Conn Improved Precision mouthpiece measurements

[WC8KCY]

Does anyone have the inner rim diameter and throat size measurements for Models 3 and 4 of the Conn Improved Precision mouthpieces?

Donn on that other forum mentioned a 2008 post by cjk with the following measurements for Models 1 and 2:

Conn 1: 1.287 inches rim interior and .355 throat
Conn 2: 1.244 inches rim interior and .328 throat

[cjk]

My ears were burning.

I *had* a 1, 2, and 3, but sold them all as a lot. I don't remember who bought them. The 3 was quite small. Far too small for me to actually use. I can't imagine something smaller than that (the Conn 4) being useful. I'm not even sure the Conn 4 was a tuba mouthpiece. I don't think it would be by modern standards. :)

[WC8KCY]

Thanks for the reply, cjk.

I am most curious about the model 3. I've been getting along well with the PT-64 and Kelly 25 lately--except for the rim profiles, which don't have quite enough bite--and would like to know how the Conn 3 compares measurement-wise.

[cjk]

A post of mine I found on the other site. I’ve since sold all of this stuff except the Chief.

I have Conn 1, 2, and 3, a set of calipers, and a set of both fractional and letter drill bits, so I measured. The throat measurements are pretty accurate. It's not exactly standard where you're supposed to measure the inside of the cup, so somebody else might get different measurements. Consider those just to be "in the ballpark".

The Conn 1 is the same as a Conn Chief except for a different exterior. I measured both. The inner dimension is around 32.7mm (1.287") and the throat is around 9 mm (.358"). A machinist's "S" (8.839mm, .348") drill bit is pretty loose, but a "T" (9.093mm, .358") is very tight. I'm guessing the throat is around .355". External diameter for the Conn 1 is 49.77mm (1.959") and the Conn Chief is 49.52mm (1.95").

The Conn 2 is pretty much the same as a Conn Helleberg 7B, but I think the rim might be more rounded. I don't have a 7B for comparison so I can't say for sure. It's extremely similar to the smaller 1930's (?) Hellebergs. The inner dimension is around 31.6mm (1.244") and the throat is 8.334mm (.328"). A 21/64" bit is a perfect fit. External diameter is 48mm (1.89").

My particular 1930's Conn Helleberg is 31.5mm (1.240") and the throat is 8.334mm (.328"). A 21/64" bit is a perfect fit. External diameter is 47.5mm (1.87").

The Conn 3 is a quite a bit shallower than a Conn 2. I figure it probably came with an E-flat tuba. Inner dimension is around 30.5mm (1.201") and the throat is 8.7313mm (.34375"). An 11/32" drill bit is a near perfect fit. External diameter is 49.4mm (1.945").

I know that nobody asked (but it's the only old Conn mouthpiece I have that I hadn't measured yet) a Conn Geib is 33.1mm (1.303") and the throat is 7.9375mm (.3125"). A 5/16" drill bit is a perfect fit. External diameter is 46.7mm (1.839").

[WC8KCY]

That's exactly what I was looking for! Thanks, cjk!

From the 1956 Conn Accessories catalog:
Model 1 - For BBb bass. Large, deep bowl with wide rim. Produces exceptionally full, deep, rich tone.
Model 2 - For BBb bass. Large bowl, not as deep as No. 1 . Gives full, rich tone in all registers. Medium rim.
Model 3 - For large Eb bass. Deep bowl with medium rim. Produces full, round tone in all registers.
Model 4 - For small Eb bass. Shallow cup with medium rim. Gives full, rich tone.