- 1 year ago
In this thought-provoking video, Luthier Tom Sands delves deep into the world of acoustic guitars and tackle the age-old question: "Is Master Grade wood worth the investment?" Join Tom as he uncovers the truth behind master grade wood, comparing spruce boards of each grade with a series of tests which you can replicate at home. He dissects the myths and facts surrounding master grade wood, providing you with expert insights to help you make an informed decision before your next guitar purchase. Whether you're an experienced musician or a beginner, this video is a must-watch for anyone considering a premium acoustic guitar.
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MusicTranscript
00:00There's so much mystery regarding grading woods,
00:03especially master grade,
00:04and today we're going to get to the bottom of it
00:06with a series of experiments.
00:08We're going to do some science.
00:10So firstly, what is wood grading?
00:12Wood grading is how we categorize
00:15the quality of a wood set.
00:16Typically we see four or five grades
00:19or bands from suppliers which are A,
00:21double A, triple A, master grade,
00:23and sometimes exhibition grade,
00:25master plus, or collector grade,
00:27or something like that.
00:28The thing is, everyone grades their wood differently.
00:31Most suppliers will rate their wood
00:32based on their visual characteristics,
00:34but the big question,
00:35do these traits correlate to the quality of the sound
00:38or produce in a finished guitar?
00:42Today, we're going to find out, so stick around.
00:45All right, so we have five pieces of alpine spruce
00:49from one supplier.
00:50We've got an A grade, double A, triple A,
00:52master grade, and master plus, or collector's grade.
00:56So let's have a look.
00:57First up is our A board.
00:59This is a very affordable piece of wood.
01:00As you can see, it's got quite uneven, wide grain.
01:04The color is not perfectly even.
01:07There's a little bit of run out,
01:08but for the money, can't go wrong.
01:12Next up, we have the double A,
01:14which is slightly tighter grain.
01:17The grain is slightly more straight,
01:18but very, very similar to the previous A grade board.
01:22Next up is the triple A.
01:24This is a big step up, in my opinion.
01:27I think this board cost me about 90 euros,
01:29and I think it's really, really good value.
01:31Has notably straighter grain, way less run out,
01:35and the color is nice and even too.
01:38Moving on to the master grade.
01:40This is really beautiful, no question.
01:43There's little to no run out whatsoever.
01:46The grain is arrow straight, and it has great color.
01:50So finally, we have the master plus,
01:52or the collector's grade,
01:53and this really is as good as it gets.
01:56And you would expect as much,
01:57because this top costs 10 times
02:00what the A grade top cost.
02:03It is really gorgeous.
02:05Grain density is beautiful.
02:07There's figure in there.
02:08The medullary rate is perfect.
02:11It really doesn't get any better than this.
02:14So yeah, if I was grading these soundboards on looks alone,
02:17I would definitely agree with the supplier's designations.
02:21But which one performs the best?
02:23Before we get into the numbers of it all,
02:25let's do a little blind test, shall we?
02:28All right, so my beautiful assistant here, Mr. William,
02:32has mixed up these boards, numbered them from one to five,
02:35and I'm going to order them from best to worst
02:36based on tapping and flexing.
02:38Get ready in the comments to write your order too
02:40if you want to test out your lutherie prowess.
02:42No cheating.
02:45Wow.
02:48Wow, okay.
02:49So I feel like we need some elevator music or something
02:52to come on while I'm doing this.
02:55Ah.
03:00Wax eight.
03:03Ooh.
03:17Sounds pretty good, but it's really floppy.
03:22Feels a bit stiffer.
03:26Sounds better.
03:28I'll leave that one there.
03:35A bit floppier, a bit stiffer across the grain.
03:49It's so hard to...
03:56I'm going to put this one here.
04:11Let's roast it.
04:20Put that one there.
04:25Ooh.
04:32It's amazing how similar they sound.
04:41All right, I feel like this is the stiffest.
04:44Quite floppy across the grain.
04:51Feels quite light too.
04:55Ooh.
05:03Doing it very quickly, but
05:07I think I'm going to go with that order.
05:10I think.
05:11I don't know.
05:12Okay, so this is really interesting.
05:14Just looking at these, I can't see the grading,
05:16but it's kind of gone in the opposite direction
05:20to what I might have expected.
05:22So in the board I would use last is the Master Plus.
05:28Can you believe it?
05:31All right, so in last place is the Master Plus.
05:35Then we have the AAA.
05:41Then we have the Master.
05:44Then we have the AA.
05:53Single A is in first place for me.
05:57Wow.
06:00Wow.
06:02I agreed with the visual grading,
06:04but from a sonic and flexing perspective stiffness,
06:10I reverse ordered them.
06:14We need to go a little bit deeper.
06:15Let's dive into the numbers.
06:17I'm going to show you how to assess
06:18the properties of the boards
06:19a little bit more scientifically.
06:22All right, so long story short,
06:24we want our soundboards to be light and stiff.
06:27Light or less massive,
06:29so it takes less energy to get the board moving,
06:31and stiff so we can take the board down in thickness,
06:34further reducing its mass
06:35while maintaining its structural integrity.
06:38And I have to say,
06:39this is largely why I was drawn to these boards.
06:42They were very light and very stiff.
06:44At a basic level,
06:45we can assess stiffness to weight ratio
06:46by measuring the density and the deflection.
06:49So let's do that with this A board,
06:52and we'll compare results at the end.
06:56Okay, so the way that we calculate the density,
06:59super simple, is to divide the mass by the volume.
07:02The way we get the volume is to multiply the length
07:05by the width by the thickness.
07:07I've gone ahead and cut all of these boards
07:08to the same dimension,
07:10which is 545 long, 210 wide, and four mil thickness.
07:15So our calculation is going to be 0.545 by 0.21 by 0.004,
07:21which gives us a volume of 0.0004578 metres cubed.
07:29Seems like mass has gone a little off here,
07:30but I promise you it hasn't.
07:32Next, we want to take the mass,
07:38which comes out at 184 grams.
07:42So in kilograms, that's 0.184.
07:45So our final calculation for density is 0.184
07:48divided by 0.0004578,
07:52which gives us a density of 401.92 kilograms per cubic metre.
07:58That is mass.
08:04All right, now for deflection.
08:06Deflection is a degree to which
08:07a structure is displaced under load,
08:10which in layman's terms means
08:11how much the wood will bend when we put a weight on it.
08:15This is going to give us an idea
08:16of how stiff each piece of wood is,
08:18and as we say for a soundboard,
08:20the stiffer, the better,
08:21and that applies to many things in life.
08:24So we've made this glorious contraption here.
08:28We're going to raise our piece of wood up on both ends.
08:31We're going to take our dial indicator.
08:34We're going to take our one kilogram weight,
08:35place that in the middle,
08:37and we can see that the board
08:39is deflecting by two millimetres.
08:41So for this A-grade soundboard,
08:43we have a density of 401.92 kilograms per cubic metre
08:47with a deflection of two millimetres,
08:49and you can do these tests really quickly
08:50and easily on your soundboards at home
08:53to get a good idea of how they'll perform,
08:55but before comparing the results in full,
08:58I want to do one more test
08:59to take the experiment even further
09:02and get even more delicious data.
09:05This next test is taken from this outstanding book,
09:08Mastering the Sound of an Acoustic Guitar
09:10by Giuliano Nicoletti.
09:13Get this book.
09:14Link's in the description.
09:15It's a game changer.
09:16The book comes with an accompanying spreadsheet,
09:19which is going to help us with our calculations.
09:22So we're going to use
09:22some frequency spectrum analysis software
09:25to measure how these soundboards are responding.
09:29Before we get into the experiment,
09:31we're going to talk quickly about nodes and modes.
09:33We're going to use the example
09:35of a 12th fret harmonic on the guitar.
09:38When you play the 12th fret harmonic,
09:40you're going to be isolating the node point on the string
09:43so that the overtone becomes primarily audible.
09:46What you're hearing when you hit that 12th fret harmonic
09:48is the second mode of the string.
09:51And furthermore, playing the harmonic
09:53as opposed to fretting the note at the 12th fret
09:56means that you're isolating the mode
09:59without interfering with the vibration
10:01of the string as a whole.
10:02The opposite of a node is the antinode.
10:04It's the point at which the sound wave,
10:06or in this case, the oscillation of the string,
10:09is at its peak.
10:10And the node is where it's at its lowest.
10:12So when we do the tap test,
10:14we're going to hold the piece of wood from a node point
10:17and to produce the different vibrational modes,
10:20we're going to strike or tap or hit the piece of wood
10:24at an antinode point.
10:25Think of it like we're playing different harmonics
10:27on a guitar string.
10:29With Giuliano's experiments,
10:30we're going to analyze the three vibrational modes,
10:34the long bending mode across the length of the board,
10:38the cross bending mode across the board,
10:40and the diagonal mode from corner to corner.
10:43Thankfully, using Giuliano's spreadsheet,
10:47it gives us a template as to where
10:49the approximate location of the nodes
10:52and antinodes are going to be.
10:54So we know where to hold and where to strike.
10:56Using the FFT software,
10:59we're going to take the frequencies produced
11:01and plug those into the spreadsheet,
11:03which is going to calculate,
11:05it's all magic.
11:06It's not magic, it's maths.
11:08It's going to calculate the modulative elasticity,
11:11which is a figure that describes how elastic the boards are.
11:14And it'll also, as if that wasn't enough,
11:16it'll give us a sound radiation coefficient.
11:20I know.
11:21So long story short,
11:22the higher that number is, the better,
11:25as it means it takes less energy
11:27to excite the monopole of the soundboard,
11:30which is the key frequency
11:32in determining the character of the guitar's voice.
11:34The software is free.
11:35The mic I got from eBay.
11:37They are both referenced in the book,
11:39so don't panic.
11:40First up, we're going to measure our long bending mode.
11:43I'm just going to do one of these measurements
11:46just to show you quickly.
11:48We're going to hit record.
11:51Let me tap here.
11:58So you can see pretty quickly
12:00that we get a peak.
12:02So I'm going to take that 75 hertz.
12:06I'm going to plug that into
12:09the column for the long bending mode.
12:13And I'm going to go through all of these boards.
12:16I'm going to measure them in three different locations.
12:19I'm going to put all that data into the spreadsheet.
12:22And why don't I just see you at the end?
12:24Because it's going to be pretty dull to watch.
12:28So that is it.
12:29The results are in.
12:31And we're going to start with the densities
12:33from most dense to the least dense.
12:35And remember that generally speaking,
12:36the least dense is the better.
12:39Fifth place, our A top,
12:43the most dense.
12:45Then it's our AA.
12:46Then it's our AAA.
12:48Then it's our master grade.
12:49And then it's the collected grade,
12:51which is the perfect result, really.
12:53It's pleasing to see that the density,
12:56which is such a key metric,
12:57correlates to the supplier's grading.
13:01So we've got the deflection and the elasticity.
13:03Again, the stiffer the better.
13:05We have, in first place, the most stiff is the A grade.
13:10Then in second place, it is the master grade and the AA.
13:14Third place is the master plus.
13:16And in fourth place, bringing up the rear,
13:18is the AAA.
13:20So this is the really interesting bit.
13:21We can see that the more dense woods
13:23appear to be the stiffest,
13:25with the exception of the master grade tops,
13:27which sneak into second place and third place.
13:29It gives us a rough idea of how stiff a board is.
13:31The way we measure for modulus of elasticity
13:34using frequency analysis is far more accurate.
13:38If we look closely at our results
13:40for modulus of elasticity,
13:41we can see this clear trend.
13:45A having a long modulus of 11.1 gigapascals,
13:49AA is 10.8, AAA is 9.1, master grade is 9.2,
13:54and master plus has a long modulus of 8.8.
13:59So finally, the sound radiation coefficient score.
14:02They all scored 13.
14:04They all scored exactly the same.
14:07So at the end of all of that, which is the best
14:09and which would I choose?
14:11What have we learned?
14:13It would appear that from this selection of five tops,
14:16the AAA is hitting the sweet spot.
14:19It's stiff without being too dense,
14:20it's got a good sound radiation coefficient,
14:23it's great value for money, and it looks awesome too.
14:26For this sample of five, it would seem that master grade
14:30is largely an aesthetic metric.
14:32That being said, I've just tested another board
14:35from a different supplier.
14:36This is a master grade board,
14:37and it blows these boards out of the water,
14:39both in terms of aesthetics and performance.
14:42So it just goes to show you
14:44that it's who's grading the wood
14:45and which parameters they're assessing
14:47is really what matters.
14:48Empirical data is important, measuring is important,
14:51but so is the age-old practice
14:53of the traditional assessment
14:54using intuition and experience.
14:57When we tap a piece of wood and listen,
15:00we're measuring the vibrational modes.
15:02When we flex a piece of wood,
15:03we're assessing its density and its elasticity.
15:06But by doing the scientific and the intuitive work in tandem,
15:11objective and subjective assessments will converge.
15:16So what is master grade?
15:17For some, it's just a pretty face,
15:19but to me, it needs the numbers to back it up.
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