Are f-hole wings tweeters?

[jezzupe]

jezzupe, I visited your website, www.jessupegoldastini.com . Really special! Does your instrument sound like violins or do they have a distinguish sound?

Thank you so very much, I will post a sample later that compares one of mine to a German "workshop" fiddle that is quite nice. I have samples on my site, but they are horrible, done too quickly, not enough time to get the mic right. The sample I will post is with the same recorder, just in the right location. I think I can be "educational" in that I can be used as a comparison to "normal" design. I think that my instruments sound pretty "violinish". I generally steer my sound towards the treble end. My instruments push lots of volume.

[jezzupe]

I have consistently found the strongest radiation of high frequencies (3500 Hz or so)  comes from an area about 1 or 2 cm from the neck block on the top.

 

I have looked for this a few times before, and not found anything significant.  "Some", yes, but not anything that came near the levels coming from the top.

However, I have just upgraded my equipment and methods, so another look might be worthwhile.

Crap, no way, that's what I "think" I'm glad you have found it. I divide it into 3 ranges in 3 locations. The highs are at the top, the mids are in the middle and the low is in the bottom. There are "lines" that are blurred where they meet and then they all mix together when the come out. "Balance" in tone seems to come from treating each of these sections as individual and then how they all mix together. For example thicker graduations in the top near the neck will yield a sound that is a "thin" yet high, high frequency and so on and so forth. "Tone" to me, comes form creating, or focusing on the individual parameter and then thinking of how the high,mid, and low work together. Its like if we listen to the same high note played on different instruments the "feel" of the same note can be different, a high E on a violin and then a piccolo have a distinct "palette" even if they are the same frequency. I think of it much like orchestration where we can have a chord played in root position with the bass and the treble note very far apart. Only certain instrument tone combos work well , or better than others. Like a low octave D on a piano sounds better with Dmin cord played on top with either a piano, or 3 violins than say the same octave with 3 kazoo's forming the chord on top. Different graduations in different areas yeild different "tone" "palettes" that can be mixed and matched.

[Don Noon]

I took a survey of the rib response (bridge driver, white noise input) and found that the strongest output was from the middle of the C-bout ribs.  Here is the plot of the strongest point on the ribs, compared to a few points on the top... taken on the trebel side, near the fingerboard, at 2, 4, and 6 cm from the edge near the neck.

So, yes... there is some HF sound coming from the ribs, but it's not a major power source.  Only a few narrow frequencies appear to get near the levels of the top.

 

Also, the area of the ribs is small compared to the top, so this plot may mislead one into thinking the ribs are even more important sound producers than they really are.

 

I have no idea what the bulging rib effect might do; these measurements are on a new-ish instrument with unbulged ribs.

[Anders Buen]

At around 4kHz we will be close to the critical frequency for spruce at that given thickness. Lothar Cremer describes what happens to the sound radiation when we get closer to he critical frequency. There will be a sort of beamforming going on I think, where the vibrations in the whole plate may add up along it to getting the apparently largest contributions from the ends of the plates. I may scan the pages from Cremers book.

I do not think it is possible to determine the source of the sound pressure level from measuring he sound pressure alone. What would be needed is the sound intensity, which takes special transducers to perform which can determine the particle velocity and direction. If Cremer was right the direction of that highest sound radiation is somewhat in plane with the plates.

[Anders Buen]

Two figures from Cremers book on the critical frequency and beamforming.

[jezzupe]

Two figures from Cremers book on the critical frequency and beamforming.

Hmm, like a dragonfly, might not be too far off from reality.

[Don Noon]

I believe I am getting a decent reading of the activity directly where the microphone is placed.  I now use a small lapel mike, with the windscreen removed, held by a fixture to as close to the surface as possible (1mm or less).   If I was reading a pressure wave generated parallel to the surface, it should not show the alternating active and null zone patterns that I find, which to me indicates the position of antinodes and nodes.

[Peter K-G]

Two figures from Cremers book on the critical frequency and beamforming.

 

 

So that's why we should tune plates

[Marty Kasprzyk]

I took a survey of the rib response (bridge driver, white noise input) and found that the strongest output was from the middle of the C-bout ribs.  Here is the plot of the strongest point on the ribs, compared to a few points on the top... taken on the trebel side, near the fingerboard, at 2, 4, and 6 cm from the edge near the neck.

Rib Response.jpg

So, yes... there is some HF sound coming from the ribs, but it's not a major power source.  Only a few narrow frequencies appear to get near the levels of the top.

 

Also, the area of the ribs is small compared to the top, so this plot may mislead one into thinking the ribs are even more important sound producers than they really are.

 

I have no idea what the bulging rib effect might do; these measurements are on a new-ish instrument with unbulged ribs.

 

Oliver Rogers tested one of my violins and found that it didn't produce much high

frequency output.  He suggestedthat I thin the ribs. 

 

I argued that thinning the ribs would reduce their resonance frequencies.  He argued that thinning the ribs would

raise them because their edges were clamped not free.

 

I gave in and thinned the ribs.  He retested the violin and the high frequencies output did significantly increase

as he predicted and the violin sounded much better.

 

This suggested to me that the rib wood's elastic modulus and thickness might be important

but neglected variables.

[Don Noon]

Did he specify thinning any specific areas of any specific ribs, or just in general?

[~ Ben Conover]

f hole wings are not tweeters, they use facebook instead.
I didn't read any of this topic so don;t blame me if I'm wrong.

[Anders Buen]

I believe I am getting a decent reading of the activity directly where the microphone is placed.  I now use a small lapel mike, with the windscreen removed, held by a fixture to as close to the surface as possible (1mm or less).   If I was reading a pressure wave generated parallel to the surface, it should not show the alternating active and null zone patterns that I find, which to me indicates the position of antinodes and nodes.

A microflown sensor would do the job. :-) It is not possible to determine the direction of the sound by using an omnidirectional mic. I do, however, not have your skills and experience doing this.

Stoppani used a mic like that to see the airflow around the fiddle using his modal analysis software.

[Anders Buen]

I believe I am getting a decent reading of the activity directly where the microphone is placed. I now use a small lapel mike, with the windscreen removed, held by a fixture to as close to the surface as possible (1mm or less). If I was reading a pressure wave generated parallel to the surface, it should not show the alternating active and null zone patterns that I find, which to me indicates the position of antinodes and nodes.

I think we may expect the sound radiation to increase along the edges because there are nothing outside the edges cancelling the sound. If you do a test on a window, where do you get the highest readings?

The textbooks give the answers, but Ill keep shut until we see the answer. I can do this test myself when I have a loudspeaker for the purpose here at hand. I have a glaced in balcony.

[Don Noon]

I think we may expect the sound radiation to increase along the edges because there are nothing outside the edges cancelling the sound.

Also, with a fixed edge, the antinode closest to the edge should have a larger radiating area than those in the middle.

[Anders Buen]

image.jpg

 

So that's why we should tune plates

The tap tones does indeed say something about where the critical frequency will end up. Jim Woodhouse is not so enthusiastic about this idea, but Frank Fahy and George Bissigner are. I am sorry about the "name dropping" here. But these are all scientists I have a great respect for. :-)

[Marty Kasprzyk]

Did he specify thinning any specific areas of any specific ribs, or just in general?

I think he recommended everywhere but I didn't thin at the blocks.

[Don Noon]

The tap tones does indeed say something about where the critical frequency will end up. Jim Woodhouse is not so enthusiastic about this idea, but Frank Fahy and George Bissigner are.

I'm with Woodhouse on this one.

 

It may be of some academic interest to see where the critical frequency is, but trying to "improve" the high frequency radiation by creating a lower critical frequency doesn't look like a reasonable path, for several reasons:

1.  A lower critical frequency means that all of the mode frequencies will be higher, and modal density will be reduced... the overall tone will be different.

2.  It is not clear to me that the increased radiation efficiency due to the lower critical frequency would be any better than lightening the plate and have a higher critical frequency.

3.  With arching and graduation, it should be possible to affect node area and position, which I believe would be far more effective that the critical frequency in controlling the radiation efficiency of the instrument.

 

These are all assuming one wants a particular tonal goal, or maybe keep everything as-is and just try to get a little more top-end power.  However, if the goal is to shift the entire spectrum upward in frequency, then thicker grads, higher radiation ratio wood, and higher taptones might make sense.  You could probably come to that conclusion easily without knowing anything at all about the physics behind it, just by building a few instruments.

[Joe Doe]

Since top players are very interested in what happens in the basses I make my f-hole wings work as subwoofers.

[Peter K-G]

The tap tones does indeed say something about where the critical frequency will end up. Jim Woodhouse is not so enthusiastic about this idea, but Frank Fahy and George Bissigner are. I am sorry about the "name dropping" here. But these are all scientists I have a great respect for. :-)

 

You know from our previous debates my experience with platetuning, we probably don´t want to go there. But just to clarify, do you meen local tap tuning or plate tuning (M2, M5 modes) ?

[Peter K-G]

Since top players are very interested in what happens in the basses I make my f-hole wings work as subwoofers.

 

How?

[Peter K-G]

If I may join this interesting discussion  I think f-hole wings are tweeters, but mostly depending on the < 600 Hz body modes (A0, B1-, B1+). If we learn how to control the pitch and deltas between these modes and relative dB deltas between them, I think we have the equalizer we need to control the sound spectrum.

 

I have experimenting with moving the modes, by attaching lumps of clay in different places, while playing the violin. It seems that this has the most significant shift in sound (and spectrum), than anything else.

 

BodyModesEqualizer.jpg

 

 

No one seemed to like this idea as a simple solution to equalize sound spectrum

[Anders Buen]

You know from our previous debates my experience with platetuning, we probably don´t want to go there. But just to clarify, do you meen local tap tuning or plate tuning (M2, M5 modes) ?

Mr Kreit: I think you might try to lead us onto a different feld than we are teally discussing here.

[Anders Buen]

No one seemed to like this idea as a simple solution to equalize sound spectrum

Because it is nonsense! :-)

[Peter K-G]

Mr Kreit: I think you might try to lead us onto a different feld than we are teally discussing here.

 

Here we go again Anders, you obviously want to know how I am. The reason why I'm not using my real name on this forum is because I want my name to come up with my business in Google search. I might send you an e-mail if you promise not to publish my name on this forum and tell that you where wrong about my identity ? I find violin making and violin sound very interesting and do it as a hobby. It's a real contrast to software technology whitch is changing rapidly. The violin havent change in some 350 years. This forum get a lot of hits in search engines.

[Peter K-G]

Because it is nonsense! :-)

 

Thanks!