TubaForum.net

I am an engineer. I like to measure *stuff*. To my surprise, actual measurements of tuba mouthpiece cup volumes are nowhere to be found. We are only left with vague descriptors ("medium shallow", "deep"...). To measure the volume with decent accuracy isn't that difficult to do: fill the mouthpiece to the brim with water, empty the water to a container on a balance, record the weight. Repeat, but only fill the shank up to (what you perceive as) the bottom of the cup. Record the weight again, and subtract from your first value. If you do the sensible thing and measure with grams, divide by the density of 1 g/mL (...) and get the answer in mL.

Is this interesting? I don't know, but I think there is a correlation between the volume and the sound output. Now, I can only contribute "n=2", but if others want to join in on the fun: be my guest

GEWA-CUP 25 (Bach clone): 19 mL
Kosikup 1 1/2 (17 printed on shank): 14 mL

I think the potential problem lies in the perception of "where you think the bottom of the cup is," which is iffy.
Also -- most of this stuff started "somewhere" and was modified who knows how many times based on suggestions by people who played them and made those suggestions. A whole lot of finagling to get a mouthpiece, methinks.
Unless it's a Lawson cup for a horn, in which case it was likely Walter's specific genius that designed it. He could do advanced math, and did.

Unlike something like automobile engine camshafts specs, all tuba mouthpiece companies measure their specs at a different point with different criteria. There is no standard, as there is for camshafts, "### degrees at .050 valve lift." So you are on your own. This is not only true for cup depths, and therefore by extrapolation cup volumes, but also for where to measure for cup diameter, since each manufacturer has different depths to measure from the top of the rim, different amounts of "bite" (the contour of the inner rim) machined into the internal rim from which to measure, and so on. I have many friends who were/are band players who also went on to engineering school. The final consensus is that we simply did not talk about it, lest we devolve to consuming way too many adult beverages.

Venture Mouthpieces VennCAD has a decent library of tuba mouthpieces.. and it can calculate a cup volumed
https://www.vennture.mp/venncad/download-venncad/

They recently added the tuba mouthpiece library to the Trumpet Mouthpiece Comparator.. but being an online tool there is a lot less capability than VennCAD.

The biggest thing is the scans are generally missing critical information about the throat (chokepoint) location and the backbore taper. Both of which have a profound effect on a mouthpiece. Ask @bloke for a schoolin' there.

Agree. I work in machining and made measurements of all my mouthpieces as well. I was going to do the water measurement similar to what you described for volume but haven't gotten around to it. My thought was to make a plug of some sort that would go down into the throat. That way the measurement would start from the same I'd of the throat on each mp. I have found that I like the mps that have a smaller throat id. They seem to allow me to play with more flexibility.

Also, I did look at the scans on the venn cad program. I found it interesting that the cup shape on the conn helleberg and the conn 2 are nearly identical. Biggest difference is the the rim id. I have both mps, side by side, the conn helleberg plays well and the 2 doesn't. For me anyway. Same bowl shape, same throat id, very close depth, different rims....

A few additional comments on this exercise:

1. No, it is not going to be very accurate. It is limited by the accuracy of a kitchen balance, and as mentioned, determining what is actually the bottom of the cup. However, In the scale of things, due to the cups being so large relative to the volume changes near the throat, we should still be within +/- 1 mL at worst, I would think.

2. Someone (@iiipopes) mentioned extrapolation from cup depths. As this is an actual measurement, we are hopefully doing a bit better than that.

3. Finally, thanks for reminding me about the Trumpet Mouthpiece Comparator. I had forgotten that you could click on the graph symbol and get the actual calculated volumes from the scans. For example (as they were mentioned in the thread) it has Conn 2 at 17.3 mL and Conn Helleberg at 19.0 mL. So some data is actually available (But then you don't get to play with water! ).

ThirdHorn wrote: Thu Sep 17, 2026 3:01 am A few additional comments on this exercise:

1. No, it is not going to be very accurate. It is limited by the accuracy of a kitchen balance, and as mentioned, determining what is actually the bottom of the cup. However, In the scale of things, due to the cups being so large relative to the volume changes near the throat, we should still be within +/- 1 mL at worst, I would think.

2. Someone (@iiipopes) mentioned extrapolation from cup depths. As this is an actual measurement, we are hopefully doing a bit better than that.

3. Finally, thanks for reminding me about the Trumpet Mouthpiece Comparator. I had forgotten that you could click on the graph symbol and get the actual calculated volumes from the scans. For example (as they were mentioned in the thread) it has Conn 2 at 17.3 mL and Conn Helleberg at 19.0 mL. So some data is actually available (But then you don't get to play with water! ).

Remember that for tone, response, intonation, and all the rest of it, that the cup volume is a minor detail. The rim, bite, taper of the cup, the throat, and the backbore all contribute to how the mouthpiece functions. For example, on a Wick Aaron Tindall mouthpiece, it appears very, very similar on the trace to any number of other mouthpieces. But the combination of all the above, at least for me, give that mouthpiece better response, intonation, tone, and flexibility than many of the others on the Comparator, which I own too many. Your mileage may vary. So please do not think that cup volume is a be-all-end-all. It is at best an interesting exercise, but has no practical value for playability.

I am not so sure that cup volume has no practical playing value for playability. My daughter has been using a Sellmansberger Solo with a #2 throat backbore combo... adding the deleting extend and adding a few extra millimeters of depth made a noticeable difference in centering for her.. Granted the difference in #2 versus#0 and the rim #2 32.3mm (what she is using) versus 32.9mm (my choice) did have a larger effect for her.

edit: @arpthark has correctly translated my "brain faster than my fingers" not noticing autocorrect error. Yes Delrin extender.

Translating from gocsick-ese: deleting extend = Delrin extender?

I'm considering offering some 34mm i.d. mouthpieces - combined with deep cups.
If released, I would designate those mouthpieces as "The Sweeney Series".
The objective would be to loosen up the embouchure.

Oh, but Joe, you can loosen up the embouchure by free buzzing pedals!! How could you have missed that?

@ThirdHorn et al, there is at least one online tuba mouthpiece comparison chart. This one is courtesy of Dave Werden. Go here:

https://www.dwerden.com/Mouthpieces/tuba.cfm

Mary Ann wrote: Thu Sep 17, 2026 6:49 pm Oh, but Joe, you can loosen up the embouchure by free buzzing pedals!! How could you have missed that?

"motorboating"?