Any experience with the Guild George Barnes Acousti-lectric

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Freeman Keller
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Any experience with the Guild George Barnes Acousti-lectric

Post by Freeman Keller »

Don't know if this belongs in the archtop or electric forum - lets try here.

I have been asked to build an archtop with a sound hole rather than f-holes. Mounted in the middle of the sound hole on a "pedestal" from the back or attached to the neck block is a single humbucker. There is a gap around the pickup - the idea is that allows air movement for the acoustic side of the guitar and the pickup is independent of the top. The George Barnes guitar has two P90 or humbuckers somehow mounted to the neck block but has a gap all the way around and no f-holes.

I would make the sound hole oval and big enough to at least approximate the area of f-holes and my customer feels that one 'bucker in more or less the neck position would be what he likes. The Barnes guitar also has the pots mounted on the pick guard, an idea I would follow.
Brian Evans
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Re: Any experience with the Guild George Barnes Acousti-lectric

Post by Brian Evans »

The pickups were mounted to a bar that joined the neck and tail blocks. I think such a longitudinal brace is a great idea for an archtop, it frees the top from having to carry any of the string tension load since the bar takes up all of that, and I installed a longitudinal brace in my current archtop project. Some Epiphones had such a brace as well. F holes vary widely in area, I suspect the length of the F hole is as important as it's area and recall Allan Carruth writing on this subject. I have this idea that F holes fully release the middle section of the top to vibrate, both freeing it and restricting the area of the vibrating top at the same time. Obviously with holes in the middle of the top around a pickup no top will be vibrating there. My current project has holes in the upper bouts and no F holes, the idea being to get as much of the top vibrating as possible. Once I get to grips with the sound I will be planning my next experiment. I hope you build it, I would love to see what you do with the idea, which I think is a great one.
Freeman Keller
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Re: Any experience with the Guild George Barnes Acousti-lectric

Post by Freeman Keller »

Yes, thats the general idea. My customer only wants one humbucker and thought that if we made a big enough oval sound hole the pup could be mounted in the middle but not touch the top. You can see the one in your picture has a gap around each pickup - don't know whats going on inside for bracing.
Joshua Levin-Epstein
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Re: Any experience with the Guild George Barnes Acousti-lectric

Post by Joshua Levin-Epstein »

Hans Moust is the Guild Maven. He might know what is going on inside the George Barnes. You should pick up Hans' "The Guild Guitar Book". Lotsa nice pictures of Guilds you've never seen. There is a guitar built for George Benson with a D shaped sound hole. Its original pick up was "bar mounted".
Brian Evans
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Re: Any experience with the Guild George Barnes Acousti-lectric

Post by Brian Evans »

The George Barnes guitar has an internal longitudinal brace to mount the pickups. That could be termed "bar mounted"

https://www.guitar-list.com/guild/elect ... ti-lectric
Freeman Keller
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Re: Any experience with the Guild George Barnes Acousti-lectric

Post by Freeman Keller »

I've told the potential customer that I'm not interested in building this. To carve an archtop plate, try to figure out how to brace it, cut an oval hole in it and expect it to sound "decent" and still charge him what my time might be worth doesn't make any sense at all.
Brian Evans
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Re: Any experience with the Guild George Barnes Acousti-lectric

Post by Brian Evans »

There's a reason that luthier made archtops start around $5K and rapidly go north of that... I figure I take close to 400 hours to build a fully hand carved archtop. I appreciate you bringing that Acousti-Lectric to my attention. It would be simpler to build than my normal design and I think it's an elegant solution to mounting pickups. The square holes would be a lot easier to cut than hand-cut F-holes, my recent thinking on sound holes emphasizes the perimeter dimension of the holes vs the area (so putting the pickups in the middle of the holes doesn't make much difference) and I already do the longitudinal brace that the pickups would mount to.
Patrick Hanna
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Re: Any experience with the Guild George Barnes Acousti-lectric

Post by Patrick Hanna »

Brian, maybe I've missed something, but you have me VERY confused. If I understood you correctly, you said that a longitudinal brace which carried the pickups would free the top from any string tension. Huh? Did I misunderstand you? Such a brace could carry the weight of the pickups, but as long as the strings run over the bridge and the bridge stands on the top, then the top is carrying string tension, regardless of where the pickups happen to be mounted.
Brian Evans
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Re: Any experience with the Guild George Barnes Acousti-lectric

Post by Brian Evans »

If there is a solid brace bar running from the neck block straight to the tail block, it will carry a significant portion of the string tension load. Some load will be shared to and carried by the top, which runs in parallel with the straight brace. The brace bar is not connected to the top in any way, it's only joined to the neck and tail block and runs under the top. String downforce load, created by the string break angle over the bridge, is a different thing. The top will indeed carry that load, which is usually around 35 lbs.
Patrick Hanna
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Re: Any experience with the Guild George Barnes Acousti-lectric

Post by Patrick Hanna »

Brian, it seems to me your hopes for the brace bar are pretty optimistic. I can see where the bar would take up a lot of potential load that is trying to pull the tail block to the neck block. But, down pressure from strings over the bridge? No way. Not unless it's a lattice sort of brace supporting the underside of the top.
David King
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Re: Any experience with the Guild George Barnes Acousti-lectric

Post by David King »

It'd be an easy thing to measure the down force under the bridge with a little piezo force sensor or one of these: http://www.kr4.us/force-sensitive-resistor-square.html. I'd guess that the down force would be closer to 75 lb. Imagine how hard you would have to pull up to lift all the strings off the top of the bridge at once.
Brian Evans
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Re: Any experience with the Guild George Barnes Acousti-lectric

Post by Brian Evans »

Don't guess, calculate or measure. The downforce of a set of .011 - .052 strings with a 14 degree break angle is right around 35 lbs. Completely normal, understood, anticipated and expected in an archtop. While the string tension creates that downforce, the 175 lbs of string tension pulling down the neck and against the tail block can be dealt with separately. If you put a longitudinal brace between the neck and tail block, it will take up a portion of that tension load proportional to the stiffness in compression of the brace compared to the arched top. That part is just engineering, or maybe physics. Two springs in parallel split the load in direct ratio to their spring rates. My feeling is that a 1/2" by 1" maple brace is a lot stiffer in compression than an arched spruce top carved to a thickness of .200" or 3/16". Probably an order of magnitude stiffer. So a longitudinal brace is going to take up the majority of the load of tension from the string load. Now, I'm not worried in the least about the preload on the top from downforce of around 35 lbs. You need that downforce for a lot of different reasons, and no one suggests that you don't. But the tension load of 175 lbs trying to collapse the box for 20 or 30 years - reducing and controlling that load is more than welcome, I think.
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