Official Luthiers Forum!

I'm curious how each of you select the sounboards you will use on the guitars you build. I'm guessing most of you have a particular sound you are trying to create......so I'm guessing you have an idea in your head what species and what stiffness top you are looking for. Assuming you don't have a tonewood dealer near you, how do you explain the soundboard qualities your looking for to the dealer over the phone? For example, how do you quantify your idea of a "moderately stiff" top to someone on the other end of the phone? Or if you were looking for a top that wan't too stiff so you could leave teh top a little thicker and brace lightly, how would you convey this in any meaningful way? Do you buy most of your soundboards in person? Or when you find what you are looking for, do you go back to that dealer and ask for more sets from the same billet or tree?

Another question, how would you describe Lutz spruce as compared to Englemann, Sitka, and Red Spruce? Sitka and Red spruce seem to stand up well to being played harder/louder as when stumming (seems some call this head room if I understand correctly). The Engleman and Red are often described as having good color or overtones. Where would you place Lutz on this scale? And if there is someway to quantify or compare it, how does the stiffness of Lutz compare to the others (along and across the grain)? I realize (just as in the brace wood discussion) that it's difficult to generalize about an entire species as there is considerable generalization. Maybe Lutz is in a specific area and consistent enough for a comparison to be meaningful.

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Formerly known as Adaboy.......

Probably the best advice is to build a guitar with the wood in question and see how it sounds. The same Sitka top is probably going to sound different with three different builders. I'm finding it is a very long process getting a good feel for how woods of a certain species and stiffness sound on your guitars. Think in terms of years and many instruments.
I tend to buy from the same vendors because I develop a feel for what their classifications actually mean.
I've built with Sitka and Lutz and like both but I have a hell of a time describing the tone. It's so subjective. The buyer pretty much just has to play it and see if it speaks to them.
Terry

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It's not what you don't know that hurts you, it's what you do know that's wrong.

I think you've actually asked many related questions!

For my part, I generally do not buy soundboards through the mail. There have been exceptions, some of which I've regretted and some not, but as a rule I like to see, flex, and hear the wood before purchasing. Going to conventions/symposia and to guitar shows are good ways of meeting dealers and checking out their wood.

As far as the differences between species, I can generalize about the results I get but not about other people's experiences. At a show a few years ago, another experienced and respected builder commented on the tone of my red spruce guitars and wondered how I achieved it. As we talked, it became apparent that everything we did was different! His wood came from a different region of the country, he used different bracing designs, and so on. So many variables = no simple answer.

Also, Bob Taylor once reported that he tested the stiffness of many spruce sets and found as much variation within billets as between different logs and even between different species!

You mention using a thicker, more flexible top and bracing lightly. I'm not sure about this. Most of the mass of the soundboard (including rosette and braces) is in the top itself. Using a thicker top ensures that your soundboard will be significantly heavier than it would be if you used a stiffer wood and thinned it to the same flex. Most people most of the time prefer to make their soundboards as light as possible. Also, I was taught (and still believe) that the whole soundboard has to work as a unit. That is, the braces and top should be in proportion to each other; one should not try to overcome a loose top by making overly stiff braces or the other way around. I tried this purposefully once -- making a jazz-oriented guitar by thinning the top and overbracing it. Tom Ribbecke played it for less than a minute and said, "Thin top, big braces, right?" Not a rousing success.

And finally you touch on a problem all instrument makers and players face: our lack of a good, consistent vocabulary of sound. It's hard to describe the tone of a particular wood for all the reasons I've mentioned. It's also hard because we just don't have the words! I guess that as our language was developing it wasn't necessary to find words for the precise tone of an angry sabretooth tiger -- "Run!" was good enough. So finding a common language is one of the tasks of a luthier trying to communicate with a client, or wood vendor, or other luthiers. It's one of the hardest, in my experience.

I pick tops by weight & stiffness.
I buy only from dealers I trust & have dealt with for years.

keep records of weight & stiffness ;brace pattern & stiffness and species of braces.

There are so many varibles -box size,depth of box,sound hole size & placement.
Thickness & stiffness of the sides& back !
Strings to be used !
Bridge & saddle height .

Follow a good plan and keep records of all thicknesses and such.

Mike

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Mike Collins

What type or species of Sound board wood I select, first, is what fits the design, appearance and objective style of the guitar being built. I have puchased all my inventory from just a few suppliers, none of which are close enough for me to see before I buy. Either I am real lucky or the suppliers I buy from apply their knowledge in knowing what it is we are looking for because I have not received what I would consider a "bad" soundboard to date. I prefer to use certain types/species of soundboard with certain types/species of back & side woods. These preferences are both for appearance and sound. I have an inventory and use Red, Sitka and Engelman Spruce's and Western Red Cedar, its all good.

Mike Spencer
White Oak, Texas

I'm learning from your responses......thanks and keep them coming.

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Formerly known as Adaboy.......

Rick,

I'm trying to get better at keeping records on my builds (I'm just starting my 12th, so it's still early), but don't have any real 'system' yet. I've kept a few notes here and there, but haven't really gotten systematic with it.

Do you (or does anyone out there) have a more inclusive punch list of information to take note of as you go through a build?

That could be useful, if people don't mind sharing.

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Ken Mitchell
Durham, NC

The hardest question is to figure out what are the most important properties to you....
Make up a list 1-10 of Most Important (#1) to Least Important (#10)

Color
Uniformity of Color
Tightness of Grain
Uniformity of Grain
Straightness of Grain
Amount off of "Perfect" quartersawn
Cost
Density (Hardness and Stiffness)
Presence of knots and sap pockets outside the guitar outline
Amount of grain runout.
......................
If your list goes:
#1 Perfectly Quartersawn
#2 Runout
#3 Density
#4 Cost
#5 Knots/Sap pockets
#6 Grain straightness
#7 Grain tightness
#8 Grain Uniformity
#9 Color
#10 Color uniformity
You will get 1 sort of top.... Probably very nicely quartersawn... but with lots of racing stripes, grain squiggles, color streaks, and non-uniform grain lines... Maybe a knot outside the guitar outline... Etc.

And... since COST was high on your list.... above Color and Grain tightness.. This top will be CHEAP!

If your list goes:
#1 Color
#2 Color Uniformity
#3 Grain Straightness
#4 Grain tightness
#5 Grain Uniformity
#6 No sap pockets or knots
#7 Runout
#8 Degree off perfect quartersawn
#9 Density
#10 Cost

You will get a totally different sort of top..... and it will probably be called "Mastergrade!" and will Cost $$$$$$$$...

Good luck

John

I'm one of those oddballs who thinks that the way a guitar sounds and plays is probably more important in the long run that how pretty it is. I have nothing against pretty, mind you, and do the best I can in that regard. However, since grading standards for spruce are all about pretty, and have nothing to do with sound, I find that pretty (expensive) tops are often dissappointing. The worst top of the four in my plate tuning video was the most expensive and 'prettiest', except for the terrible runnout along the bark edge.

Anyway, I start out by thinking about the weight of the finished top. If you want to draw an analogy, 'accelleration' in a car is like 'high end sound' in a guitar, since they both require you to get things moving an a hurry. Similarly, 'top speed' relates to 'acoustic power'. We've got small 'engine' to work with; there's not much power stored in a plucked string, so if we're going to get high end and power, we need to keep things light. It's more important in classiacals than steel strings, because they have a little less power (lower tension, but usually higher action that makes up for some of that) and much less high frequency energy than steel strings. On a 12-string you've got power to burn by comparison, and can afford to use a heavy top.

Another consideration is dynamic range, and particularly how likely the guitar is to 'over drive'. That seems to be a function of overall weight, so long as the stiffness is high enough to keep you out of trouble. Remember that, for this purpose, the bridge is part of the top.

It turns out that the potential stiffness along the grain (Young's modulus, or E value) scales linearly with density (with some scatter, of course), but that actual stiffness of the top itself is a product of that E value times the cube of the thickness. What that means if you work out the logic of it is that a low density top will usually end up a bit lighter at a given stiffness, even though you have to leave it thicker.

So, for classical gutiars I tend to use the lower density pieces of wood, so long as they are otherwise reasonably stiff. I use somewhat more dense pieces for larger steel strings, and denser ones for smaller boxes, since you can reduce the thickness a bit when you reduce the span. The really dense tops go into 12-strings and flatpicking instruments.

You have to go by the piece, and the only way to do that is to measure. I measure the lengthwise and crosswise E values, the related damping factors (Q), and the density of every top I get in. This allows me to match them up with their uses without worrying about the species or apearance, at least at first. Obviously, if I'm making a really high-end box, with Brazilian B&S and lots of inlay, I try to use the prettiest piece of wood that's otherwise suitable.

In general, in my tests so far, cedar tends to have the lowest density, followed by Engelmann, Euro, Sitka and Red spruce. Redwood varies, and I have not tested much, and I've only tested two Western Hemlock tops, both of which were quite dense and commensurately stiff. But those are averages: I have a REd CEdar top that exactly matches a Red spruce top in everything but the damping factor; the density, and lengthwise and crosswise E values are all exactly the same. With enough testing, and given the variation in wood, you'd expect that if you look at enough samples.

I'm a big fan of 'balanced' construction: with the bracing and top both doing their share of carrying the load. I tend to end up with somewhat hicker top plates and lighter bracing than some folks, and maybe that's costing me some power, but so far I'm happy. You have to figure out what's going to work for you.

Great reply Al, thanks for taking the time to write that.

A question about this statement:



Do you use the really dense tops for flatpicking because it will be strummed hard? I would assume the stiff top won't give you the best bass "cut" while flatpicking......true? Maybe you can thin the top considerably around the perimeter of the lower bout and still get a good "cut". I'm assuming this is created by a strong jump of the soundboard when the string is released......probably in a monopole mode??? If true, seems you wouldn't want the soundboard too stiff......at least not around the perimeter. Thoughts?

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Formerly known as Adaboy.......

If you really want to save some cash (and make, IMO, prettier guitars) then put 'colour' at the top of the list and then go with physical properties (stiffness, density, etc). By 'colour' I mean as much of it as possible. 'Master Cosmetic Grade' is booooooring!

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Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

Daryl Young asked:
"Do you use the really dense tops for flatpicking because it will be strummed hard? [snip] I'm assuming this is created by a strong jump of the soundboard when the string is released......probably in a monopole mode??? If true, seems you wouldn't want the soundboard too stiff......at least not around the perimeter. "

Yes, bass 'punch' does come from having a really active monopole on the top that can move a lot of air. The questions then become, how do you get that, and what does it cost? Remember, there's no free lunch.

If you think about it, the guitars that define that 'Bluegrass whomp' are the old Martins with scalloped bracing. The bracing is low in the center of the top, and taller between the center and the edge. Curious, no?

Several years ago, in an article in the late lamented Catgut 'Journal', Bernard Richardson talked about ways to get more power out of the monopole, in this case on Classical guitars. He did some modeling, and decided that thinning in the center of the top was more productive than thinning around the rim. Basically, the pattern of displacement was such that the top that was thinned in the middle moved more air. Of course, if you're going to thin in the middle, you need to think about at least two things; 'wolf' notes, and static torque.

Static torque is, of course, the thing that sets the limit on how thin you can make the top. Generally speaking you're going to do better with that if the plate is thick and the bracing tall in the middle, and everything tapers down to a thinner edge. This is the way I usually make my guitars, but I'm more into a 'fingerstyle' sound, with less 'punch', less low end, and more sustain. I've made some scalloped tops, though, where 'punch' is the object, and that's what you get. You do have to be careful not to thin the center or lower the braces too much, lest the instrument swallow itself prematurely through it's own soundhole.

'Ideal' strings, the kind that have perfect intonation and true harmonics, have fixed ends. The more the bridge and top move, the more likely it is that you'll have problems with those things. You'll also have to deal with the 'guitar wolf', where the top extracts the energy from the string really fast near it's resonant pitch, and the instrument goes:"bong, bong bong, thud, bong" as you play up the low string. You can get around that to some extent with a more massive bridge.

The idea is that getting the string to behave properly requires a pretty large impedance mismatch at the end point. Impedance is proportional to the square root of (mass*stiffness), so if you're making the top thin in the middle to get it to move, then adding some (a lot, even!) mass at the bridge will get you back to where you need to be to make it all come out right. A heavy bridge will also have higher impedance at higher frequencies: it cuts down on the high end some, and gives a more 'bassy' sound. The dense top is going to be heavier for a given stiffness too, so that will help raise the impedance, and it lowers the pitches of the main resonances. It's that higher impedance, I think, that gives it more 'headroom'.

All of this is just the nature of the tradeoffs we make when we build guitars.

On another forum there was a post by a chap who selected his top wood blinded folded so as not to be biased by cosmetic aspects of the tops.He is after a certain tap tone,stiffness,weight, etc. This no doubt could not be used by the vast majority of folks due to the fact most of us purchase by mail. Seems to me to be a reasonable system if you have the opportunity to go through a large number of tops. Have often thought that the grading system should be a two level thing. Still use the conventional Master ,AAA,AA,A grading but do it twice .Once for looks and once for tonal possibilities.A master top for looks may only be an AA for tone or the other way around.This would cause problems in the supply world but would sure help folk who have to select by e-mail.

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

Well gee, lots to be spewed forth regarding tops.

For me, I work back ass wards...

Each top ( billet in my case ) is examined (planed sanded and scraped, smelt and tasted) while I am talking to and with the wood, listening to what she says back to me (its kind of an intuitive thing I picked up back in the sixties) then I decide what and how be the best way to put that billet to use.

In other words ... I let the wood determine whats gonna be built.

Then of course , I occasionally get a notion in me head to build a this that or another... so then I approach the wood with this set of criteria when talking with it to decide which billet is best to use.

This rather unorthodox approach ain't for the anal retentive type builder who rely on plans, drawings, measurements and uses calipers measuring everything in thousandths. It only comes with experience and having no qualms about building fancy fire wood.

When I remain true to communion with the wood, things work out...even when I have found internal knots, runout and pitch pockets....that still voice inside has never lead me astray. But boy have I messed up when I don't listen.

And ya, this post don't directly answer your question...but after you been building a few dozen or so...maybe, just maybe you might get the gist of me drift.

Guess what me trying to say is...listen to all the different ways and suggestions offered in choosing,
then follow your heart in making your choice.


Blessings
the
Padma

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Audiences and dispensations on Thursdays ~ by appointment only.


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Al, that is a great response!!! I learned alot from that post. I'm very appreciative you took the time to write out that detailed post. Thanks!

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Formerly known as Adaboy.......

I appreciate everyones responses. I'm learning a great deal and appreciate you sharing your point of view.

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Formerly known as Adaboy.......

I learned One important thing about selecting raw, rough cut soundboard blanks for "Stiffness"....

The Cube Rule is at play..... in a BIG way.

In general, it seems like raw soundboard halves are *All over the place* thickness wise.... especially if you don't buy them from a Stew Mac or LMI sort of company....

I have found the raw incoming thickness can vary ~200% (I have gotten halves as thin as 0.140" and as thick as 0.250")

What this means... A 0.200" thick rough cut ultra light, floppy, soft top will be far stiffer than an Ultra-dense top rough cut at 0.140"...

I think this is probably part of what Al has experienced when he asked for "Ultra light and soft" Englemann and got Ultra hard, Dense Englemann.... The soundboard fellow flexed and picked the least stiff sets..... which were actually the THINNEST... not the least dense.

Thanks

John