridge as a backup.

Jeff Moore

Wow. After reading Bob's comment I tried to think where I'd put bridges I'd saved off of my guitars. I found two Lebretons and a Manouche. My gauges don't go that high, but the Manouche is visually flat - no arc and the Lebretons are flatter by some amount than my flattest gauge - 20" radius: There's an arc on both Lebretons, about equidistant between flat and 20" radius.
These bridges are untouched, a rarity in my house. Took me a while to learn not to whack my resale value by altering guitars.
I might find a couple more if I look, but as Bob says, these things are personal, but a radius like a fretboard seems like it would unnecessarily raise the middle strings a fair amount once you had the two E strings right.

I bet this is one of those cases where the builder knows exactly how to build but just made a mistake in relating something they do without rethinking it every time. I wanted a wider neck on a custom Lebreton and I'd worked the measurements out for it. Jean and I couldn't agree on figures, but I had no doubt he knew exactly how to build a wider neck, so I dismissed my measurements and just told him to build like he always does but with a 47mm 0 fret. It was perfect of course.

Buco

What would the advantage be for the bridge to have a slight radius?
It makes sense for the bowed instruments but for the guitar I would think, as Jeff said, flatter makes more sense.
Although the last bridge blank I fitted on my guitar, I gave it a slight arc, only because I like the esthetics of it better.
I've seen both on the this style of guitars but I think it's more important that the bridge is well intonated, the bridge is seated well and the guitar is happy with the action.
I've also seen deeper slots cut in on the guitars coming from the reputable luthiers or techs, I think what's important is that the strings sound free, clean and clear.

I love your user picture @Chiefbigeasy!!! Such good looking pair. You sure are lucky to own them. I'd especially like to strum a Dupont some day.

Chiefbigeasy

Now we're talking. Now that this observation is out there, I'm wondering if anyone has noticed how crowned vs flat bridges affect your playing. The answer may be "not much at all," but I'm asking the brain trust that is our forum members whether you've even noticed the difference.

On the one hand, there appears to be some obvious logic to keeping the bridge radius relatively flat for the predictable flat plane it affords one to pick across. Since I seldom see players looking at their picking hand, it is part of our technique we do by sense and muscle memory. Personally, there is one tune, however, where I find glancing at my picking hand helps--it's the intro theme of "Minor Blues" with its expansive sweeping intro triplet melody from the high E to the low E string and back to the high E.

I'm approaching this bridge tweek carefully. It first occurred to me as I was adjusting the action and trying various strings on my newly acquired Dupont. I noticed that action was generally measured by the relative height of the two E strings at the 12th fret. This method, however, ignores the action of the four middle strings that are closer to the frets because of the radius of the neck and frets themselves. I reasoned that if I used an under-string radius gauge as a guide, I could lower at least strings 6, 5, and then 2, and 1 leaving the middle two as set. This is much easier to do on my Strat, of course, with its individual string bridge pieces and adjusting screws. It's another matter entirely with a one-piece wooden bridge.

I'm hoping that one of the end results of this tweek will be better playability in the upper fret ranges. The trick, is to not mess up and cause string buzz in the lower fret area closer to the nut.

I haven't seen much by way of illustrations about this when it comes to acoustic guitars, especially GJ guitars. I did find a pic depicting the way Taylor sets up some of its guitars.

Don't want to get too far in the weeds on this, though these kinds of obsessions are common to some of us (guitar pick choices, anyone?). As I'm figuring this out, I'm still regularly woodshedding my technique drills to continue to improve; that's where most of my time and energy goes. It's just that every now and then, you pick up a guitar and it plays like butter. I've got to believe that, idiosyncratic as they may be to each player, some setup choices make things better.

I'll see if I can attach that Taylor illustration plus the original picture I'm using as my avatar. Anyone who's interested can see good pictures of my instruments in the guitar archive section of this forum. Yeah, they costs a few bucks, but they're safer than sports cars and more tolerant of my shortcomings than pretty younger women.

And, Buco, anytime you come back for a visit, that Dupont will be waiting for you to play when we jam.