New Luthier Tips du Jour Video - The Tornavoz

[Erik Zurcher]

Hello Tobias,
as a new member, will you introduce yourself here? viewforum.php?f=28

[Robbie O'Brien]

Thank you for the clarification Tobias.

[Robert Webster]

So, the $64 question has to be "Why hasn't the tornavoz been much more aggressively pursued/resurrected in our modern times?". Surely someone as experimentally minded as Contreras would have taken a swing at it if the effect had solid merits. I'm not putting the idea down. Quite the contrary. I'd love to try it with one of my old beaters just to see what it's all about. I like the idea of the shorter device and can't imagine that it wouldn't be possible to make it removeable.

My suspicious nature tells me there must also be adjustments to the top bracing to accomodate the downward shift in the lowest air resonances. It all seems too good to be true. Tobias, can one really brace and graduate the top to favor the mids and trebles and still get great bass response with the toravoz?

I can see that I'm talking myself into some work. It's not fair.

Bob

[jfdana]

Gary Southwell uses a 15 mm wooden "lip," aka mini-tornavoz, on his A Series guitars.

[Doug Ingram]

So, the $64 question has to be "Why hasn't the tornavoz been much more aggressively pursued/resurrected in our modern times?". Surely someone as experimentally minded as Contreras would have taken a swing at it if the effect had solid merits.

Bob

So many people are of the opinion that its all just hocus pocus, builders and players. So much resistance and so little real information and understanding of how to make it work right, etc.

[Tobias Braun]

So, the $64 question has to be "Why hasn't the tornavoz been much more aggressively pursued/resurrected in our modern times?". Surely someone as experimentally minded as Contreras would have taken a swing at it if the effect had solid merits. I'm not putting the idea down. Quite the contrary. I'd love to try it with one of my old beaters just to see what it's all about. I like the idea of the shorter device and can't imagine that it wouldn't be possible to make it removeable.

My suspicious nature tells me there must also be adjustments to the top bracing to accomodate the downward shift in the lowest air resonances. It all seems too good to be true.
I can see that I'm talking myself into some work. It's not fair.

Bob[Tobias, can one really brace and graduate the top to favor the mids and trebles and still get great bass response with the toravoz?

Hi Robert,

You are asking a good question! Being honest, I cannot answer it (after 26 years of guitar-making). Of course I have some ideas about what is going on in a guitar - but it is still such a complex instrument and I have more questions than answers.

I follow José Romanillos´ ways of looking at the guitar (I have attended several of his classes since 1984 in Zürich) in which he believes that it is important to control the fundamental note of an instrument. That means: There is a good basis for a balanced sound. I know that that sentence gives much room for contradiction and/or interpretation - but I want to put the focus on another thing to answer your question.

The "proof of the pudding" is a little experiment that Paul Galbraith did on his guitar: He just fixed a ring of thick cardboard (depth varies according to your wishes) with masking tape inside the guitar.
I recommend this to you (and all interested readers) to see what will happen!
Good luck and have a nice weekend!

Tobias Braun
Gaaden, Austria

[Kintla]

That is a great idea Tobias, just to get an idea ahead of time!
Sherman

[Robert Webster]

The "proof of the pudding" is a little experiment that Paul Galbraith did on his guitar: He just fixed a ring of thick cardboard (depth varies according to your wishes) with masking tape inside the guitar.
I recommend this to you (and all interested readers) to see what will happen!
Good luck and have a nice weekend!

Tobias Braun
Gaaden, Austria

A good idea indeed. I have one here that I could do that with and do some recordings. I'll report back.

Bob

P.S. It occurs to me that the ring might not even have to protrude so far as to have the outer rim precisely flush with the soundhole. Of course, it shouldn't interfere with plucking, but it might open the door for a removeable tornavoz, no?

[Silverbach]

Okay, I'm almost ashamed to admit that I don't know how (Luddite) to link a Website (yet). So while I try to sort out just how to do that try the following:

http://www.hago.org.uk/faqs/contrabass/construction.php

A temporary tornavoz experiment.

S

Well, how about that. It worked. For my next trick: Smilies.

[Ole Thofte]

Silverbac, Robert England already linked to that page, which has a very interesting demonstration of the sound from the guitar with and without the Tornavoz and a diy description.

This is a funthread. Maybe I'm a bit OT in the following but I think it's close to the topic: resonances.Someone in this thread mentioned the likeness of a guitarbody to a loudspeakerbox and how the Tornavoz could resemble a resonance port. I have done a little loudspeaker diy and remembered how I used to dampen resonances with wool or acoustilux inside the cabinet (+ some sticks to stiffen the cabinet which is hardly good with a guitar body, but maybe some flexible rubber sticks placed at strategic places inside the body could change something ).

I did try acoustilux inside the body, just a couple of handfulls carefully stuck inside the soundhole (with strings on). This floffy white material didn't touch the strings but placed itself nicely without moving around. Initially I thought it would dampen the sound. It didn't. It just left an impression of a more steady and pure tone and a feeling of more sustain. My idea is that it damped some of the resonances inside the body. This was (maybe) confirmed when I tuned the guitar: it was easier to tune using an electronic device because the tone was more steady (the green light on the device stayed on and didn't alternate so much between red lights below and above the right frequency, if you understand). So maybe this way (with dampening material) the tone isn't quite as colored by resonances from the body. I tried with a cheap guitar and an expensive luthier guitar: the result was that they seemed more alike now, the cheaper one more improved in sound quality! Now why would that be?

Ole

[Silverbach]

Ah, sorry, I missed Mr. England's link. I am very much the novice on here (the learning curve is pretty steep). I have an interest in the tornavoz because I am just tooling up up to build a replica Torres guitar and it features one.

Something like this: http://www008.upp.so-net.ne.jp/Jun-Naka ... n_foto.jpg

S

[Alan Carruth]

I've worked on one or two guitars with 'sleeves' in the soundholes, and also ran some experiments with a removable 'tornavoz' in one of my 'test mule' guitars. The tornavoz was of cardboard, but patterned after the one illustrated by Romanillos in his book on Torres.

In all cases, the effect of the tornavoz/sleeve has been of the sort that theory would predict: as you make the soundhole into a longer effective tube, the pitch of the 'main air' resonance drops, and it becomes less powerful. This shows up quite clearly on a spectrum chart. With the full depth tornavoz the 'main air' resonance practically dissappears, and the spectrum can closely resemble that of a small 'Baroque' style of guitar with a parchment rose. In the latter case the drag of all those edges cuts the power of the main air mode 'way down, although the pitch of what remains is high.

Playing the 'test mule' with the tornavoz in it confirmed what the spectrum suggested: it has the timbre of a small, early style of guitar, but since it's bigger it's a bit more powerful. Like the small bodied guitar it tends to 'project' well, but the lowest bass notes lack fundamental. This may not come across in all cases as a lack of power in the low end, but simply as a difference in timbre.

The folks making guitars equiped with tornavoz' say that there are certain design differences that need to be incorporated to get the best results. Obviously, my 'test mule'; did not have those alterations made, and that will no doubt be cited as the reason for the 'failure' of the experiment Perhaps that's so. However, I'll note that, for all their complexity, these are physical objects that must obey physical laws. I saw the sorts of changes that one could predict from an understanding of the physics of the thing, and would expect to see the same sorts of changes no matter what the starting point was. Wth a different starting point the outcme might be 'better', but I can't see any way to avoid the lowering of the 'main air' pitch, and the loss of power.

I will also note that most of Torres' guitars that were originally equiped with tornavoz' have had them removed. They are still useful instruments without the sleeve in the soundhole. This suggests that a similar guitar with a usable sound should change in similar ways with the insertion of a tornavoz. It can't be magic.

The other objection will be that I did not make my tornavoz from copper or brass, as Torres did. It was impossible on this guitar to modify the soundhole in such a way as to allow for the insertion of such a rigid device of the 'correct' size. I hope at some point to make another test guitar that will allow for this. Meanwhile, I'll stand on the experimental results I have, and remain a skeptic.

[Pepe Vergara]

.. The other objection will be that I did not make my tornavoz from copper or brass, as Torres did. It was impossible on this guitar to modify the soundhole in such a way as to allow for the insertion of such a rigid device of the 'correct' size. I hope at some point to make another test guitar that will allow for this. Meanwhile, I'll stand on the experimental results I have, and remain a skeptic.

Alan: that could make a big difference in the results you obtained. Are you sure you can not make a foldable type brass tornavoz or remove the back. I think I saw one of those guitars with removable backs in your shop. Could you take couple of bear cans and model a tornavoz flexible enough to get in?

[Ole Thofte]

A Tornavoz with a flexible design? I have a picniccup with a sort of telescopic design: when not in use it's 'flat' but you can pull it 'out' so it forms like a conical cup... if you can picture this... here is an illustrational link (not a promotion!): http://www.gadgetpens.com/mugs/flasks/t ... c_cup.html

A similar telescopic Tornavoz, resting og the back of the guitar and with some holes for airflow seems possible and would make access to the inside of the body possible, wouldn't it. Problems with rattling could be solved, I think, with a damping material of some sort, like a rubber surface...

Ole

[Alan Carruth]

Thanks for the ideas. The basic problem is, iirc, that Torres' tornavoz was conic, and wider at the bottom than the diameter of the soundhole. What I need to have is a test mule with a larger soundhole: for various reasons I could not enlarge the one on the guitar I used.

The more basic issue is one of credibility: unless you can replicate the experiment exactly people won't accept it, and that's absolutely correct. We can't know what effect rubber gaskets or hinges would have, and although one could argue that the effects ought to be 'minimal', they are nonetheless real. Given that it's difficult to measure the differences between merely 'good' and 'great' guitars, those small differences might count.

One thing that could be tested in such an experiment would be the differece that various tornavoz materials make. I'm not at all convinced that there would be a lot of audible difference between a cardboard tornavoz and a brass or alumuinum one. Once a guitar was built that would allow for switching of different tornavoz' mounted to a 'donut' that was fixed to the top, it would be easy enough to make six or eight of different materials, and check them out. Other size and configuratyion variables could also be checked easily.