Differences between full-circle Eb and BBb sousaphone

[bigtubby]

My Reynolds full circle Eb sousaphone has a bore of about 0.689". The difference between the bugle length of an Eb tuba and a CC tuba is about three feet.

Is the difference between your 0.640" valve section and the beginning of the Reynolds bugle at 0.7195" (large side of the main tuning slide) effectively conical or cylindrical over a three foot stretch?

[bigtubby]

My Reynolds full circle Eb sousaphone has a bore of about 0.689". The difference between the bugle length of an Eb tuba and a CC tuba is about three feet.

Is the difference between your 0.640" valve section and the beginning of the Reynolds bugle at 0.7195" (large side of the main tuning slide) effectively conical or cylindrical over a three foot stretch?

I know the King and Reynolds/Olds share similar bores and size. It's the small branches on the Eb and BBb that I'm curious about. The taper should be quicker on the Eb (if it's a King) and possibly the same on the Reynolds/Olds depending on where the main tuning slide is (before or after the valves). And yes, I know the open bugle lengths between the two, hence the question.

From the pictures I've seen, I should be able to add the small branch after the main tuning slide (on a Reynolds BBb sousaphone) and be close enough to D or Db. The main tuning slide could reside anywhere (the valve section has the slide after the valves, while the body has before) and could, in theory, make up for the extra length.

Put it this way, given the perfect alignment of the planets, what's the length of the branch following the main tuning slide from a Reynolds BBb sousaphone or after the valves on a King BBb sousaphone? From what I can recall about my King, it should be around 2 or 2.5 feet. If the tuning slide remains before the valves, I could then add a small loop of tubing (like a fine tuning slide) or just extend the existing main slide to achieve the CC bugle length (~16ft).

In my Reynolds Eefer (bore ~ 0.689"; bell ~ 22-7/8"), the bore is straight (cylindrical) through the valve section. The distance through the gooseneck and leadpipe isn't much more than a foot (I can measure it if you like). So my suggestion was that virtually all of the taper is after the valve section.

On the assumption that you have a 0.640" bore valve section to graft into a horn like this ... you are probably getting very close to getting rid of a long length of cylindrical tubing. Surely there is a bit of fudge factor from a sousaphone engineered for the key of C.