Small changes make a big difference at the bridge

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John Clifford
Posts: 180
Joined: Mon Dec 18, 2017 3:08 pm

Small changes make a big difference at the bridge

Post by John Clifford »

Never underestimate the importance of details at the bridge in bringing out the sound of an archtop!

I had originally made a two-piece adjustable ebony bridge for this guitar. I thought I’d done a good job with it. The strings all sounded cleanly, and the intonation was excellent. But I felt there was something lacking in the tone of the instrument. It lacked clarity and definition, and felt somewhat unresponsive. I attributed this to the sitka spruce top, and my carving and bracing work.

Then I decided to try making a one-piece bridge for it, again using ebony. When I first got it strung up with the new bridge, the action was a little high and the sound was . . . not that much different. This seemed to confirm my feelings about the top plate.

But THEN, I recut the top of the one-piece bridge to bring the action down, and I paid a LOT of attention to cutting the string slots, making sure they were angled back toward the tailpiece, and widened slightly in that direction, to ensure a clean break over the front edge of the bridge. When I brought the strings back up to tension, it sounded like a completely different instrument! Really open and “sparkly” on top with a solid, clean midrange. And significantly louder. My wife even remarked on the increased volume.

So the lesson is, the small things really matter at the bridge. It makes sense when you think about it. 100% of the sound energy of the instrument is transmitted from the tiny point at which the strings contact the bridge. The vibrations at that point are very low amplitude and very high impedance, so very small physical changes have a big impact. Also, for reasons I don't completely understand, high action seems to have a detrimental effect on tone - too bad for me, because I tend to like fairly high action.
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Brian Evans
Posts: 873
Joined: Sat Aug 30, 2014 8:26 am
Location: Tatamagouche, Nova Scotia

Re: Small changes make a big difference at the bridge

Post by Brian Evans »

I agree. I've found that the lighter I can make the bridge, the better. The slots can be infinitesimal - only half string diameter, but definitely angled back towards the tailpiece. I try to split the angle towards the tailpiece so the string is supported by the full width of the saddle top. I am planning to experiment this winter with a spruce or redwood bridge, very light, perhaps hollow, with an ebony or bone saddle strip on top. Never experienced that with high action, but high action would contribute to a high break angle over the bridge, and I have found that reducing the break angle can be helpful. I seem to end up with 12 degrees or so. I also find that my acoustic archtops benefit from low tension, high mass strings and tuning down a step to D-D. In fact, I've about decided that E-E tuning is a hold-over from nylon/gut stringed classical guitars that should be done away with! :) Lovely guitar, BTW - beautiful!

Alan Carruth
Posts: 947
Joined: Sun Jan 15, 2012 1:11 pm

Re: Small changes make a big difference at the bridge

Post by Alan Carruth »

If the action change is enough to significantly alter the break angle/down bearing on the bridge I think that can alter the sound.

I once set up a guitar with a 'hook' type tailpiece that allowed for varying the contact point at the lower end. The tailpiece was 'L' shaped, with the leg of the L hooked down over the lower end of the top, and retained only with a light tailgut, since string tension served to hold it on. It was fairly easy to slack off the strings and slip in a pivot between the leg of the L and the side. The line the strings made behind the bridge pointed toward the pivot on the side, so they could effectively go 'through' the top, and there was no limit on the break angle.

At that time I didn't know as much about strings as I do now, and I bought into the notion that a higher break angle and more down bearing would produce more sound. Wrong. I started with the pivot up at the edge of the top and moved it down in steps. The sound really didn't change until, at a certain point, it just died. The change was sudden and repeatable: too much down pressure killed the sound.

Of course, at that time I didn't have the facilities to really measure things and find out what was going on. Since then I've come around to the notion that minimal break angle is probably better. I have to admit that while my model is probably better these days I don't have much more data backing up the current prejudice than the old one. It does seem to work, though....

John Clifford
Posts: 180
Joined: Mon Dec 18, 2017 3:08 pm

Re: Small changes make a big difference at the bridge

Post by John Clifford »

Brian, what string gauge do you use for your D-D tuning?

Brian Evans
Posts: 873
Joined: Sat Aug 30, 2014 8:26 am
Location: Tatamagouche, Nova Scotia

Re: Small changes make a big difference at the bridge

Post by Brian Evans »

Usually regular light gauge acoustic, which seem to be .012-.052, but sometimes a "bluegrass" set which is .012 - .056. Depends on the guitar. I have never found a guitar yet that benefited from higher gauge strings, regardless of what the "archtop" guru's seem to say, but I do find that light gauge strings have some intonation and floppiness issues if they are tuned down too low.

Eldon Howe
Posts: 67
Joined: Thu Oct 29, 2015 11:23 am

Re: Small changes make a big difference at the bridge

Post by Eldon Howe »

Are the tailpiece holes drilled all the way through the tailpiece?
I like that look with the D’Addario colors exposed.

John Clifford
Posts: 180
Joined: Mon Dec 18, 2017 3:08 pm

Re: Small changes make a big difference at the bridge

Post by John Clifford »

Sorry Eldon, I've been away for awhile. No, the holes don't go all the way through. They are just deep enough to hold the ball ends, and lined with brass tubing.

Olivier Vandebroucke
Posts: 5
Joined: Mon Jan 28, 2019 9:58 am

Re: Small changes make a big difference at the bridge

Post by Olivier Vandebroucke »

It's true that the bridge does make a difference: the slightest half-of-a-millimeter change will radically change the behavior of the entire string, how it can vibrate, how long... I remember having the bridge changed on my first guitar, and the cheap trainer instrument I had started to sound like a good mid-range guitar! It was no world level concert material, but it still wasn't something I was afraid to play on in front of other guitar players.

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