Steve Inman wrote:(However, from the photos posted so far, the Yamaha CSO York copy still looks like it has a beefier bell flare to me!)
Naw. These pictures are all subtly different in the position of the camera, and have different angles and perspectives that will make the sort of comparison you are making difficult.
These are all 6/4 tubas, plain and simple. The Gronitz and 6450 are almost as big, and really fit in that category, too.
But none of them are really appreciably bigger than, say, a Rudi Meinl 5/4. That the Rudi is a 5/4 and the Holton a 6/4 says more about shape than size, and is more a matter of definition than difference.
I think it was Hirsbrunner that first put "6/4" on a tuba description, and they did that probably just to distinguish the Yorkbrunner from their kaiser tubas they had previous labeled as "5/4". As always, it's a label used by manufacturers to describe differences in their own line. There is no objective measure.
The instruments give meaning to the terms, not the other way around.
Instead of a numeric code, I would prefer less precise but more accurate word categories. Such as:
1. Solo/Chamber--all instruments intended for solo and chamber settings. This would include most current 3/4 and small 4/4 instruments, and would say as much about sound and application as physical size. Diverse examples: Miraphone 184, Rudi 3/4, Conn xJ.
2. Ensemble--Most standard instruments would fit here, such as a 186 or a 56J or a 2145 (and I think that 2145 is on the big end of what works in most quintets, unless the other four players are beyond mortal).
3. Orchestral--I'm thinking of instruments like the Alex 163, Miraphone 188, and Meinl-Weston Thor, to name three extremely diverse examples. The 1292 would probably land here, too, as would a Rudi 4/4 and a PT-6. People buy these to play in orchestras, not brass quintets, right?
4. Grand Orchestral--all Yorkophones and other fat American-style tubas intended for large works played in large ensembles in large settings, in the CSO/American band style. (THAT will get me in trouble, heh, heh.)
5. Kaiser--Rudi 5/4, Alex 164, etc. As above but in the Berlin style.
There would still be overlap, of course, and gray areas. But I contend that describing a 6450 as a Grand Orchestral tuba conveys more useful information than arguing about whether it's a 5.5/4 or a 6.2/4.
Rick "duck and cover" Denney