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Duh! I should have deduced that by your name. I do what a lot of techs I know do, and that is to use the Yamaha recommended keyheights as a starting point. AFAIK they are the only make that has provided this type of spec for their saxes. I have included that list as an attachment. I set key heights based upon the RH F key. All of the other key heights fall in place once lost motion is removed. This includes the upper stack as well through the Bis/A pearl relationship. The upper stack heights can be set independently of the lower stack, but this involves changing the curvature of the arm that is closed by the F# adjusting screw.

On both models of tenor Yamaha's spec for the F key is 8.4mm. One caveat, is that a repair student of mine who has overhauled a Mark VI tenor has found the low E to be unstable, because the opening of the D key based upon this setting does not vent the note properly. He and I are working on a key height "compromise" that will solve this problem, but it is still a work in progress. I can let you know how that turns out if you like.
 

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Interesting that across Yamaha tenor models only the low 3 keys and middle C and set differently. I wonder whether that's because they want them to sound/respond differently or whether it's because their design differences require that. I suppose these are measured at the widest point of the keycup opening, from tonehole rim to pad surface?

I happen to have an all original early Mark VI, never played. I was just thinking of going through it, capture and document its key heights. Others must have done this before. Maybe we could start a spreadsheet comparing great sounding Mark VIs key heights against the original factory setup?
Yes they are measured that way. I compared Yamaha's measurements to 30% of the tonehole diameters on a Mark VI alto and tenor and found most of them to be very close. Then I learned that the "acoustic" 30% opening should be measured to the center of the pad, not the outside edge. I'm afraid it will take someone with a better understanding of trigonometry to come up with a conversion factor since it is much easier to measure the outside opening than the distance of the center of the pad to the plane formed by the top of the tonehole.

I for one would be very interested in learning the Selmer factory openings. An easy way to accurately measure the key openings is to use a "Small Hole Gauge Set" shown below and a set of calipers. You simply expand the gauge until it barely touches both the tonehole and the pad and then measure that diameter with your calipers---a trick I learned from Jeff Peterson from Yamaha at a NAPBIRT saxophone workshop.

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Low keys = speed
High keys = bigger sound

correct?
Correct, but over simplified. If a key is not open far enough to "vent" the note properly, the timbre suffers and the pitch is lower. There are some occasions such as on a D2 where the note is so sharp that it sometimes helps to compromise by lowering the low C key. This brings the pitch down to a more manageable level, but the trade off is that the D sounds even more stuffy, and D1 may be too flat. Making the keys higher than about 30% the diameter of the tonehole makes no further difference in either the pitch or the tone and I find it highly questionable as to whether there is a perceptible increase in volume or projection. What I am certain about is that the increased distance in key travel makes fast playing even more challenging.
 

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Thanks for the update. Of note, Randy Jones of Tenor Madness recommends 7mm for upper stack B key and 9mm for lower stack F key for mk Vi tenors, for proper venting. he also added that Yamaha's don't work that high.
Thanks for that information. We will try that setting on my student's tenor and see if the E improves.
 
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