Double-Socket necks
1 - 20 of 41 Posts
Joined
·
2,990 Posts
that's probably why the SML system is deemed so wonderful - four slots instead of one with a floating locking ring - very clever.
In theory the double socket design separates the functions of mechanically holding the neck (the outer sleeve) and sealing it to the body (the inner sleeve). The theory is good, as the standard neck joint is a weak point of saxophone design - the whole thing's an inch long, and the upper half is dedicated to mechanical fixing which only leaves a half inch at the bottom for sealing. Compare this to the flute head joint tenon where the entire 2" length goes to sealing (it doesn't need mechanical fixing in the same way a sax neck does). However, I don't see evidence that the inner sleeves of double socket necks are closely fitted to the ID of the body sleeve. In fact, I don't even see how this can be done except by disassembling the solder joints. So in practice I think the double socket neck substitutes a long, loosely fitted leak path for the normal short, closely fitted leak path.
A few alternate solutions to saxophone neck sealing have been tried but none has overtaken the standard. I don't know why this is, what combination of difficulty in service, unfamiliarity, and/or ineffectiveness.
A few alternate solutions to saxophone neck sealing have been tried but none has overtaken the standard. I don't know why this is, what combination of difficulty in service, unfamiliarity, and/or ineffectiveness.
Joined
·
2,990 Posts
the issue with er, um, traditional tenon receivers is the single slot in the receiver which pinches the neck tenon to effect closure. Over time and with metal fatigue this system can lead to leaks - something the SML design avoids. The double socket systems, unless the instrument is damaged, is also less prone to metal fatigue and associated problems. The issue of repair is a moot point. If the instrument is undamaged the double socket system is MORE than fine.
Joined
·
961 Posts
I've tested a number of double-socket necks with a magnahelic machine and they actually leak more than traditional tenons. They worked great for Conn / King's advertising departments but don't work great for acoustics.
Joined
·
20,669 Posts
Exactly.
The 'draw' is....ummmmm......:|......'they're sorta cool'....
I guess.
But trust me, as a repairer......they offer nothing performance wise whatsoever.....and oftentimes, if they get damaged...it's complete or complicated rebuild time for the double-socket, as opposed to a much quicker repair on a conventional-tenon neck....
are they 'bad' ?
No.
Do they 'work' ?
Yeah...
I mean it's not like "they inevitably will fail or cause problems".
They just offer no real advantage....
Joined
·
20,669 Posts
Clever but a bit delicate....not as robust a detail as far as longevity goes (having refurbished a good two dozen or more SML's....)
In other words, what I wrote above, they substitute a long loosely fitted leak path for a short tightly fitted one.
I have serious questions whether static leak tightness of the type referenced is actually what is needed in a musical instrument. Why do we care if the tenon "leaks"? Because it'll create a vent in the wrong place and try to cut off the standing wave in the bore of the horn. OK, what kind of vent is needed to be able to cut off the standing wave? What we need in order to have a problem, is a vent that can pass a certain (small) amount of air back and forth at some (tiny) level of fluctuating differential pressure between the peak internal pressure of the standing wave and the average pressure outside. I would suggest that a long circuitous leak path, while it might leak more in a static test like using a Magnehelic manometer, might well be better than the standard joint at preventing partial cutoff of the standing wave in the bore.
I am not convinced till someone brings data or calculations, that the effectiveness of "sealing" at pads or joints in the application of a saxophone, where "sealing" needs to prevent that in and out flow of air at very tiny pressure differentials and rapid alternation, is appropriately measured by applying a static flow test at a relatively high differential pressure.
It may well be that a long, loosely fitted leak path is actually BETTER for preventing the development of an unwanted vent, than a short tightly fitted one, given the inevitable inaccuracy of manufacture and wear of both types.
Joined
·
2,713 Posts
Most leaks in a double socket neck can be easily addressed. Roll a couple inches of teflon tape into a thread. Feed it down into the socket. Place lightly on the horn and rotate to make a "packing gland" at the end of the double socket. Yes, in theory the tenon might not sit into the neck quite as far. Maybe by .5 mm. So make the adjustment (if necessary) with mouthpiece placement. A pin can remove or adjust the teflon packing.
Something similar can be done with the traditional single slot. Pack teflon tape into the slot. It is also possible to make a wrap around the tenon and smear the tape on (shown on a Martin at the start of this blog).
Packing the double socket slot can work for years. Teflon tape on the tenon can become fiddly and might be best as a diagnosis as to whether the tenon needs expanding.
Mark
Something similar can be done with the traditional single slot. Pack teflon tape into the slot. It is also possible to make a wrap around the tenon and smear the tape on (shown on a Martin at the start of this blog).
Packing the double socket slot can work for years. Teflon tape on the tenon can become fiddly and might be best as a diagnosis as to whether the tenon needs expanding.
Mark
Joined
·
1,461 Posts
Just a thought, cork seems to work well on clarinets etc., one might think that could work, or an o-ring... Probably not cost-effective for a manufacturer to explore since it's not such a huge problem, but I've lived with enough sloppy fitting necks, necks that don't tighten, necks that resist assembly, etc. that I'd love to see it improved!
Joined
·
961 Posts
Which part fails, the tenon or the tightening ring / screw section?
Joined
·
5,209 Posts
How does that make it easier to repair when they are damaged than a regular double socket neck?
selmer 26 nino, 22 curved sop, super alto, King Super 20 and Martin tenors, Stowasser tartogatos
Joined
·
3,454 Posts
To understand why any leak is a problem, it is necessary to understand the physics. A standing wave inside the horn produces two different types of antinodes, whose position depends on the length of the air column. There are pressure antinodes and displacement antinodes. A pressure antinode is a place where the air molecules do not move, but the pressure varies. The displacement (or velocity) antinode is where the pressure does not vary at all, but the air molecules move. In between the antinodes, there are combinations of variations in pressure and in air displacement.
The end of the horn, or the first open tone hole is clearly a displacement antinode, since there is nothing to contain the air, so the energy wave displaces the air. The mpc tip is a pressure node, where air compression happens. Inside the horn there are complex things going on, as there are many potentials for where the wave will form, depending on the length (obviously) but also the shape of the bore. These are called impedances. Impedances also have maxima and minima, and just FYI in a sax the waves form around the maxima (the opposite for the flute). Anyway, my point is that at the pressure antinodes, all the energy that produces the sound at the end of the air column goes into pressure variations, and they are not insignificant.
At the end of the day, the question is really whether at maximum pressure at a pressure antinode, there is a transfer of energy out of the wave caused by the leak. It doesn't matter if the pressure is static as with a Magnehelic or whether it is caused by a varying standing wave, if at a certain applied pressure some of it is lost due a leak, then there will be consequences.
It's not quite like a garden hose, that takes time, once you turn on the faucet, to squirt out the end. That is down to two factors: the hose is not full and the hose expands under pressure. While it is true that air is compressible, the amount of air in any possible length leak channel in a sax is minimal. And even if the leak channel were long enough that a momentary pressure variation did not cause an "escape of air" to the outside, the pressure of the standing wave at the pressure antinode is still lost to friction as the air is compressed in the leak channel.
The only condition that applies in terms of using a static leak test is that the pressure generated by the Magnehelic be equivalent to that of the maximum pressure generated at the point of the leak by the standing wave. And generally speaking a higher pressure generates a leak by compressing non-rigid material. This is mostly to do with pads, where a finger or a spring is compressing a pad enough to make a seal able to withstand the maximum pressure exerted on it by the air column. As the pressure increases, it eventually exerts enough pressure to deform the pad enough to break the seal. This is obviously not the case at the tenon joint.
kymarto,
I agree that in theory it seems like a leak under static differential pressure, and a leak under the fluctuating pressure found in the saxophone bore, ought to have the same effect. (Certainly even if the static test pressure is much greater than any experienced in operation, it's not going to deflect the materials at the tenon!)
However, my question is one that needs testing: is it actually true, or not, that static test leak results under a higher static differential pressure, are (or are not) predictive of behavior at a double-socket tenon in actual operation - where the presssure is not static but rather varies as a sine wave, and the maximum amplitude is considerably less than the static pressure applied in a static leak test?
I wouldn't be asking this question, except that the real world results tell us that King Super 20 saxophones with double-socket necks - which are NOT as tightly sealed as traditional neck joints - and Conn 6M alto saxophones with both double socket necks AND leaky worn microtuners - perform fantastically well as saxophones! So here we have a case where our standard theory of how a leak causes a saxophone to misbehave, is contradicted by observed evidence that these instruments do NOT exhibit behavior characteristic of a saxophone with a big honkin' leak at the tenon joint. When your observations contradict your theory, you've got to reconsider the theory, thus my suggestion that leak rate under a static differential pressure may not be sufficent to characterize a joint in a saxophone.
I agree that in theory it seems like a leak under static differential pressure, and a leak under the fluctuating pressure found in the saxophone bore, ought to have the same effect. (Certainly even if the static test pressure is much greater than any experienced in operation, it's not going to deflect the materials at the tenon!)
However, my question is one that needs testing: is it actually true, or not, that static test leak results under a higher static differential pressure, are (or are not) predictive of behavior at a double-socket tenon in actual operation - where the presssure is not static but rather varies as a sine wave, and the maximum amplitude is considerably less than the static pressure applied in a static leak test?
I wouldn't be asking this question, except that the real world results tell us that King Super 20 saxophones with double-socket necks - which are NOT as tightly sealed as traditional neck joints - and Conn 6M alto saxophones with both double socket necks AND leaky worn microtuners - perform fantastically well as saxophones! So here we have a case where our standard theory of how a leak causes a saxophone to misbehave, is contradicted by observed evidence that these instruments do NOT exhibit behavior characteristic of a saxophone with a big honkin' leak at the tenon joint. When your observations contradict your theory, you've got to reconsider the theory, thus my suggestion that leak rate under a static differential pressure may not be sufficent to characterize a joint in a saxophone.
selmer 26 nino, 22 curved sop, super alto, King Super 20 and Martin tenors, Stowasser tartogatos
Joined
·
3,454 Posts
It is true that any hole (including a leak) between the air column and the outside air acts with two properties, as an inertance and a resistance, and the acoustic behavior of small holes, such as register holes, changes depending upon their length and therefore the ratio of inertance to resistance, so there may be something to explore as to the difference of a leak that admits a certain airflow at a given pressure with a longer "hole" as opposed to a shorter one, but my guess is that a comparable leak in terms of size between single and double socket necks really would not make a big difference.
I don't think you can count on "impressions" or anecdotal evidence--you really need to do tests of a double and single socket horn with comparable volume leaks as measured with a static pressure test, both being otherwise in good regulation. I think what is clear is that a physically loose double socket tenon might be leaking less at playing pressure than a single tenon that seems comparably loose to the touch. In all these cases, it is necessary to carefully test different horns at a given static pressure. Obviously if a double socket neck that "seems" loose is leaking less at a given pressure due to the extra surfaces, it is going to play better than a single socket neck that is actually leaking more. Really good static testing is the key.
I don't think you can count on "impressions" or anecdotal evidence--you really need to do tests of a double and single socket horn with comparable volume leaks as measured with a static pressure test, both being otherwise in good regulation. I think what is clear is that a physically loose double socket tenon might be leaking less at playing pressure than a single tenon that seems comparably loose to the touch. In all these cases, it is necessary to carefully test different horns at a given static pressure. Obviously if a double socket neck that "seems" loose is leaking less at a given pressure due to the extra surfaces, it is going to play better than a single socket neck that is actually leaking more. Really good static testing is the key.
1 - 20 of 41 Posts
