TromboneChat

Did, or does Bach produce the "GM" version of their pieces in the larger 1.25 or 1?
I have seen the 1.5GM but not the bigger ones...
Just curious.

Sam

Yes they make a 1 and 1/4GM. Past that you're on your own with a drill and a prayer.

The 1G already had the larger (per spec) .319" throat and 800S backbore built in, no "M" necessary. They just decided to add this back end combination to the 1½G and 1¼G sizes to make the 1½GM and 1¼GM. The 1½G and 1¼G normally have the standard large bore .276" throat and 429 backbore.

I wish they would utilize the .296" or .302" throat and the 428 backbore for these sizes, but no...

(Not like I could stand the standard Bach bass rim shape to begin with, but that's a different topic.)

I've had a couple of 1 1/4GMs they're around, it may be that most don't know to order them. Even though the spec sheets list the 1 1/4GM throat as being a .319 like the 1G, the ones I've had have been smaller. The Bach mouthpiece manual under the throat section lists .296 as the standard size for the 1 1/4GM but under the mouthpiece descriptions it indicates .319. Based on a couple of samples I've had the .296 is correct and the much quoted .319 is in error.

Perhaps it's because of the rounded rim contour, or perhaps just more Bach inconsistency, but to my face both the Bach 1 1/4 and Bach 1G feel larger than the published specs. The 1 1/4 is listed as 27.5, but it feels to me more like 28mm and the 1 G also feels larger than the 28mm size, almost like 28.5. considering the sizes most commonly used nowadays, that's not necessarily a bad thing. They are still smaller than corresponding sizes from some other well known brands.

modelerdc wrote: ↑Fri Jan 26, 2024 11:42 am The Bach mouthpiece manual under the throat section lists .296 as the standard size for the 1 1/4GM but under the mouthpiece descriptions it indicates .319. Based on a couple of samples I've had the .296 is correct and the much quoted .319 in error.

Agreed, I have a .296 (and I expect the same is true of the 1 1/2GM)

For almost any bass mouthpiece, but especially a Bach bass mouthpiece, .319 would be just stupid large. I would think it would be a lung sucker, unstable, difficult to play up to pitch, and out of tune. Quite likely all of the above.

It comes down to the backbore attached to the throat and how long the throat is. You can have a dumbly wide throat with a tight backbore attached to it and potentially have a very balanced mouthpiece.

It's not just "large throat = too open and out of tune."

I find the 1 1/4GM to be a pretty good piece, actually. I was using one on my yamaha until recently.

A dozen or so years ago when I was casting about in the wilderness for a mouthpiece, I tried the usual Bach ones. The 1 1/4GM was the only Bach mouthpiece (for any instrument) I've sort of liked. But not enough.

The standard 1 1/4 G has the same .277"/429 throat/backbore as the 1 1/2 and 2.
There are two different 1 1/4GM's:
->The "stock" (standard blank) which has the same .319" throat / 800S backbore as the 1G
->The "Megatone" which has a .302" throat with the 800S backbore.
All of the above is also true for the 1 1/2 G/GM.

The 1 1/4GM (stock) was my go-to for many years of primarily big band playing. The open throat lets you move tons of air for volume, and the cup isn't too big for high stuff and is capable of blending with pea-shooter tenors (although it would never pass for one in a direct comparison). But I found the double-trigger C/B didn't have as much meat/core as I wanted, and the tenors in my section aren't super-bright (tonally or otherwise ).

I do have the megatone version but it's just a bit... odd... Maybe it would have been better if it had a backbore that matched.

Kbiggs wrote: ↑Fri Jan 26, 2024 11:50 am For almost any bass mouthpiece, but especially a Bach bass mouthpiece, .319 would be just stupid large. I would think it would be a lung sucker, unstable, difficult to play up to pitch, and out of tune. Quite likely all of the above.

It is stupid large and a bit of a lung sucker, but the moderate cup size means it's not hard to play up to pitch. And I wouldn't call it out of tune since the extremes don't require major corrections. This applies only to the 1 1/4, not the 1G (which is all the things you describe, and more).

For what it's worth, I have available for purchase a Bach 1½GM in excellent condition:
viewtopic.php?p=232196#p232196

TomInME wrote: ↑Sat Jan 27, 2024 8:43 am There are two different 1 1/4GM's:
->The "stock" (standard blank) which has the same .319" throat / 800S backbore as the 1G
->The "Megatone" which has a .302" throat with the 800S backbore.
All of the above is also true for the 1 1/2 G/GM.

Doing a little home measuring with some pencils revealed that the published specs do not match the actual mouthpieces...

The 1 1/4 G (no M) appears to be the same throat/backbore as the 2G. (.277"/429)
The 1 1/4 GM (non-Megatone) does indeed have a bigger throat and backbore, but it does not match the 1G (even though published specs are identical).
The 1 1/4 GM Megatone appears to have a slightly bigger throat and backbore compared to the non-Megatone. Not a huge jump like the 1G, but a little bigger.

I suspect that the Megatone might have the correct published specs, but without calipers I have no idea what the deal is with the stock 1 1/4 GM. It would make sense to have the same specs for both Megatone and non-, but they are not quite a match - maybe the non-Megatone bits were wearing out?.

(Another oddity: the throat on the Yeo appears to be somewhat bigger than the GM's (still not as big as the 1G) but the backbore appears tighter - almost the same as the 429 backbore of the 2G.)

Coincidentally, I pulled out my 1 1/2 GM (got it one day 20 years ago when it was the only bass trombone piece in the store) for a ringer job with a youth orchestra.

I compared its specs to my Shilke 51 and was surprised that in terms of rim diameter and cup depth there weren’t as big differences as I thought there would be. But I didn’t find the backbone or throat dimensions. It does take more air. That must be where the bigger differences are.

Thanks to all of you for helpful words of wisdom.
I was surprised how well the 1G played. Especially on my Holtons!
There is room for pedal range + the upper range is solid and comfy.