Size of Soundbox and Loudness

Matt Berg
Matt Berg
@matt-berg
yesterday
62 posts

Funny, I showed my instruments to Butch a couple years ago at Evart.  I guess he remembered.

Bob Stephens
Bob Stephens
@bob-stephens
2 days ago
12 posts

That is interesting.  Butch Ross mentioned the concept in our last meeting and I have it on my list of things to learn more about.  My latest steel string design seemed to sound best with no soundhole and I have been wondering if the rounded back would still work.  I guess I will have to try it with and without a soundhjoe and see how it turns out.

Matt Berg
Matt Berg
@matt-berg
2 days ago
62 posts

Yes, the rounded bottom seems to focus the sound back to the soundboard.

Bob Stephens
Bob Stephens
@bob-stephens
2 days ago
12 posts

Your bracing is very similar to the Taylor V bracing.  I have attached a photo of the bracing used on the dulcimer that Butch Ross is getting.  I refer to it as parallel bracing.  It is used with strings terminating at the bridge like a guitar.  On my dulcimer it yields a rich tone with a strong bass response.  

The next photo is of the dulcimer for Aaron O'Rourke.  It is a modified X-braced pattern that has more attack and is less bass focused.  I would say it is closer to a traditional dulcimer sound.

The remaining photos are of my newest design with strings that terminate at the end block.  Very close to the prior X- braced design with one small addition.  This is the loudest dulcimer I have produced (the one with the 0.100 soundboard).

Are you using a rounded bottom for more projection?

Matt Berg
Matt Berg
@matt-berg
2 days ago
62 posts

I use fan bracing that comes together at the head and spread all the way to the tailpiece.  With a double neck design, you need to have a more or less wide and flat tail piece .  With a single neck, generally just two braces.  With double necks I find four braces emphasize the treble, three helps the bass.  Similarly, straight bracing emphasizes higher pitches, scalloped bracing lower.  Haven't tried mixing them in one instrument. Pick your poison.

The picture shows a build in progress from a couple years ago.  You can see the fan bracing on the soundboard.  The X-bracing on the bottom is used so the bottom can be rounded.

inside.jpg
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Bob Stephens
Bob Stephens
@bob-stephens
2 days ago
12 posts

I am very intrigued by your solution to the problems of dulcimer design.  The fact that you found a way to improve volume and still retain the tone you were after is particularly impressive.  Are you using any bracing on the underside of the soundboard?  As far as bowing of the fretboard goes, you have effectively isolated it from the forces and torque that would normally cause it to bend by limiting its contact with the body to a very small area.  This is a significant improvement over most approaches.  

My latest designs use a violin style bridge, but in some cases I found I needed to alter the bracing pattern in order to obtain an acceptable tone.  In a few days I will be delivering new steel string designs to Aaron O'Rourke and Butch Ross, and another design to Aaron  that may be usable for both steel and nylon strings.  Interestingly, Aaron and Butch chose instruments with quite different tones when presented with prototypes, which supports the theory that there is no one perfect design.  I am anxious to hear what each of them do with the dulcimers.  Aaron and Butch are about as far apart on the technique spectrum as you can get so it will be an interesting comparison.

Matt Berg
Matt Berg
@matt-berg
2 days ago
62 posts

The neck rests on a single post under the 0 fret.  The maple fretboard rests about 3/4 from nut to saddle on a bridge on the soundboard.  The strings are set to pull down at a 15 degree angle causing both a bowing down and bowing up tension in the fretboard.  I have been using this technique for about 5 years and have not seen any deforming of the fretboard.

I tried using violin style bridges, bridges that stand alone on the soundboard, but felt too much of the unique dulcimer sound was lost.  Using a fretboard that runs from nut to saddle restored the unique dulcimer sound.

And, yes, the voices of my instruments are much stronger than other dulcimers.  The bass in particular is able to cut through the buzz of a jam, especially when flat picking.

dulci-peg.jpg
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Bob Stephens
Bob Stephens
@bob-stephens
4 days ago
12 posts

Matt, Thank you for posting your recent build.  Not only does is show your excellent workmanship, it has some interesting design features.  I am happy to see others getting the neck up off the soundboard.  We might be starting a revolution.  Could you further explain “single peg”?  I also see that you are interested in bass dulcimers, which is great.  There is a lot of opportunity for improvement in both baritone and bass dulcimers.  The elevated neck will be a big benefit for the lower frequencies as I am sure you realize.  I put bass strings on one of my new steel string designs recently and was pleasantly surprised at the result.  It too had an elevated neck and modified X bracing.  It sounded great when Aaron O’Rourke played it, but he could make a peach crate with a wire stretched over it sound great.  I am building one for a client that will be ready soon.  

I do not sand my soundboards to a set thickness.  I attempt to sand them to a known stiffness, letting the thickness be the variable.  Each soundboard is tested for deflection with 12” hanging over the bench and a known weight put on the end.  I then sand until I reach an established deflection.  It is surprising how much the thickness varies even within a species.  I have seen thicknesses form 0.140 to just under 0.100 with one very stiff piece of Port Orford Cedar.  This is a very large range when you consider that the stiffness varies with the cube of the thickness.  Put another way, if you sand to a set thickness you will have widely ranging stiffnesses (and therefore volume and tone).   If you are interested in this sort of thing, I highly recommend “Left Brain Lutherie” by David Hurd.  It is a bit technical for some, but you don’t have to be an engineer to get some useful information.  The book is written for guitar family instruments, but most of it is transferable to dulcimers.

Matt Berg
Matt Berg
@matt-berg
4 days ago
62 posts

Bob,  you mention that your recent soundboard was thinner than typical at 0.100 inches.  My general target for the soundboard is 3/32, roughly 0.100.  Depending on the ping of the wood, I may stop earlier.  What is your general target for soundboard thickness?

(The attached picture is my current build.  You can see the thickness of the soundboard which is made from recovered white cedar.  All of my builds have the neck suspended over the sound board on a single peg and a true bridge.  This is a double neck, treble and bass.)

dnbuild.jpg
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Bob Stephens
Bob Stephens
@bob-stephens
one week ago
12 posts

Nate,

You always have such great questions.  I wish we had more answers that we know to be absolutely true.  I have a few thoughts based on a recent dulcimer that I just completed.  This is the loudest dulcimer I have ever built by a considerable margin.  It contradicts almost everything I thought I knew about how to make a loud dulcimer.  Since my instruments are non-conventional in design, these comments may not be of much value.  The entire top of the dulcimer is free to vibrate independent of the fretboard since the fretboard is held above it on posts from below.  The top is western red cedar and is thinner than is typical for my dulcimers, about 0.100 inch.  It is braced from below with a modified X-braced pattern.  The strings terminate at the end block.  The bridge just sits on the top.  So acoustically, it is very similar to an X-braced flat top mandolin.  As an aside, mandolins prove that size is not the key factor in making a loud instrument.  This dulcimer also has a double back, which I am pretty sure helps the volume- especially if you play with the dulcimer in your lap.

The big surprises were that this string configuration was louder than terminating the strings at the bridge- guitar style.  One would have thought that the torque put on the top from the guitar type bridge would generate more volume than the slight downforce from the mandolin arrangement.  Apparently not.

The second unexpected result was that blocking off the soundholes completely made no perceptible reduction in the volume.  So there goes the large soundhole theory.  Blocking did affect the tone, however.

I think you are on the right track to keep the vibrating mass as low as possible.  I don't think the total weight of the dulcimer is all that important.  The more soundboard you can get into play will likely help too.  Fretboards that are in contact with the top for its entire length put severe limitations on volume and tone.  I know that this is the way it has traditionally been done, but if you want to break away from result that is typically achieved, you will probably have to strike off in a new direction.  I applaud your attempts to push the envelope.  Please continue to push the rest of us and share your results.

Ken Hulme
Ken Hulme
@ken-hulme
one month ago
1,769 posts

Steve, welcome!   We look forward to insights from everyone.  As you mention, the dulcimer creates its sound differently than the guitar. 

Changing out a hardwood top for a softwood one seems like it would work, but doesn't really since there is so little top to vibrate.   What works much better, IMHO, is to completely free the back to vibrate -- hence the "false bottom" of the Galax style instruments mentioned below.   

A lot of guitar builders come to the dulcimer and try to apply guitar style bracing on the top and back.  Which does nothing, of course, except make those surfaces even more stiff and less sound producing!  With dulcimers, fewer braces are generally better.  That big brace on top can be massively hollowed, and arched to cut down on overall mass, but for conventional "on the lap" play it needs to be a minimum of 1/2" deep for Chord-Melody style play.  We Traditional players want a fretboard closer to 1" high so there is room for fingers to clear, but also like narrower fretboards since we are fretting only one string.

It's not sacrilege to consider moving at least the bridge inboard, and some builders bring it quite far in.  The nut is harder to move inward unless you restrict construction to flat guitar style tuning heads.  If there is "too much" dulcimer beyond the nut and bridge, balancing the instrument on your lap can become an issue.  

Steve Denvir
Steve Denvir
@steve-denvir
one month ago
3 posts

Some thoughts, and some caveats. I come at this as a guitar maker. I’m just in the process of putting a tung  oil finish on my first dulcimer.

Having established that, I think that appreciably changing the volume of a dulcimer would be very difficult.

A guitar’s volume is a function of its responsiveness. A small guitar can be every bit as loud as a large one. Responsiveness is determined by stiffness and density of the top, and the stiffness of the bracing.

Stiffness and density? That’s why guitar makers use softwoods like sitka spruce and red cedar. The greatest stiffness with the least weight.

So I’d suggest that the first thing you do is sub out the traditional North American hardwood top for a good, stiff softwood.

But you still have this monstrously large brace running the length of the instrument. The fretboard. And make no mistake. It is a brace. Can the depth be lessened? A lot? I don’t know, I’m still learning about how the instrument works.

But one thing that immediately strikes me. Both the nut and the bridge are over the respective end blocks. They’d do a much better job of activating the top if they were actually on the top, as opposed to being supported by a couple of hunks of hardwood. Would it be sacrilege to move both of them a few mm closer to one another?

Anyway, those are just a few thoughts, and worth exactly what you paid for them :-). Happy to listen to any arguments, cause as I said, I’m new at this.

Steve

denvirguitars.com

Dan
Dan
@dan
one month ago
117 posts

NateBuildsToys:

Dan:

I'm going to suggest a large Galax with heavy strings drawn up tighter than a banjo.......like a MawHee on steroids?



Hello Dan. Does 'galax' mean a dulcimer with a 'false bottom' or 'possum board?' Or is it the wide oblong shape that denotes a galax? I do not have access to any means to curve wood into the shape of traditional dulcimers such as a lozenge dulcimer, however if you are referring to the false bottom, I have been adding these with noticeable benefit!
Thanks, 
Nate

Like KenH said, elliptical, deep body and false bottom. (Built in possum board) I also put feet on the bottom of my false bottoms! I may look into one of these... just have to figure out what to call it?


updated by @dan: 07/09/20 03:19:19PM
Ken Hulme
Ken Hulme
@ken-hulme
one month ago
1,769 posts

Nate -- Dan is referring to the more or less traditional Galax shape and construction -- a deep-bodied elliptical (not teardrop) shaped body with a double bottom.  That sort of shape needs no special tools or anything to make the elliptical sides.  

Many builders today do not use any bracing.  The top and bottom are simply glued to the edges of the sides without kerfing even; especially with teardrop and elliptical designs.  

John C. Knopf
John C. Knopf
@john-c-knopf
one month ago
220 posts

Nate, I just wanted to increase the size of everything on that dulcimore by 3 times, to see what would happen.  I guess some tweaking is still in order?  The string material, for one thing.  Right now it's music wire, but maybe weed-whipper line might work better.

NateBuildsToys
NateBuildsToys
@natebuildstoys
one month ago
33 posts

John C. Knopf:

Nate, look at a mariachi guitarra quintet.  They have all sizes of guitar soundboards.  The largest is pretty BIG.

But then, a dulcimer is not a guitar.  "Uncle Eddie", the world's largest (and longest) dulcimer is not particularly loud for its size and soundbox volume.  Usually taller sides equal more bass response, and maybe more loudness too.  I think overall loudness is derived from several factors working together, such as wood thickness, bracing, design, string gauges and tension, etc.



Hello John. 'Uncle Eddie' is quite a sight to behold. Very cool! I am curious to know if in hindsight you feel some alterations could have produced more loudness for its size, since you say it is not particularly loud for it's size.

Also, I have been reducing my bracings more and more in favor of loudness and I think I have reached a point where I am sacrificing the longevity of my builds by making the bracing so minimal. Ditto for wood thickness. 
This leaves me to wonder which matters more for volume of sound; having a sturdy build with heavy gauge strings, or a very lightweight build with lighter strings so as to not stress it?

Would love some input 

Thanks,
Nate


updated by @natebuildstoys: 07/07/20 04:32:09PM
NateBuildsToys
NateBuildsToys
@natebuildstoys
one month ago
33 posts

Dan:

I'm going to suggest a large Galax with heavy strings drawn up tighter than a banjo.......like a Mahhee in steroids?



Hello Dan. Does 'galax' mean a dulcimer with a 'false bottom' or 'possum board?' Or is it the wide oblong shape that denotes a galax? I do not have access to any means to curve wood into the shape of traditional dulcimers such as a lozenge dulcimer, however if you are referring to the false bottom, I have been adding these with noticeable benefit!
Thanks, 
Nate

Matt Berg
Matt Berg
@matt-berg
2 months ago
62 posts

Nate,

Many things impact loudness, size of the sound box, thickness of the soundboard, weight of the strings, size of the soundhole and how hard the player hits the strings.

Matt

Dan
Dan
@dan
2 months ago
117 posts

I'm going to suggest a large Galax with heavy strings drawn up tighter than a banjo.......like a Mahhee in steroids?

Ken Hulme
Ken Hulme
@ken-hulme
2 months ago
1,769 posts

The general rule of thumb for loudness and 'baritone-ness' is that the larger the volume of the soundbox (not just width or length, but volume), the louder the overall sound... especially when accompanied by more than 4 or 5 square inches of sound hole.  

Size (square inches) of sound hole is important to creating volume.  There's a complex mathematical solution called the Helmholts Equation (Wikipedia has a good write up on the subject).  As a dulcimer gets bigger it needs more soundhole to let out the sound, and it's not a linear progression.  John's Uncle Eddie has soundholes that are scaled up from the originals, but it needs maybe almost twice as much area of soundhole to "let it all out".  If you are truly interested in maximizing performance, I think you'll want to find someone who can help you solve the Helmholtz equation specifically for the volume of the proposed body. 

Mass of the body isn't as important as you might think. 

Look at the traditional Tennessee Music Box -- roughly 4" deep, 14" wide and 26'-28" long, with planks (sides/top/bottom/back) averaging about 3/8" thick!   Usually on feet to allow the back to vibrate as well, and a solid (seldom hollowed) 2x2 freboard.   

Without a lot of "messing about", the simplest solution to a LOUD dulcimer is, IMHO,  to build something about the same dimensions as the Tennessee Music Box I described above.  Look at pictures of original TMBs to get an idea of how many soundholes/how much area of hole you'll need for something that size.  Then here's my suggestion.  Make twice as many soundholes as an original TMB of the same dimensions.  Then start blocking off holes two at a time, and see the effect on the sound. 

John C. Knopf
John C. Knopf
@john-c-knopf
2 months ago
220 posts

Nate, look at a mariachi guitarra quintet.  They have all sizes of guitar soundboards.  The largest is pretty BIG.

But then, a dulcimer is not a guitar.  "Uncle Eddie", the world's largest (and longest) dulcimer is not particularly loud for its size and soundbox volume.  Usually taller sides equal more bass response, and maybe more loudness too.  I think overall loudness is derived from several factors working together, such as wood thickness, bracing, design, string gauges and tension, etc.

NateBuildsToys
NateBuildsToys
@natebuildstoys
2 months ago
33 posts

Hello all, I was wondering how much loudness is affected by the size of the soundbox. I am trying to make an extremely loud dulcimer that doesn't rely on any metal cones, pickups, or microphones, and have been testing lots of concepts to try to get the most efficiency I can, but my understanding of the physics of acoustics is very limited. I assumed bigger means louder, but i would also imagine that the more wood which has to vibrate, the more energy is needed to get the whole box vibrating before it can project any sound. So it would make sense to me if a small box lets the energy be more concentrated and therefore agitate the air more, but it would also make sense to me that a bigger box is more wood moving more air and therefore more loudness. I really am out of my depth so I'd love some input. 
1: Is taller louder?
2: Is a larger soundboard louder?
3: Is there a size that is accepted to be loudest?

Also, I have reduced as much extra mass as I can off my last build with the most minimal bracing necessary to not warp or flex, a false bottom, an almost entirely hollow fingerboard, and a saddle that sits directly on the soundboard. Pretty dang loud but I want to leave no stone unturned so I am very open to more ideas for loudness.

Thanks!


updated by @natebuildstoys: 06/30/20 03:32:07PM