Domed vs Flat tops

[ken cierp]

Pretty good video -- points out that there are different approaches to the doming concept as it relates to the neck set. I again will point out however this is not how Martin does it now or did it in the past. Nor is it the system used by the top Martin replicators, Henderson, Greven, Olson, Hoffman and Thompson to name a few. -- the Martin factory and afore mentioned use the flat rim top edge and predetermined and accurate sloping of the upper bout. Explained here:

http://www.kennethmichaelguitars.com/neckangle.html

"keep it simple!!"

[ken cierp]

Bob Taylor seems to be in line with the same thinking as John Greven -- in that curving the braces inhibits the top thus changes frequency response shifting more to the higher end. So his base top of the line model is constructed flat.

http://www.rtaylorguitars.com/Woods-Bracing-04.aspx

The surprise to me is the indication that a tiny contour 65' has an effect and is audible

http://www.rtaylorguitars.com/Woods-Bracing-05.aspx

Makes me wonder how a 25' or 28' radius could be a good thing?

[John Parchem]

My understanding of the slight doming was to add some protection against climate changes. Doming the top does adds stiffness which would shift the sound toward the higher end. This added stiffness can be something to work with. For example: The top can be a made a bit thinner which removes both stiffness and mass. On a custom made guitar each top can be hand and ear tuned depending on the skill of the builder.

A lot of classical guitars could use a shift toward the higher end as the basic design of the thin top and light fan braces required to get sound out of one with nylon strings tends toward good bass and weaker trebles.

[John Link]

John,

Thanks for the video. He talks about Englemann Spruce in a positive manner. I just received my first shipment of this species a couple of months ago and must second what he says. I found the average sustain of a tap, once I found the node at about 22% from the edge, was over three seconds. Adi and Sitka spruce sets I have do not reach three even though some of them were outrageously expensive. The Englemann cost just $17 a set, delivered.

I think he is on target when he asserts that structure in the upper bout is more responsible for neck resets than failure of the glue joints.

His use of .100" as a target top thickness is interesting, as is his distrust of scalloping. (There is no denying sharply scalloped braces are the most exciting to look at, though.)

As far as doming the top goes, that discussion will last longer than I will. But I can't agree that large boxes automatically give us good bass. It is the nature of steel strings to "twang" and if one wishes a darker, woodier bass, it must be worked for. Getting the top to easily move as a unit - the "monopole" that Trevor Gore and Ervin Somogyi write about - seems the path most likely to yield rich bass in any sized guitar. Dave Bagwill posted a video some time ago of a small guitar that had very rich bass.

Thanks again for digging up this video.

[ken cierp]

Good point about sharp scallop peaks (no pun intended) I believe Bob Taylor recognized this early on as a cosmetic feature. Look inside the first Taylors and you will likely see some very simple bracing profiles. I suppose the massive marketing chatter regarding old time Martin's and their use of scallops forced Taylor into incorporating this feature to stay with the competition. Roger Siminoff states in his publication that the peaks really do nothing at all for structure or sound quality. For sure the early J45's and L00's look like they are braced with a pile of sticks -- mostly the same size 1/4 x 1/2.

[John Link]

Interesting fact about early Taylor.

Both Somogyi and Gore point out that peaks introduce great variability into the stiffness of the top, thanks to the "cube rule". If a peak is twice as high as its neighboring scallop, it makes the top EIGHT times stiffer underneath its footprint. While there is no denying the first Martin steel strings sound great, it may be despite the peaks, not because of them.

But if the peaks are pointy but small, I'm inclined to think they don't matter much either way. They are little more than a hiccup in an overall triangulated structure. There is a difference between "not much" and "nothing" however. (Did I manage to adequately dodge the controversy here?)