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I've never exhibited exceptions with Conn, Holton varies, and the Martins (not that Martin's offer to be played perfectly in tune) don't have the problem.

2165/2265/6450 - C instruments - are worse when cold and become less of a problem when warm.

I’ve never played one of those Martins before; it would simply be there as another variable of “large tuba with fat bows” to compare.

As far as the leadpipe - I suspect mine isn’t completely and totally round. It’s the best we could get it in the least amount of time for the least amount of money.

It’s also too big.

If/when someday, I get a 6450 leadpipe from Buffet, I may stick the current pipe from my 2165 on my Holton and see what happens. That pipe is, again, probably smaller. Or, if that won’t work, I could see about making a smaller pipe.

It’s got to start somewhere.

Yes, and now for even more "I have no idea" observations.

So many things to consider, like that tuba builders now have much more high tech at their disposal but master craftsmanship is thinning out.

I used to own a Martin Mammoth sousaphone. The F was very sharp.
I own a Martin Medium sousaphone. Intonation is really brilliant across the board.

The peeve I have with the larger Conn's (I've owned a 20K, 38K, 40k and a 42K) is that out in the work field they cost me too much muscle power to fine adjust them with the lips, mouth, air or anything else that isn't a slide. If I was stronger maybe it wouldn't be an issue but often I'll split or just miss the "out-of-tune" note. I'm guessing because my lips set-up a vibration which the tuba doesn't want to resonate at.
Sure, there are stronger players out there who don't have an issue with this and
Sure, there are the instruments that are exceptions. (The 1925 38K I used to own didn't have the low F issue. It also had massive denting on the bottom bow but if this means anything......?????)

So for me my Martin Medium (emphasis on me and my) not only has less intonation issues to start with (than the also smaller sized Conn 14K or 36K) but I generally can play almost every note spot on without having to pay extra attention to tuning. So YES, with 3 valves I pull a good 1" on either the 1st or 3rd for low C, but I can still play it in tune on shorter notes without fear of the note breaking.

I was impressed with the intonation on the two Chinese ZO Thunderbird Holton/York/whatever copies.

Last useless observation; as is well known the 14K and 38K (20K w/long valves) share the same valve block, neck and bits etc. In general the "larger" sousaphones have the low F (and often E) and the "smaller" ones are low on the B and C in the staff. I assume we can conclude from this that the size of the larger branches can change where the flatter notes hang out.

Good points.

I think what I'm going to try first is ruling out any factory defects or "old age" issues that this tuba may be hiding.

That includes:

Dent removal
Re-soldering/aligning big body joints/branches

Again, I have no intentions of letting this tuba go. This is truly the prize score of my stable. I'd just merely like to make it better, while figuring out if we can solve the mystery intonation issues.

Unfortunately I´m not in a position to provide inside on specs that may or may not lead to this phenomenon.

That immensely flat F happens to be a problem of my Willson 6405, though, and of other specimen of that exact type of horn to the point that it was referred to as the "Willie-F" by their owners. I´m using "1-3" as an alternative fingering, which solves the intonation problem nicely.
The fun part is: All valved pitches using that very same partial provide a very good intonation.

That horn is neither old, nor American, nor does it strike me as exceptionally huge, to the point I´d characterise it as a solid 5/4 tuba. So I wouldn´t search for leaks, dents in leadpipes etc. for too long...

Have you ever considered that the F might be in tune and the rest of the tuba is just sharp?

arpthark wrote: ↑Tue May 14, 2024 8:21 am Have you ever considered that the F might be in tune and the rest of the tuba is just sharp?

With ~some~ of the Holton 345 tubas that I've worked on for other people, I've noticed that the third partial F and the fourth partial B-flat are not that out of tune with each other, yet the second partial B-flat is quite sharp compared to the other two (which it's going to make the F seem to be flat with those particular instruments, when it's compared to the B-flat below it).

=======================

Regarding the six quarter Martin tubas - which never seem to have this flat F problem, am I the only person who has noticed that - right after their approximately .710 inch bore valve section - these instruments swell up gigantically and suddenly in bore size, rather than gradually?

And with that particular model from Willson (6400?) I think it must have something to do with the body wrap, since it’s just a re-wrapped 3100, right?

ALL of the 6400’s exhibit that flat F, but SOME (most?) Holton 345’s exhibit that F.

What I’m trying to say is, that note is flat on every single 6400 Willson, and is a known idiosyncrasy of the wrap of that tuba.

If it were in the wrap of the 345, all of them would exhibit this flat pitch, too.

Another long-winded way of saying “IDK!!”

I would be willing to say (based on experiences) that 345's differ more than any other 6/4's.

Second...I'm now wondering if "a remarkable amount of expansion" (rather than the top bow being overly large) pushes the 3rd partial lower.

ie. (my previous post)

Martin 6/4's get REALLY large right after the valve section...so that means less bugle expansion...and (sho-nuff) the Martin 6/4 3rd partial is not low.
Some other 6/4's large upper bows (and perhaps some of the inconsistent model 345 large upper bows...??) aren't quite as large...so that ALSO means less bugle expansion.

bloke "I can type crap, but that doesn't mean that I know anything."

bloke wrote: ↑Tue May 14, 2024 3:07 pm …
Martin 6/4's get REALLY large right after the valve section...so that means less bugle expansion...and (sho-nuff) the Martin 6/4 3rd partial is not low.
Some other 6/4's large upper bows (and perhaps some of the inconsistent model 345 large upper bows...??) aren't quite as large...so that ALSO means less bugle expansion.

Conical valve blocks on piston tubas aren’t a normal thing, right?

With the Martin...

There's a curvy piece of tubing that connects the valve block with the small side of the main slide (which sports a tremendous amount of expansion) and then the main slide bow ITSELF sports a tremendous amount of expansion...

...I haven't looked at one lately, but (yes?) after the main slide, the bore is already an inch or so....(??)

Interesting point. Is it then logical to ask if the King tuba also makes a radical expansion after the valve block? Or is this an apple-orange question?The ratio bore-to-bell expansion obviously works in this size.

bloke wrote: ↑Tue May 14, 2024 5:08 pm With the Martin...

There's a curvy piece of tubing that connects the valve block with the small side of the main slide (which sports a tremendous amount of expansion) and then the main slide bow ITSELF sports a tremendous amount of expansion...

...I haven't looked at one lately, but (yes?) after the main slide, the bore is already an inch or so....(??)

Seems like a lot of good or bad stuff happens is this transition area of brass instruments, especially tubas because the rapid and dramatic expansion. Too often ignored or at least not given enough consideration.

There's a very cool component of the BIAS (Brass Instrument Analysis System) which can do physical modeling: The program can predict results from simulated changes to an instrument, and you can prioritize elements: tuning, response, resonance, etc. https://www.artim.at/en/bias-for-brasses_extended/

pjv wrote: ↑Wed May 15, 2024 1:46 am Interesting point. Is it then logical to ask if the King tuba also makes a radical expansion after the valve block? Or is this an apple-orange question?The ratio bore-to-bell expansion obviously works in this size.

4/4 tubas sometimes feature this problem, but - as none of them swell to gigantic proportions - the problem is rarely as severe as with (may of) the great big tubas.