Can you assess this?

[Jim_H]

That DeJong top is definitely interesting. I wonder how thick it is, how thick/tall the braces are, what the bridge plate material is and how thick it is?

Hmmm...

[kencierp]

Here's the deal -- and I think Jim is spot on --- "what are the parameters and specifications" for a good sounding double X braced or any exotic braced guitar? Look inside side the vast majority of steel string guitars made today and you'll find similar slightly modified versions of the Martin X brace pattern and on nylon string guitars a Torres fan brace pattern --- there is historic evidence that these patterns result in very pleasant sounding well balanced guitars. That's my goal, the work been done for me, I can construct and even sell Kits with a high level of confidence the finished instrument will sound good..

[Darryl Young]

Ok, I'll play and pretend I know what I'm talking about! <smile>

As already mentioned, some call this pattern the "Double X". I imagine it can be made to sound good, even very good if you work with it. The challenge of this type pattern is that it's inheritantly very stiff.......so you have to work hard at compensating for this to loosen the top up.

A singular brace adds a lot of stiffness locally to that area of the soundboard. Think how much stiffer the soundboard is at the intersection of two braces. Now look how many intersections there are in the double X pattern and where the intersections are located and you start to see the issue. Notice how many "X" or "+" shaped intersections there are instead of "T" shaped intersections.

Also, look at how stiff the bracing is around the perimeter of the soundboard. If you top doesn't move around the perimeter, then you don't have the strong bass you likely want. I sure wouldn't want all those braces inlet into the lining around the perimeter of a guitar I built.

Lastly, I want little to no bracing in the very bottom area of the soundboard. If you drew a crossgrain line from between the points where the lower X-brace arms connect with the lining, I prefer having nothing below that line.......and the double X has 2 braces going into this area. I'm beginning to think the Martin X-brace pattern could be improved by removing the lower portion of the lower tone bar (still debating that). Remember the middle of the lower bout is prime real estate producing much of the tone and volume of the guitar. So at the least, the lower portion of the double X brace should be very, very short.......tapered down to nothing very quickly.

One thing I like about this brace pattern is that it is symmetrical. The challenge would be getting good bass and volume from this bracing pattern.......but it could be done if you work with it.

[deadedith]

Darryl, let's suppose we did the following to change that pattern: first, eliminate the x joints at the 'finger brace' junction with the main x brace, and use standard finger brace joints. Second, do not inlet the lower x brace into the linings, instead, as you mentioned, feather the lower braces short of the lining.

Essentially, just replacing the asymmetrical standard tone bars with the lower x brace, nothing else, for no other reason than symmetry.
Just speculating - what do you think?

And I recognize the strength of Ken Cierps' argument - that the work has already been done as far as how to make a good to great sounding instrument. I don't see any compelling reasons to get too innovative - but it is fun to think about when one has a little time to...think about it..

[Jim_H]

Sounds like some prototyping is in order...

Get started! :p

[Ken Hundley]

That last one was interesting....I would assume it was for a pinless bridge?

I have mentioned this conversation before, but I think it has relavence here. I recall a thread on the old acoustic guitar forum regarding converting to a lefty guitar versus building a lefty guitar. the concern was that converting to a lefty doesn't have the benefit of having the assymmetrical tone bars oriented properly, as they would in a built for lefty guitar. The end opinion was that there is no noticeable differnece between a built for and a converted lefty. The conclusions drawn were that the benefitof the tone bars was derived from their assymmetry, not so much their orientation. Now I am not sure why this is the case, but you can't argue with the sound of a traditionally braced guitar, asymmetrical braces included. no matter what design changes I make to my patterns, I will more than likely always have asymmetric tone bars.

[Darryl Young]

Darryl, let's suppose we did the following to change that pattern: first, eliminate the x joints at the 'finger brace' junction with the main x brace, and use standard finger brace joints. Second, do not inlet the lower x brace into the linings, instead, as you mentioned, feather the lower braces short of the lining.

Essentially, just replacing the asymmetrical standard tone bars with the lower x brace, nothing else, for no other reason than symmetry.
Just speculating - what do you think?

I would do this at a minimum. I would make sure and not let any of the lower X (the part replacing the tone bars) go below an imaginary horizontal line connecting the points where the lower X brace arms connect to the lining. Also, the lower X brace gets very stiff at the joint of the 2 braces........so I trim the braces very short in that area and taper off to nothing fairly quickly before the lower arms go very much further (a V shape with small lower arm extensions that make it X shaped).

Of course I have a lot of experimenting to do myself so take all this with a grain of salt. I think I like the idea of a PMTE brace along the back of the bridge plate and a single tone bar better than a lower X......at least on a smaller body guitar.

[deadedith]

How about just a 'v' terminating at the tailblock? Saves the symmetry and no 'x'?

[Darryl Young]

Again, I don't want any bracing down that low as I want the perimeter free to move. I certainly wouldn't terminate any bracing in the lower bout save the X braces (and I don't terminate the X-brace in the lower bout). I also bevel the tail block so it only makes contact with the top for the width of the linings.

I didn't mention this but I also wouldn't use a bridge plate that large.

[deadedith]

Darryl, since I have 30 terrabytes of processing power in my 3 year old piece of doodoo laptop, I was able to make the detailed drawing below.
Would not even this simple change present a symmetrical, viable alternative?