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Keilwerth saxes (S/A/T), Selmer clarinets (S/B), Altus Azumi flute
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Discussion Starter #1 (Edited)
I just finished overhauling a 1980 Keilwerth Toneking alto. It sounds great, but I'm having a really baffling issue with intonation, and I have no idea how to fix it.

The problem is that, when the lower octave stack keys are in tune (D1-C2), the lower part of the second octave (D2-F2) is very sharp.

For example, when I adjust the mouthpiece on the neck to tune to G1, all the lower octave notes are also in tune to within a few cents (except for C#2, which is about 15 cents flat). However, the 2nd octave lower stack notes are all quite sharp: D2 (+15), E (+30), F (+20). In contrast, the upper stack notes (G2-C3, as well as F#2) are again all within a few cents. This holds true regardless of whether or not I use the octave key.

I'm using a fairly standard mouthpiece (Meyer 7M) and the neck is undamaged and original to the horn (it has a matching serial number).

Does anyone have any ideas regarding what the problem might be and how I might go about ameliorating it?
 

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I'm not familiar with the quirks of older keilwerths but if the intonation is odd on a horn I'm working on I'll push/pull the mouthpiece until I find a spot the horn is in tune with itself.(I.e. 10 cents sharp up and down.) If that doesn't happen I'd look at pad heights or adding crescents to the tone holes in the extreme. Did you use domed resos? Those do take up some minor interior volume in the cone.
 

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Keilwerth saxes (S/A/T), Selmer clarinets (S/B), Altus Azumi flute
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Discussion Starter #3
I'm not familiar with the quirks of older keilwerths
If it helps, I think that this horn is equivalent to the last iteration of Couf Superba II's. The keywork is pretty modern and, except for the alternate F#, the tonehole size and placement doesn't seem to differ markedly from modern Keilwerths.
Did you use domed resos? Those do take up some minor interior volume in the cone.
I did use domed resonators, but that's what the original pads had, so I figured that it was designed for them.

if the intonation is odd on a horn I'm working on I'll push/pull the mouthpiece until I find a spot the horn is in tune with itself.(I.e. 10 cents sharp up and down.) If that doesn't happen I'd look at pad heights or adding crescents to the tone holes in the extreme.
I'll try pulling out the mouthpiece to see if I can find a spot where the horn is in tune with itself. If I do find such a spot, I predict it will be very flat. The mouthpiece has to be pushed in completely (so that part of the neck protrudes beyond the bore and into the mouthpiece chamber) to get G1 (and most of the other notes) in tune.

Regarding key heights, crescents, etc.: the problem is that I'm not sure how to do this so that it would help. As it is, the first octave lower stack notes tend to be a little flat. For example, I've played around with lowering the D key, but then E1 gets a bit flatter and E2 gets stuffy, but the relative intonation of the two notes doesn't really change much.
 

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I'm no technician, but here's what I have been finding while playing around with different altos (a very modern Mauriat and a very vintage 6M) and a lot of different mouthpieces:
- If you have to pull way out to get the scale even (horn in tune with itself), the chamber is too small (and/or overall length of MPC design too short).
- The above ("chamber too small") may be an oversimplification. Chamber geometry (and I think some facing considerations as well) is worth looking into. Having a variety of MPCs to test with is helpful.
- I don't think MPC chamber cross-sectional shape (square/round, etc.) makes much difference. How the cross-sectional area changes from tip into chamber is, I think, more important.
- All of the above may well be, to some extent, dependent also on the "internal geometry" of you, the player.

For what it's worth (and I am not about to try to determine the whys and wherefores), I found that, for me, the setups that work are as follows:
Mauriat: Fat, round, large-chamber mouthpiece with fairly short shank (Woodwind Co. B5) and open up all the bell key bumpers to the maximum (to include slicing off felt with a razor blade).
Conn 6M: Round, medium-chamber mouthpiece with fairly short shank (Kessler Custom "N, NY").
These very specific setups are the only easy way for me to get these horns to play (a) in tune with themselves, and (b) in tune (A=440Hz).

I think the higher-voiced horns (alto and soprano) are far more sensitive to these mouthpiece/player considerations, at least for me.
And the specific mouthpiece requirements are not necessarily intuitive.
I find it strange that this ultra-modern Mauriat works for me only with a fat old mouthpiece. OTOH, my 1928 Conn Bb soprano works best for me with a S80-type (small chamber, long body) mouthpiece.
 

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In my experience, there is no easy or simple acoustic explanation for what you describe. For F# to play with octaves well in tune and then F natural to play with octaves that wide is an anomaly. My knee jerk response would be to lower the key heights of the lower stack keys along with the low C, but this can produce the undesirable "side effects" of the low octave lower stack notes being too flat and both octaves being stuffy. You can experiment with putting stacked layers of masking tape under the key feet of the lower stack.

The second issue which is unusual on a fairly recent saxophone and a "middle of the road" mouthpiece is to have to push the mouthpiece on that far to bring the instrument up to A=440. The note that should be the most in tune with and without the octave key pressed is F natural since the body octave vent on most saxes is in the ideal location for this note. You may try finding the mouthpiece position compromise that gets the octaves of this note as close as possible and use that as your tuning "starting point".

The only other thing I can think of would be playing ridiculously low on the mouthpiece input pitch forcing the mouthpiece on too far to get up to pitch. Making the length of the saxophone and its missing cone too short would have the effect of messing with the tuning of the octaves. Although I am not sure whether it would make them wider or narrower. I do know that making a sax more cylindrical stretches the harmonics, and making a sax more conical makes the intervals smaller. Good luck with this problem. Let us know if you discover a cause or a solution.
 

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If it helps, I think that this horn is equivalent to the last iteration of Couf Superba II's. The keywork is pretty modern and, except for the alternate F#, the tonehole size and placement doesn't seem to differ markedly from modern Keilwerths.

I did use domed resonators, but that's what the original pads had, so I figured that it was designed for them.



I'll try pulling out the mouthpiece to see if I can find a spot where the horn is in tune with itself. If I do find such a spot, I predict it will be very flat. The mouthpiece has to be pushed in completely (so that part of the neck protrudes beyond the bore and into the mouthpiece chamber) to get G1 (and most of the other notes) in tune.

Regarding key heights, crescents, etc.: the problem is that I'm not sure how to do this so that it would help. As it is, the first octave lower stack notes tend to be a little flat. For example, I've played around with lowering the D key, but then E1 gets a bit flatter and E2 gets stuffy, but the relative intonation of the two notes doesn't really change much.
I wonder if the neck is physically too long. What you're describing sounds similar to my problem on a Conn baritone when the mouthpiece chamber was too small and thus I had to pull out too much. I don't recall the D being a problem but E and F certainly were. When I put a larger chamber piece on and thus shortened the tube length by close to an inch at the mouthpiece to neck interface, the sharp E and F problem went away. Of course in your case you can't shove the piece further on; which also is most unusual.

If you can try the horn with a different neck, even one from a different make of alto, it might show you something.
 

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Discussion Starter #7
It turns out that I missed a very small leak in the middle C pad (i.e., the first pad in the upper stack). The distortion caused by the pad rivet, combined with the fact that the pad was slightly off-center, resulted in a small leak at the back of the pad that I had somehow missed when going over my work with the leak light.

After I fixed this leak, the problem disappeared. The funny thing is that nothing else seemed to be affected by the leak. The response across the full range of the horn (including the bell tones) did not change noticeably after I fixed it. It's just that the second octave lower stack is now in tune.
 

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It turns out that I missed a very small leak in the middle C pad (i.e., the first pad in the upper stack). The distortion caused by the pad rivet, combined with the fact that the pad was slightly off-center, resulted in a small leak at the back of the pad that I had somehow missed when going over my work with the leak light.

After I fixed this leak, the problem disappeared. The funny thing is that nothing else seemed to be affected by the leak. The response across the full range of the horn (including the bell tones) did not change noticeably after I fixed it. It's just that the second octave lower stack is now in tune.
Interesting. Typically that pad does not have a rivet or resonator ostensibly to avoid the type of problem you ran into. I am glad you found a solution.
 

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It turns out that I missed a very small leak in the middle C pad… the second octave lower stack is now in tune.
Wow! I was about to recommend you get rid of the horn. That is amaZing
 
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