Dual bore slide design

[Retrobone]

Several years ago I had an old 1950's 88H slide rebuilt as a .525/.547 dual bore. The work was done on a very high level by a major EU craftsman. He replaced the upper tubes and upper cork barrel (to allow different leadpipes) and kept the original slide crook. I was surprised to find that this new slide blew much less easily in the upper register than I expected it to, and I've always wondered why that was.
So my questions are aimed at the techs and instrument builders here...
If you (re-) build a dual-bore slide, would you use a tapered slide crook? Or a crook that is more compatible with the upper inner tube bore (525 in this case)? I suspect that the stuffiness in the upper register response is related to this part of the slide where the 525 upper slide bore meets the old .547 slide crook.
It could also be the leadpipe as well, I guess.
Curious to have some input from those who really know how these things work!

[Matt K]

My dual bore slides are all not tapered, perhaps with the exception of the Getzen 525/547 (I haven’t removed it to be measured to confirm that). I don’t think that’s the reason for your lack of ease in the upper register. After all, the return to the inner diameter of the lower slide is pretty large, and the crook is typically much larger than the inner diameter of the upper and lower slides regardless of taper.

I would almost certainly put the difference in perception on the mouthpiece and leadpipe. If you’re using a large shank, you’re invariably using one of perhaps six pipes: a Conn X, Shires MT1/2/3, or a Brassark 36/78 custom made for large shanks. If that’s the case, it probably isn’t the mouthpiece assuming you’re using the same thing on your large bore. But the X pipe is remarkably open. I used one and actually kind of like it for certain applications, but it definitely has a different blow than say, a stock 88 pipe.

You have lots of options on the smaller side, but if they used the Conn 88 pipes for 525 I’ve likewise been underwhelmed by them too. There is one Conn pipe that I’ve found to be borderline magical, especially for 525/547 slides: the Conn 52H pipe, which makes sense given it’s a dual bore slide. The stock pipe for the Getzen 725 (also a dual bore) works well for me.

Doug has now played two of my 525/547s somewhat extensively doing r&d on them and other smaller dual bores. He’s long had a shank intended for 562/578 too. The new 2.5 and 3.5 were created for dual bores, the former being for the 2B. There’s something he does to tweak the taper that makes these respond much better, though the 525/547 design is still being worked on.

[ithinknot]

The crook is matching the outers, not the inners. So you're already around .040" above the nominal bore (stocking thickness and clearance). If you wanted a crook that matched the upper outer rather than the lower... Bach 36/.525 Yamaha models/Shires. But it's probably not the cause of your issues.

The Burkle Conns have tapered crooks (hydroformed), and it wouldn't surprise me if German designs had tapered crooks (almost certainly hand bent). But normal American-style stuff doesn't, and on tenors the match is with the larger side, so the step up is from the upper outer into the crook. I bet the 79H used a ".525-specific" crook, but the modern Conn 2525, 2547 and 4747 slides all use the same 88H crook. 4762 and 6262, the 62H crook. Conversely, dual bore basses retain the standard bass crook, so the change is between crook and lower outer. Plus the inevitable moving discontinuities wherever the inner tube ends are.

[Retrobone]

The crook is matching the outers, not the inners. So you're already around .040" above the nominal bore (stocking thickness and clearance). If you wanted a crook that matched the upper outer rather than the lower... Bach 36/.525 Yamaha models/Shires. But it's probably not the cause of your issues.

The Burkle Conns have tapered crooks (hydroformed), and it wouldn't surprise me if German designs had tapered crooks (almost certainly hand bent). But normal American-style stuff doesn't, and on tenors the match is with the larger side, so the step up is from the upper outer into the crook. I bet the 79H used a ".525-specific" crook, but the modern Conn 2525, 2547 and 4747 slides all use the same 88H crook. 4762 and 6262, the 62H crook. Conversely, dual bore basses retain the standard bass crook, so the change is between crook and lower outer. Plus the inevitable moving discontinuities wherever the inner tube ends are.

Good point on outer slide matching... that's why I'm a player and not a tech. Further experimentation with leadpipes is already leading me to think that is more the problem here.

[hyperbolica]

When I had my 32h slide widened, it started out as a dual bore and ended as a dual bore, but I used a wider dual bore crook (from a Yamaha 456). I'm not sure what difference it would have made if I hadn't used that crook, but I didn't want to find out. It turned out well.

The 525/547 slide is a popular one for the 88h, so the overall concept is sound. They probably use a 52h crook. I've had several straight 525 slides for my 88h, and they have all been glorious. I prefer the Conn T 525 leadpipe and a small shank mouthpiece, DE XT104E4. It will play nicely with F and G cups as well.

[OneTon]

FWIW, when Chuck Ward replaced the tubes on an Olds Studio slide, the original outers were both 0.500. The outers were replaced with the same size tubing. The original inners were 0.485 and 0.500. The inners were replaced by 0.490 and 0.500 tubes. The leadpipe supplied with King Jiggs Whigham 0.490 tube was retained. It was very similar to the Olds Studio leadpipe. And the fit of the original leadpipe was thought to be superior to the fit of removing the Jiggs Whigham leadpipe and re-fitting the Olds leadpipe, designed to 0.485, to 0.490. The refurbished slide was nearly indistinguishable to play from the original, well within the difference between two identical examples of the same trombone model.

[ithinknot]

When I had my 32h slide widened, it started out as a dual bore and ended as a dual bore, but I used a wider dual bore crook (from a Yamaha 456). I'm not sure what difference it would have made if I hadn't used that crook, but I didn't want to find out. It turned out well.

Just out of interest, is the 456 crook actually tapered if you measure both sides away from the expanded sockets? It's hard to be precise because there's hardware in the way and crooks tend not to be perfectly round in section, but it should be reasonably clear whether there's a gradual .025 expansion over the whole length.

Obviously, it has the two different socket sizes for the different outer tubes, so for what you were doing it's the ideal choice regardless.

[hyperbolica]

Just out of interest, is the 456 crook actually tapered if you measure both sides away from the expanded sockets? It's hard to be precise because there's hardware in the way and crooks tend not to be perfectly round in section, but it should be reasonably clear whether there's a gradual .025 expansion over the whole length.

Obviously, it has the two different socket sizes for the different outer tubes, so for what you were doing it's the ideal choice regardless.

I never actually measured the top/bottom bores. We had to cut off the swaged sleeves because they didn't fit the Conn tubes, and just used regular ferrules. It wasn't as straight-forward as you would hope. End result is that it looks good and plays good. Plus, the slide is wide enough to not be uncomfortable to play like the original 32h.

[ithinknot]

I never actually measured the top/bottom bores. We had to cut off the swaged sleeves because they didn't fit the Conn tubes, and just used regular ferrules. It wasn't as straight-forward as you would hope. End result is that it looks good and plays good. Plus, the slide is wide enough to not be uncomfortable to play like the original 32h.

Fair enough. Glad it worked out, though... I can't play those narrow Conns either.

[JohnL]

FWIW, when Chuck Ward replaced the tubes on an Olds Studio slide, the original outers were both 0.500. The outers were replaced with the same size tubing. The original inners were 0.485 and 0.500. The inners were replaced by 0.490 and 0.500 tubes.

Seems odd that the outers would be the same size as the lower inner...

[OneTon]

FWIW, when Chuck Ward replaced the tubes on an Olds Studio slide, the original outers were both 0.500. The outers were replaced with the same size tubing. The original inners were 0.485 and 0.500. The inners were replaced by 0.490 and 0.500 tubes.

Seems odd that the outers would be the same size as the lower inner...

The original upper and lower outer tubes were both the same size. Chuck Ward had me check beforehand and didn’t seem to be surprised. They were each replaced with 0.500 “nominal” outer tubes supplied for King 2B+. I never measured the actual outer tube diameter. Sorry for causing confusion.

Chuck Ward had tools to swage the upper inner receiver. I didn’t ask if any other interfaces were reworked.

[Crazy4Tbone86]

Tim,

Since you are a symphonic player, you are probably very accustomed to the resistance of your original Conn 88H .547 bore slide and leadpipe. Going with a smaller bore on the top slide will not necessarily equate to greater ease in the upper register. It will result it greater resistance that could work against your style of playing.

It sounds like you are already experimenting with different leadpipes. That is a very good idea. To equalize the feel, you might end up playing a “3” (more open) leadpipe with the dual bore to match the resistance closer to a “2” (medium or standard) leadpipe on the .547 straight bore.

Same thing applies to the mouthpiece, particularly the throat. Since 95% of my playing is on .547 bore and larger, I must use a tenor shank mouthpiece with a slightly more open throat (compared to the the throats on the most common mouthpieces) in order for the resistance to feel correct on my .525 straight bore and .525-.547 dual bore slides.

On a different topic……tapered slide crooks. There is a very specific reason why some trombone makers do not use tapered slide crooks on the larger bore horns. I remember discussing this with Christan Griego when I bought my Edwards back in the early 2000s. He said that Edwards (and/or someone else) did experiments with tapered slide crooks on the larger-bore instruments and it made some of the trombones take on a “French Horn quality “ in the timbre. Thus, they (Edwards) stuck with straight bore slide crooks.

Some years after that, I replaced a slide crook for a guy who specifically requested a tapered slide crook for his .547-.562 slide. If I recall correctly, I think I started with a tapered tuba leadpipe but had to work on it quite a bit because the original taper was too pronounced. I warned him about the possibility of it having a “French Horn quality.” I guess he didn’t like the result because he brought it back a year or two later and requested a standard Bach 50 crook!

[Retrobone]

Tim,

Since you are a symphonic player, you are probably very accustomed to the resistance of your original Conn 88H .547 bore slide and leadpipe. Going with a smaller bore on the top slide will not necessarily equate to greater ease in the upper register. It will result it greater resistance that could work against your style of playing.

It sounds like you are already experimenting with different leadpipes. That is a very good idea. To equalize the feel, you might end up playing a “3” (more open) leadpipe with the dual bore to match the resistance closer to a “2” (medium or standard) leadpipe on the .547 straight bore.

Same thing applies to the mouthpiece, particularly the throat. Since 95% of my playing is on .547 bore and larger, I must use a tenor shank mouthpiece with a slightly more open throat (compared to the the throats on the most common mouthpieces) in order for the resistance to feel correct on my .525 straight bore and .525-.547 dual bore slides.

On a different topic……tapered slide crooks. There is a very specific reason why some trombone makers do not use tapered slide crooks on the larger bore horns. I remember discussing this with Christan Griego when I bought my Edwards back in the early 2000s. He said that Edwards (and/or someone else) did experiments with tapered slide crooks on the larger-bore instruments and it made some of the trombones take on a “French Horn quality “ in the timbre. Thus, they (Edwards) stuck with straight bore slide crooks.

Some years after that, I replaced a slide crook for a guy who specifically requested a tapered slide crook for his .547-.562 slide. If I recall correctly, I think I started with a tapered tuba leadpipe but had to work on it quite a bit because the original taper was too pronounced. I warned him about the possibility of it having a “French Horn quality.” I guess he didn’t like the result because he brought it back a year or two later and requested a standard Bach 50 crook!

Thanks for your thoughts. I do own a 36 and a have some dual bore German trombones in my collection. So I do have a bit of experience with 525 and smaller instruments as well as dual bore instruments. After a few replies I'm now fairly convinced that my leadpipe and mouthpiece combi may be the culprit. I only own two 525 leadpipes for the slide and one doesn't fit the thread of the receiver. So some adjustments need to be made. But the loose fitting pipe seems to function much better than the one the builder made for me, so I'll look.into other 525 pipes with pull ring.