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So I'm a bit confused about the break angle of the strings over the saddle. I'm sure like most things it will be a trade off. I thought that having a sharp or steep angle where the strings meet the saddle would give the best transfer of string vibration to the bridge and top and provide maximum volume/tone. It would also eliminate buzzing or sliding of the strings on the saddle. But, my best sounding CBG and my commercially made resonator guitar both have a very shallow break angle over the saddle and they both are very loud and clear (CBG is not a resonator but does have a nice Punch Chateau box) I see many builds here that have very shallow break angles but are said to sound good as well.
What do you folks think about break angle at the saddle, steep, shallow, does it really matter?
I'm talking about acoustic guitars, not electric.
Thanks for your input!
I was all set to answer this post but see now that it has been answered many times. Oh, I think I typed to much already.
I think the Cremonese F holes are a bit more practical... fiddle makers have to set the sound post in when the violin is almost finished , they do this by putting in the sound post through the F hole., the shape allows the tool they use to fit into the cavity. The sound post makes the top and bottom of the fiddle vibrate in unison, that's why they use a chin rest to get both the top and bottom vibrating If not the fiddle would be damped by the shoulder, one reason why some folk fiddlers play the instrument on their biceps (ie on the end joint of the violin) , and why fiddles are loud for their size, they have a relatively huge surface area singing. And being a symmetrical instrument, 18th century taste made the F hole as it is
I happen to love these threads. I have been following, and have some responses that may create another dreaded word wall, but I am on vacation, and have no intention of spending it typing that much.
But oddly enough I am following along as I get time, and getting that deja vu feeling.... John Maw where are you? LOL!
Funny thing is that although these threads wander off topic, and some people dont seem to quite get it, while others seem to be intent on preaching their own version of the gospel, there is always a learning opportunity that seems to rise up.......
I kind of try to use it as a chance to get a feel for where people are at.
I have some responses to some of the previous questions and comments that will be forthcoming, meanwhile you can look for me at the tiki bar. I shall return.
Could we not all learn here from banjos as it my understanding that. this is very key in how banjo works and its bridge height sound relation etc.
Am I correct in thinking that this all realates to tension on the material used.
I have tried most materials from plastic to metal and I would say although difficult to work out,it is important. However the material used is far more important and its bracing. But if the wrong pressure is not correct all fails.
There is a guy in a guitar shop I know and he has seen may a tricone and single cone, and very few of them work... but a few ,just a few, have something very special..and this combined with the right strings and pressure all add up.
Get it right and you have something.
Also must be key that the material can resonate, has anyone tried a peg below the bridge like the fit to some vioins to improve the sound, as again this must affect where the pressure and tension goes and affect how the wood resonates?
I have many a parlour guitar all basically the same but all sound different, from mahogany to spruce to plywood etc.
I also think we understimate strings...big fat stings have great tone but may detroy your guitar and are a bitch to play.
Somewhere they may be a mathmatical formular.. ..
I tried a piece of Meica as a resonator! Strong and thin and loud!....I think string pressure is very improtant... but cant answer how much..just enough and a bit.. I would say, but do some Banjo homework for clues and then tell me why a biscuit tin sounds so good.
I hope I understood you all correctly and would love to know the answer if there is one.
Oh Bug is oh so close!
I think we can rule out the tone bar though. "peg below the bridge like the fit to some violins" I am going to go with the opinion that those:
A: Are an advantage on instruments that can use both the top AND back to project sound such as they do in the Viol family. And:
B: Probably really work best on instruments that sustain string energy when bowed, not plucked.
But the Banjo analogy is useful. Look at how one is set up professionally- head tension, bridge height, break over the bridge (Often adjusted to be increased with a special tailpiece designed just for the purpose) and head deflection considered such a critical setting that special guages and dial indicators are sometimes used. And what are they tuning for? Volume and tone! Definitly all factors to the answer to the original posters question.
I think an even better analogy might be found in the design considerations of the bluegrass Mandolin and its family.
I will explain that though in more depth when I get home.
"Get it right and you have something." I think thats the point. Exactly. And I think thats why the question arose in the first place and that its why its a good one.
Take for consideration the string angle of a Les Paul nut compaired to a strat, with out a string tree a strat can be worthless. What sounds best is what is right, Les Paul stop tail piece has an ajustable angle and useually the angle is steep. I have a new Martin 00-17v if you don't wind the high e string all the way to the bottom of the tuner post it's a rattle trap. String wear can be a real problem with a step angle. Metal bridges bolts, pipe are tone killers even on electric guitars I know its part of CBG history but they kill vibration regardless of angle.
Examples of angles of dangle....
I note a parlour not designed for steels has an amazing sound...so extra pressure aids volume and tone?
Note note angle of Les Paul and Mandolins,Banjos,Balalki from stuff hanging around here, for easy photo access
Also I find where a steel Bolt bridge can kills volume, a hardwood and fret bridge allows more to transfer..so the frequency transfer material can afffect the tone and sound.
Note many rosewood, ebony,Ironwood hard parlour bridges and the affect of bone nuts etc.
Like wise a softer wood biscuit howit affects the sound on a resonator cone affect.
The angle of dangle must be key,to correct string pressure. Hence a Banjo with a warped neck can never acheive the correct angle of dangle and will always sound poor.... so I am told!.
String pressure ,angle of dangle,material,bridge strength &,material, soundboard flexibility = Tone Volume
An intreresting example of an 3 sided soundboard is my plant pot resonator, this allows the metal front to flex and gives a unique sound from the front of the guitar.
I also find that strings through the neck piece, give a good angle and maximum susain. Also Ash wood seems to aidp this over mahogany.
I find the whole tone thing facination and have run many unconvntional experiments.. most of my projects all sound differnt. Also see the affect of a large sheet of steel on my Toilet seat resonator. Here a hardwood Bridge is best over a Bolt. and small holes which don't look enough work a treat.
So what about air Volume and pressure then in this whole equation?
Perhaps we need to understand more the science of sound waves and their transfer.
As I note with my Balaliki, the read of the guitar is angles in facets to direct the sound waves through the cross over point of the tiny hole... yet its very loud !
I understand Sound frequency travels in straight waveform lines, so we produce them from the sound board... them bounce off the back of a hardwood back and then though the apperture.
Perhaps we understimate this reflection of sound waves in the whole equation, however if the string angle and pressure is not correct to strart with it all falls down.
Do ya catch my drift?
Also Note sound board support structure positions, as straight across has never been any good in history. I have a dirt cheap acoustic and they run at angles and it sound so much better yet very cheap!... perhaps some martin research is required?
I will shut up now......
Allright, so I have spent a vacation on the road thinking about this thread, while driving, lunching at the tiki bar, resisting (sometimes unsuccessfully) a 3 (+) mojito nap in a beach chair staring at the ocean. Couldnt even concentrate on a good book, thanks guys!
As these discussions go, some of the content has wandered off course a little, sometimes into related territory, sometimes perhaps off base entirely. My thinking at the moment is to try to condense some thoughts on the original question and immediately related information and save the bigger word wall for a more appropriate time and place, as these threads just tend to wander too much.
But an better understanding of this could be gained with some background in topics ranging from acoustic theory, stringed instrument theory, and so on and we just cant go into fully here in a forum thread without it turning into a book. And anyone who remembers the "Ideal bridge location" thread from some time back knows how crazy this can get. Maybe a future post somewhere else? Maybe I should be working on my own book.
I'll try to keep this response as short as possible....... but its not easy given the vast area of the topic.
Someone suggested a comparison with the banjo, which I think is close, but if we look at the typical (man, is there a "typical" CBG?) construction techniques relative to this discussion, the way the strings are often terminated, the bridge types used and so on are of what is commonly known as the "moveable" bridge, (or what I call a "compression" bridge arrangement) as used on Banjos, archtops, mandos, the viol family and others, as opposed to the "fixed bridge" (Or what I call a "tension" bridge arrangement) commonly used on flat topped acoustic guitars, ukes and others.
When a string is tuned to pitch it stretches and exerts tension equally at the tuning peg and tailpiece. The tension varies somewhat by string guage and scale length, but we will use 25 lbs as an example. When plucked, the string streches further and tension increases by perhaps 4 pounds during normal plucking, and when the tension is released that additional tension slackens and a this energy is transmitted down the string in waves of tension from perhaps 24 to 30 pounds.
This energy can be divided into two seperate entities of lateral and longitudinal, and the systems of fixed vs moveable bridges use these two different energies in quite different ways. A basic understanding of string modes, partials, nodes and nulls is helpful, but not fully necessary to further understand this.
The soundboard of an acoustic guitar with a fixed bridge (no tailpiece) is driven almost entirely by longitudinal vibrations, pulling and releasing the bridge and torqueing and twisting the soundboard back and forth, causing the soundboard to act as an air pump causing compression and rarefaction inside the guitars soundbox. On a fixed bridge guitar, the bridge "rocks" back and forth as opposed to moving up and down. In theory a fixed bridge uses nearly all this vibration to drive the soundboard, as there is no tailpiece to absorb any of the strings energy. In reality as much as 50% of the energy can be lost at the nut and tuning machines. This is why we put so much effort into insuring stiff necks, hard well fitted nuts and accurately fitted and installed tuning machines. The less energy absorbed, the more is sent to the bridge.
This same action is also very important on moveable bridge instrument such as a mandolin, but because of the high string angle over the bridge and the way the soundboard is loaded by the strings pressure on the bridge, both the lateral and longitudinal vibrations are of almost equal importance. And fitment of the bridge is critical to the properly and fully transmit the strings energy to the soundboard.
With a moveable bridge such as the mandolins, the strings tension is captured by the tailpiece, and the lateral string energy becomes an important contributor. The bridge and soundboard function in an entirely different manner. than on fixed bridge instruments. here the soundboard is placed under load, and responds to the lateral slackening and tensioning of the strings.
When strings are brought up to tension, the soundboard is loaded. In the case of a mandolin with a 15 degree string angle over the bridge, there is about 24 pounds of pressure on the soundboard.
The pressure of the strings puts the soundboard in a state of compression, with the soundboard pushing back at an equal 24 pounds of pressure and an equilibrium is acheived. Otherwise the string pressure would cause the soundboard to fail.
When the strings tighten, the soundboard moves down, when the strings slacken, the soundboard moves up, thousands of times a second at different frequencys and amplitudes, and in various modes producing the sound from the instrument.
On a flat top acoustic guitar, internal bracing is critical to keeping the soundboard shape from distorting, or failing under pressure, and to "tune" its stiffness.
However the arched and graduated soundboard of the mandolin is very strong and stiff, so bracing is uneccessary. A tone bar may be used, but is used to "tune" the soundboard more than brace it. In fact most of it is usually trimmed off in the process anyway.
On a fixed bridge instrument, the bridge rocks back and forth on its axis as opposed to moving up and down as might be expected. Moveable bridge instruments rely mainly on the up and down movement of the bridge. Most of the longitudinal movement is captured in the tailpiece with only minimal amounts transferred to the soundboard through the tailblock and possibly from the headstock down through the neck and neck block as well. But most sound production is through the bridge.
The important aspect of transferring vibrations via downpressure through the bridge is the angle at which the strings are bent as they cross over the bridge. This determines how much pressure forces the bridge down against the soundboard. This important angle is called the "string break."
If the string goes nearly straight to the tailpiece, just touching the bridge, all you might hear is weak sound and buzzes. Too much angle and pressure and the soundboard may fail.
Bridge height and neck angle go hand in hand. The greater the neck angle, the taller the bridge and the greater the string break angle.
Ok as for my theorys:
*And a disclaimer, I am making no claim to a mastery of this subject, I have just studied (and continue to study) instrument design and am comparing what I have learned to what I observe.
First, as to my previous statement about too much string break angle at the bridge, pressure and possible muting of the soundboards output. I will concede that this is probably an imaginative point, either near or beyond the physical ability of most any soundboards structural integrity. I was just attempting to illustrate a concept.
The reasoning behind my comparison with the mando on the subject of neck set angle, bridge height and resultant string break angle over the bridge is that beyond the very short scale length and the arched soundboard, there are too many similaritys to ignore. String termination, moveable bridge design, relatively small body and soundboard area and so on. I am not saying identical, just similar enough to consider on this topic.
The lack of an arched top may be compensated for by the fact that we use thicker soundboards as a general rule, but I find it odd to see people applying cross and x-braced designs and then installing a moveable bridge. It may work, but I suspect its not ideal. But hey, no rules, anything goes and I love to see these experiments!
I would also be of the opinion that many of the bridge designs I see at CBN have excessive mass to be ideal, possibly reducing the acoustic potential of the instrument. Fine for electric, not so good for acoustic.
Soundholes, f-holes and the related theories have been beat to death and beyond here in these discussions, but I have stated before and will again, that I am totally in agreement with the statement that soundholes are misunderstood and the idea that "thats where the sound comes out" is misguided. I am of the opinion that in most applications, the effect of freeing up or "tuning" the soundboard is a far greater and more important result. Many round hole designs are far bigger than necessary for "pumping air" and that the Heimholtz theory thinking simply doesnt apply or work in many cases due if nothing else than consideration of size and scale and related complications. I may be wrong on this, but thats my opinion. Note how some very lightly braced acoustics have very small soundholes, and how some traditional large soundholes are postioned relative to the big crossbrace intersection and bridgeplate. Its just not as simple as the big hole you see from the outside.
Take note of the application of f-holes on the mandolin and viol family. their position relative to the bridge is critical to the movement of the soundboard. They are sized and positioned very specifically along with the thickness graduation to "tune" the soundboards resonance.
Lastly, some thoughts on fixed bridge systems. Before I understood them better I thought they were poor designs, they just didnt make much sense from a mechanical engineering view to me. What I would still note is that in many full sized acoustic guitar applications they seem to have a weakness in design that is caused by an unfortunate truth. That is the best sounding designs seem to be the lightest braced, and therefore likely to eventually fail. The classic Martin is a perfect example, take it from someone who has seen a vintage wonderful sounding example repeatedly self destruct in the bridge area. I have seen this example require repeated repairs and bridge replacements, bridge plate reinforcements and so on decade after decade since the 60's. I am of the opinion that this light construction (combined with some nicely aged old wood) is what makes the better sounding ones superior. (dont fall for the reputation that they all do!) But this same design also makes them highly prone to long term problems that are well documented by busy luthiers through the decades. Many a vintage Martin has had bridge and bridge plate repairs, and an even more unfortunate truth is that the value of some of the finest examples has been dimished by the necessary repairs to keep them playable, or by some very poorly executed repairs that nearly eliminated their collectors value altogether. But once in a while that old wood still gets to sing.......
Sorry this got so long, I really tried. And sorry if I repeated myself anywhere as this took several sessions to create, so it happens.
Hope it helped or entertained!
OMG that was epic Bliss !!
nice, well thought out...
heres how i see it: (all hypothesis only..)
1. we tension a number of strings to a pitch..
.. this involves storing energy in the string. Different strings of different materials (silk, nylon, gut, high tensile steel etc) will have different capacities to store this energy.
..energy is kinda like a toddler. It does not want to stay in one place and be good. It wants to move on, to manifest itself in different ways, heat, light, sound, even in extremes, motion..
.. it wants to escape by bending our necks, by stretching or breaking our strings, any means necessary
2. the focal point for this energy is the anchor points of the strings, the ball / loop / knot ends and the tuning mechanisms. But where we introduce a bend in the string, at the nut and the bridge (and possibly other places, string trees etc) we create another outlet for this energy. altering the angle of these bends (the break angles we are discussing??) definitely appears to affect the way energy escapes from the string whens its moving. I think that whilst the majority of the pressure (energy seeking escape) is applied at the ends (tuners and tail) a percentage is applied at these bends, and and there is some formula or algorithm which could be derived to calculate it.
3. when we strike the string it wont sing forever. We prolly all saw Mr oil's Les Paul quote about going solid in a quest for sustain, that he wanted to minimize (or slow as much as possible) the rate at which this extra kinetic energy leaves the string. In a perfect world I guess it'd sing forever until silenced, like a pendulum its to would exactly equal its fro.. but it cant. or it'd be silent wouldnt it? The sound (also energy) has to come from somewhere according to mr Einstein.. so energy leaves the pick or fingers to the string, where a whole bunch of it is wasted or lost, but a portion (affected by break angles ??) goes onto making the soundboard sing (by making air move) until there is insufficient energy in the string to sing anymore, hopefully it has returned to containing the same amount of stored energy as when we tuned it.
As to your last paragraph Mr Bliss, yes well exactly so mate :) isnt everything a tradeoff ? shaving the soundboard a tiny bit thinner or bracing a little less will make it louder and louder and louder until... pop!! :D
Wow, I love you guys! Amazing and thought provoking discussions! And yet still, it is somehow magical in how it all works or not and like everything else, is a complicated set of compromises. I truly appreciate all of you taking the time and energy (and nearly ruining vacations) to share your knowledge. The members of the Nation are AWESOME!!