Official Luthiers Forum!

Mornin' Y'all,

I hear a lot about how Adirondack Spruce bracing produces better reliability and tonality than Sitka, or Engelmann Spruce bracing. I'm curious as to where I might find scientific proof of that. I'm not trying to however I know that may be inevitable regarding this subject. I'm just genuinely interested in facts that prove this thought to one way or the other, or if it is simply another long lived tradition in lutherie that some believe to be factual without sound evidence (no pun intended ). I am not against using either/or I just would like to be able to support the subject with factual knowledge if ever I must answer this for a prospective client. And, for all my guitars, I choose to use only the best of the best. I personally have heard many hand crafted guitars with each type of bracing and am hard pressed to hear any true difference. One thing I heard (can't remember if from Charles Fox or another master luthier) is it would be best to brace with like materials as that of the top when possible. I know with redwood and cedar this may not be such a great idea depending upon the size and type of acoustic guitar being built. I will check in from time to time for everyone's input but my participation will be limited somewhat because I'm trying to complete 4 guitars I have on the bench before summer's end. Thanks to everyone in advance who will offer their input.

_________________
Bill Hodge


One does not simply, own enough guitars!

All I know is that if you take some brace material of sitka and adi and drop a piece on your bench you hear a difference. The adi rings a lot more than the sitka.... Try it.

each of those species acts a bit differently so would sound a bit different used as bracing. although there's probably quite a difference just between two boards of sitka. as for a reason behind picking what kind of bracing i was taught to use the same kind of wood so the whole top had the same properties and would move and react all in unison.

I have some data on damping of spruce samples in lengthwise bending handy, and the results are interesting. I have data so far on six samples each of Sitka and Red spruce, and 18 of Engelmann. Basically, if you just look at the avarages of the samples I've tested, Sitka has the lowest damping, with an average Q value of 89.5, Engelmann is next, averaging 76, and Red spruce has the highest damping, with an average Q of 69.5. However....

The Sitka and Red spruce samples are small, so that, for example, a couple of data points at one end or the other of the range can really skew things. That seems to be the case here; there are two Red spruce samples that are below 60 for Q values, and two Sitka samples at 100 and 108.

The larger Engelmann sample set probably reflects reality more closely, and what I found there was quite a wide variation. The lowest damping in that set was one sample with a Q value of 106, and the highest damping was a Q of 34; a range of more than 3:1. This gives me to believe that with larger samples of Red and Sitka I'd see more variation than the already wide range I do have, and that there would perhaps be less average difference than there seems to be.

The most important take-away, IMO, is that you have to look at the piece, not the species lable. Some of that Engelmann I have is so dense that I'd have sworn it was Red, if the supplier had not sold it as Engelmann. Interestingly enough, those are the samples with the lowest damping. If you switched those five tops into the Red column, the average damping for Red spruce goes down, from a Q value of 69.5 to 86.8, very close to the average of the Sitka, and the average Q for Engelmann drops from 76 to 67.5. This is much closer to what the 'lore' says the ranking 'should' be. It also brings up the interesting notion that maybe damping in spruce (and other softwoods?) is correlated with density. I'll have to look into that in my copious free time.

Last of all; although it seems as though the damping of the brace stock ought to matter, can we show that it does? That seems like a tough one to me.

Note:
Q value is a measure of the proportion of energy the piece loses per cycle as it vibrates. A piece of material with a Q value of 100 loses 1% of the energy stored in it per cycle, while a Q value of 50 is a loss of 2%, and so on. High Q = a long 'ring' time, and low damping.

what, no euro spruce in there?

_________________
sweat the small stuff.

I regularly use sitka and red spruce for bracing, and have used some Carpathian in the past. I fail to hear what difference in tone the species of the bracing makes. When all is said and done, the mass of the bracing is nothing compared to the mass of the top. Although hard and stiff specimen do exist and show up (rarely), most Englemann I've seen is rather soft and IMHO not suitable for bracing a steel string.
The sitka and red spruce stock I have are identical in terms of stiffness and weight. I tend to prefer carving red spruce though, sitka can be fibrous and less pleasant, it's personal.

_________________
Laurent Brondel
West Paris, Maine - USA
http://www.laurentbrondel.com/

I appreciate Al's thought that one can't generalize in this case.
Take it piece by piece, and not species by species.
When we get a load of brace stock in, first thing that's done is to test each piece for its deflection values.
If you want to go bonkers with it, do a test at one height, and then another test when the brace is thinned down near to its finished dimension. You'll get interesting readings for sure.
Me, I'm sold on Sitka, both for stiffness and weight.
As far as same species for tops/braces, and them acting "in concert" beacuse they are the same species, that's a hard sell.
Once you glue a brace across a top, at 90 degrees, 45 degrees, whatever, it will be behaving differently, reacting differently.
To me, the lighter the brace, the stiffer the brace, the better.

Steve

_________________
From Nacogdoches...the oldest town in Texas.

http://www.stephenkinnaird.com

Interesting results and thanks for posting them Alan.
I would say, without having anywhere near the knowledge that Alan has, but just observation, that it is wood, an organic material, that we are dealing with. It is too inconsistent in it's growth to throw a blanket statement over it and say one species is better than the other because even in the same species there are great variances between pieces, maybe even from the same tree(growth rings closer on one side of the tree for instance). Granted a species may have general characteristics that can be applied to it but that's where it ends. So I think that for you question Bill, the best we could tell a client is that "this type of wood is generally good for this but it varies" And at the end of the day each brace(unless they are produced on a CNC machine) is going to be different than the last one we made because we shaped it slightly differently and then shaved it to tune it to a particular top. I guess what I'm trying to say in all this drivel is summed up in Steve's second statement, "take it piece by piece".
Just my 2.5 cents?

_________________
Nick Oliver

http://www.oliver-guitars.com

I have spoken with John Greven on this issue quite a bit. He has stated that he has a sound he wants out of his guitars. He further states that he is now consistently getting sound using Lutz tops and Adi braces. But as others have said it is not really the species but rather the properties. He reports that the Lutz tops are as stiff as he likes with the density that suits his building style and that the adi bracewood he gets at Old Standard tends to be denser than the Lutz I have sent to him. So although we talk species it really is the properties he is getting that is working for him, likely from geographic specific harvesting of these two different species.

Hope that helps!

Shane

_________________
Canada

One thing I take from Al's discussion - I hope that his soundboard dealers know exactly what it is they're selling!

_________________
The member formerly known as erikbojerik....

Are you standardizing your test sticks as to dimensions rather than stiffness? I don't build guitars but wouldn't you cut a brace from very stiff spruce stock rather smaller than one from less stiff material?

My materials background is decades dormant but I think "Q" in a long, thin stick or brace would be strongly dependent on dimensions. So comparing like to like cross-sections for "Q" would give a different result than comparing like for like function (stiffness). Or maybe a given builder cuts them the same no matter the stiffness is which case...Never Mind!

I've got data on Euro, also red cedar, redwood, and some others, but the OP didn't ask about them. I'm just about to leave for Montreal, but maybe I can post some more info when I get back.

I'm taking Q value to be a material property that's more or less invariant. I realize that's not the case, but you have to start someplace.

I start with all of my bracing oversize, and then trim it according to what the Chladni paterns tell me. My notion is that the best guitars have a certain 'balance' between the braces and the top. The shapes of the patterns show the balance in the particular top, and the frequencies tell you something about the ratio of stiffness to weight. Given the variation in material properties, cutting all the braces tot he same exact sizes with a CNC will pretty well guarantee that you'll end up with a range of different stiffnesses.

Good Mornin' again!

I appreciate everyone's input. My thoughts, and the reason for my posting this have been pretty well addressed. I suppose the area that disturbed me the most was in the fact that there are so many out there who do generalize according to species rather than the rigidity or quality of a specific piece(s). Take Engelmann for instance, you can cut several sets out of the same billet of wood, and get pieces that range from extremely hard and stiff (for that species) to floppy kindling. Laurent, you had mentioned Engelmann is too soft for bracing yet if my memory serves me correctly, doesn't Mario Proulx use Engelmann exclusively for bracing? There are some other well known builders who also use it though I'm not sure about the exclusive statement in their cases. Selective choosing of the brace materials for density and rigidity (properties ) I too believe is the key. Not based upon species alone!

Al your test results are great and I was hoping you'd participate in this because I have a great deal of respect for your knowledge, and the fact that you have a perpetual drive for R&D to build the best instruments you can possibly build. Not to mention, your heart for the craft and teaching what you've learned to others. Like Laurent and Steve, I too am sold on Sitka for it's consistent strength to weight quality. I have about 60 bolts of Sitka that have been aging for years and every time I resaw into tops and bracing, I'm amazed at the consistency of it's quality, density, and strength. Three of the four guitars I'm currently building all have Sitka tops from the same bolt and they are as stiff in both directions as I've ever experienced. When tapped after thicknessing, they ring like bells. (each singing it's own particular song ). Shane that's interesting about Greven's findings and that inspires me to get some Lutz from you at some point for some future builds. I am not opposed to using Adirondack, and will absolutely do so upon request, but I don't know that it is really worth the extra expense one would have to pay when many of the finest sounding guitars I've ever heard have Sitka bracing on Sitka tops. And some of the sweetest sounding guitars I've heard have Engelmann tops. So it all boils back down IMHO to the builder, what they learn about materials selection, and how they apply that to each individual build according to the needs and desires of the specific client (player). Am I not correct in this thinking?

Sorry that I didn't address every one individually, but my post is getting a bit wordy and I must return to the shop and get busy. Again I do appreciate the input of everyone.

_________________
Bill Hodge


One does not simply, own enough guitars!

Mario might be using soft Engelman, but coupled with his CF inserts.

I'll follow the grain and say it is the actual qualities of that piece of wood that matter, and not the species.

On my last guitar, the top while nice and stiff along the grain, was cut a bit off quarter, feeling rubbery across the grain, so I've used some incredibly dense German spruce of about 520Kg/m3 (!!!) for the braces and it worked unexpectedly well, as the guitar is bright and cuts.


The density also seems to vary a lot within the tree indeed. From a large Italian spruce wedge I measured from 360 Kg/m3 for the young growth with wide rings, also a bit spongy feeling, to about 470Kg/m3 in the outer sapwood, where it is almost impossible to count the rings... That stuff was tough as nails and I used it for fan braces. The lighter bits were great for doing back braces.

_________________
Build log

Bill: Think the general concenus is to use the stiffest material. Have some standard to use for deflection testing and select your braces on this basis. As Al has pointed out to us many times,we can reduce top weight more effectively by thining the top plate itself rather than trying to lose the weight by reducing the size of the braces.Thus ,stiff braces,thiner top,less weight.As to the damping factor on braces,that's way over my head,no doubt it has some effect ,but think there are many more things in the over all process to worry about, at least for me there is.

_________________
A person who has never made a mistake has never made anything!!!