Tech/maintenance Saxophone Pad Acoustics Study

[jbtsax]

Have people been saying that saxes sound different with these different pad materials?

It is well known that the popular "roo" pads are more porous than traditional leather pads. This is for two reasons. (1) The roo pads have no waterproofing treatment so they don't stick, and (2) the cell structure of the "roo" skin is quite different from other leathers.

Some techs (and players) believe that saxes with "roo" pads don't play as well---equating porosity with leaky pads. My personal experience with white "roos" in my alto is that this is not the case. I can play to low Bb softly without subtoning which I couldn't do on a leaking saxophone. This study hopefully will help determine whether there is a relationship between porosity and acoustic energy losses in different pad covering materials.

 

[Bernie]

It is well known that the popular "roo" pads are more porous than traditional leather pads. This is for two reasons. (1) The roo pads have no waterproofing treatment so they don't stick,

I don't quite follow the logic of (1). They are more porous because they have no waterproofing treatment so they don't stick??

 

[jimmylh]

Aldevis is correct in that it is positive air pressure. I wasn't going to go into this much detail, but here goes:

1. The magnehelic (mag) machine named after the gauge it uses measures "differential" pressure or the "difference in pressure" between two enclosed areas.
   
2. There are two chambers inside the gauge, one that is perfectly air tight and one that is connected by a hose to what you are trying to measure the "leakage" of.
3. The scale of the gauge is 1 to 10 inches of water, so you set the incoming air pressure at whatever pressure you choose which becomes the air pressure in the airtight chamber of the gauge.
4. If what you are trying to measure has no leakage at that pressure, then it gets a perfect reading of zero difference---what you are testing measures the same as the airtight chamber.
   
5. Say if your initial pressure is set at 4 and your pad reads at .6, that means that the pad is losing .6 in of pressure by air seeping through the leather covering.

I hope this doesn't make it more confusing. Magnehelics are more commonly used on flutes, clarinets, and oboes with cork or bladder pads to detect leaks. They are not practical for saxophones because of the larger tone holes and types of pads used.

Thanks for the explanation. I get what you're doing now.

 

[jbtsax]

I don't quite follow the logic of (1). They are more porous because they have no waterproofing treatment so they don't stick??

As I understand it, the cellular structure of the kangaroo skin makes them naturally less prone to becoming sticky on the saxophone. Most modern pads have some type of waterproofing treatment that many believe adds to the pad's tendency to be sticky. The roo pads could easily be made waterproof, but that would take away from their advantage of being less likely to stick to the tonehole than other pads. I hope this makes sense.

 

[DavidUK]

Two things...

1/ I have noticed my waterproof SA80II pads get sticky whereas my non-waterproof YAS-62 pads never do. Your theory here is watertight.

2/ Are you doing your measurements with dry pads, moist pads, or wet pads? The latter would perhaps best replicate a sax being played. Spit may fill the pads' pores and make an acoustic difference.

 

[Bernie]

The roo pads could easily be made waterproof, but that would take away from their advantage of being less likely to stick to the tonehole than other pads. I hope this makes sense.

Yes, thanks. Do you detect any difference in the sound when using roo pads?

 

[thomsax]

Roo-pads (TM) but I guess we are talking about all kangaroo pads? Black, choclate, white ...

I'm just going to install black kangaroo pads with oversize brass resonators/reflectors on my "The Martin Baritone". Some techs says; Don't do it! Other says; Pads ok but resonators are not good any more! .... I don't know what to believe? I still want to try this combination on my baritone even if it cost me more money and time. If anyone else is going to install pads and resonators/reflectors on a (1962) "The Martin Baritone", feel free to PM me. Both toneholes diameter for resonators and keycup diameter for pad size. Always thin pads on "The Martin", around, 3,9-4,1 mm.

Back to topic. It's going to be interesting to see the result of the pad study.

 

[jbtsax]

Recent studies have shown that resonators act as "pad covers" to decrease the amount of sound energy lost by absorption. The material makes virtually no difference since the metal and plastic test almost identically and advanced players could not tell which was which in a blindfold test using the same neck on saxophones 1 serial number apart. Of course, size does make a difference, but not the material. Unfortunately the "wavy" resos were not part of the test.

 

[aldevis]

I am not sure I got how you are going to test the influence of pads/resonators on sound.

 

[jbtsax]

I am not sure I got how you are going to test the influence of pads/resonators on sound.

My study has to do with different pad leathers and other types of coverings like the Jim Schmidt gold pad. To keep it simple there will be no resonators in the pads tested. My part of the study will test the "porosity" of the pads, the advanced part of the study will test the "absorption coefficient" of the pads which is basically the acoustic energy the pads absorb. Theoretically pads with a higher "absorption coefficient" will make a saxophone feel harder to blow and less responsive. Pads with a low "absorption coefficient" will seem easier to play and have a better response. This study then has to do more with how the instrument "feels" to the player than the sound produced.

A previous study of resonators by Dr. Eveno did measure and analyze the difference in sound produced by a saxophone with and without pad resonators along with the perceptions of advanced players. For those who are interested, here is a link to the study: An Acoustic and Perceptual Evaluation of Saxophone Pad Resonators

 

[abadcliche]

So will the magnahelic measure both suction and pressure? That's what a pad experiences in real usage, so I'd think that would be a good way to go.

Also the setup looks super cool, but perhaps the acrylic sheath should be moved out of the way so that the fringes of the "tonehole" are unencumbered like they would be on a real saxophone.

How do the pressures of a magnahelic compare the the pressures of a wave passing by inside a saxophone bore that is actually being played? Do we know what maximal pressure is? At least enough to blow a low Eb open for some people. I'd wager that's fairly high, and the equivalent of suction when the low pressure part of the wave passes by. If ANY air leaks in- or out- during playing, well you've brought the peak and the trough of the wave closer together, decreasing amplitude, which is a to say turning down the volume.

It would be interesting to do the same experiment with a tiny leak, like perhaps you could lay a grain of sand or a beard hair on the tonehole rim.

 

[thomsax]

@jbtsax Thanks for the link.
Now I'm looking forward to your pad study. It's going to be interesting.

 

[aldevis]

the advanced part of the study will test the "absorption coefficient" of the pads which is basically the acoustic energy the pads absorb. Theoretically pads with a higher "absorption coefficient" will make a saxophone feel harder to blow and less responsive. Pads with a low "absorption coefficient" will seem easier to play and have a better response. This study then has to do more with how the instrument "feels" to the player than the sound produced.

Can you disclose how is the experiment designed?

A previous study of resonators by Dr. Eveno did measure and analyze the difference in sound produced by a saxophone with and without pad resonators along with the perceptions of advanced players. For those who are interested, here is a link to the study: An Acoustic and Perceptual Evaluation of Saxophone Pad Resonators

I've seen it in the past. Really interesting and opens the doors to a world of experiments to define the concept of acoustic absorption.

 

[Alphorn]

What types of pads are you going to test? As science is all about statistical significance, how many replicates per type are planned? As this will probably be published at some time as kind of a follow up investigation of the paper you linked to, numbers should't be to low. From your original post it seems that all pads are different at least colourwise. Since leather is a natural product, the results within one pad might differ depending on which portion is positioned on the chambers. Don't get me wrong. I think it is a great idea to test this, I am just wondering what sample size is used in accoutical sciences.

Alphorn

 

[aldevis]

As science is all about statistical significance, how many replicates per type are planned?

I can smell inductive reasoning, almost banned in this kind of subjects.
In general on the Anglosaxon world I can get strange looks when I mention that at uni I was very keen on epistemology.

Numbers will be low. Money plays a big role.
I think that only Yamaha could invest (in the past) on serious, unpublished, research.

 

[jbtsax]

So will the magnahelic measure both suction and pressure? That's what a pad experiences in real usage, so I'd think that would be a good way to go.

Inside a sounding instrument there is pressure at pressure antinodes and flow at velocity antinodes. There is no suction.

 

[aldevis]

There is no suction.

Wrong: many players I know really suck.

 

[Alphorn]

Wrong: many players I know really suck.

I am especially great at this down low on Tenor

 

[kevgermany]

Inside a sounding instrument there is pressure at pressure antinodes and flow at velocity antinodes. There is no suction.

I think the lower pressure at the flow points is less than atmospheric and would count as suction.

btw, why do you refer to antinodes twice in different contexts?

 

[Targa]

I can smell inductive reasoning, almost banned in this kind of subjects.
In general on the Anglosaxon world I can get strange looks when I mention that at uni I was very keen on epistemology.

They probably wonder why you're mentioning it, at uni most people are keen on finding ways to get pissed.