Bach 6.5 AL vs A throat (small vs large)

[JLivi]

So according to Hickeys the Bach 6.5AL has the same throat regardless of shank size. But the Bach 6.5A has a smaller throat with the smaller shank, but a bigger throat with large shank.

Does anyone know why that’s the case? Here’s the listed specs for reference.

Bach 6.5A Small Shank = 0.2283"
Bach 6.5AL Small Shank = 0.261"
Bach 6.5AL Large Shank = 0.261"
Bach 6.5A Large Shank = 0.276"

[Dennis]

Bach treats large shank mouthpieces as bass trombone mouthpieces and uses the same drill for all large shank mouthpieces but the M suffixes (e.g., 1½ GM and the 6½ AL, 6½ AM, and 5 GS. So the 6½ A has a 0.276 inch throat. (The M's have 0.319 inch throats, which appeared in the original Megatone mouthpieces. Bach later brought out Megatones with the conventional mouthpiece throats and backbores.)

It's confusing, but that's Bach.

[Kevbach33]

Bach treats large shank mouthpieces as bass trombone mouthpieces and uses the same drill for all large shank mouthpieces but the M suffixes (e.g., 1½ GM) and the 6½ AL, 6½ AM, and 5 GS. So the 6½ A has a 0.276 inch throat. (The M's have 0.319 inch throats, which appeared in the original Megatone mouthpieces. Bach later brought out Megatones with the conventional mouthpiece throats and backbores.)

Edited it so it reads a little more clearly. At first I read it as if the 6 1/2AM had the same .319" throat and 800S backbore as the bass M mouthpieces (and the 1G) which isn't true. (It's .265" for the throat if I'm remembering correctly, both small and large shank. Don't quote me on the backbore.)

[Dennis]

Thanks, Kevbach.

It didn't occur to me that the 6 1/2 AM isn't a Megatone mouthpiece. It's a smaller throat/backbore (in between the small shank A and AL). I've never run across a 6 1/2 AM in large shank, but the Bach catalog claims it exists.

Confusing? Yes, but that's Bach.

[tbonesullivan]

Bach, like Schilke, made a lot of custom mouthpieces, and came up with the names after they had the mouthpieces, which is why the numbers and letters don't always make sense. Just look at Bach: the 7, 8 and 8 1/2 mouthpieces are all 24.75mm rim diameter. The 9 is 24.72, there is no 10, and the 11 is 24.70. The 12 and 14 mouthpieces are all 24.50 mm, and there is no 13 (superstition?).

It's not really a perfect system, and there is little motivation for Bach to make any type of change.

[Matt K]

So according to Hickeys the Bach 6.5AL has the same throat regardless of shank size. But the Bach 6.5A has a smaller throat with the smaller shank, but a bigger throat with large shank.

Does anyone know why that’s the case? Here’s the listed specs for reference.

Bach 6.5A Small Shank = 0.2283"
Bach 6.5AL Small Shank = 0.261"
Bach 6.5AL Large Shank = 0.261"
Bach 6.5A Large Shank = 0.276"

To understand this, it helps to look at their catalogue.

From page 9:

page9.PNG

You can see the "Bass Trombone * Large Shank Tenor Trombone" heading where the "standard" is .276"., whereas the standard for the small shank is .230".

To complicate... on page 23:

pg23.PNG

The description for a 6.5A (small shank) is:

Slightly larger than medium with standard-size throat and backbore. Rich, compact tone of large volume.

(emphasis mine)

So from that we would actually surmise that the throat for it should be .230" as that is the "standard" from a few pages above. So wherever you are seeing that as the listed spec is contradicting this claim; that doesn't mean its wrong... this is Bach after all. For all we know, there could be differences between years or any number of possibilities.

Also, my personal favorite hyperbolic description of a mouthpiece is found on this page:

The same rim and cup as No. 61⁄2A, but with a larger “G” throat and #420 backbore for trombonists who strive for a Teutonic tone quality. Recommended for euphonium players who desire a round, mellow tone of great carrying power and substantial volume.

(emphasis mine).

From the large shank page 26-27:

26-27.PNG

First, it is interesting to note that now we suddenly have specific throat sizes in the table whereas these information are not provided in any other part of the manual as far as I can tell.

We see that the 6.5A is described as:

The same cup, throat, and backbore as No. 6 1⁄2AL small shank tenor trombone but with bass shank. It requires a well developed embouchure.

So here too, the "A" is also the "standard" which for large shank, which is .276.

But the description of the 6.5AL is:

The same cup, throat, and backbore as No.6 1⁄2AL small shank tenor trombone but with bass shank. It requires a well developed embouchure

The best way I have found to think of the 6.5AL variations is to think of them as small shank mouthpiece for which large shank mouthpieces later came as an after thought. This is the way Bach describes them "the same cup, throat, and backbore as No 6.5AL small deep shank tenor trombone but with bass shank..." and this is quite literally true of the design, which if you've ever seen a large shank 6.5AL they have a ridiculously thick wall with a dramatic gap from the inside bore to the leadpipe; memory serving, the "A" does as well but its slightly more subtle. The reason for the inversion you find between the "L" series is that the "L" specifies the particular backbore, #420. A small shank, having the default of .230, is therefore made larger by modifying to having a .261". However, a large shank, having a default of .276 is made smaller by having a .261" throat.

[JLivi]

To understand this, it helps to look at their catalogue.

Wow Matt! You always have the best answers to my posts. Thanks for the well detailed response. And with pictures

That was really informative and helpful

[Matt K]

To understand this, it helps to look at their catalogue.

Wow Matt! You always have the best answers to my posts. Thanks for the well detailed response. And with pictures

That was really informative and helpful

And when I talk about the gap between throat and leadpipe, I don't necessarily mean it's a bad thing. One of my favorite mouthpieces in my collection is a Shires 6.5AL, which is a copy of some well-playing Bach 6.5AL and that includes the shank. I had it threaded and use my regular Elliott rim on it so it isn't 100% the same, nor is the outer shape, but a piece like that paired with the right horn can work really, really well.