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The following information has been disseminated on the web and in a recent clinic on saxophone repair.

"A resonator is a mirror. It reflects the wave. If you want the wave to be reflected accurately, the resonator must be of the same material as the saxophone body. If you want to "color" the sound, you can alter the material, which will change the degree of refection of some partials".

I thought it might jump start a discussion on the acoustic effects of resonators and the myths and realities surrounding size, shape, and materials.
 

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I'm interested in reading this thread. I am also interested to know if anyone has changed resonators on their horn multiple times and what the effect was.
 

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"Change the degree of reflection"? He can't literally mean the angle can he? I haven't read anything about this, so correct me if I'm wrong -- There should be a difference between damping (pad) and non-damping material (reso), but I doubt there is a significant difference in the damping effect between, say, nylon and brass, and none between any two metals. That said, it seems to me resos of significantly larger diameter should dampen less (to what degree this is desirable is a matter of aesthetics). Resos of significantly greater height should alter the chimney height enough to alter the partial alignment (the degree to which this exists IRL I'm sure you and Lance will discuss thoroughly as soon as he takes the bait ;)). As for different shapes (like domed vs. flat), I suppose they should matter a negligible amount, as long as they have the same functional (probably average) height (or maybe surface area? I'm not sure.), which they probably won't in practice. I'm not sure whether domed vs. flat is a significant difference but I assume it should make somewhere between a negligible and 'noticeable to very few' sized difference.
 

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Lance and I famously disagree on just how much different reso thicknesses change partial alignment. I'm not going there again. But I think we basically agree on other points. Mostly: pads are soft and pads are rough, and both those properties cause acoustic losses in the bore. Resos help to eliminate those losses. As long as the material is rigid and smooth, what they are made of doesn't make a damn bit of difference, acoustically. Lighter is probably better in terms of key action, and they should certainly not have any sharp edges to create turbulence. Personally, I think Lance's super-thin, oversize resos are the best from all standpoints.
 

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I like Pisoni's seamles SLIGHT domed resonators for a number of reasons

A) they have a very slight dome but a concave back with helps in them don't protruding inside the horn when properly riveted
B) they come in handy when replacing a missing snap (they have the same sizes and roughly the same shape
C) they're made of brass
D) tonal response matches my taste. I have replaced pads due to resonators choice on a number of previously perfectly well functioning horns and they all gained "body" and tonal stability and coherence between registers without any undesirable side effects, although I think it may have more to do with previous plastic resonators seating more on top of the pad surface and robbing space from the effective internal volume
 

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Well, I won't say anything as I'm not familiar with the term "refection". Maybe that means, "to fect again"? :bluewink:
Ok now I get the joke. This was a "cut and paste" by the way so I am not responsible for the spelling. It does beg the question of whether the standing wave is actually "reflected" off the sides (and by extension the resonators in the pads of closed toneholes) in its longitudinal path through the tube, or whether the sides of the saxophone merely "contain" the vibrating air column influencing the wave only at the level of the boundary layer itself.
 

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... whether the sides of the saxophone merely "contain" the vibrating air column influencing the wave only at the level of the boundary layer itself.
This is an interesting suggestion. Could be, AFAIK. In that case material can't matter, only shape and texture. OTOH, I can feel the horn vibrating in my hands, so there has to be some transfer of energy from the standing wave to the body. Anybody studied this well yet?
 

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The following information has been disseminated on the web and in a recent clinic on saxophone repair.

"A resonator is a mirror. It reflects the wave. If you want the wave to be reflected accurately, the resonator must be of the same material as the saxophone body. If you want to "color" the sound, you can alter the material, which will change the degree of refection of some partials".
Could you reveal the source of this quote? It sounds as if the effect is frequency dependent. Also, if one can "color" the sound using different materials, which characteristics do the various materials impart? One should be able to use this "phenomena" creatively.
 

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Discussion Starter #11
This is an interesting suggestion. Could be, AFAIK. In that case material can't matter, only shape and texture. OTOH, I can feel the horn vibrating in my hands, so there has to be some transfer of energy from the standing wave to the body. Anybody studied this well yet?
A team of French acoustics scientists have studied the Influence of wall vibration on the behavior of a simplified wind instrument.

The conclusion on p. 19 of the study finally puts the matter to rest. A good summary is also found in the abstract at the beginning of the report.

There is no question that the body of the saxophone is set into vibration as it is played, similar to a brass instrument. The question has always been, does that wall vibration have any effect upon the sound transferred to the room. Anecdotal evidence has long held that it does. There is now convincing scientific evidence that it does not to any perceptible degree, and then only under very specific conditions and circumstances. Will this convince readers on SOTW who believe otherwise? Not a chance.:TGNCHK:
 

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A team of French acoustics scientists have studied the Influence of wall vibration on the behavior of a simplified wind instrument.

The conclusion on p. 19 of the study finally puts the matter to rest. A good summary is also found in the abstract at the beginning of the report.

There is no question that the body of the saxophone is set into vibration as it is played, similar to a brass instrument. The question has always been, does that wall vibration have any effect upon the sound transferred to the room. Anecdotal evidence has long held that it does. There is now convincing scientific evidence that it does not to any perceptible degree, and then only under very specific conditions and circumstances. Will this convince readers on SOTW who believe otherwise? Not a chance.:TGNCHK:
This study deals primarily with acoustic coupling of the air column and wall mediums. Benade and Nederveen describe the effects of uncoupled wall vibrations, which can have noticeable effects on the air column, provided the resonance frequency of the wall is higher than that of the fundamental of the note played. In such cases, the bore behaves as enlarged, in that area, possibly affecting intonation and resonance alignment.
 

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The point about vibrations at discontinuities of the cross-section of the bore (like around tone holes) is that if the resonance frequency of the tube is lowered enough at those areas, the tube there could conceivably couple at playing frequencies and vibrate enough to look like a bore enlargement at those points to act as a local perturbation. But Gilbert's study does apply, AFAIK, since he set the whole tube into breathing mode, which should act as a "super-perturbation". His abstract concludes:

"A theoretical model of coupling between the plane inner acoustical wave and mechanical modes is developed and suggests that in order to obtain measurable effects of wall vibrations, the geometrical parameters of the studied tube have to be unusual compared to that of real instruments. For a slightly oval-shaped and very thin brass tube, it is shown theoretically and experimentally that a coupling between the inner plane acoustic wave and the ovaling mechanical modes occurs and results in disturbances of the input impedance, which can slightly affect the tone color of the sound produced. It is concluded that the reported effects are unlikely to occur in real instruments except for some organ pipes."
 

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Could you reveal the source of this quote? It sounds as if the effect is frequency dependent. Also, if one can "color" the sound using different materials, which characteristics do the various materials impart? One should be able to use this "phenomena" creatively.
I recently read it on the "Saxophone Repair Digest" although not sure if that august publication is where it originated.
 

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Discussion Starter #15
Wherever it came from, it is complete nonsense to claim that the resonator must be made of the same material as the sax body in order to "reflect the wave accurately". This is another example of the voodoo science promulgated on the internet by those who don't have a complete understanding of the principles of acoustics.
 
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