The Bach Stradivarius 42B is a large bore symphonic tenor trombone made by Vincent Bach Corp. in Elkhart, Indiana, USA. They are part of Conn-Selmer, Inc., also makers of Conn and King trombones. The Stradivarius is the Bach professional line, and the 42B has been the standard trombone for symphonies and bands since 1952. The Bach one-piece bell with its hand hammered construction and proprietary annealing process is the envy of other makers. This is the standard for a fine trombone bell. The hand slide is hand fitted and ready for smooth action.
This 42B has the traditional rotary valve and the traditional closed wrap F-attachment. Why...why would you buy this? Because it's a terrific player. There is something magic about these horns with the wrapped F-attachment. They are braced differently than the open wrap horns like 42BO. The F-slide tubes are longer, adding mass. The top of the bell connects with the neckpipe not through a straight brace, but rather through a curved tube. I think these differences leads to a quickness of response.. This 42B doesn't need a huge amount of air, the tone is really stable. (I deem it good.) Also for closed wrap F, though not an often used feature these days, this F-slide can be pulled to E. Maybe you will play the Bach as a small bass trombone and you need to
fwelp, blat, burp-out, play a few low B naturals. It can be done and is very satisfying. Photo number four shows the F-slide pulled to E. It is properly referred to as a tenor-bass trombone, so there is that, which is nice. The open wrap 42BO F-attachment does not have E-pull. Lastly, if you play in an opera pit or in front of a choir, it's nice to have a compact trombone without a long crook behind you to bang into things. And in 2020, closed wrap trombone style says, "Bro, do you even vintage?"
Does the closed wrap F-attachment have more resistance? I don't know. Yes, it does have two tightly curved crooks within the F loop. But when they fabricate these crooks, they press a ball bearing all they way through with hydraulic fluid. It's round inside, not like the tube gets oval or smaller within the bend. ¯\_(ツ)_/¯
Who plays the Bach 42B? David Rejano: Los Angeles Philharmonic. I heard him; he's pretty good.