Lead Pipes

[Dickie]

Can someone please explain to me the concepts of lead pipes. How do they change the sound of the horn?

[hyperbolica]

Tbone leadpipes are thin metal tube around 8" or so long. They go inside the first part of the top slide. The first part of the leadpipe is just the mouthpiece receiver. After that, it generally tapers down to a minimum and then expands back out to the inner diameter of the top slide. They compress the flow and set up the vibration that forms the tone. And they are probably the fastest piece of metal to corrode on a trombone.

The venturi (minimum diameter constriction) can be altered by changing diameter or moving up or down the pipe. Overall length and shape/rate of expansion from the venturi to the open end also affect the sound in various ways. Material, construction method and heat treat also can influence characteristics of the sound and/or response.

Because there are so many factors involved, leadpipe design and manufacture is viewed as pretty subjective, although there are certain tendencies of each parameter. The result is never really deterministic, but predictable within a couple city blocks. It is recommended to try before you buy, or at least be ready to unload a bunch you don't like.

[Dickie]

I wondered because I received three lead pipes with my new trombone (Y-Fort 763) and frankly, I can’t tell the difference in sound between any of them.

[Burgerbob]

Those pipes aren't going to sound massively different, but they certainly play differently.