Buc McMaster Posted January 11 Share Posted January 11 I like trying to figure things out.......to understand things, why they are as they are, and how they work. For example, while I'm not trained to do so, I spend a lot of time studying particle physics and quantum theory. Much of it still escapes me but I do have a layman's understanding of what underlies the reality we (most of us anyway!) experience......which some insist is all in our minds! Several years ago I started a thread here concerning the possible sonic influence of a belly up vs. a belly down acoustic bridge.........Gibson vs. Martin, generally speaking. (Those who have heard it all before are excused from class!) We all recognize the obvious tonal differences between these two iconic instruments......not easy to verbally describe but we hear it. Across a variety of models, both are built with the same woods and in much the same way..........spruce tops with scalloped or non-scalloped bracing.... mahogany/rosewood/maple back & sides.......rosewood and ebony fretboards.........they are so very similar in materials and general construction.......agreed? What really jumps out as an obvious physical difference is the belly up/belly down orientation of the bridge. It seems to me that the difference in the way these two bridges load the top could account for at least some of the sonic attributes of these brands....... This rather poor drawing is a effort to illustrate this difference.......proportions may not be exact but you get the idea. With the pin holes as the fulcrum, it appears that the belly up Gibson style applies more of the torque forward due to longer length ahead of the fulcrum point: more surface area of the top is being forced downward forward of the fulcrum than behind it, while the reverse is true of the belly down bridge. Could this account for the tonal differences between a Gibson and a Martin........the manner in which torque is applied to the top? There have been Gibson models built with a belly down orientation, some during the 1940s and again in the early 1970s. Perhaps a sonic comparison of a belly down Hummingbird and a belly up build of the same model could shed some light here (though guitars being individuals casts some suspicion on this thinking). And what of the rectangular bridge on the earliest generations of Gibson and Martin guitars.............how much if any did the change to belly-style bridges change the instruments tonally? Hard to say. Just food for thought and discussion.............I'm the curious sort. 1 Quote Link to comment Share on other sites More sharing options...
DanvillRob Posted January 11 Share Posted January 11 Interesting.....I think your theory has merit. I kind of put a lot of stock in the scale length as a huge difference. There are songs I perform on the Hummingbird BECAUSE of the short scale, (more "bend" in the strings). My "practice" guitar, (the old "beater Jubilee) has a short scale, but I use it because of the Bursitis in my right shoulder, (because the body is smaller than a dread). I hear people compare Doves to Hummingbirds, and they focus on the Hog vs Maple, and never mention the scale length. Quote Link to comment Share on other sites More sharing options...
zombywoof Posted January 11 Share Posted January 11 I am sorry but this is all too much for me to wrap my head around. I figure Gibson went with the belly bridge in the early-1940s simply to go with a larger gluing surface. To my mind what would seem to come into play when it comes to bridge design is the distance between the pins and the saddle. But while I get the difference in sound between a floating bridge/tailpiece and fixed pin bridge because they funnel the energy into the top differently, I do not see how the difference between a belly up and belly down pin bridge would be that much. Quote Link to comment Share on other sites More sharing options...
egoidealmusic Posted January 12 Share Posted January 12 Interesting, and I've wondered equally if the belly up bridge means greater strength at the base of the bridge makes for a stronger bond again bridge lifting (i.e. wider straight base), but this also makes sense in terms of tone delivery. Love me some science! Quote Link to comment Share on other sites More sharing options...
E-minor7 Posted January 12 Share Posted January 12 Oh yea, the 'dated' thread was remembered the same moment I threw my eyes on the first lines of this one. And it's always better to get some re-theories presented than to see them (actually not see them) disappear down the crack of time. . However I believe we are out in an exaggeration. There might be an effect, , , also due to the down belly reaching further over the vibrating mother-zone of the top, but to mark the up/down as a factor in the Gib/Mart identity-variation is, , , may I say a bridge too far. . 13 hours ago, DanvillRob said: I hear people compare Doves to Hummingbirds, and they focus on the Hog vs Maple, and never mention the scale length. Rarely happens - and it's a mistake. These 2 fliers are just so apart and intriguingly related at the same time. Vintage Kalamazoo made a master-move by filling that gap between the then new Bird and the grand old 200. How I wish it was possible to watch a movie of the very moment somebody got the 💡 for and suggested the name. 1 Quote Link to comment Share on other sites More sharing options...
Murph Posted January 12 Share Posted January 12 Everything effects tone. Even the humidity. The REAL question here is... Who drew the drawing? 1 Quote Link to comment Share on other sites More sharing options...
Murph Posted January 12 Share Posted January 12 21 hours ago, DanvillRob said: There are songs I perform on the Hummingbird BECAUSE of the short scale, I chose the J-45 and J-15 because of scale, as well. I was "used" to that scale and do a lot of slides, up and down, it's just the way I play. I'd still like to get a Hummingbird someday. 1 Quote Link to comment Share on other sites More sharing options...
DanvillRob Posted January 12 Share Posted January 12 59 minutes ago, Murph said: The REAL question here is... Who drew the drawing? Maybe they farmed it out to India! I started working for GILLIG in 1981. We had 4-5 Engineers....one VP, one electrical and one mechanical....plus one draftsman and one guy who specialized in hardware. When I left in 2020 there was 140, plus another 20 we hired in India. I recently had lunch with my old boss, (who is also retired, but sits on the board of directors) and he said there are now 200 engineers plus about 50 in India! Quote Link to comment Share on other sites More sharing options...
Murph Posted January 12 Share Posted January 12 They must have a lot of trains. 1 Quote Link to comment Share on other sites More sharing options...
DanvillRob Posted January 12 Share Posted January 12 Just now, Murph said: I chose the J-45 and J-15 because of scale, as well. I was "used" to that scale and do a lot of slides, up and down, it's just the way I play. I'd still like to get a Hummingbird someday. I"d love to get a Standard 'Bird....but I just can't justify it, (and I have no place to keep it anyway!). I'll just have to muddle through with what I've got! Quote Link to comment Share on other sites More sharing options...
Buc McMaster Posted January 12 Author Share Posted January 12 1 hour ago, Murph said: Who drew the drawing? I did. 1 Quote Link to comment Share on other sites More sharing options...
Murph Posted January 12 Share Posted January 12 44 minutes ago, Buc McMaster said: I did. Mighty fine work there, Buc. Quote Link to comment Share on other sites More sharing options...
Dave F Posted January 12 Share Posted January 12 You have a line at the fwd side of the pins that I assume is the energy from pull of the string tension? Should that be at the energy of the vibration of the string contact point on the saddle? Quote Link to comment Share on other sites More sharing options...
Murph Posted January 12 Share Posted January 12 6 minutes ago, Dave F said: You have a line at the fwd side of the pins that I assume is the energy from pull of the string tension? Should that be at the energy of the vibration of the string contact point on the saddle? And, if the string is seated against the bridge plate, is there actually any upward pull on the bridge anyhow? Quote Link to comment Share on other sites More sharing options...
Buc McMaster Posted January 12 Author Share Posted January 12 There is a rotational force applied to the bridge by string tension. The fulcrum of this rotation is at the pins: behind the pins the force wants to lift the bridge away from the top, forward of the pins the bridge is forced downward onto the top.............hence the "bellying" apparent on some instruments: bulged up behind the bridge and concaved in front. String tension wants to roll the bridge off the top (this happens with either bridge, belly up or down). In the belly up orientation, there is more force applied forward of the fulcrum point (the pins) than behind it. The belly down orientation reverses this: there is more rotational force applied behind the fulcrum (pulling up on the top) than forward of it. Perhaps it makes no difference at all, but has has been said many times, everything matters to some extent. I just wonder how much this obvious physical difference in construction accounts for the obvious sonic differences we hear between Gibson and Martin builds. Just curiously thinking out loud.................. 1 Quote Link to comment Share on other sites More sharing options...
Sgt. Pepper Posted January 12 Share Posted January 12 3 hours ago, Murph said: Everything effects tone. Even the humidity. I agree with you. What affects tone the most is my horrible playing. 1 Quote Link to comment Share on other sites More sharing options...
Red 333 Posted January 12 Share Posted January 12 My twotwo favorite guitars, my Legend 1942 J-45 and My Fuller's Vintage 1939 J-35 Reissue, have no belly. They have the straight bridge. There's a head scratcher, no? Red 333 1 Quote Link to comment Share on other sites More sharing options...
Lars68 Posted January 12 Share Posted January 12 My guess is that what affects tone the most between these two variants is the amount of vibration created in the lower bout. The more flexible this area is, the better would be my guess. Wouldn't a belly-up bridge create more free area in the lower bout for vibrations, given the pin holes are in the same spot for both variants? Also, a Gibson with a straight bridge and one with a belly-up bridge sound very much the same. So any difference in bridge construction is probably small enough to drown among any other natural variants among guitars made out of wood. Lars Quote Link to comment Share on other sites More sharing options...
Dave F Posted January 12 Share Posted January 12 What about an acoustic with a tailpiece instead of bridge pins? Or as in some of the Everly models, there are no pins? Or as in the case of the J160, the sound hole is in the same location, but the bridge has been shifted forward by 1"? I have questions 🙂 Quote Link to comment Share on other sites More sharing options...
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