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The sound hole is a ducted port with a length that is the thickness of the
top. It is in theory possible to tune the system (technically a Helmhotz
resonator) to the same frequency with different size ports of different
lengths. The mass of the air in the port damps the resonant peak of the
motor and produces two peaks in the impedance curve. A well designed
system can be accomplished. With loudspeakers it is a very involved
process of trade off. Does this sound applicable to guitars? It's just much
easier with speakers because we have very accurate mathematical models
of the system. Guitar building is much more of a craft with good and bad
example of any design type. Good results are possible by cut and try.
There are amazing examples of acoustic design that date from the middle
ages.

I am amazed that there are cathedrals with tuned Helmhotz bass traps
built in that are over 500 years old!

Steve, I am quite aware of basic loudspeaker design theory having done cabinet design for the Grateful Dead's Wall of Sound...

As far as history...the Greeks used passive EQ in amphitheater design. Large amphorae were selectively filled...tuned...to specific frequencies and used as passive resonators 3,000 years ago...

But, yes, guitars are the issue here, and they're unwieldy beasts much prone to mythtreatment...

[QUOTE=Rick Turner] So if one build with a tornavoz and it isn't wonderful, then it's not because of the tornavoz; it's because the builder didn't understand it. But as there's no clear explanation of how to build with it, the whole thing is held as a dark arts secret. [/QUOTE]

Basically - Yes.

Can you accept such an answer?

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[QUOTE=jfrench] [QUOTE=Rick Turner] So if one build with a tornavoz and it isn't wonderful, then it's not because of the tornavoz; it's because the builder didn't understand it. But as there's no clear explanation of how to build with it, the whole thing is held as a dark arts secret. [/QUOTE]

Basically - Yes.

Can you accept such an answer?[/QUOTE]

I'm sure Rick must understand; I think he's just trying to stimulate discussion here.
After all, just a few days ago somebody asked Rick for some guidelines for optimizing an acoustic designed for pickups and the response was essentially: "Do your own experiments; don't ask me for the recipe!"

Cheers
John

John, if you'll go back to that thread, you'll notice that yes, I did say do your own experiments AND I gave my "formula" for building successful semi-hollow guitars and basses optimized for amplification.

In this case, we are being told by Joshua that we're not worthy of learning the great secret.   He's saying that the tornavoz requires some sort of special guitar, but he's not even giving a hint as to what that may be.   I'm basically saying that such a "dark secrets" attitude is bull...t.

It is not hard to understand the physics of what a ducted port does to a resonant chamber...tens of thousands of words have been written on the subject.   With a guitar, there are trade-offs. From what I've heard back from both Al and from David Berkowitz is that my theoretical understanding of the tornavoz exactly coincides with practical evidence.   You gain something (a bit of a bass bump), and you lose something (output).   As I understand Joshua's comments...reading between the lines, so to speak...is that there is a secret formula for compensating the design of the guitar that optimizes it for the tornavoz. I still don't believe in something for nothing, and we're not worthy to know the secret, so basically the answer to the question posed in the very start here is that the theorists who have (or in my case have not) run the experiments don't know what they're doing, and the builder who says there's magic here won't tell us what it is, which leads me to be suspicious of the whole thing.   Kinda like turning lead into gold...Yeah, I heard about that, too...

[QUOTE=Rick Turner] John, if you'll go back to that thread, you'll notice that yes, I did say do your own experiments AND I gave my "formula" for building successful semi-hollow guitars and basses optimized for amplification.
[/QUOTE]

Actually, Rick, I had re-read that thread. For anybody that missed the details of how Rick builds his acoustic-electrics, and wants to duplicate one....

"My standard formula for the Renaissance line includes a Western Red Cedar center block, bent sides, a book matched back and often a cedar top.   The neck is mahogany. The neck is tremendously important to tone, and so is the center block."

No secrets there!

John

I think you are correct Rick in terms of how a Tornavoz affects the sound of a guitar.  I dont believe Joshua was dodging anything in the information when describing what makes a Tornavoz guitar successful in that what is known physically is based on the information in the Romanillos Torres book. 

The issue as to how to successfully integrate this into a classical guitar is that it really is a matter of adjusting the voicing of the instrument as closely as possible before inserting the Tornavoz but this has to be after factoring into the voicing the affect that the Tornavoz would make on the instrument before inserting it. 

My thinking on this is the fact that there were alot of builders that built with Tornavoz but of them only Torres was considered successful.  Think of how close the dimensions and construction of classical guitars are and yet there is a world of difference between a good classical guitar and a great classical guitar.  I assume the same is true of guitars with Tornavoz.

  

So here's the question of the hour...

If Torres was successful, then what did he do different in the tornavoz equipped guitars?

Oh, sorry, another question...or three...

If it was so good, then why don't all classical guitars have a tornavoz?

Why don't all extant de Torres guitars have the tornavoz installed?

Or is this a case of blind luck being disguised as secret knowledge?

A case in point, and bear with me on this.   A friend of mine is an Indian sitar master named Kartik Seshadri. He is one of the two foremost disciples of Pandit Ravi Shankar and is a sublime musician trained in the deep tradition, but also schooled Western-style (MBA degree), and with a deep interest in improving the sitar.   Kartik has made or recarved the tops on all his own instruments, and I helped him with his number one sitar back in about 1996.   He took the top off, and we put in a couple of "A" splayed longitudinal braces and he then regraduated the top violin/archtop style.   It came out great.

Several years before all this, Kartik had gone to the Indian builder who made Ravi Shankar's #1 instrument...a sitar with an incredible deep and very vocal quality to the tone.   Kartik asked the builder what the secret was of that particular instrument.   The builder said something to the effect of, "It's a secret, and I'm carrying it to my grave..." Kartik's belief is that the instrument was, in fact, a lucky accident; the builder had no idea why it was so special; and that there was no secret to take to anyone's grave.

Do you get my drift?

Google Kartik Seshadri and know that this guy is the real deal who sees through false secrets.   He's also on hell of a musician.

 Jose' Romanillos writes:

"All guitars with a Tornavoz had open harmonic bars"

 

pg. 177 Antonio de Torres, Guitar Maker-His Life and Work  

And I would imagine that open harmonic bars would enhance a particular frequency range that coincides with what a Tornavoz would complement. Or the Tornavoz might help control an excessively high Q bass resonance by smoothing out the impedance curve... In that case, the air resonance would be tuned far enough away from the main top resonance that you wind up with a kind of double bump in the low frequency response.   The roll off would probably be fairly steep below the lowest resonance, but that might be OK as guitars don't put out diddly below about 80 Hz...the low E being at 83 Hz.

I feel like I'm the fulcrum point between the scientists here and the touchy -eelie old guard... I respect both camps, but come on now guys, let's try talking a common language. There's nothing to be lost and a lot to be gained. Speaking in riddles begets confusion...and customers who may someday wonder what they fell for.

I think that the real problem here has more to do with the significant lack of successful guitars still equipped with the Tornavoz, and new ones being built with one.  We're all just talking theory here.  We need some nuts and bolts experience here.  There are just so many unanswered, perhaps even unanswerable, questions here.

La Leona (The Lioness) is an intact Torres guitar, still sporting its Tornavoz.  You can see some very nice video of it in concert.  Check out Youtube and Guitargourmet.  I forget the musicians name, I can check up on it.  A simple Google search will find it, too.  There is also at least one CD recorded on it.  This guitar is anything but small or lacking in sound.  Its a beautiful sounding guitar able to hold its own against anything else I've heard.

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Expectation is the source of all misery; comparison the thief of joy.
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We have had parts of this discussion before.  The artist is Stefano Grondona, and the CD from the book "La Chitarra di Liuteria" (Masterpieces of Guitar Making) has him playing a number of the Torres guitars.  Pretty amazing experience to listen while reading about those guitars and looking at the great pictures of them.  It is, IMO, a nice addendum to the Torres book by Romanillos.  It certainly gives voice, if you will, to some of the arguments about how good his guitars were.

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Waddy

Photobucket Build Album Library

Sound Clips of most of my guitars

There is that, but I was referring to Wulfin Lieske.

Check out one of the Youtube videos here: http://www.youtube.com/watch?v=MGnlB9rYhAg

Or a full length piece at Gourmet Guitars at:
http://www.gourmet-guitars.com/video.asp?mofile=lieske_live. mov

_________________
Expectation is the source of all misery; comparison the thief of joy.
http://redrivercanoe.ca/

Thanks!  Good post.

_________________
Waddy

Photobucket Build Album Library

Sound Clips of most of my guitars

Rick Turner wrote:
"I feel like I'm the fulcrum point between the scientists here and the touchy-feelie old guard... I respect both camps, but come on now guys, let's try talking a common language. "

I know the feeling, man.

jfrench wrote:
"I wasn't aware that Rick had any experience with the tornavoz... "

Rick was simply putting forth the physics of the situation; once you understand the principles they should be applicable anywhere.

I mentioned that the guitar I experimented on was not built for a tournavoz, and jfrench replied:

"A fair objection, no? I could have saved you the time on this experiment. "

It was not a really time-consuming experiment, and I was not expecting to end up with a world-beating guitar, so I was not dissappointed. I wanted to get an idea of what would happen, and saw more or less the sorts of changes I expected to see. I was a little surprised by the magnitude of them.

Rick asked:
"So you build the guitar with a hole in it's bass response that gets filled by the higher Q resonance from the tornavoz? The plain soundhole contributing to a lower Q filter, and the higher Q of the tornavoz fixing that?   Is that what I'm understanding? "

What I saw in my test was a significantly lower Q value with the tournavoz. It was, as I say, rather like a guitar with a parchment rose: there seemed to be a lot of extra drag, so that the peak height was much reduced. I finally dug out the data, and the air mode pitch went from 97 Hz in the 'normal' configuration to 80 Hz with the tournavoz.

The open harmonic bar is an interesting observation. I have a little data on one or two of those that were built by my friend Aaron Green, and I should look that up.

There is also the question of perception vs reality. Many of the accounts I read talk about the 'remarkable' bass timbre of guitars with a tournavoz, but remarkable in what way? The so-called 'English bass' that was used on pipe organs, which involved using a series of pipes tuned to overtones whan one could not fit in a pipe long enough for the fundamental is also often called 'remarkable'. If a guitar that was to be fitted with a tournavoz was built so that the overtones were enhanced it could well be percieved as having a particularly 'penetrating' bass tone. Such a sound could be very fine.

Shawn wrote:
"My thinking on this is the fact that there were a lot of builders that built with Tornavoz but of them only Torres was considered successful. Think of how close the dimensions and construction of classical guitars are and yet there is a world of difference between a good classical guitar and a great classical guitar. I assume the same is true of guitars with Tornavoz."

The devil is sure in the details.

Rick mentioned Kartik Seshadri. I'm awful with names, but I bet that's the same person who came by my shop to work on a couple of sitars, at the recommendation of Carleen Hutchins. We did some 'free plate tuning' on a couple of tops, and got some marginal improvements in tone. One thing that I noted was that the top of Ravi's fine instrument looked like quite a different sort of wood. We speculated that it might have been something like a mahogany, rather than the teak tops that we had worked on. The reduction in weight alone would have made a big difference in the tone. At the time I did not have the setup to do much real acoustic testing, but it would be fun to get those instruments back and find out more about what was going on.

[QUOTE=Rick Turner] So here's the question of the hour...

If Torres was successful, then what did he do different in the tornavoz equipped guitars?

Oh, sorry, another question...or three...

If it was so good, then why don't all classical guitars have a tornavoz?

Why don't all extant de Torres guitars have the tornavoz installed?

Or is this a case of blind luck being disguised as secret knowledge?
QUOTE]

Hi Rick. I appreciate your comments here and I understand well that you're motivated towards information. If I hadn't enjoyed your contributions to this forum I would not take the time to respond (I'm busy moving, at the moment).

There has been some research about the tornavoz. Not a lot, but enough for someone to get a general idea of how to make it work. Much of the rest is experience. For anyone wanting to try a tornavoz guitar I'd start with the technical information available about La Leona.

There is no great secret, but air resonance and speaker theory is only part of the equation.

Let me answer your questions:

If it was so good, then why don't all classical guitars have a tornavoz?

I don't believe anyone is claiming it to be some great improvement of the instrument. For me, I've had very good results with the tornavoz especially in terms of projection and responsiveness. I've already stated that it makes for a different kind of instrument. A different kind of instrument.

But to the question at hand - Torres worked in a time when materials were expensive and labor was cheap. He made his tornavozes out of bronze. That should be answer enough, especially considering the poverty Torres was striken with. But to add to that, it involves extra work that he tended to reserve to his finer instruments in his first epoch. As we know, he was also making cheap instruments for laymen. When he came back to guitar making in his second epoch, who knows the reason for not making any more tornavoz guitars? Changes in the cost of material? Old age? Repairabilty - the restricted interior of the instruments in a time without the kind fo climate control of today? Added work when he needed to make instruments as fast as possible to feed his family? Great results with his non-tornavoz guitars?

Really... that is the kind of question you ask after someone says: "tornavoz guitars are the best guitars".

Moving on...

Why don't all extant de Torres guitars have the tornavoz installed?

Because he didn't install tornavozes on all of his guitars. Many that he did have been modifed since, many in the early 1900s.

Or is this a case of blind luck being disguised as secret knowledge?

Personaly, my positive results with the tornavoz are the product of blind luck in the fact that I had early guidance from someone with intimate first-hand knowledge of some of these instruments (including La Leona).

For Torres, his entire guitar making life could be blind luck. It could also be empirical knowledge and an adventurous spirit.

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Here's a link to Wulfin Lieske's website where he shows photos of "La Leona", including a photo of the Tornavoz showing small wooden blocks which brace it against the back.  Another mystery element to work out!

http://www.wulfin-lieske.de/english/antonio-torres/index.htm l

Also, Michael Thames has an article on his website describing how he understands it to work and how he can to use it, at least as an option in is instruments.

http://www.thamesclassicalguitars.com/sub5.htm

Its a Word document, and the link is a little tricky to notice.  Its on the Guitar Models page, look for the Brazilian, where the details links are.  The word Tornavoz is hard to see against the background photo if you're not paying attention.

I've decided to leave the Tornavoz for a later instrument.  There is just so much more to learn about this device and how to optimize it, I don't feel that I have a good handle on it yet.  I want to leave it for a little later when I can do something more comparative, and have more knowledge about how to succeed.  The gauntlet is down!

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Expectation is the source of all misery; comparison the thief of joy.
http://redrivercanoe.ca/

The "small wooden blocks" look like hardware store dowel sections. Are they original or are they Home Depot?

Also note that in this mounting method, the top and back look to be directly mechanically coupled in a manner not unlike the sound post in a violin. So there's another tonal wild card on the table...

In looking over Romaillo's chapter on the tournavoz last night I noted that he said the posts to the back were an early method of supporting it, and tended to be abandoned as the design was worked out in favor of a flange around the soundhole.    

Another tonal wild card for sure.

Just for the record, (in case anyone was wondering) I'm not looking for any sort of magic pill or Holy Grail  of guitar making.  I just want to understand this device, how to make it work, and what effect it has.

I did send off an email to Mr. Lieske.  Perhaps he'll respond and I can get some more information.  He does NOT seem to be the sort that would stick in Home Depot dowels.

BTW, he has some nice photos of Torres' house on his site.

_________________
Expectation is the source of all misery; comparison the thief of joy.
http://redrivercanoe.ca/