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Not me--but similar setups have been produced by a number of manufacturers, Alexander and Gronitz included.

The problem is that it's not really a "double" in the sense that the conical-to-cylindrical profile isn't that of a standard CC tuba. One might as well use a 6-valve F as deal with the (heavier) double rotors and two passes through the valves..

I suppose one could also call this a "compensating" F.

Chuck, just how much slower does it make the valves being rotars and that long?

I don't think the rotors get any slower--you can always compensate for that by increasing the spring tension, but it does make them heavier--about twice as heavy.

Okay, so do two stacked rotors amount to a hill of beans?

Well, let's see--the volume (and therefore the mass) is product of pi times the square of the radius times the height. The radius is at minimum equal to the bore plus a bit, and the height is equal to the bore plus a bit. So the volume (and by extension the weight) of a rotor goes up proportionally with the cube of the bore.

Okay, suppose we had a rotor with a bore of 0.750"; to double the rotor volume, we'd have to increase the bore to about 0.950"--or we could simply stack two 0.750" rotors on top of one another.

I once owned a beast of an Italian BBb with an 0.900" bore. The rotors were fast, but your fingers hurt after about 15 minutes of playing because you needed truck springs to move 'em fast enough.

Maybe this doesn't make a whole hill of beans when you're dealing with little bitty french horn valves; a 0.500" bore double valve should weigh about the same as an 0.625" bore single valve. Still well within the range of normal human digital endeavor--and a little more than half the weight of the 0.750" rotor.

Caveat: Strictly back-of envelope stuff, Wes.

That being said, there's a reason why these doubles aren't very popular-and I don't think it's the weight of the valves. The way it's been explained to me by those who have put in serious time on them is that the CC side helps out with the problematical low range on an F--but the intonation isn't good enough that you can lock the switch valve down and play it like a CC throughout the range. That's also 10 passes through the valves--and 8 tuning slides in addition to the main to fiddle with.

Chuck(G) wrote:That being said, there's a reason why these doubles aren't very popular-and I don't think it's the weight of the valves. The way it's been explained to me by those who have put in serious time on them is that the CC side helps out with the problematical low range on an F--but the intonation isn't good enough that you can lock the switch valve down and play it like a CC throughout the range. That's also 10 passes through the valves--and 8 tuning slides in addition to the main to fiddle with.

Double "French" horn players seem to manage (with a lot less slides, though... )

True, but at least in the case of the Alex double F/CC, the second pass through the valves just adds more tubing to the F side. Probably done that way to keep the weight down.

Horn players gots leetle tubes and valves.

There was one just like it in germany not long ago

http://cgi.ebay.de/Doppeltuba-Stimmung- ... dZViewItem

bloke wrote:I'm thinking of selling mine...' any interest?

I'd love to see more pics! Is it in two keys? If so, which ones? Does it have the two sets of slides like the other double tubas or do you pull the slides?