Official Luthiers Forum!

I recently read an article on how to lower the
Helmholtz frequency of a guitar (in this case a
classical contrabass),with the aim of adding warmth
to the lower octave notes. The article advocates the
use of a Tornovoz port (as originally experimented by
Torres(?) I believe)..(apparently Torres used a
conical shape piece of brass permanently fixed on
the soundhole of the guitar),,,.this port however is a
piece of acetate sheet rolled into a TUBE shape..the
circumference of the tube being the circumference of
the sound hole of the guitar,The length of the tube
could vary up to the depth of the body. This was just
literally 'taped' onto the guitar..and apparently worked
really well.
Has anyone experimented with a tornovoz of this
shape (or any shape for that matter) on steel strung
guitars..it sounds worthwhile..and as it is not fixed on
the instrument permanently...it could be used or
removed.
Just wondered......

I once worked on a baritone guitar that had a tunable soundhole: the sleeve was made in telescoping sections, and you could adjust the length simply by sliding one in and out. It worked as advertised to alter the pitch of the main air resonance.

The thing was, though, that after a certain point lowering the air mode pitch made the bass sound worse rather than better. The lengthened tube cut down the power of the air resonance, as well as dropping the pitch. Eventually the loss in power did more harm than the drop in pitch did good.

I tried putting a cardboard tornavoz in a classical guitar once. It virtually eliminated the air mode. The timbre of the guitar was 'brighter', but distinctly lacking in power. I suppose it's just possible that the copper ones Torres used worked better, and one day I hope to try it out, but I'm not getting my hopes up too high.

I agree with Al. Adding a tornavoz to a guitar is probably a bad idea. As an after-thought addition it just doesn't do any good. You've pratically got to design the guitar around the tornavoz, as Torres did, to make it work. In that case, it works quite well.

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[QUOTE=jfrench] I agree with Al. Adding a tornavoz to a guitar is probably a bad idea. As an after-thought addition it just doesn't do any good. You've pratically got to design the guitar around the tornavoz, as Torres did, to make it work. In that case, it works quite well.

[/QUOTE]



Colin

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I don't believe in anything, I simply make use of a set of reasonable working hypotheses.

HA!!! I thought it sounded too good to be
true.....Shame ..it sounded good on paper

    I immediately thought that that was interesting but extending the port into the guitar brings it closer to the back, which would have obvious negative results in extreme extention.

     I saw a classical being played on TV yesterday by a reaonably accomplished guitarist and he had taped the port about 2/3's closed(duct tape at that), which was intriguing.

    This brought up the obvious idea of a flat lexan plate that pivots internally from the top above the soundhole. This would affect Helmholtz and maybe reflect an unusual aspect of sound more directly out the sound hole. An interesting experiment.

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Billy Dean Thomas
Covina, CA

"Multi famam, conscientiam, pauci verentur."
(Many fear their reputation, few their conscience)