Martin DCME sinking top...ideas?

[Light]

To put it as simply as possible, the braces are carved to the smallest dimension possible, while the luthier periodically taps the top listening for the effect on the 'tap tone' as the brace dimension changes, all the while attempting to maintain a structurally sound top.

Well, that's the way some guys do it. But to be frank, the guys who tap their tops do it because they are trying to get a more consistent sound from guitar to guitar, and they are unsuccessful. There are a lot of hand builders who do NOT tap tune their tops, and they make guitars which are every bit as good as those who don't. Tap tuning is an attempt to bring some degree of science into an area which is really not quantifiable. It may work on arched top instruments (arch top guitars, violin family, etc.), but on flat tops it is really a waste of time.

The biggest problem I see with it (which may be unrelated, but which seems to be the case with most "tap tuning" guys) is that they build their tops WAY too light. You want it to be fairly light, yes, but if you go too far you lose a lot of bottom end, and all of your dynamic range. If a guitar is too light, then as soon as you start really laying into it, it completely falls apart. The guitar starts to sound really farty and nasty. They also become much more prone to structural damage and decay, which is to say you will need your neck reset much sooner than with a guitar which is made with a slightly heavier top. It is something which will vary a lot from guitar to guitar, but there is no question that a guitar which is too light will lack the range of a guitar which is built right.

As to why guitars don't have sound post, the answer is very easy:


Because they don't.


That's just not the way they were designed when they were getting designed. These days, we are so used to the sound of certain guitars that if someone does something drastically different, it doesn't sound right (take as an example the collapse of C. Fox Guitars ... He tried to make something which didn't have a X brace, and the company didn't even last two years).


Now, if you want me to spin some bullshit theory as to WHY guitars where designed without sound posts, think about how you hold the violin family instruments. In each case, the back of the instrument does not have any major contact with the player. It is left free to vibrate, and so it makes a contribution to the sound. Now, think about how you hold a guitar. The back of the guitar is pressed right up against the body. All that would happen with a sound post is that the vibration would get sucked right up into your body, and it would get robbed from the top, making for a quieter instrument.


But the real answer is because that's the way people are used to guitars sounding.



Light

"Cowards can never be moral."
M.K. Gandhi

 

[Light]

But why is that not true of other stringed instruments? Granted, they are not braced. But then the bracing keeps the top from vibrating too

Well, seeing as how a guitars top would explode under the tension of the strings without bracing, I would say that quite the opposite is true. The bracing allows the top to vibrate by keeping it in one piece. Additionally, if the top weren't braced, it would flop around so much (before it exploded) that it would just suck all of the energy out of the string, and you would have no sustain at all. Bad ju-ju.


I think the first thing you need to get away from is the idea that you would like a guitar if it was a more effecient acoustic machine. You most likely would not. It would sound quite a lot different from what you are used to, and you would probably find it too forgin sounding (just ask the Kasha style guys if they have an easy time selling classical guitars which are not fan braced, for instance). The sound we like in a guitar is the sound we are used to.


Oh, and by the way, arched top instruments ARE braced. Violin family stuff have something called a tone bar, and arch top guitars have two of them, sometimes parallel, and sometimes in an X pattern. In addition, the arch of the top provides a great deal of extra stiffness as well.


Finally, always remember that no guitar builder actually knows what he is talking about to the degree that we claim we do. I can lead you in the general direction of a guitar you will like, but I can't actually tell you exactly what a guitar will sound like when it is done. Anyone who tells you they can is lying to you. Our guesses are certainly more educated than yours, but in the end we are still just talking to make the breeze blow.


Light

"Cowards can never be moral."
M.K. Gandhi

 

[gbdweller]

I think mshilarious was more interested in the use of a soundpost as a structural member to help prevent top collapse. As to tap tuning. I tap tune when bracing my tops, but not to make each guitar sound the same. The goal is to make each top sound it's best while maintaining structural integrity. The goal is not to make the top as light as possible, but as strong as possible while allowing the top to vibrate. It is obviously a delicate balance, because too heavy and you have a dead, muddy top. Too light and you have a fragile tinny top with no bottom that will inevitably collapse. If you want to get into scallopped bracing and the effect of string tension on the soundbox and top, that's a different story. Some builders do try to tell their clients exactly how a particular guitar will sound when done, and yes they would not be telling the truth. I tell my clients what basic tonal qualities to expect from particular body styles and scale lengths, and then advise them that I will provide them with the best possible tone I can for their chosen style. No two guitars can sound exactly the same, because each is different no matter how exact your building techniques. I do advise my clients that I will 'eat' the guitar and build them another if they are not completely satisfied with the tone. I have yet to be taken up on that offer. I have that luxury as I operate on a one on one, order by order basis. I also complete every step from materials selection, to final set up so I know exactly what went into every detail of the guitar. And Light is right. Most of us talk for the sake of talking, many of us know what we are doing, and we all do things a little differently. We will also tell you that our way is the only way, but the bottom line is if it works, and you the customer are happy, then we are all right in our own way.