Cubic inches

[pelone]

In looking under the hybrid catagory of the "eye candy" section, I notice that a bit of divergence has occured from the traditional F and A style. Have any of the builders of these mandos attempted to build the body of the instrument to the same volume per cubic inch as the traditional F's and A's? I would think that the ephemeral tone quality that identifies a mandolin might be compromised if the body was either too large or too small. Any thoughts on this, please.

[Bill Snyder]

Pelone remember that the F and A styles were predated by the bowlbacks AND the guitar shaped mandolins. They sound like mandolins.

[Hans]

[QUOTE]
"I woiuld think that the ephemeral tone quality that identifies a mandolin might be compromised if the body was either too large or too small."
Nope. No one has ever said the the A or F body size is the optimal size for a mandolin, and how would you tell? What is the optimal tone for a mandolin? I'm sure you would be able to get a couple of different answers to that question!

[mandroid]

Ideal Cubic inches? , do you want acceleration , or fuel economy ?

[JeffD]

Well we could do like Archimedes and submerse various great sounding mandolins in water and do a statistical analysis of their displacement. Of course we would have to plug up the F holes or ovals.

Ummmm...

Or not.

[pelone]

I just thought that somehow with the process of elimination or trial and error that someone would have worked out some very quantitative conclusion on how to maximize the sound that typifies a mandolin. Of course, I am sorry to exclude the bowl backs and guitar shaped instruments. I notice in the "hybrid" section of eye candy that the silhouettes of some of the instruments are varied and with the depth of the bodies are likely to exceed the depth of the traditional F's or A's. I am mid project on my fourth mando and I am one of those who is unfettered by tradition. But, I do not want to venture too far from the norm and build an instrument that is ineffectual. Perhaps Dr. Cohen could weigh in with some opinions?

[Loren Bailey]

I believe Rolfe Gearhardt did some fairly extensive work when developing Phoenix mandolins on chamber volume in an attempt to reproduce Loarish tone/volume results in his two-point design. You might want to search here on the Loar A5, It's reputation seems to designate it as one of the finest sounding Loars ever, on par with or better than most with pointy and curly things attached.

Loren

[John Bertotti]

I would ask a similar question in the builders section. Dr Cohen has done some measurements that relate to internal volume and frequencies and in a round about way it shows how the plates couple with the internal resonance thus giving a sort of answer to your question because you can see how the different types of mandolins function. IE a bowl is one way and a F is another etc.. Dr. Cohen I hope I got this close. I have long since lost your original reply to a question I had about internal volume when my hard drive crashed and burned. I would certainly like to see the info again and it might help with the original posters question.

[Dave Cohen]

I've written a chapter for a book on the physics of stringed instruments, edited by Tom Rossing, to be published by Springer-Verlag. The answers to a lot of these typical questions will be in there.

My good friend Rolfe Gerhardt has a keen interest in the matters of the physics of mandolins, but hasn't done any work on that subject himself. He prefers to leave the work to those with the necessary background.

It seems inevitable in scientific endeavors that the more you learn about something, the more new questions there are. I have done the (holographic) modal analysis and air resonance measurements on f-hole mandolins, oval hole mandolins, Neapolitans, and a Vega cylinderback mandolin, as well as mandolas (both f-hole and oval hole). By the winter of 2004, it was apparent to me that air mode/body mode coupling is not all there is to the matter of a stringed instrument's sound. It does strongly influence the bass/treble balance, but there is more to the subject than that. Neapolitans have low air resonance frequencies and high main body mode frequencies. The coupling, analogous to the bass reflex mechanism in a loudspeaker, is thus very weak in Neapolitans. Even more extreme examples are the (Russian) Domra and the (Chinese) p'ip'a. Those instruments have even weaker coupling than does the Neapolitan mandolin. But all three instruments are much loved, and in the hands of great players, produce plenty of sound. Anyone who has heard Carlo Aonzo or Ugo Orlandi live can attest to what I am saying here.

At lower frequencies, the sound radiation from a stringed instrument is dominated by the body mode/air mode coupling. But the body modes are also moving air outside the instrument, and that mechanism becomes dominant at higher frequencies. While the coupling is not the only contributer to sound radiation, it does strongly influence the bass/treble balance, and to a lesser extent, the "timbre", which is related to the harmonic content of the sound of an instrument. So if you want a mandolin to sound like a typical f-hole mandolin, you use the typical f-hole mandolin dimensions. Even there, though, you have some latitude. If you make the body volume larger, you can compensate by making the soundhole area and/or length greater. That will get your main air resonance frequency back up to where it was with the original dimensions. There is no one set of dimensions that has a monopoly on sound quality and/or acoustic volume, but there are relationships between body mode and air mode frequencies that can get you close to the type of sound that you want.

In the Mandolin Family Instruments chapter, I give a detailed comparison of f-hole mandolins to oval hole mandolins to ladder-braced mandolins. I left out all of the partial differential equations, but I do assume that the reader will have read some of the basic articles on the physics of guitars, such as those which have appeared in American Lutherie.

[billhay4]

Dave,
Are you suggesting that generalizations about the relationship between interior volume, soundhole size, internal bracing, top and back woods, arching, and their relationship to the type of sound an individual instrument produces might be arrived at?
If so, I'd like to read your venture into this realm of mandolin speak.
Lots of us non-scientists and wannabe luthiers look for such generalizations to hang our hat on. Of course, the real test is building many instruments and taking notes of their differences, what we did that might create those differences, and so forth.
Still, I'd like to see what a recognized scientist has to say about what combination of factors best produces the Loar sound, the oval hole sound, the Montelone sound, the bowlback sound, etc.
I also realize this is a big task, one you might be unwilling to touch with a ten foot Wegan.
Thanks,
Bill

[John Bertotti]

Dr. Cohen, when will it be in print and where do I get it?!

[TonyP]

Thanks for the post Dr.Cohen. I love reading through your stuff. And while I'm not familiar with all your terms just the sheer logic shines through. What I'm always left with though is even more appreciation for pioneer luthiers like M.Lewis and Bussman that have really gone far afield and somehow, get these wonderful results. I think it's the "art" part that will always be a little beyond scientific measurement and always be the wild card that will make someone try something different. Some will make it work, some won't.

[Dave Cohen]

I particularly like Bill's "melandolin" and "cheesebox mandolin" (the one with the lizard or whatever it is crawling out of the box).

BillHay, you gotta avoid the giant leaps and not take what I say further than it is capable of going. I have found substantial differences between Neapolitans, oval hole archtops, and f-hole archtops. You'll be able to read about that. I have also looked at numerous f-hole type archtop mandolins by now. I find some generalizations, which you can also read about. But there are still variations within the f-hole genre. For two given "good" f-hole type mandolins, the body mode frequencies can be significantly different. The situation parallels that in violins somewhat. You can look at two golden age Italian instruments, say two Strads, or a Strad and a Guarneri, and find different body mode frequencies. But there are certain relationships between the modal frequencies and/or other properties, that both instruments will share. I have no idea what the relationships are for mandolins yet. I couldn't even begin to think about distinguishing a given Monteleone from a given Loar. For one thing, Loars aren't all alike. Neither are Monteleones, nor ..... So I am nowhere near being able to distinguish quality factors. Maybe some day.

[billhay4]

Dave,
Thanks for the reply and the cautionary note.
Of course, it is the push for big leaps that spur on the small steps in many cases, but I realize mandolin research is still in its infancy and such questions cannot be answered now (if they ever will be).
As a non-scientist, I appreciate the work you do and the constant effort you make to reign the rest of us back to realities.
At the same time, I wonder if all instruments develop via a process of uninformed choices as much as they do from true experiment. Take Gibson's scroll. No reason for it as far as I can see, but it sure is the norm now. Did Gibson just decide a scroll would be neat or did they have a "scientific" reason for putting them on instruments?
It's an interesting process at any rate. I'm presently trying to short circuit it somewhat (a totally futile endeavor, I agree) to see what comes out, but the actuall process of musical instrument development is, as far as I can see, a historical, cultural, folklore, and occasionally scientific process that is extremely complex just like life.
Bill

[mandolooter]

I'll bet its a good and informative read either way...