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This may seem like an ignorant question but it's one I've been trying to answer.
I know why Archtops were designed and I know how they are designed. I know the history of them and who designed them, so that is not my question.
What I really want to know is, how does the shape of the top and back make the difference in tone?
What is it about an arch that creates a more focused/louder tone than a flat top?
I've been playing the damn things long enough and yes, I have even got Benedetto's Book and DVD set. Still this question is for me, unanswered.
Is it because having an arch allows for a greater neck angle, thus more pressure on the top, so greater volume? but why does that make the tone so different etc.
I know that it is essentially a violin design. But I'm not sure as to what role the Fholes play and the arch, beyond allowing for greater string tension.
And, if an arch creates more strength and less bracing, why doesn't the arch become even more pronounced to remove the need for bracing all together and thus allow for more tone and volume?
Look forward to hearing some answers :-)Last edited by GoergeBenson; 03-28-2014 at 02:02 PM.
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03-28-2014 01:59 PM
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The bass sound is more prominent in a flat top. See the Rebecke halfling guitar.
Welcome to Ribbecke Guitars
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I am very curious about this too. Can an arcthop be carved as thin as a flattop ? What's the range of thickness of tops ?
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Look at the section titled design and construction...
All About Archtop Acoustics | GuitarPlayer
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I had a "flat archtop" jazz guitar built by a luthier, it definitely had more bass than my carved jazz archtop's distinctive mellow sound.
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To my dumb ears the quintessential flattop tone - exemplified by Martin - has a rich deep bass and bell-like treble but not much middle. The archtop tone is more balanced and mellow - not as boomy in the bass and avoids any twang or excessive ringing in the treble. I'm sure someone more knowledgeable than I about guitar construction can explain how the arched shape and bracing contribute to the archtop sound, but for me it's all about the middle.
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Originally Posted by iim7V7IM7
Thanks for the link, but I have already read that and it doesn't really answer the question.
What is it about an archtop that makes it sound the way it does. That article only really describes what an archtop is and how it sounds, which I am already familiar with.
But once again, thanks for the offering :-)
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Originally Posted by medblues
Well thats really my second question. My first one is, what exactly is it about an arched piece of wood, that makes it perform the way it does, besides sting tension pushing down into the top from a grater angle (apparently) than on a flat top.
:-)
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I build flat top acoustics and some electrics. I have built arch top mandolins, but not guitars. I do it for fun and sell my work to folks I know mostly, but over the years I've built about twenty guitars and in the process I have learned a thing or two. It is my opinion that a flat top guitar bridge moves more like a boat on water in that it rolls and pitches in a way that spreads the acoustic vibrations around the top of the instrument. You can make a flat top louder and more focused by slightly arching the top with shaped bracing in a concave bracing form. An arch top by virtue of its shape is much stiffer then a flat top so this becomes more pronounced. The bridge can't move like a flat top can. The tailpiece also puts a very different pressure on the bridge of an arch top, and tends to drive the top up and down more then a pinned bridge. This allows the guitar to be significantly louder than a guitar with a pinned bridge. Again just for discussion and certainly just my opinion.
Bill
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I've often wondered this myself. Even just given the availability of flat tops vs arch tops, I've wished I could just put a set of flats on a flat top and treat it like a jazz guitar. If it's down to flat tops having more bass and less mids those two elements could be compensated for at the amp. There must be more to it. Curious to see what the more knowledgable say.
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archtops are supposed to project the sound more in front of the player, while a flat top's sound envelops the player.
read that somewhere.
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Originally Posted by Socalbill
No offense to all the other contributions but this is precisely the type of answer I was searching for.
Thank you :-)
Would you say then, that by these design virtues, that people who would describe the Arch top as having a more focused tone, are right, because the vibrations are not dispersing around the top as they would on a fat top.
Notes are certainly rounder and firmer on the arch top design.Last edited by GoergeBenson; 03-28-2014 at 04:17 PM.
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I was just about to write this but you beat me to it. I might add that on the archtop, just like in the violin family, the forces are more or less balanced out. The downward force of the strings on the bridge is more or less counteracted by the compressing force of the string pressure on the end of the guitar (via the tailpiece) which will tend to drive up the arched top against the downward pressure from the bridge. On the flattop (and classical guitars) the string pull on the top is not counteracted in the same way, and the top tends to warp with time. That may well be the reason that well kept archtops (and violins) can last for many, many decades, while flattops and classical guitars tend to become useless after 20-30 years (though a neck reset can sometimes postpone that somewhat). Originally Posted by Socalbill
Thus, one can say that an archtop is a very different instrument from a flattop.
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Yes. This is why I know the trick about slightly arching a flat top. I have built a few guitars that were slightly arched, X braced and had a tailpiece and floating bridge. They were very loud and had more midrange but still had lots of bass as well. Kind of like a Django style instrument. Originally Posted by oldane
Bill
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Originally Posted by Socalbill
When you say an arch, makes the sound more focused, what is it about the arch that does that?
The added stiffness?
The lack of over all dispersion of vibration across the top?
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That is the way I think of it , yes. When I was learning to build, one of my teachers said that a braced flat top is like a speaker cabinet with the bracing making tight "tweeter" areas and large "woofer" areas. I don't know if the physics is exactly right with that, but it was helpful to me in learning to think about bracing. I believe that arch tops are simpler in this regard given the way they are driven and by how stiff they are. More like a guitar speaker that does a narrower range acoustically, but can really put out some power. I hope that helps, and again, just my opinion. Originally Posted by GoergeBenson
Bill
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An interesting discussion and a question that has been on my mind as I work through the planning stages of making myself a nylon string "Jazz guitar", Archtop vs Flat top....
Generally speaking, the best sound in any guitar is a result of the weight to strength to stiffness ratios of the soundboard. There are other factors taken into consideration as well but this is the main element a luthier looks at when choosing a piece of wood for the soundboard. Originally Posted by GoergeBenson
So, the lighter and stiffer one makes the top the better the sound in terms of volume, projection etc. An arch then means that the top can be made thinner with less robust bracing (lighter) while maintaining the same overall strength as a flat top.
This is a bit of a generalization as one can find exceptions to this. Some amazingly loud late 19th, early 20th century Viennese instruments are some of the loudest nylon/gut strung instruments I've ever heard and they have absolutely flat tops.
Also, it's not just the arch that makes an instrument " focused'. Bracing pattern, body size/depth, material choice, graduation of the top/back, what the builder is trying to achieve (an experienced builder can manipulate many things to achieve the desired sound/tone) so any one thing may not be the single pinpoint to the sole determining factor in a sound), etc...
An interesting point, I think, which might be a little off topic but may shead some light, that came up in a similar discussion with a colleague. It would seem that most guitar designs are limited by their bracing pattern. Beyond a certain size they tend to loose their ability to deliver a satisfactory optimum tone/sound. For example, the transverse pattern (ladder) found in 19th century instruments appears to have a most effective size at around 12" to a maximum body size of about 15" for the lower bout, the Spanish style fan braced "classical" is very similar maxing out at about 14 - 15". The X braced steel string flat top seems to be most effective as a bracing pattern up to about 16" -17" (Grand Auditorium/Gibson J200). After that there seems to be no more gain to be had by making the instrument bigger. In fact much seems lost over these maximums.
Archtop guitars, on the other hand, seem to be just the opposite with a bigger the better theme being the norm (speaking acoustically). In fact the upper limiting factor here seems to be human ergonomics rather than anything directly related to the actual instrument design. I've not played one but reputedly, the Stromberg Master 300 -400 with their 19" lower bout, were/are incredibly loud being designed to chug out the chords and be heard in the big bands in which they excelled. But from a brief discussion with an elderly gentilman who played in one of the local dance bands back in the day and owned a Stromberg, I can guess they were a real chore to play.
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Very interesting discussion, and some intriguing thoughts/ideas/concepts coming across.
Socalbill - I would be very interested to see a photo of one of your 'slightly arched flat-tops with floating bridge and tailpiece.' I've wondered myself if this type of configuration would give me the sort of guitar I'd enjoy playing and also with a tone between the two types of guitar. Takamine (not one of my favourite makes) built some guitars in this sort of style for Ry Cooder back in the 80s, but it never seemed to get beyond prototype stage, as far as I'm aware. (Yes, I know Ry is not generally thought of as a jazz guitarist.)
GuyBoden - as a fellow UK resident, can I ask who the builder of your arched flat-top was, I might be interested in pursuing this type of guitar.Last edited by bananafist; 03-29-2014 at 09:52 AM.
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Traditionally flattop guitars have a slight top arching, a radius of 40 feet on Martins. Many modern guitars have a more pronounced arching, 20 and 28 feet radii are common.
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Interesting discussion. I come originally from the piano, and there it is common knowledge that the 'crown' (=arch) of the soundboard serves to enable the bridge (and thus the strings) to put high pressure on the soundboard, so that the vibrations are properly transmitted to (and thus amplified by) the soundboard.
This seems to be quite in line with Bill's comments above.
The Piano Deconstructed
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One difference is the way the top is tuned. During preparation of the top we check the progress by holding the wooden plate in a certain spot and tapping in a certain spot to hear how it sounds and how it changes as it gets thinner. There are several spots to hold and tap that elicit different modes of vibration. Originally Posted by GoergeBenson
With a flat top we keep the thickness even all over. And it really is flat. We make it thinner by running the whole thing through a drum sander (or do it by hand). As it gets thinner the fundamental pitch gets lower and lower until eventually fundamental disappears. All you hear then is a wash of mostly indistinguishable frequencies, kind of like a low pitched gong. (The back is not as critical, but usually is about the same thickness as the top.)
On the archtop we establish the outside shape first then carve out the inside so that a graduated thickness pattern is created, thicker in the center, thinner on the edges. The overall thickness is greater than a flat top. To tune it we thin it by carving and scraping more out of the underside. Again, the fundamental pitch gets lower. But instead of trying to quench the fundamental we go for a pure tone and stop thinning when the pitch gets within a certain range. The back is tuned the same way, and it is usually tuned to a different pitch, sometimes slightly higher than the top. I'm sure there is a lot of variation in the results, but that's sort of the goal. I don't think I've ever heard of what pitch specific makers shoot for or whether there is a consensus of opinion on what the target should be. I have read that some violin makers aim at a pitch somewhere near F and tune the back about a step higher.
So before bracing, the arched top will have a clear fundamental resonant pitch while the pitch of the flat top is sort of non-specific. In both cases the bracing determines the final tone.
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I recently read that the f holes were put into the tops of bowed instruments in order to eliminate top vibrations and sustain--which makes sense in that with those, when you stop bowing you want the sound to stop. The location and shape of the "f's" essentially breaks the grain of the top, which runs in the same direction as the neck, without weakening the top.
So those guitars are supposed to have less sustain, more "punch" and separation of notes. Just my 2 cents and recent reading.
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The whole tap tuning thing is interesting, because Bob Benedetto doesn't seem to think its actually that important. He claims its something that luthiers do but is a little bit like a red herring. They do it cause they feel they have to, or should but not that it makes any difference. Originally Posted by kenbennett
"to the inexperienced ear, these subjective terms may mean nothing (ref tap tuning) and could even be misleading. I therefore encourage the beginner to go through the motions of tapping and listening as described"
"I believe there is no such thing as a bad tap tone and would never discard a piece of wood for that reason".
Bob Benedetto (Making An Archtop Guitar)
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SourceThough the purpose of sound holes is to help acoustic instruments project their sound more efficiently, the sound does not emanate solely (nor even mostly) from the location of the sound hole. The majority of sound emanates from the surface area of both sounding boards, with sound holes playing a part by allowing the sounding boards to vibrate more freely, and by allowing some of the vibrations which have been set in motion inside the instrument to travel outside the instrument.
The round sound hole of a flat top and f-shaped sound holes of an arch top perform the same function. It would not seem that the the shape of the hole is responsible for the difference in tone between two types of guitars.
I have played an archtop with no f-holes, and I didn't notice that it had any more sustain. Perhaps it did. I wasn't listening for that. The biggest difference was that it had a muted tone and was not nearly as loud. This was a completely finished guitar in the final assembly room at Benedetto's shop. It was destined to be an electric guitar, but they wanted to hear what it sounded like acoustically before routing for the pickups. Bob said they left the f-foles off to reduce feedback.
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Bob has - like we all do - changed his mind about a few things over the years. In his book (first published in the beginning of the 1990s) he speaks for a one piece bridge, like on the violins, without height adjustment posts. Years later he did an actual comparison and concluded that it didn't make any audible difference to the sound of the guitar. Originally Posted by GoergeBenson
As for tap tuning, Jim Triggs doesn't do it. When I ordered a guitar from him some years ago, he said that tap tuning could mislead the aging luthier, because a progressing hearing loss of treble frequencies is common as we get older (especially if a luthier is a player too). If the older luthier keeps aiming for the same tap tone - as heard by him - the guitar may in fact end up not sounding as intended.
I have noticed a parallel to that in saxophone players who seem to get an increasingly hard and bright tone with age. I hear it in recordings of say Coleman Hawkins and Don Byas who both started with warm butter tones and ended with bright, reedy and steely hard tones. They may have heard it as the same tone quality themselves, but because of the progressing treble hearing loss, their tone unconciously changed over the years. The same thing happened to a lesser degree to Dexter Gordon.Last edited by oldane; 03-31-2014 at 09:31 AM.
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