Bach 5 Throat Size

[Trombola2112]

Anyone have any experience opening the throat. Recently got one and I like the sound, but it cuts me off in the upper ranges compared to my 5GS. I understand that the throat may be too small for some players/horn combos. Might just need to play on it longer, haven't had it terribly long.

[Posaunus]

I agree that Bach's standard 5.85mm throat is too small for a mouthpiece the size of a small-shank Bach 5.
If you must stick with Bach, the 6.63mm throat of the Bach 5GS makes a lot more sense to me.
Alternates (for your King 3BF?):
• Bach 6½AL
• Josef Klier 7C
• Marcinkiewicz 9B (Stroup)
• Schilke 51
• Denis Wick 5BS
• Yamaha 51
• Doug Elliott

[JohnL]

Curry 5M would be another possibility. 1.003" (25.5 mm) cup, .257" (6.5 mm) throat; deeper than a "C" cup, but not as deep as a "G" cup.

[Tbarh]

Could also be the cup…I am not a fan of the «no letter»cups… and its very shallow too ..

[Trombo]

Anyone have any experience opening the throat. Recently got one and I like the sound, but it cuts me off in the upper ranges compared to my 5GS. I understand that the throat may be too small for some players/horn combos. Might just need to play on it longer, haven't had it terribly long.

Maybe try Bach 5GS small shank?

[harrisonreed]

Opening the throat will likely completely ruin the mouthpiece. If you just bore it, you are left with a longer cylindrical section in the throat, which basically causes the resistance to be completely unchanged even though the bore is wider, and compresses the octaves. If you bore it, and then open the backbore to reduce the cylindrical length, it will most likely be completely too open and the backbore will be unbalanced.

In my experience, which is limited for sure, mouthpieces with the smaller throats already will have a pretty open backbore (the material around the shank tip will be very thin). The ones with really open throats, like the Alessi mouthpiece, will actually have a tighter backbore and you can see a thick circle of metal at the tip.

Also, I have noticed that good mouthpieces with smaller throats are designed to go further into the leadpipe by having a narrower tip diameter. The 15CL goes WAY into the alto leadpipe. The 5CL is also designed to go about an eighth of an inch further in than normal. This makes them play more open than their specs.

On the other end of the spectrum, the Alessi mouthpiece is wider at the tip and goes in less than is standard (and is also slightly short overall). And that is probably part of what balances the larger throat.

So, TL;DR, try a different mouthpiece.

[Posaunus]

Bach has already addressed the issue of the small-shank Bach 5 narrow throat.
The small-shank Bach 5GS is 'Same [Cup] as Bach 5 but with larger “G” [6.63mm = 0.261"] throat and #420 backbore.'

[blap73]

The Bach catalog https://www.bachbrass.com/application/f ... 89_web.pdf
states on page 9 (page 11 of the pdf) that you can request "special" throat sizes. Standard is .230". They note "Special (Standard Mega Tone) is .234" (or nearly 6mm)

Separately on the prior page you can specify special back bores.
On page 23 (25), the 5GS, compared to the 5 has a considerably larger throat and a different back bore.

What I don't know is if you ordered the 'special' .234" throat... would they change the backbore? It seems unlikely unless you requested a different one. So I suspect a 5 'special' would just be a larger throat, and maybe a little different work on the entrance to eliminate any sharp transition.

If you want to mess about... the way to do it is to ream the throat, not drill it. Much smoother, cleaner, and unlikely to chatter or go oversized. 6mm reamers are inexpensive, and only slightly larger then the .234" 'special'. To eliminate any step going into the throat a 5mm taper pin reamer can help bevel that area.

Will it be better? No idea. You may create a paper weight. I've got a Bach 4 that I'm tempted to do this to, but I haven't worked up the nerve to do it. The 4 is like new. Now if it was scratched, bad plating, etc... I wouldn't hesitate.

Some have done some similar changes... see viewtopic.php?p=80017&hilit=bach+7c+drill#p80017

Tiny changes do make a difference. They were making a .004" larger throat.

[Kevbach33]

I had looked at that section in the manual, thinking how pieces might be better with different throats and backbores. What size throat would they pair the no. 411 backbore with, I wonder? (413 goes with the F (.257" or 6.53mm) throat, 420 with G throat (.261" or 6.63mm)) Has anyone played a piece confirmed to have the 411 backbore? If so, how did it compare to stock (402)?

For small shank:

E and D cups (and small diameter cups, 14-22) can keep the small throat size and 402 backbore.
C cups (12C and larger) could all use the .234" (6mm) size except maybe the 4C: I'd give it the .250" (6.35mm) throat with a corresponding change in backbore (either 411 or 413).
Any piece with "M" at the end (like 6½AM) have the F throat and 413 backbore. This can be special ordered.
Any with "L" at the end (like 6½AL), and the 5GS, have the G throat and 420 backbore. Also can be special ordered.
Then there's the no letters (not as shallow as you think), B cups and the 6½A. This is where the 6½A, 6, 5, 4, and 3 could all benefit from a larger throat and different backbore. Like the 4C above, I'd give these the. 250" throat and probably pair them with the 411 backbore.
The small 5G has the full large bore back end (.276" or 7mm throat and 429 backbore, huge for small shank).

For large shank, this thinking is more focused on all bass trombone sizes, rather than in general...

Put the 428 backbore on the 2G, 1½G and 1¼G. .277" (7.04mm) throat for 2G and 1½G, .296" (7.53mm) for 1¼G.
Why not flip flop the throats for the 1½GM and 1¼GM? (New standard: .296" (7.53mm) throat; .319" (8.1mm) for new Megatone, vs current production) Keep the 800S backbore.
Give the 1G the .302" (7.67mm) throat but keep the 800S backbore... How much more resistant (or efficient) would that feel?

Just random thoughts from a gear head...