Mouthpiece "Venturi"

[Tabert]

Looking through the Kelly Mouthpiece selection available online, I found a new addition (at least from what I had known of their lineup) to their lexan tuba mouthpieces, "similar to Stofer-Geib & pt50".

What's interesting to me is the last statement made about the design of the mouthpiece, saying:

KELLY-50 Tuba Lexan Mouthpieces

KELLY's custom series - Deep, bowl-shaped cup design - similar to Stofer-Geib & pt50 & with KELLY's extended venturi!

Now, I am no physicist, and I don't want to pretend like I know what I'm talking about, but after a quick search query, the "venturi effect" seems to deal with the velocity of a fluid (in this case air flow, I suppose) increasing as the diameter of the flow is constricted. How does this apply in the case of mouthpiece design?

I've never seen the marketing point mentioned for any mouthpiece advertising "extended venturi". To be frank, this doesn't seem to make any sense as the effect seems to be limited to the initial constriction and not necessarily in the case of a brass mouthpiece where the shank tapers down to a consistent point and then remains roughly at a similar diameter for a number of feet of tubing.

Does anyone have any insight as to what "extended venturi" may mean when it comes to mouthpieces?

[Donn]

I've never seen the marketing point mentioned for any mouthpiece advertising "extended venturi". To be frank, this doesn't seem to make any sense as the effect seems to be limited to the initial constriction and not necessarily in the case of a brass mouthpiece where the shank tapers down to a consistent point and then remains roughly at a similar diameter for a number of feet of tubing.

I'm not sure I follow you there - the variety of tapers that occur through the mouthpiece and leadpipe are very significant to how a tuba plays, I believe.

The venturi is just the narrow point in the mouthpiece. Most of us I think would call it the throat. Marcinkiewicz uses "throat" for the convex taper from the mouthpiece cup into the venturi. (Trombone players use "venturi" for the front of the trombone's internal leadpipe, since the leadpipe is narrowest there, but since it's even narrower in the mouthpiece, that's kind of beside the point acoustically.)

There's a widespread belief that the length, shape and diameter of the throat/venturi are particularly important to how a mouthpiece plays. Rumor has it that length affects "slotting", for example. Who knows what Kelly is up to. I guess you'd really have to slice a mouthpiece in half to know.

[imperialbari]

If the throat has a short cylindrical portion, intonation is said to be less determined by the mouthpiece, hence more controlable by the player. Flip side is that the player has to actively control the intonation all the time. Otherwise the intonation will be all over the place. Long uncontrolled notes will fluctuate in pitch. A short cylindrical throat will imply less resistance

A long cylindrical portion of the throat will lock or slot the intonation more, which is all fine, if the slot is at the right pitch. Which is not always, if ever, the case with tubas.

As I interpret your report of the Kelly presentation, Kelly wants to accomodate two main segments of its customers: younger students and amateurs/pros, who do outdoors work at low or high temperatures, which most often is about doing parades, where many consider it a benefit that notes are more stable and there is more resistance due to the longer cylindrical throat.

Klaus

[Doug Elliott]

A lot of marketing talk doesn't make any sense, except as marketing.

[Lee Stofer]

Since this was brought to my attention, and I need to talk with Mr. Kelly anyway, I'll ask him about what he meant by, "extended venturi". The PT-50 may be a deep funnel, but the KT-50 does have a bowl, although I think that the KT-50 is a little shallower bowl, and has a slightly wider opening and rim than my mouthpiece.

As far as the "supposed to have copied" comment, I'll say that you can ask Mr. David Fedderly how my mouthpiece compares to the late Mr. Jacobs' Conn-Geib. If you do not believe me, perhaps you will believe him.