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How do receiver and shank sizes affect the sound of the horn? Why do people switch out small receivers for larger ones? I'd be interested in hearing your experiences. Thanks.

on one end you have a bigger mouthpiece shank for potentially wider mouthpiece backbore.
on the other end you have a larger leadpipe starting bore.

Either one can be an advantage or disadvantage, depending on the rest of the instrument.

Basically, to a smallish degree:

Starting smaller = more conical with its intonation tendencies (compacted overtone series).

Starting bigger = more cylindrical with its intonation tendencies (stretched overtone series).

flyingdogs wrote:Why do people switch out small receivers for larger ones?

What's "small"? If it's the small size found mostly on older Eb tubas, then surely that's most often for the sake of being able to use normal tuba mouthpieces, regardless of any acoustic difference. If people are switching out normal size for larger ... does anyone do that?

Very few tubas I have seen have a receiver-leadpipe situation much like that drawing, however.

It's often a relatively smooth transition or even a reverse of that, with the leadpipe starting larger than the receiver.

As someone who has worked on many Besson Tubas over the years.
Many people took the smaller receiver off the instrument and put larger ones on.
The result of this was the mouthpiece didn't go in as far as the turned down mouthpieces we had used for years. And I don't think they played as well after!
Certainly with Besson, they didn't spend much time on the receiver/leadpipe relationship.
I bought a new 980 Eb in 2005/6 it had the new large leadpipe, but felt very rigid in the way it responded. Notes locked easily but slurring was a pig. I bored the reciever so my mouthpiece went in about 1/4" further. Wow! what a difference.
I currently play a Cerveny CBB 693. I've used Laskey and Doug Elliott mouthpieces on it. I've stopped with the Laskeys, as the Doug Elliott is just far better intune. But this time, because of the DE sticking out further and having a huge throat it has the same effect, but is physically opposite to what worked on the Besson.

Voilà, another picture.

Doug Elliott wrote:It's often a relatively smooth transition or even a reverse of that, with the leadpipe starting larger than the receiver.

So if I could relate that to this picture, you're saying that the receiver feature I labelled "shoulder" may be larger than the leadpipe wall thickness? thus making a narrower-to-wider transition in the air path at that point.

bloke wrote:Again, the only real point is that it is much more easy to match the receiver size (and, thus, the mouthpiece shank size) to the size of the small end of the mouthpipe tube (i.e. the choke point), rather than to choose some shank size that is perceived to be some size that "a bunch of people like to use".

How would you define "match"? Given that the shank end wall thickness is non-zero, and there may or may not be an acoustically significant "gap", with the leadpipe on the other side? Also, for the folks following along at home, what's a good practical way to get the measurements, to assess how close the match is?

Put a small right angle bend on the end of a paperclip wire so you can use it to feel down inside the receiver of your own horn and see what it does.

Mine don't have any abrupt changes in diameter, unless you count the sousaphone's bit joints.

It's true, there wasn't any epiphany. I don't know what the O.P. had in mind, but in the typical situation where an Eb tuba has a relatively exotic small receiver and the owner is tempted to swap it out, for the sake of being able to try normal mouthpieces ... are you saying, that's a mistake, because it will reliably play worse that way, than it will with the original receiver with whatever small shank mouthpiece may be had for it?

Installing a larger receiver on a small leadpipe is creating a bump (or gap) that wasn't there. It's definitely different and quite possibly not in a good way. If you're going to do that it probably makes sense to change the whole leadpipe.