Starting with the early horns, I have played a 612 way in the past- I think the 611 and 612 fall into the same-ish camp. They are good horns but dependent, and the early ones don't have split triggers (and some don't have D slides either). If this is your cup of tea, then I think they are a solid choice, much like a Holton 180 but with much more modern valves.
Along comes the 613 and 613G (yellow and rose bells). These are very similar to the 612 but with independent valves in F/G or F/Gb, as far as I know they all came with both slides. They have a lightweight brass slide and a light 10 inch bell. I currently own and use a 613 regularly for commercial settings, both at Disneyland and big band playing. These are great basses, easy to play, light, by far the most modern valves of the time (mid-'80s), efficient, you name it. A broad sound with a nice color to it, these are NOT boring. They are not perfect- the ranges are not quite even. High range is not bad on these but many modern horns will have a bit more focus and ease up there. The low range is easy enough, but not in a way that makes playing Bordognis down an octave or two a fun exercise, more in a Phil Teele way instead. I've tried to use my 613 in more "classical" settings a couple times, both in trombone choir and wind ensemble- for me it fell flat, as the sound just doesn't have the depth that some other more orchestrally oriented basses do.
The 613H comes along a decade or so later, and despite carrying the 613 name only carries a couple parts across- I think only the valves themselves (which are very good, again). These have a yellow slide with nickel oversleeves and a rose bell. This is largely a Bach 50 copy with nice valves. In that way it definitely succeeds, this has that depth the previous 613 lacks and a much more "legit" articulation. Ranges are more even, high range is quite good, low range has more of that ease for lines. These slides are compatible with Bachs at this point and I find it to play quite well with a 50 slide. And yes, these have the ability to be in G or Gb and come with both slides as well. Quite forward looking of Yamaha in many regards. Despite all the advantages this instrument has over the 613, I will be selling mine- I have Bachs to do Bach things, after all!
The 622 is Yeo's first design with Yamaha, and is largely similar to the 613H in many ways- it's again a Bach 50ish copy with some differences. I really liked the way the one I borrowed played, but my main gripe (other than it being dependent, of course) is that all the wraps are on the outside of the bell section, which makes the balance for me not very comfortable. Otherwise, this struck me largely as the 613H did, as a nice even instrument with a good orchestral sound. Neither the 613H or this horn is boring, but there is some "grain" lost to a good Bach 50... perhaps the bell making process, I couldn't tell you.
Now we get to the Xenos! I'll talk about the 822 first, Yeo's successor to the 622. It's largely similar to the 622 but now with a rose bell, fancy valve caps, and a few other small changes. I really like how these play and sound- some of that grain lost in the earlier horns is back, and these are very good orchestral basses. If there were some way they could make an independent version of this, I think it would be Yamaha's best bass trombone. Again, all the wraps are on the outside which is a bummer. Both the 622 and the 822 are designed with Yeo's mouthpiece in mind- pretty short, 1 1/8G sized, large throat. If you play with something tighter, smaller, etc., I find these horns to not play nearly as well. The leadpipe and rest of the instrument is definitely designed to give efficiency to that large mouthpiece.
Last up we have the Xeno 830 (and 830G, though I have not personally seen one of these in person). These are a continuation of the 613H, with a couple changes here and there. I've played 7-8 of these in various places and Disneyland provides one for the bass trombonists. For some reason, whether it's due to the handmaking of the bell or other QC factors, these are one of the least consistent Yamaha models they've ever produced- I have two friends with 613s and they play JUST like mine, to the point that I'm not sure I could tell blindfolded. The 613H strikes me the same way, and I've liked all the 822s I've played. The 830 is all over the map, both in playability and sound. The one I've played the most, at Disney, is right in the middle- easy enough to play, strangely inefficient, very little sound, and more boring than I can put into words. Some have been bright, snappy, colorful. Some have been huge, dense, orchestral. Some are plainly bad, with no focus anywhere and even less sound. From what I hear, Steve Fissel (Seattle Symphony former bass trombonist) bought one sight unseen from Hornguys and received one that rivals Mt. Vernon Bachs in terms of sound and playability (I've heard the same thing about Murray Crewe's prototype). This is definitely a horn I would play before buying, DO NOT be fooled into thinking that all Yamahas are the same and yours will be just as good as the last one you played.
One thing to note about all of these Yamahas- they all have that deep mouthpiece engagement, in that the mouthpiece goes in just a bit farther than it would in almost any other instrument. It's enough that Christan Griego offers a different Yamaha shank version of his mouthpieces. I'm actually considering it for my Markey 87 in my 613. Some pieces (like big Greg Blacks, for instance) are a bit short already, and make the horn even a bit harder to center and play consistently.
Earlier Yamahas, 613 and before, have chrome loss issues on the inner slides. Mine has a bit of loss, and so do all of the others I know. My slide is eminently useable, but it's an issue to keep in mind.
Also of note- starting with the 613H/622 generation, Yamaha started using very soft brass for many of the parts and these and later horns are much more susceptible to damage. 6 of the Yamaha 830s I've played were bought for the UCLA marching band. I played them before they were handed out to the kids. Within a couple weeks, every single one of them had a bent rotor knuckle and scrunched bell brace. My 613 (and actually, another that I played next to last night of all things) has a ripple in the F attachment on the top tube around the brace to the tuning slide receiver. There's a reason we don't see many of these surviving school use or even minor accidents.
Well, there we go. If I had to rank the horns in order of usefulness for me:
613/613G
613H
822
622
611/612
830
If you really enjoy your 830, I'm glad for you- the one I used at work was so soul-sucking that I've had to buy another instrument to use there just to avoid it, and it ended up being a 36 year old Yamaha that's better in basically every way.
There are some great Yamaha basses out there (some for cheaper than they perhaps should be) and hopefully this helps someone look for theirs.
Bonus photo of 613 and 613H for differences:
…Do You (or anybody else who read This) happen to know what the attachment bore is?…Standard ‘594 ?
