[Jorns Bergenson]

Any ideas about how to cure side-C and side-Bb being blown open? This is on a "The Martin Tenor", which is a model I've had lots of experience setting up, but this is the first one that no matter how much I increase spring tension, I get warbling when playing low E. No problems when I hold them closed or put cork under the key arms to keep them shut.

I've got teflon tubing around the round lever that goes through the open oval on the operating key. There is no lost motion at the joints, but they move freely. The springs are original and in good shape. To get any more tension, I'll need to drill the posts for bigger springs or add additional flat springs, but those just seem like bad options since the keys require quite a bit of force to open already.

The pads seal very well. With just gravity holding the keys closed, they seal fine. I've checked them with a strong light and a feeler as well. The horn does have Noyek resonators. I've even wondered if putting smaller flat resonators might help.

Any suggestions would be appreciated.

 

[Jorns Bergenson]

Ok, I used Google to search the forums and found this thread: http://forum.saxontheweb.net/showthread.php?108976-Yani-Alto-Side-C-Key-blows-open

I've covered everything in that thread except changing the pads, springs and resonators (maximum sized Noyeks were installed at the client's request and are not my choice of resonator). I'm probably going to work from the least likely: attempt to remove the Noyeks without damaging the pads. That would be wild if that fixed the problem! If that does nothing, then I'll try new springs.

 

[Stephen Howard]

You might have a 'through leak'.
This is where there's an air path through the pad itself, typically down the reflector rivet hole, along underneath the base of the pad and out up the side of the key cup.
Such a leak would by nature be small, and impossible to detect by conventional means - however, it would respond to excessive force being placed on the key cup, which would distort the pad and thus seal the gap, either beneath the pad or by expanding it into the cup wall.

I've seen such leaks once or twice in over thirty years - the problem being that as you heat the cup to remove the pad you melt the glue and so destroy the 'evidence'. Once or twice though you might be lucky, and when the pad is removed you can see a clear path...and you might even see a water track on the base of the pad.

The only way to know for sure would be to remove the pads and reglue them. If the symptoms persist then it's something to do with the type of reflector.
It would be worth trying it while you have the opportunity.

Regards,

 

[Jorns Bergenson]

Stephen,
Thanks for that suggestion. I'm sure that it isn't a "through" leak since I did the overhaul on this horn and I always seal the back of the pad with shellac and use a generous amount in the cup.

I just drilled out the rivet and replaced the resonator on the side-C with a smaller flat seemless resonator. I cut the stem on the back of the resonator and filled the hole in the pad with high-temp potting and pressed the new resonator in. As expected, a new resonator made no difference. I rechecked the soldered tone holes for leaks and checked the pad again with a leak light and a feeler. No leaks found. Keywork is tight, no binding.

I don't know what else to do at this point except step up the spring size.

 

[slausonm]

I've seen the term "blowing open" used by a variety of players. The last person that told me this was a trumpet player that claimed he was blowing open his water keys and wanted his springs changed because of this. I personally don't think it is possible for any human to blow open a key or a waterkey to an instrument that has normal or even fairly weak spring tension without plugging every other hole in the instrument including the bell. The lung capacity and pressure is just not there.

So why do they think they are blowing open a key? There is a leak somwhere. It may be a mal adjusted pad, uneven or chipped tone hole, bad regulation/articulation, bad technique (resting your hands on keys or letting fingers over hang, or a variety of other things that cause air leaks.

I would love to see blowing open a key demonstrated. I don'y think it is possible. FYI, I changed the waterkey springs and corks on the trumpet:mrgreen:

 

[Jorns Bergenson]

Its not the amount of pressure blown by the player, it is the pressure node at the particular tonehole that is pounding away at the key. I wish I had a camera, you can actually see the pad cup vibrating the slightest bit. On this horn, low E will cause the side-C and side-Bb to vibrate open. It plays fine at medium volume but as you push, the keys start vibrating. An assistant can feel the pad cup start vibrating and I can feel the key touches start to vibrate if I barely touch them as I play low E. I'll try to see if a camera can pick up the subtle vibration.

I installed new springs, increasing from 1.2mm to 1.3mm. It did help quite a bit, but I can still get it to happen at loud volumes. I was thinking of putting flat springs under the keys.

Long ago, another tech told me that Martins could be improved by thinning the tone hole rims. He said that it helped pads seal and it helped prevent normally-closed keys from blowing open. I had never heard of this sort of problem being associated with Martins but now I wonder.

[Edit]: I just drug out five Martin tenors from my collection: a couple of mid 1930 stencils, a 1959 Indiana, a 1939 Handcraft Committee II, and another 1954 The Martin Tenor. I can get the last two to blow open the side-C when playing low E at very high volume. The other tenors all have flat springs on the RH-side keys and no matter how loud I play, the side keys do not blow open. I am using the client's mouthpiece which is a Dukoff LD10, a fairly aggressive piece. It is actually very difficult to get the keys to blow open with a more subdued mouthpiece like a Broadus S4. In any case, my client's tenor is worse than the other two horns I have that do it. I find this all very strange.

 

[Stephen Howard]

There's an easy way to test the proposition. Take any horn with decent well-set pads and slacken off the low Eb spring. Leave it just strong enough so that no leak can be detected with a light or a feeler - then blow the horn. It'll give way.

If the closed keys didn't act in this way all those vintage horns would have feather-light low C# keys.

Regards,

 

[Stephen Howard]

I installed new springs, increasing from 1.2mm to 1.3mm. It did help quite a bit, but I can still get it to happen at loud volumes. I was thinking of putting flat springs under the keys.

Long ago, another tech told me that Martins could be improved by thinning the tone hole rims. He said that it helped pads seal and it helped prevent normally-closed keys from blowing open. I had never heard of this sort of problem being associated with Martins but now I wonder.

I guess it's all down to leverage then. Thinning the tone hole rims will up the PSI, as will increasing the strength of the spring.

Regards,

 

[clarnibass]

I have no idea what it would do, but just curious if you can try increasing the weight of keys by temporarity tying something to them, or gluing something with contact glue to them. Not especially heavy but more than pieces of papers, etc. Just wondering if that makes any difference in any way (possibly making it worse?!).

Long ago, another tech told me that Martins could be improved by thinning the tone hole rims. He said that it helped pads seal and it helped prevent normally-closed keys from blowing open. I had never heard of this sort of problem being associated with Martins but now I wonder.

IMO it's important to explain what that does, more than just "help pads seal" (i.e. why it helps). This is a bit similar to increasing the spring tension for closed keys and weakening the spring tension for open keys, but in reverse.

Imagine sticking a tack into some wood with your finger vs. trying to stick a thick nail with same size head. The tack will be easier. Or one of my favorite examples (from the kids section of the local science museum) imagine how painful sitting on one nail is in comaprison with a bed of crowded nails. Essentially less force needed with less contact area. These are exaggerated examples but show the point.

So with closed keys, decreasing the tone hole rim is essentially the same as increasing spring tension, but without affecting the feel of the key. For open keys this means less pressure needed by the finger to seal. This is specifically for the sealing that happens from the moment the pad touches the tone hole until it achieves a seal. As I'm sure everyone knows, the pad touching the tone hole doesn't actually seal, it is the addition slight travel and pressure after that moment that is achieving the seal.

I found thinning the tone hole rims to help in requiring less pressure to seal. Of course even thick tone hole rims like on Martins, when pads are installed accurately, will seal with no problems with playing finger pressure. IMO the less pressure needed helps more also can last longer, when the pads eventually become harder and need more force to seal, etc.

I don't always thin the tone hole rims on Martins, but when I have, I and high level players who owned the instruments found no negative effect acoustically. Actually no effect at all except better response from more easily sealing (i.e. less pressure needed etc.). The thinning is is only the top of the tone hole, I'd say at most about 1mm in height, and tapered, meaning a diagonal from full thickness to chosen thickness happen in a length of 1mm i.e. not the entire top 1mm is thinned (sorry for the messy explanation, I hope it's clear enough).

 

[slausonm]

Its not the amount of pressure blown by the player, it is the pressure node at the particular tonehole that is pounding away at the key. I wish I had a camera, you can actually see the pad cup vibrating the slightest bit. On this horn, low E will cause the side-C and side-Bb to vibrate open. It plays fine at medium volume but as you push, the keys start vibrating. An assistant can feel the pad cup start vibrating and I can feel the key touches state to vibrate if I barely touch them as I play low E. I'll try to see if a camera can pick up the subtle vibration....

I would love to see a video of this. Sustaining a loud enough note that vibrates the instrument enough to keep a sprung closed /non-leaking tone hole and pad open would certainly be interesting to see. This would be on par with the opera singer capable of breaking a crystal wine glass with a long sustained/loud high note.

Your explaination also leads me to believe that the trumpet player that used this term "blowing open" does not have the same issue as the sax player. Trumpet waterkey holes are placed in a location that would presummable least affect the sound should they either leak or the bore shape affect a node in the sound wave.

Matt

 

[Henry D]

While not exactly common, this is not the first time a competent tech has reported this. See http://forum.saxontheweb.net/showth...ey-blows-open!&highlight=yanagisawa+side+open

Trumpet spit valves usually fall almost exactly at either A or Ab. Its location in relation to the wave varies. The degree of pull on the tuning slide (where the spit valve is located) moves it through a range where it may well be spot on the node. While one would like to think that the engineers carefully consider node placement when placing the spit valve I think in practice it comes out at the bottom front of the main tuning slide in the best place to dump spit rather than based on some serious acoustic consideration. The Yamaha nipples and Amado keys are concessions to the theoretic disruptions caused by the <closed> water drain holes.

That said, I can think of no reason why you wouldn't have a nice strong spring on the spit valve key. The size of the hole involved* being operated upon by the sound wave is so much smaller than in sax tone holes that it'd take Maynard and a really, really, feeble spring to even contemplate a scenario where a blow open would happen.

*air pressure times area of pad/ water key cork exposed to the sound wave would equal the force. The force on the much smaller spit valve cork is usually actually more than the hold closed force on most side C or Bb key cups.

 

[Turnaround]

Blowing a valve open in an interesting concept. I wonder how much pressure is really in the horn. I have wondered about this and tried this to figure out if my curiosity was warranted. Take your mouthpiece off your horn. Blow through it with a reed on. Then, using the same force, blow on your hand. Feel the pressure... Then blow through your mouthpiece again and put your hand at the end of the mouthpiece by about an inch.

Do you feel anything?

Now, that's just wind pressure. It's amazing how much of that energy is being turned into sound.

If the sound wave is blowing open your side valves, I think the springs are pretty weak. You must be an impressive triller... just playing...

 

[Henry D]

...blow through your mouthpiece again and put your hand at the end of the mouthpiece by about an inch.

Do you feel anything?

I don't think anyone is under the impression that the pressure of the air being blown under the reed and through the mouthpiece could blow out a weakly burning match- much less blow even a lightly sprung cup off a tone hole.

On the other hand there's some pretty decent presure generated at the nodes when playing a note. That pressure has nothing to do with the air moving thourgh the mouthpiece. A small speaker at the mouthpiece window would move no air through the horn but would still excite a sound wave at the proper frequency and generate pressure at the nodes.

I've never, to my knowledge, encountered in person such an issue myself- but I didn't see it as much of a stretch to credit it as possible if the sound wave wound up aligned "just so".

 

[lhoffman]

Physics to the rescue!

Any mass/spring system will have a resonant frequency. If you have a periodic force that drives this system (such as a sound wave), and its frequency is close to the resonant frequency of your mass/spring, you can get some rather dramatic effects. My guess would be that the resonant frequency of your side key is just right for a low E to make it oscillate. More to the point, you might want to try lowering the key's resonant frequency.

Roughly speaking, the resonant frequency for such a setup goes as the square root of the strength of the spring over the mass attached to it. When you switched to the stiffer spring, you were actually increasing the resonant frequency, perhaps by an insignificant amount. To lower the frequency, you can either try a softer spring (simply adjusting the tension in the spring will not do it), or increasing the mass of the key. It might be worth your while to use some blue tack to attach a washer to the outside of the key, just to see if it helps at all.

 

[Turnaround]

I don't think anyone is under the impression that the pressure of the air being blown under the reed and through the mouthpiece could blow out a weakly burning match- much less blow even a lightly sprung cup off a tone hole.

On the other hand there's some pretty decent presure generated at the nodes when playing a note. That pressure has nothing to do with the air moving thourgh the mouthpiece. A small speaker at the mouthpiece window would move no air through the horn but would still excite a sound wave at the proper frequency and generate pressure at the nodes.

I've never, to my knowledge, encountered in person such an issue myself- but I didn't see it as much of a stretch to credit it as possible if the sound wave wound up aligned "just so".

I only made a comment out of personal curiosities. I've given this thought in the past from other questions and made me try this home experiment. It proved a lot of things to me at the time, yet, as a full time audio engineer, these type of questions still intrigue me and I am still curious about the pressure of sound in an environment. It really is amazing what happens within a conical tube, and what really amazes me is the transition of physical wind energy to sound energy via the vibrations of the reed with minimal heat loss. What a wonderful thought. It makes me feel better about the effort I put into the horn.

 

[KEN K]

Instruments have a big hole at the end call the bell . That is where most of the air go out. I don't think it is possible to "blow open" a key unless you stop up the bell. People say it can happen but I have never seen it.

Had a trumpet player that was trying to tell me when he played he sucked in his tuning slide. Somebody explain that.

 

[Jorns Bergenson]

Interesting thoughts all around.

I tried putting a lump of putty on the key cup. That helped quite a bit, in fact, I had to grossly over-blow in non-musical way to blow the side-C open. I don't see this as a solution, though.

Tonight I compared two of the Martin tenors: one with flat springs and my customer's with needle springs. Acoustically, these horns are very similar. I've measured the body tube and tone holes and they are virtually identical (the tone holes have a different bevel style, but the inner diameters are virtually the same).

The one that does not have a problem (with flat springs), is set up with very light action, much much lighter than the one with fluttering side-C. The keys are the same length, but the one that flutters has its pivot about 8mm further away from the key cup than the one that does not flutter. Also, the tenor that does not have the flutter issue has thicker tone hole edges. Now that I look at problem horn, there isn't much thinning that can be done to the tone hole walls.

I do know that the force required to open the key from the key touch is much greater than with the problem horn. Tomorrow I'd like to measure the force closing the key cup.

It's time to put this thing away for the night and come back to it tomorrow.

Thanks all!

 

[Jorns Bergenson]

I don't think it it possible to "blow open" a key unless you stop up the bell. People say it can happen but I have never seen it.

Well, I wish I could create a video, but I don't have the means to do so at the moment. Maybe my son can help me make a video tomorrow.

So, "Blow open" isn't the best terminology. "Vibrate open" is better but doesn't do it either. It is more like "the pressure wave associated with a played note beating against a normally closed key causing it to bounce open due the the resonant frequency of the affected key" or something like that

 

[Stephen Howard]

So, "Blow open" isn't the best terminology. "Vibrate open" is better but doesn't do it either. It is more like "the pressure wave associated with a played note beating against a normally closed key causing it to bounce open due the the resonant frequency of the affected key" or something like that

Sounds about right - the term has more to do with the meaning 'to fail'.

I'm sceptical that the resonance of the spring is a major factor. I'm sure it's all going to be down to where the closing power is applied - the nearer to the touchpiece it is, the more power is going to be lost by the time the energy gets to the key cup.
Check out the difference in snap between those horns that have the side top E keys sprung at the lower pillar and those sprung at the top pillar. For the same spring size and tension the latter setup gives a more positive response at the key cup.

I suspect the fix is going to be to fit a flat spring to the key.

Regards,

 

[clarnibass]

I tried putting a lump of putty on the key cup. That helped quite a bit, in fact, I had to grossly over-blow in non-musical way to blow the side-C open. I don't see this as a solution, though.

I'm suprised you don't think a chunk of putty on the key is a good solution![/sarc]

But cool that my whacky idea worked, in a way. But it doesn't seem good enough anyway since some players grossly over-blow in a musical way, or purposely grossly over-blow in a non-musical way that is musical. So at least for those players it would still be a problem regardless of how ugly it is