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Setting arch top intonation
http://mowrystrings.luthiersforum.com/forum/viewtopic.php?f=10101&t=56625		 Page 1 of 1
Author:  SnowManSnow [ Fri Jun 07, 2024 6:40 pm ]
Post subject:  Setting arch top intonation
Hi folks.. I’ve jumped off into learning some jazz and of course bought an arch top ha.
I went to install strings on a new Eastman Ar503ce only to discover that the bridge isn’t glued down… duh

So now I’m worried about getting the intonation as close to exact as I can.

I know it seems strait forward, but I always find ppl here who have a “better approach “ do doing things ha.

So, in archtop noob lingo… how do you go about getting that floating bridge in as close to exactly the right spot as you can?


Also… and I tried asking in a FB group only to get some pretty goofy answers… where is a good place to start w the 12th fret height?

I appreciate any help.
B


Sent from my iPhone using Tapatalk
Author:  Ken Nagy [ Fri Jun 07, 2024 7:14 pm ]
Post subject:  Re: Setting arch top intonation
12th fret height is where you like it! I like mine lower, so it is 6 and 3 64 right now. I don't have an adjustable bridge for height so I'm happy there.

You just put the bridge where is should be, and get the intonation right on the E strings; with the bridge HIGH. Then get all the other ones right, and then work on getting the heights even.

Pretty soon it is done.

It didn't seem that hard. A guy tested it in West Virginia with harmonics and things, and couldn't figure out how I did it.

I just told you.

The bridge should stay put. the curve and down pressure should hold it fine.

I had an adjustable and 2 nonadjustables on it, and the were not that bad. The adjustable is easier, it is already shaped. Making 2 from scratch is more trouble.
Author:  Darrel Friesen [ Fri Jun 07, 2024 8:39 pm ]
Post subject:  Re: Setting arch top intonation
Measure to the scale length and add 1/8" to the center of the bridge edge will get you very close.
Author:  jfrench [ Fri Jun 07, 2024 10:17 pm ]
Post subject:  Re: Setting arch top intonation
If you're already somewhat close, using a tuner, tune the guitar, on both E strings, one at a time, play a harmonic at the 12th fret, then press down on the 12th fret and see if there is a difference. If the fretted note is sharper than the harmonic move the bridge to the right (increasing the string length). If the fretted note is flatter than the harmonic move it to the left (decreasing the string length).

Once that is right, next time change your strings one at a time, or temporarily tape down the bridge.
Author:  Ken Nagy [ Sat Jun 08, 2024 5:26 am ]
Post subject:  Re: Setting arch top intonation
Ahh. I missed the part where it is a new, bought instrument. That makes it a lot easier; it should already be set.

The tailpiece will be in the right place. If you make it, you have to make sure the strings are set straight on the neck.

Then you have to measure like Darryl said, and mark the bridge area with tape, and fit it. You shouldn't have to fit it.

Then adjust the height of the strings a where you want them, and check intonation. I don't think a brand new bridge has slots, so you would have to put those in. File them straight; you don't know where the intonation will be. You should check to be sure the strings taper back to the tailpiece, just like the strings need to taper back to the pegs at the nut.

A new bridge will have a large adjustment. You have to have the bridge a little north, so it is slightly sharp, so you can file/chisel them in.

You have it even easier. But check each step. Manufacturing is pretty good, but nothing is perfect.

Have fun with it.
Author:  Hesh [ Sat Jun 08, 2024 5:34 am ]
Post subject:  Re: Setting arch top intonation
So the "F" holes on arch tops have a purpose. The points in the middle of the F holes are most of the time, the vast majority of the time located exactly where in a perfect world the bridge should be. But manufacturers/makers can't know what strings you will use making it a starting point only.

The bridges are left floating on arch tops and mandolins so we can change to different strings and still dial-in intonation. If you are sure you are set on one type of stings the bridge can be "pinned" in place with either very thin tape (appropriate for some instruments) or actual pins. Tape is not a favorite of mine but commonly used on less expensive instruments. The bottom half of the bridge needs to follow the contours of the top perfectly too for maximum vibrational transfer but they rarely do so some folks bring them to us to be fitted to the top in the proper location.

So use the F hole points to position the bridge to start placing the bridge centered with the F-hole points. Tape it in place if you need to until the first string pressure can hold it in place.

1) Tune to pitch.
2) Adjust truss rod.
3) Retune to pitch.
4) Cut nut slots
5) Retune to pitch
6) Set action at the 12th and check truss rod again incase it moved
7) Retune to pitch

8) In the playing position check the intonation for the two E's. Place guitar on bench and clamp neck in an appropriate vice and move the bridge forward or aft (under string tension, it's hard but I do it every day) AND left and right to ensure string spacing to the sides of the neck as per your measurements when you checked intonation.

9) Retune to pitch in the playing position and check the E's again and repeat step 8 until you are 1 - 2 cents off/close/etc. Be mindful of your pressure fretting that can change your results. I try to simulate what the average player would do unless I know who I am working for and have more information about how they play.

Also avoid using a pick when checking intonation picks bring out more overtones and many confuse the tuner. Use your thumb.

Now.... this is how I do it and of course the A,D,G,B are functions of where the two E's are and we don't adjust them they are what they are.

When you are done look at where the bridge is in relation to the F-hole points. Bet ya the centering the bridge on the points was a very good starting point for you.

Now this is a perfect example of why when we set-up an instrument there is a proper sequence to what we do. If you set the intonation and ignored the truss rod when you finally address the truss rod it very likely may throw the intonation off and you will have to do it again. Nut slots same old song and dance/story do them in sequence and be able to move on.

All these things, intonation, nut slots, action, relief (truss rod) are functions of each other and must be addressed in sequence or the person attempting these things is chasing their tail correcting one thing and making something else worse.
Author:  Hesh [ Sat Jun 08, 2024 6:16 am ]
Post subject:  Re: Setting arch top intonation
So if you're wondering why when you just want to throw strings on it and have intonation OK I gave you such an involved answer. By the way the same holds true that I wrote for mandolins too.

Once the instrument(s) have been set-up and when you are using the same brand and gauges of strings and it's just a string change you can either pin the bridge and be done with it or start at number 8 above. But be aware if the other things are not addressed at some point you are not determining the end intonation points they will move when you address the other adjustments.

For guitars, mandos, basses and arch top guitars intonation is the last thing we address once all the other things have been addressed. So naturally someone coming into this at the intonation stage only is going to suggest that all the other stuff should be addressed first.

And lastly, for real this time... ;) never, never, never pin a bridge without going through all the steps I suggested above or you will be pinning it in the wrong place. Intonation is a function, again of relief, nut slots and action as well as string gauges, tuning pitch and even the brand of strings used.
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