Official Luthiers Forum!

so i just got a student grade sound board from rc tonewoods. To me, it looks as good or better than anything i have ever made. Nice ring count, feels pretty stiff, nice color. Im thinking what a bargain. Except what am i missing? I guess i really dont know much about choosing sound boards. So far i have chosen full boards that show a good ring count and clean grain and resawn them myself. What goes into grading? Can i expect a decent guitar from this sound board? Btw great price, fast shipping thanks rc.

Usually it's pure cosmetics. Some of my nicest tops are grade 'B' stock (or equivalent), simply because they have a bit of color and slightly irregular (not super tight) grain lines. The 'bargain box' of lower grade Lutz tops I got from Shane several years back has made me very curious what he considers master grade, but I don't really need more tops right now. Although I did recently notice about 1/3 of my stock is bear claw....

I personally like character in my guitar tops. A bit of color is a good thing.

What I look for in a top is:

How well quartered the top is?

A well quartered top will show strong medullary ray (once sanded. Harder to spot when rough). More visable medullary ray usually makes for a stiffer top which makes for a better stiffness to weight ratio.

How much grain runout is there?

You can often see the runout by looking at the edge of the top. You will see a sharp angle in the grain running from top to back. If the top pieces have been sanded you can hold the book matched pieces together and look at light reflected off the surface. If they appear to be lighter or darker on one half than the other, it's a pretty good indication that the top has excessive runout (Chatoyance).

Anyway, that's my 2 cents..

Cheers, Michael

Check out what John Greven has to say on the subject. http://www.grevenguitars.com/voicings.html
Tom

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

What Michael said.

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Mike Collins

I think all of us who are Shane's usual customers all have one or two guitars made out of Shane's packing material!

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Alain Moisan
Former full time builder of Acoustics, Classicals and Flamencos.
(Now building just for fun!)

Well, not always. One can expect to get more runouts from a lower grade top. And it is believed by some of us that runout does affect sound.

One thing that is for sure is that grading is absolutely not standardized. Two AAA tops from two different vendors will quite probably be very different.

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Alain Moisan
Former full time builder of Acoustics, Classicals and Flamencos.
(Now building just for fun!)

Our spruce supplier is also very stringent on his grading. Sometimes when we get in a batch of student grade soundboards in I can't believe how nice some of them are. The main difference is purely cosmetic. Glad you like yours Bybee.

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Beautiful and unusual tone woods at a reasonable price.
http://www.rctonewoods.com/RCT_Store
The Zootman
1109 Military Rd.
Kenmore, NY 14217
(716) 874-1498

You know what? I've compared tops I've sawed out of the same billet and they were different.............. Woods amazing

The main things I do look for is Run out and internal flaws like pitch pockets. You really can't learn a lot about a top by tapping on it , other than it isn't cracked. . Runout I think is more of a tone killer and grain width is not always a bad thing.
I do agree most grading is more based on visual than tonal properties. Martin used a light table to do the grading , and the one thing that will reject a top is runout and the other id pitch pockets.
I have used some pretty ugly tops learning this trade and one thing , I feel matching the braces to the top is a big plus. One of the reasons I go by deflection testing.
RC has always treated me well. Can't go wrong with the Zootman

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

Hi John, what is a pitch pocket? Have not heard that term before.

Thanks

Ed

[quote="bluescreek"] You really can't learn a lot about a top by tapping on it , other than it isn't cracked.


John: I have to disagree with you. Listen for musicality, look for sustain, look for a willingness to ring. Some tops sound like crap, some sound like a beautiful church bell and most are right in the middle. The thing is most dealers don't select or grade in this direction. And that was not meant as a put down.It's just that most folks are more cocerned with looks.
Tom

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

Tom it's virtually impossible to grade by tapping. What I hear and what someone else hears could be totally different. If a customer request that we tap then I will and explain what I hear. What's good for the goose ia not always good for the gander.

_________________
Beautiful and unusual tone woods at a reasonable price.
http://www.rctonewoods.com/RCT_Store
The Zootman
1109 Military Rd.
Kenmore, NY 14217
(716) 874-1498

Bob: Not sure if your saying for yourself as a supplier or me as a builder. I find it strange that folks will exalt the tap tone of various sides and backs but dismiss testing tops by listening to the tap tone. Brazilian Rosewood comes to mind. Some people will go to almost any lenght to get BRW because of it's tap tone and it's willingness to ring(Todd's scratch test for tops) and the fact that just rubbing the wood over adjacent pieces one can feel them vibrate. The very essence of a guitar is vibration,and the vast majority of the vibration takes place in the top. For me then I want to look for top wood that wants to vibrate and move air. My experience is that most of my better sound guitars have been made from tops that I considered above average especially in resent years.A more consistent approach to building as I move along??? This also takes into account weight to stiffness,quarter and runout along with listening to tap tone. Some analysts might say that I have been preprogrammed to get this result just by my own thinking. Could be, I do know I try to take advantage of every possible thing to help me along. Others might say that the guitars would be just as good if built from what I would say was lesser quility wood. There in lies one of the biggest rubs in building guitars,how does one prove that,we can't flip a switch and listen to other tops on the guitar or compare similar guitars because there are just too much variability in the building process and the various woods themselves. As Bob says maybe one can't use tap tones as part of the grading process. But no one will convince me that I can't and I feel sure lots of other folks use tap tones for grading. Enough of the rant for today.
Tom

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

From what I've read Trevor Gore derives the final thickness of a top by tapping on it and recording the frequency response, to determine the modulus of elasticity. The pitch tells him how thick or thin he needs to go for his particular bracing scheme.

He may pop on and correct me if I'm wrong, but it seems he keeps his bracing the same and matches the top to his parameters, the other way around from what most people do, which is pick a top and modify the braces to a target.

Tapping the top in this case tells him everything he needs to know.

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Old growth, shmold growth!

Also, for what it's worth, Here's what I would consider a perfect top for my purposes:



It has fairly straight and consistent grain lines, it has even and consistent medullary rays across the entire face, no pitch pockets anywhere, and it has some beautiful red striping and other "wood" features that add a ton of character. It lays perefectly flat with no cupping or twisting, and it's SUPER lightweight while being very stiff, which seems to be characteristic of Lutz spruce. It's also nearly perfectly split with zero long grain runout when viewed with a jeweler's loupe. I ordered this special for a dreadnaught I'm building for a California guy.

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Old growth, shmold growth!

Part of my time at Martin was spent in the wood grading department. All of their criteria (at least back then) were visual, and assigned numbers from 1 through 8 depending on several factors. The main criteria were evenly spaced annular rings, minimal color variation, and when candled no "sap lines" or "sap pockets" could come near a part that would actually become part of the top when cut out. Passing all of these criteria will generally be enough to have a 3. Uneven annular rings and color variation appear in the 1's and 2's. The standard basic models usually get a 3, and increase for fancier models or can be special ordered to a higher grade for a couple hundred bucks. As the annular rings become more even and tightly spaced, the grade increases, while medullary rays (aka silking) appear on the higher grade tops. By the time you get to the 7's and 8's you're splitting hairs because even a 6 is their normal premium grade.

Generally unknown to the public are the 8+ grade tops, which are reserved for special builds. Generally speaking they are used on instruments that are being built for a well known artist, employees who are friends with the grading people, or other special builds. I have such a top on my custom HD-28V, and it has ~30 annular rings per inch and tight medullary rays over the entire top. When I worked there back in '00 they were producing about 60k guitars per year and had a couple hundred grade 8 tops and only a dozen or so 8+. When picking out the 8+ for my custom it was honestly ridiculous because they were difficult to even tell apart from one another. But then again, we're talking about the top 0.05% of everything they have. As far as the all important topic of tone is concerned, structurally sound tops all sound pretty good or are at least capable of it. In my experience the higher grade tops are simply more consistent and less likely to have a different tonal character from top to top as the lower grades tend to exhibit. Considering than uneven annular ring spacing will produce uneven density and strength/weight ratios across the board that's not much of a surprise. However, there is no question in my mind that bracing has a much more pronounced effect on tone, balance, harmonics, etc. than any other variable.

Yes, I'm more than a little bit proud of my Martin so here are a couple of pictures.

Here is a nice close-up of the grain. For reference, if anyone is interested, I can scan some of the pictures I took of the wood before it was made into my guitar. I might actually just scan a bunch of them in sometime since I was allowed to take pictures of areas not accessible to the general public or even most of the employees. As you can see the picture is centered on the bookmatch. Symmetry in the bookmatch becomes more of an issue during the hair-splitting process.




And a wider shot of the entire instrument.

I'm sure your custom Martin is a great guitar, but I'm not sure what the primarily cosmetic criteria for judging tops had to do with choosing a good top. What about cross-grain stiffness measures, and so forth?

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Jim Kirby
kirby@udel.edu

Five or six years ago I was talking to an USA supplier of Tonewood who specializes in Carpathian spruce. He related to me that he has a well know builder who comes to his location to select tops. He said this person blindfolds themself and then proceeds to select his tops. The wood he goes through has already been graded by the supplier himself for such things as runout, quarter, defects,looks, etc.
He said this builder will go through the various grades selecting tops based on weight,stiffness,and tap tone. This way he is not influenced by the looks of the wood. The supplier did not relate to me if there was any reselection after the blindfold came off but this disscusion reinforced with me the importance of using tap tones to evaluate wood. He never did relate the name of the builder.
Tom

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

I'm also on the side of those who think you can not get a lot from tapping (I mean just by listening to the tap tone).

I haven't found yet a well quartered, no runout, nice density board that did not tap to my satisfaction.

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Alain Moisan
Former full time builder of Acoustics, Classicals and Flamencos.
(Now building just for fun!)

That's the abridged version, of course!

As mentioned in another current thread here, tap testing tops gives you the same data as deflection testing, just more quickly. So you can compute long, cross and shear modulus and use those numbers in another equation (derived by a guy who was testing wood for aeroplanes during WW2) to figure out the thickness you need to reduce it to to get a consistent performance irrespective of the material properties. So the process takes one of the great imponderables (how thick should I work this piece to?) out of the game. I use this approach because I use CF in most of my bracing, so I don't like to mess with the bracing once it is installed. There's then a suite of trimming processes that I use during the build so that I end up with the modal resonances I want. It's the modal resonances that essentially define the sound of the guitar.

I did a whole lot of correlation testing between tap sound as I hear it and log. dec. (damping or "Q') and found that I could rank wood quite successfully by ear with respect to log. dec., even with rough sawn wood. But it's very much harder to get a good handle on stiffness just by feeling the wood and as Al C. and I are both wont to say, people think they are much better at it than they actually are. I know I can't do it very well just by feel, because thickness is such a large part of the equation. So when I have the luxury of selecting wood personally (not enough top tonewood suppliers here to allow that!) I look for good quarter and low long grain run-out (which has been correlated to damping (Schleske, 1990 iirc)), listen to the tap tone and avoid those with obvious defects. Then out of that pile I select on cosmetics, confident that I can get a decent guitar out of anything from the pile. To test for the elastic properties you have to work the wood, however you test, so you have to buy it first, generally on a no returns basis. So I still get wood with a variety of material properties but all that is compensated for when I get to measure its properties. The difference between really good wood and not quite so good results in a small difference in top panel mass and so a not quite so responsive guitar. But when the factories set the bar as low as they do, it's very hard for most people to pick the differences between my guitars compared to the difference between one of mine and a factory instrument.

Building classicals is harder because the bar is so much higher due to the prevalence of luthier built instruments. So you need your best wood and a following breeze to get into the higher echelon.

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au

In my limited experience, good tap tone on a top is more a function of the thickness of that piece of wood than anything else.

Perhaps if all the pieces you are grading are the same thickness and size then taptone might tell a story.

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Joe Beaver
Maker of Sawdust

Jim-

I actually had extensive conversations with R&D on the topics of top and side selection as well as tap tuning. The cosmetic factors tend to be strong indicators of mechanical and acoustical properties. Wood science backs up the reasons for this. While valuable information can be gained from measuring modulus and weight ratios, it does not appear to be necessary. For fun I did check the tap tones while selecting the wood for my guitar but they were effectively indistinguishable. I like to think I have a good set of ears. During my time at Martin I took part in several playing tests. I was also accepted to some of the top conservatories in the country along with healthy scholarship offerings. Not trying to toot my own horn, just trying to qualify my credentials. The best back and side sets for rosewood were invariably the most dense and oily. Part of the theory there has to do with maximized mineral and oil content.

Martin also experimented with tap tuning during the mid to late 90's and found that the scalloping process they've used for so long (and takes all of 10 to 15 minutes in experienced hands) sounded just as good through hundreds of playing tests. I personally chalk up the minor tweaks that might make a 1% difference to the overall tone of an instrument as insignificant (although I'm by no means disrespecting luthiers who take the time to tweak every last aspect to perfection.) The reason is that fingers and playing technique contribute more to tone than subtle tweaks. Anecdotally, I found this to be very true from my time in music school. After recitals it was common for people to ask me who built my classical and what it cost... All I was working with at the time was an Alvarez Yairi that cost all of $1000. A lot of snob appeal goes on in the world of stringed instruments (more so than any other type I've encountered.) I happen to be a very firm believer that once a certain minimum level of quality is achieved, the rest is due to the performer.

Hugh: Not sure what you are saying here. Wonder if you could expand?
Tom

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

Tom I'm talking about me as a supplier. If I'm building I certainly would tap.

_________________
Beautiful and unusual tone woods at a reasonable price.
http://www.rctonewoods.com/RCT_Store
The Zootman
1109 Military Rd.
Kenmore, NY 14217
(716) 874-1498