Possible?

[nimrod480]

Cutting and Compensating Eb to a F Tuba (havent heard on a compensating F) and making it a Quart Tuba ?
Adding it to compensate to Eb, to CC and to BBb.

Do you think its possible ?

[Chuck(G)]

Cutting and Compensating Eb to a F Tuba (havent heard on a compensating F) and making it a Quart Tuba ?
Adding it to compensate to Eb, to CC and to BBb.

Do you think its possible ?

I'm not sure what you're asking, but yes, it would be possible to cut a compensating Eb to F. I believe that the ill-fated Besson 985 (I think that was the model number for the prototype) F was by and large a cut-down 983.

[Chuck(G)]

I believe Dillon's music has a Besson top action compensating CC for sale on their used instruments. I did not know they made them in CC.

These CC's are pretty rare and were made during the 60's by Besson (they're not "cut" jobs)--they tend to be a little different from horn to horn. Mine has a small 16" bell, for example. If you can get used to the top-action valves, they're pretty good players.

About the same time, the little 14" bell 3+1 compensating F tuba was produced by Besson. Also pretty rare, but intonation appears to be a significant problem.

AFAIK, there was no formal model designation by Boosey and the ones I've seen have been within a few serial numbers of one another.

[ThomasDodd]

Cutting and Compensating Eb to a F Tuba (havent heard on a compensating F) and making it a Quart Tuba ?
Adding it to compensate to Eb, to CC and to BBb.

Do you think its possible ?

I'm not sure what you're asking, but yes, it would be possible to cut a compensating Eb to F. I believe that the ill-fated Besson 985 (I think that was the model number for the prototype) F was by and large a cut-down 983.

I would expect the compensation loops would need adjusted which might be difficult.
The 3v BBb Bessons at Miss. State have very short loops on #2. Not much room to adjust them.

Since and Eb is alread shorter I would expect more isues. Definately lots of work to fix them to work in F.

[Chuck(G)]

I would expect the compensation loops would need adjusted which might be difficult.
The 3v BBb Bessons at Miss. State have very short loops on #2. Not much room to adjust them.

Since and Eb is alread shorter I would expect more isues. Definately lots of work to fix them to work in F.

Oh, I don't think the 2nd valve compensating loops were tinkered with at all on the CC versions and probably not on the F versions. Let's look at the numbers.

On a BBb instrument, the 4th compensating valve lowers the pitch of the instrument to F1; on a CC, to G1; on an Eb to Bb1, and on an F to C2. So the lengths of the 2nd valve tuning slide; that is, the length of tubing necessary to produce a pitch change of a semitone for all of the above pitches is:

G1 - 41.7 cm
F1 - 46.8 cm
Bb1 - 35.0 cm
C2 - 31.2 cm
Eb2 - 26.2 cm
F2 - 23.4 cm

So, the length of the 2nd valve compensating loops (that is, the length of tubing necessary to compensate for the addition of tubing by the 4th valve) for each of these tubas is:

BBb = 11.8 cm
CC = 10.5 cm
Eb = 8.8 cm
F = 7.8 cm

So, the difference in the compensting loop length between a BBb and a CC is only 1.3 cm or just a smidge over half an inch (0.51"), which is equivalent to a slide pull of only a quarter inch.

In the case of Eb and F, the difference in the compensating loop lengths is only 1.0 cm or a little over 3/8 of an inch, amounting to a slide pull of 3/16". In the grand scheme of tuba hacking, this is small enough to be ignored. You'd get a larger change in pitch by the room temperature rising from 20C (68F) to 22C (71.6F). And I have yet to see any tuba player adjust his 2nd valve slide for such a change in temperature.

Note that if we were talking about a 3-valve compensator, the differences would be smaller still.

[ThomasDodd]

So, the length of the 2nd valve compensating loops (that is, the length of tubing necessary to compensate for the addition of tubing by the 4th valve) for each of these tubas is:

BBb = 11.8 cm
CC = 10.5 cm
Eb = 8.8 cm
F = 7.8 cm

So, the difference in the compensting loop length between a BBb and a CC is only 1.3 cm or just a smidge over half an inch (0.51"), which is equivalent to a slide pull of only a quarter inch.

In the case of Eb and F, the difference in the compensating loop lengths is only 1.0 cm or a little over 3/8 of an inch, amounting to a slide pull of 3/16".

Fair enough. Random thoughs quashed buy by an informed mind.
(Yes I was too lazy to calculate the lengths myself)

I amd surprized though. I though the whole point of compensation was to correct things like 1/2" slide pulls. To leave the system off by that much appears to negate the reason for the system. I only ever played a 3V comp horn, and don't intent to ever get one (nor a 4V). I just don't like top action horns:)

[Chuck(G)]

I amd surprized though. I though the whole point of compensation was to correct things like 1/2" slide pulls. To leave the system off by that much appears to negate the reason for the system. I only ever played a 3V comp horn, and don't intent to ever get one (nor a 4V). I just don't like top action horns:)

A good point--does it make a lot of sense to pull a slide 1/2" (oh, call it 1 cm to keep this thread "international"). So, we're talking about a 2 cm. change in path length.

Let's look at the numbers.

On a BBb tuba with no valves depressed (i.e.working at its shortest length), that represents a flattening of 6 cents. With the 4th valve depressed, a 1 cm slide pull represents a flattening of 4 cents.

On an Eb tuba with no valves depressed, the number is 8 cents; with the 4th valve depressed, it's 6 cents. More than with a BBb, but still not outside most players' capabilities of "lipping" into tune. In fact, the intonation tendencies of the instrument are very likely to be off by far more than this.

Think about that the next time you see a BBb player tune by pulling his main tuning slide by a quarter inch...

[ThomasDodd]

A good point--does it make a lot of sense to pull a slide 1/2" (oh, call it 1 cm to keep this thread "international"). So, we're talking about a 2 cm. change in path length.
...
Think about that the next time you see a BBb player tune by pulling his main tuning slide by a quarter inch...

So why do so many people constantly pull slides? What anything less that, what 1.5"?, doesn't seam to make much sense.

I do agree though, small tuning changes on a tuba are pulls close to an inch than the 1/4 to 1/2 changes I see pleople making. For fun wtch a clllege tuba section tune. Most only move slides 1/4" at a time. and they seldom seam to actually get the horn in tune,

Those Besson I mentioned, most have the slide all pushed in. And the main slide is seldom pulled more than 1/2". They all lip the note when tuning, and never check the valves. Geteat when you play8ing one not for a long time, but when the notes get short, the horns quickly pull them sharp. When I played one all the slides needed 1- 2" of pull, and the main slide needed 3.

[MartyNeilan]

One thing to keep in mind with compensating loops. On a three valve tuba, they are much shorter because they are used to compensate for 1-3 and 1-2-3. On a four valve tuba, they are a little longer, because they are put into play whenever the fourth valve is used (2-4, 1-4, etc)

[Chuck(G)]

One thing to keep in mind with compensating loops. On a three valve tuba, they are much shorter because they are used to compensate for 1-3 and 1-2-3. On a four valve tuba, they are a little longer, because they are put into play whenever the fourth valve is used (2-4, 1-4, etc)

Okay, lets look at the arithmetic for a 3-valve compensating Eb to-F conversion. On an Eb, the third valve lowers the pitch of the horn to C2; on an F, it's lowered to D2.

So, we have the following numbers for the length of the 2nd valve tubing needed to lower the pitch of a given instrument by one semitone:

C2 - 31.2 cm
D2 - 27.8 cm
Eb2 - 26.2 cm
F2 - 23.4 cm

Thus, the length of 2nd valve compensating tubing for an Eb tuba becomes 5.0 cm and for an F is 4.4 cm. The difference between the two is 0.6 cm or less than a quarter inch.

So, assuming that a perfectly in-tune 3-valve conpensating Eb valve block were used on an F tuba, the second valve wouild be too flat by a whopping 2 cents. The same numbers run for a BBb-to-CC conversion would be in the neighborhood of 1 cent, but I'll let you do your own math.

The interesting thing is that you could also get away without trimmng the 1st valve compensating loop in an Eb-to-F 3-valve conversion, since the tuning difference would amount to only about 4 cents.

So, who's got a hacksaw and a torch?