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"The non-linear reed "
To help me overcome a stumbling block, could you explain exactly what you mean by that?
 

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selmer 26 nino, 22 curved sop, super alto, King Super 20 and Martin tenors, Stowasser tartogatos
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Discussion Starter · #43 ·
Thanks for that link. As always Fletcher is a difficult read for me. I think the essential idea is stated in his introduction.
Such mode locking is favored by nearly harmonic normal mode frequencies, by large mode amplitudes, and by large nonlineartry in the driving force.
This suggests to me as was pointed out by Benade that mode locking does occur but the process is more efficient in instruments whose bore dimensions produce harmonics close to their natural frequencies.

My understanding at this point is that the measuring of an instrument's "acoustic impedance" bypasses the non linear mode locking of the reed blown apparatus and shows the acoustic "footprint" of the instrument itself.

John
 

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Gordon,

I hope this clumsy explanation helps.

Paraphrasing Benade from his FMA, Pg 395:

"" A source is non-linear if the flow thru it varies in a way
that is not simply proportional to the applied pressure.""

On page 437 he shows a graph of the measured flow produced by a reed
being blown at varying pressures. If the result had been a straight line,
the reed would be considered "linear". Since it is not a straight line,
but a curved line, the reed is considered "non-linear" for this particular
function.
Non-linearity produces some strange, unexpected results in the physical
world, but they can be shown by the math and proven by measurement.
I proved the mode-locking to my satisfaction by using a free downloaded
fft program.

Thanks for the interest and let’s pursue this.

jim
 

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Discussion Starter · #45 ·
Gordon (NZ) said:
"The non-linear reed "
To help me overcome a stumbling block, could you explain exactly what you mean by that?
The UNSW Saxophone Acoustics site at the heading "The Reed Controls the Airflow" has a good explanation of the non-linearity of the reed's function in the tone production.

John
 

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John says:

<<<
This suggests to me as was pointed out by Benade that mode locking does occur but the process is more efficient in instruments whose bore dimensions produce harmonics close to their natural frequencies.

My understanding at this point is that the measuring of an instrument's "acoustic impedance" bypasses the non linear mode locking of the reed blown apparatus and shows the acoustic "footprint" of the instrument itself.
>>>

I think both of these statements are true. But remember, Impedance is
the pressure divided by the Volume Flow. (p/U). Volume Flow takes
elaborate lab equipment to measure. (See the Fletcher book, pg 222.)
Measuring the pressure is simpler, requiring only a linear source and a
pressure transducer (microphone). See Benade FMA, page 396.
On page 442 Benade states:

"In an instrument that uses a pressure-controlled reed,
the amplitude of each sound pressure component
within the mouthpiece is proportional to the height of
the input impedance curve measured at the FREQUENCY
of the component."

Therefore, it seems to me the simplest way to measure the air-column
resonance frequencies is with a microphone in the mouthpiece with the
horn excited by a linear source.

Thanks for your input and LP! (Let's pursue),

jim
 

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I think the mode-locking concept is important enough that it
deserves its own thread. If it's all right with the crew, I will start
it with a summary of what has been said here, and we can delve
deeper into the subject.

In regard to the low note "burble" problem:

Toby is correct: Combining two tones whose frequency difference
is greater than about 20 Hz, we hear a new tone. If below about 20 Hz,
we hear an amplitude vibrato.
John (jbtsax:10-11-07, 8:00pm) gives us the info we need to address
the burble problem ("octave shifting").

Adding threads to the neck will lower some frequencies (viscous-damping)
but not the frequencies that we want for this problem. According to Benade's
W-curves, we would need to roughen the bore around the A hole.
I think it would be better to strengthen the fundamental by decreasing
porosity-damping at the proper place.

Has any one tried?:

Leave the C# key open and place something hard and smooth
over the hole. Play the low note to see if things are better. Do
the same with the other LH keys.

If this helps, seal the pad leather and/or add resonators.

Comments?

jim
 

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I've also chased the burble around and found that sometimes it's an octave shift, sometimes not. To me, the sound clip sounded like the warbling C was a C with a lower warble, which is not what I usually get. It appears that there are many reasons for warbling, thus many fixes.

One fix that surprised me was when using the Ridenour type method of reed finishing. You "test" the reed by blowing and concentrating on one side or the other of the read. If a discernable difference is detected, it is refinished to even out any difference side to side on the reed. I was surprised at how often this effected low note burble.

My kitchen sink physics explanation (to myself) was that the air flow past the reed was not really the on/off perfect vibration as described in a link above. It might be better visualized as a tarp flapping in the breeze and we are struggling to get it to flap rythmically. This would be the birth place of at least one type of funky harmonics. Add to this the harmonics which may vibrate "open" a particular key, vibrations back into the column from tone holes, the bow curve, etc., and tracing a single ultimate cause of the burble may be misguided.

Good thread. I hope it results in a check off list of likely suspects, no matter how long, and arranged logically as a trouble-shooting guide. The idea of simply putting something in the bow as a cure seems primative (e.g., one should insert food and drink through the Eb tone hole as offerings to the sax gods).

Mark
 

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OK here's a teaser to bump this thread...

So I buy a Ref 36 tenor used. I get it worked on by my shop, some pads replaced etc., and everything seals. The horn sounds fat in most of the range, and has flawless intonation (overtones lock in with fingered notes) with my JJ ESP 6.

But...

Low end (D and below) does not speak readily. I get the body soldered to the bow (replacing paraffin seal). Slightly better. I still have a problem with a low C warble unless I use a very soft reed (Rico Royal 2) that makes the rest of the horn sound buzzier than I'd like. This warble is especially pronounced when I try to subtone the low C, which I always do since I don't want the lawnmower sound.

So, after reading the above concerning slight nuances of the bore and the relative strength of overtones, it begs the question-- did I buy a lemon? Might a new mouthpiece help? A new neck?

Jim
 

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I'm stumped too saxguy. I get this warble on my low C too (54 alto) when I have my bottom lip just slightly horizontally compact I guess (my old teacher always had me do it, I guess the Larry Teal thing) but after seeing a video by Bergonzi how he doesn't like to choke the edges (almost likes to let air leak out the corners), flattening my lip out a bit I never get the warble. Aye aye aye!!!
 

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I've got nothing to add here except that someone definitley needs to figure this out and pm me when they've got it solved. :D
 

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i'm having this issue on my low B and Bb on my 1958 mark VI tenor only had this issue after an overhaul.. i've trying butting somehting in the bell a mouthpiece cap that made it worst ... another neck seemed better but a different sound that i don't want
checked that everything is sealing.. not sure what else to do
i think it has something to do with how far i am on the neck.. my mouthpiece is a gurdala superking and i have it pushed in maybe too far..

anything else to look for
 

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Discussion Starter · #53 ·
If the sax does this on low B and Bb but not on low C and it did not do so before the overhaul with the same mouthpiece, I would have the G# key checked---specifically the adjusting arm from the F# key that closes the G# when the bottom hand keys are pressed.

A leak light in a pitch black dark room should tell the story. If this is not it, write back and we will suggest plan Deux.

John
 

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my tech went through the whole horn with a leak light and found nothing he checked the g# and said it was sealing fine... i am going to check the neck cork cause the mouthpiece seem a bit loose on it.. going to try teflon tape and make sure there is a good seal..

my cork before was bigger and was tapered at the end ..
 

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think its for sure the neck cork.. when i apply teflon tape and paper its seems to be fine.. is a tapered neck better to go with?
 

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Discussion Starter · #56 ·
think its for sure the neck cork.. when i apply teflon tape and paper its seems to be fine.. is a tapered neck better to go with?
The cork should be cylindrical from front to back the same as the interior of the shank of the mouthpiece. This means that on the tapered neck, the cork must be sanded more at the back than at the front. I am surprised that the person who overhauled your Mark VI couldn't properly fit your neck cork to your mouthpiece. This doesn't make sense.

John
 

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Anyone with the lowly "burbles" should read this thread and consider a fresh fat neck cork a possible solution to their problem...

http://www.saxontheweb.net/vbulletin/showthread.php?t=88924

I swapped necks between a Ref54 alto and a Series III alto - the III neck alleviated the burbles and part of it, I feel, may have had to do with the III neck having a much more substantial neck cork on it.
 

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i'm having this issue on my low B and Bb on my 1958 mark VI tenor only had this issue after an overhaul.. i've trying butting somehting in the bell a mouthpiece cap that made it worst ... another neck seemed better but a different sound that i don't want
checked that everything is sealing.. not sure what else to do
i think it has something to do with how far i am on the neck.. my mouthpiece is a gurdala superking and i have it pushed in maybe too far..

anything else to look for
I agree with Kymarto, that in your case, the issues that this thread are about do not apply, because they apply to 'burbles' in the low B/C/C# region, but do not normally affect low Bb.

You say your technician has thoroughly checked G# sealing. But how experienced is he with saxes. The G# may check perfectly when lifting the G# lever, but may still leak badly when playing low notes. It needs to be checked when pressing the F key down while the G# lever is pressed down. A less experienced "technician" may not be aware of that. But you can check whether this is the problem by getting somebody to firmly close that G# key cup while you are trying to play low Bb.

But as far as burbles go, you are asking for trouble if your neck cork does not seal well at the open end of the cork, no matter how firm it is at the other end. This implies that the cork needs to be as JBT suggests, cylindrical not tapered (or even tapered slightly the other way). The fact that this cork is loose since the repair raises questions about the technician.
 

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i'm going to take the horn back to him tommorow.. he is a very experienced tech strange that such a simple problem would be hard to solve for him.. the mouthpiece feels somewhat firm but can be pulled in or out easy.. so i'm not sure if it was just over looked..

I will post back once the cork has been beefed up and the mouthpiece is alot tighter
 

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he also had me play the Bb while he held the side keys and the G to see if that was the issue.. and was still the same
 
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