Tone qualities due to body size?

[red7flag]

I am curious if you constructed two say mandolins of the same woods top sides and back, same style F or A, identical necks including scale, with the only difference size of body. Say one had 2x the body volume. How would this affect the tone and sustain? Thanks in advance.

[William Smith]

I'd imagine it would be way different, louder more sustain but I'm no builder for sure.

[billhay4]

The size of the internal cavity of a mandolin is a major determinant of the loudness and sound quality.
Bill

[CES]

Louder with more sustain...

[Spruce]

The size of the internal cavity of a mandolin is a major determinant of the loudness and sound quality.

This instrument has really got me thinking about this very issue...
The mandolin section on this Girouard fanned-fret 10-string is astounding, and I'm wondering if the larger size of the body is the reason...??
It's just a killer mandolin...and the mandola ain't too shabby either...

[red7flag]

Spruce, I would love to play a fan fretted cittern. From what people have written here, including you, it looks stranger than it plays and with just a short period of adapting, play feels normal. So does yours have a mandolin or mandola sized body? Looks more like mandola, but hard to be sure from a picture.

[Tavy]

I'm going to disagree a little here: what it would sound like is a long scale octave mandolin with a capo on 12. IMO you will not see more sustain as such - that's primarily a function of other things (string length, string gauges, bridge break angle etc), it would also very likely sound a little odd - lots of overtones missing since the body resonance is no longer tuned to the frequency range of the instrument. You can certainly vary things a little, and IMO a slightly larger body combined with a larger soundhole so that everything still "works" sounds really good - at least for folky instruments, bluegrassers may need to look elsewhere... or not...

[JeffD]

How would this affect the tone and sustain? .

I bet its pretty complicated. Beyond the size of the internal cavity, there is the matter of the wood itself. The grain is spaced the same, but with a longer stretch between fixed points, I would imagine lots of vibrational things are affected.

[Spruce]

So does yours have a mandolin or mandola sized body? Looks more like mandola, but hard to be sure from a picture.

Yep, 'dola sized...

[Tobin]

I bet its pretty complicated. Beyond the size of the internal cavity, there is the matter of the wood itself. The grain is spaced the same, but with a longer stretch between fixed points, I would imagine lots of vibrational things are affected.

You're assuming the body is longer. I was assuming the body was the same size, but built deeper (i.e. taller sides), in which case it would be more apples-to-apples on the sound board and back.

[fscotte]

Gilchrist makes his body deeper. It lowers the resonance which lowers the timbre of the instrument.

[red7flag]

When I first started this thread, my thought was to try to make everything equal to isolate volume as the variable. I was just imagining the basic size expanding in all directions. I did not think of just making the instrument deeper and keeping the top and bottom the same. I am curious now how that dynamic would work. So much for trying to make a question simple.

[Tobin]

When I first started this thread, my thought was to try to make everything equal to isolate volume as the variable. I was just imagining the basic size expanding in all directions. I did not think of just making the instrument deeper and keeping the top and bottom the same. I am curious now how that dynamic would work. So much for trying to make a question simple.

Well, since you mentioned that the neck and scale length would be the same, there would be no way to simply scale-up the body without changing where the bridge lands on the sound board. In other words, as the body grows larger, but the neck and scale length stay the same, the bridge has to start moving on the top. That would definitely change things in the tone department. But increasing volume by simply making the body deeper would keep the bridge location the same. I guess I just assumed that's what you meant.

[Walt]

Two or three years ago, a famous picker (Darol Anger maybe?) was selling a one-off version of a Gilchrist mandola here on the Cafe. The body size was a lot larger than your typical H-4 style. The scale length might have been different too. There was some discussion at the time that it might have been one of the best mandolas ever built.

Does anyone remember that? It popped into my head about a month ago, but I couldn't track down any of the details. I may be misremembering some (or a lot) of the details. It might be useful for this discussion if we can track down some info.

[Walt]

Two or three years ago, a famous picker (Darol Anger maybe?) was selling a one-off version of a Gilchrist mandola here on the Cafe.

This might be it. It looks huge. It has "The Mandola" on the headstock.

[fscotte]

Here's what Gilchrist says about making the body a little deeper:

}...The resonant frequency of the air chamber of my mandolins have varied over the years from D# down to C#, but generally I pitch them a bit lower to thicken the bottom end and help deliver a little more complex and richer tonal response.


As you noted, you can do this by changing the depth of the rim. But the size and shape of the F holes, overall body size and profile of the plates also contribute to the resonant frequency of the air chamber. i.e., the amount of air contained within the box. The larger the air chamber and the smaller the f hole, the lower the frequency {snip}


Best Regards,

Steve Gilchrist

L.Gnotuk

South Earth

[JeffD]

You're assuming the body is longer. I was assuming the body was the same size, but built deeper (i.e. taller sides), in which case it would be more apples-to-apples on the sound board and back.

It really does depend on how 2 X volume is accomplished.

[Dale Ludewig]

To be clear, the resonant (Helmholtz) frequency of the air chamber and its volume are two different things albeit related. A plucked string only has so much energy and using it to move a larger mass of air is going to have a different effect than moving a smaller volume (mass) of air, regardless of the resonant frequency of the air chamber, with the same string length.

[red7flag]

Dale, what you say makes sense. Could you describe the difference?

[j. condino]

As someone who builds instruments ranging from the mandolin all the way up to the double bass, I've put a mandolin neck on an old guitar and bass body as an experiment. The results were not anything you'd want to have around. You may be able to get a note, but it does not produce a pleasing musical voice. Some of the most creative minds in the world have been trying new ideas for centuries. The instruments that we know as standard designs are that way because they were the ones that consistently worked well for the music and production capabilities of their time. Air volume, body depth vs plate surface area, thicknesses, tuning of the plate and the string, mass, density, speed of sound , radiation ratios, Go to the Oberlin Acoustic physics workshop every summer if you really want to nerd out. I've been there; VERY cool stuff...

Where is Dave in this conversation? He can lay down great pure data on the subject with the best of them.

[Dale Ludewig]

Yep, pretty much what James said. There's a reason instrument sizes are the way they are. And messing around with them to any major degree is a walk down futility lane. A little here, a little there. We're trying to fiddle with the "little" stuff to get the best we can and then sometimes we find that even taken for granted ideas like exact brace placement and such isn't necessarily a big deal. Nerding out is when you have the specific parts of an instrument in your hands, having whacked the wood enough to know what it's saying back at you, and then thinking about a little this or that, doing a little this or that, gluing it together and finishing, and then wondering what it will sound like in 10 years. After years of being under pressure, in different heat and humidity conditions, being played hard hopefully...

I've never put a mandolin neck on a bass body. Nor a bass neck on a mandolin body (it's not deep enough).... I talked to Dave last week. I don't know if he'll weigh in here or not.

[Tom Haywood]

This discussion is very timely for me. I have been working for several weeks to design a travel mandolin that will sound good and play easily. Looks like it will be a scaled down version of another mandolin I made and will be made with the same woods. So I will eventually post some audio of both mandolins for comparison. From experience, I think it is impossible to declare any hard and fast rules on this because there are a huge number of variables, known and unknown. The things mentioned above all play into unknown outcomes. The scale length obviously changes the length of the strings and where the bridge contacts the body. But it also means a different spacing between frets, which my research indicates has it's own affect on tone. The different mass of the woods due to different sizes will affect the sound. Maybe the bridge is a slightly different size and mass. Maybe the sound holes are a little different size for cosmetic reasons. The Helmholtz fundamental frequency is a big player, but so is the physical size and shape of the chamber that the frequencies are bouncing around in. That's further affected by the bracing, which may be a little different in size due to different structural needs and is affecting how those frequencies bounce. I suspect none of these changes produce strictly proportional changes in tone. I think the real world necessity to make a mandolin that works and looks it's best probably precludes a simple resizing, so taking measurements from actual instruments that meet the criteria may be impossible. Still, all the theory is very helpful for informing new ideas. All the current standards in mandolins were new ideas not so long ago. Carry on.

[Dale Ludewig]

One small example from what Tony asked. Well, maybe a couple simplistic ones. Cut out a solid plank of wood the shape of a mandolin and put strings (and a neck) on it. No volume. Like an electric guitar. Start hollowing it out until the top can flex a bit and there's some hollow inside. Now you start to hear things.
Now take a regular acoustic mandolin and double its depth, leaving the ff holes in this example alone. I don't know the math off the top of my head, but the resonant frequency is going to be much lower because the Helmholtz frequency is related to the square of the ff hole size related to the body volume. You've still got the same energy from the strings that you had when the body was half as deep but now you're trying to pump twice the volume of air. Once again, I don't know the exact math but I can bet your sound volume is going to suffer. Tonal quality? I don't know but it's going to be different. You could probably excite that volume of air a bit more with a longer string.

There's a balance to all these things that the human ear decides is pleasant. None of the sounds produced by experiments is bad or good on their own. That's all the judgement of us.

[Marty Jacobson]

I vary my instrument body depths by up to 3/8" (9.5mm) depending on what I'm trying to do. It's one of the variables you can play with. It doesn't work exactly like an EQ, the differences are less intuitive than that, and I see it being more about tonal texture than bass/treble balance. You can actually get a really sweet, clean tone on the higher register with a deeper body (depending on what else is going on in the build). Conversely, my carbon fiber mandolin is nearly 1/2" shallower than some mandolins I've made, and it has extremely good bass response.

[Dale Ludewig]

Marty, I don't know anything about carbon fiber but I can completely understand the change in tone on the higher register. I don't know if you're talking oval hole or ff hole. It it's ff hole, have you experienced a drop in "percussive punch", for lack of a better term?
I would think so.