A Tale of Two Venturis: mouthpiece gap changing

[Burgerbob]

Gabe brought up a very interesting point in the MV 1.5 thread that I think can be spun out here. I thought it would also be helpful to have a visual aid that I obviously spent days putting together:

What's happening here is that the two venturis - the throat of the mouthpiece and the smallest point of the leadpipe taper - are closer together than in your 2G picture above. That dimension affects the blow and slotting. Trumpet players call it adjusting the gap.

A shorter shank like the MV 1-1/2G will blow more freely, possibly at the expense of clear articulations and well-defined slots. The sensation I get when the gap is too small (shank too short) is that the articulation and sustain of notes don't match pitch well. When the gap is too big (shank too long) the blow can feel stiff, too much effort to slur between partials, inflexible tone color, sometimes a bit harsh.

When you have a mouthpiece with a short shank like this, you can find the optimal length for it by wrapping tape around the receiver to get it sticking farther out of the leadpipe. Teflon plumber's tape works well - there's no adhesive to leave residue or anything.

And then if you determine that you love this mouthpiece but need for the shank to be longer, expert mouthpiece makers like Greg Black, John Stork, Terry Warburton, etc. can re-shank it to get it exactly where you want it. Bob Reeves mouthpieces even makes sleeve kits (Reeves Sleeves). I had a Greg Black mouthpiece converted to Reeves Sleeves a few years back so that I could play it with either a Morse or Remington taper shank. They work well.

To be clear, in this case it's not about the shank itself being longer or shorter, but the taper of the shank making it effectively longer or shorter relative to the leadpipe venturi.

I have noticed this in several horns and mouthpieces. My B&S Meistersinger, for example, very much wants to be played with my Thein BME mouthpiece, which is very long. In most horns it's obviously not the right match- it's tight, too focused, unforgiving. In the B&S (and Theins), it sounds amazing and solves most of the playing issues that crop up when playing "normal" mouthpieces in that horn- wide slots, fuzzy, not a very interesting sound.

I also have a George Roberts Replica CE 1 1/2G that is quite a bit shorter than my Bachs that does the opposite to vintage horns, makes them more open and wider sounding.

Many horns today are built around a pretty standard setup and I don't think this needs to be brought up all the time, but it's a very interesting concept.

[harrisonreed]

Your diagram is showing two different length mouthpieces with the same "gap". That's comparing apples to oranges. I'm sure they play very different!

Apples to apples would be two of the same mouthpiece, with different shank diameters in the taper. One would go in further. Otherwise there are too many variables to say why one plays more open.

If you look at the last sentence you quoted from Gabe, you'll see he wasn't talking about shank or mouthpiece lengths, but taper diameters

[Burgerbob]

Your diagram is showing two different length mouthpieces with the same "gap". That's comparing apples to oranges. I'm sure they play very different!

Apples to apples would be two of the same mouthpiece, with different shank diameters in the taper. One would go in further. Otherwise there are too many variables to say why one plays more open.

If you look at the last sentence you quoted from Gabe, you'll see he wasn't talking about shank or mouthpiece lengths, but taper diameters

I didn't change the visual past the receiver, but I'm honestly not sure how this changes anything- the venturi of the 2nd mouthpiece is closer to the leadpipe venturi, which would be the same as having a shorter insertion depth.

[harrisonreed]

Your diagram is showing two different length mouthpieces with the same "gap". That's comparing apples to oranges. I'm sure they play very different!

Apples to apples would be two of the same mouthpiece, with different shank diameters in the taper. One would go in further. Otherwise there are too many variables to say why one plays more open.

If you look at the last sentence you quoted from Gabe, you'll see he wasn't talking about shank or mouthpiece lengths, but taper diameters

I didn't change the visual past the receiver, but I'm honestly not sure how this changes anything- the venturi of the 2nd mouthpiece is closer to the leadpipe venturi, which would be the same as having a shorter insertion depth.

It would change everything. Mouthpiece 1 has a completely different backbore and backbore taper from mouthpiece 2. Mouthpiece 2 has, effectively, a massively faster backbore taper rate than mouthpiece 1. If the taper rate were the same, well, then the throat on Mp 2 would have to be huge or the shank wall at the end of the shank would be very thick. I know it's just an example, but in your drawing it looks like you kept the same throat and created a very fast open taper past that until it mates up with the part inside the receiver that you left alone.

The venturi are closer, yes, but one of the most critical components of the mouthpiece design, the backbore length and shape, is completely different too. I imagine that mouthpiece 2 would feel more open and less easy to slot because it basically has no backbore. You can't compare them objectively to say that it is the venturi distance making the difference.

[ghmerrill]

Is this what's going on with the Adams AGR (adjustable gap receiver)? I see that other companies make similar things for other instruments (trumpets, tubas).

[harrisonreed]

20260220_154519.jpg

This is what Gabe was talking about and what is going on with the MV 1.5 in that thread. So the internals of these two shanks are identical, and the outer taper on the right is more narrow (same taper shape, though).

It takes almost nothing to make a big change. Every reduction of .001" on the shank diameter will make the shank go in
.02" further.

I believe the real reason for the perceived change in the case of the MV 1.5 (assuming the throat wasn't touched!) is due to the reduction of the size of the blue area. This is air that no longer needs to be moved or vibrated in front of the leadpipe venturi point. Less resistance right at the point where the air enters the horn. The change in the distance between the two sets of red arrows might not seem like much (well, it is, but...) but the difference in volume between the two blue areas is proportionally much greater. A *huge* difference.

This is similar to, but not the same thing as the trumpet "gap" (I think gap is a great term for this, still). The trumpet gap involves an actual step in the receiver where the leadpipe begins -- the shank doesn't go into the leadpipe on a trumpet. The distance between the end of the shank and that step is the "gap".

Aidan's example does not have this effect, but *does* have a crazy difference in backbores between 1 and 2, and still would likely have less "air" between the two venturi, although along the entire length, not past the shank tip. In this case the "gap" is actually the same, but the air you need to excite is not, due to length of the mouthpiece, backbore shape, and everything different about the two mouthpieces.

[muschem]

I have a few mouthpieces converted to use Reeves Sleeves. I've been pretty amazed at the changes in sound and response going back and forth between different sleeve sizes on the same mouthpiece. I've also measured quite a wide range of "standard" insertion depths across leadpipes with formed/swaged receivers. To harrisonreed's point, it doesn't take much of a difference at all in diameter (of the mouthpiece shank or the leadpipe receiver) to result in a fairly large insertion depth change. The whole-step sizes on Reeves Sleeves will change the insertion depth by +/- 1/16", but you can also get half-sizes for 1/32" adjustments. I can hear and feel the difference in those 1/32" changes. I've measured leadpipe receivers with insertion depths that vary by more than 10x that difference.

[GabrielRice]

This is similar to, but not the same thing as the trumpet "gap" (I think gap is a great term for this, still). The trumpet gap involves an actual step in the receiver where the leadpipe begins -- the shank doesn't go into the leadpipe on a trumpet. The distance between the end of the shank and that step is the "gap".

Yes, the terminology comes from an actual gap between the end of the mouthpiece and beginning of the leadpipe for trumpets, but it's my understanding that the physics of the distance between the two venturi is the same.

FWIW, King trombones (most? all? not sure) have two-piece leadpipes like trumpets do, and therefore also have an actual gap. I have also seen Jupiter XO instruments with two-piece leadpipes.

[LeTromboniste]

Just to mudddy the water a bit....When instead of using an adapter I use tape or thread wrapped around the shank of my historical mouthpiece, I can control how far into the slide it goes. This has similar properties as what is described by Gabe. Yet, there is no second venturi, as my instrument doesn't have a leadpipe! So in my case it can't be about the gap between venturies, or shank end and leadpipe start.

[harrisonreed]

I think most kings do. My 3BFSS from the 60's has a one piece leadpipe though.

[Burgerbob]

Two-piece Kings come after H.N. White, so 70s+

[hornbuilder]

This is something Ive been saying here for ages. It doesn't matter how far the mouthpiece inserts into the receiver. What matters is what happens "after" the end of the mouthpiece.

[timothy42b]

Just to mudddy the water a bit....When instead of using an adapter I use tape or thread wrapped around the shank of my historical mouthpiece, I can control how far into the slide it goes. This has similar properties as what is described by Gabe. Yet, there is no second venturi, as my instrument doesn't have a leadpipe! So in my case it can't be about the gap between venturies, or shank end and leadpipe start.

I'm not sure how meaningful the leadpipe venturi is anyway.

Is there really that much effective constriction in the leadpipe after the end of the mouthpiece shank, but before the expansion of the leadpipe out toward the slide tube?

We know a leadpipe has a gradual constriction, or the mouthpiece wouldn't be tapered, followed by an smooth expansion to slide diameter. For that to really be a venturi requires the leadpipe constricting taper to continue a significant distance past the end of the mouthpiece shank before expanding again.

Does anyone have measurements, or a camera view? I tried looking from the slide end but I don't have an endoscope. Yet.

[harrisonreed]

It depends on the leadpipe but yes, it's a decent distance past the end of the mouthpiece. Unless the leadpipe has a really weird change in the taper past the recover, the larger the leadpipe venturi, the snake the distance will be....

Go figure, increasing the distance via the shank diameter (mouthpiece further out) makes it feel tighter. Decreasing the size of the leadpipe venturi (makes it feel tighter) would also increase that distance...

20260221_112611.jpg

It is possible that some leadpipes change taper rate after the receiver area "ends" but I doubt too many modern ones do.

Looking at the two sketches I've done now, it's no wonder tapering down your shank drastically opens up the blow. Tiny tiny adjustments can compound to make huge changes in the system. What you're effectively doing with the leadpipe venturi is changing the length of a big ramp that the air hits again past the end of the mouthpiece shank. With a tighter venturi, it's probably not that there's a choke point, it's much more likely that it's the surface area of that funnel that is responsible for the change in feel and playing characteristics.

With the larger venturi, your air ramps off almost nothing.

[GabrielRice]

This is something Ive been saying here for ages. It doesn't matter how far the mouthpiece inserts into the receiver. What matters is what happens "after" the end of the mouthpiece.

I don't think I understand what you're saying here, Matthew.

If you have two mouthpieces that have all the same dimensions except the taper of the shank, and you play them back to back in the same trombone with the same leadpipe, they might not sound a lot different to the audience, but they will feel very different to the player.

[hornbuilder]

Gabe,
The thing I'm getting at is, there are plenty of people who only look at the insertion depth as the guide as to how a mouthpiece may play. Or, will use insertion depth as a deciding factor on if the leadpipe is good or not. When in fact it is what happens "after" the end of the mouthpiece shank that matters.

Case in point. The first Shires pipe I ever played swallowed my mouthpiece by almost 1/4" more than the pipe I had been playing on. So I decided to do some experimenting with it. I removed the threaded collar, and reattached it lower down on the pipe, then cut off the excess. It didn't change in how it played in any way, because I did not alter the relationship between the shank end and the rest of the leadpipe. Externally, it "looked" very different! But internally, it had not changed

More to add, bit have to come back later..

[harrisonreed]

Matthew, what you're talking about could only be a leadpipe that has a wider receiver opening than is standard, causing the mouthpiece to only appear to go in further, which can happen on basses and also tenors with collars. You obviously know this better than most, you literally build them! So you're right, of course. Shires does this (the newest Shires horn at work eats the shanks, but play fine). Yamaha 830 basses *supposedly* do this (but they don't play like it's just cosmetic). Because it's a bass, they can have a wider receiver opening and make the mouthpiece go further into the entire trombone by quite a lot, which might or might not be cosmetic. For it not to affect anything, including overall length, the leadpipe would have to extend out of the slide more than normal and open up wider than the nominal .547 or .546 exit of the slide tube, with a longer than normal collar, and you would not be able to get it to mate with the slide tube. Either that, or on bass the collar would need to put the .546" slice of the leadpipe right at the end of the slide tube. You're limited by that dimension of the slide tube unless it's a bass. Here is the image from the Bach mouthpiece manual, showing what the nominal exit of the leadpipe should be (ie .546").

Screenshot_20260221_181407_Chrome.jpg

It is unfortunate that makers sometimes standardize their pipes to have exits larger than this, because not only does it cause the confusion described above, it also causes some makes of mouthpieces to literally bottom out in the pipe.

That said, the shank taper width change that Gabe and I have been describing would *still* affect these weird pipes you're talking about the same way -- tapering down the shank will make it go into the weird pipe deeper (or bottom out) and make it feel more open and unstable.

[Kbiggs]

Gabe,
The thing I'm getting at is, there are plenty of people who only look at the insertion depth as the guide as to how a mouthpiece may play. Or, will use insertion depth as a deciding factor on if the leadpipe is good or not. When in fact it is what happens "after" the end of the mouthpiece shank that matters.

Case in point. The first Shires pipe I ever played swallowed my mouthpiece by almost 1/4" more than the pipe I had been playing on. So I decided to do some experimenting with it. I removed the threaded collar, and reattached it lower down on the pipe, then cut off the excess. It didn't change in how it played in any way, because I did not alter the relationship between the shank end and the rest of the leadpipe. Externally, it "looked" very different! But internally, it had not changed

More to add, bit have to come back later..

I still don’t follow. In this case, you’ve changed the distance between the mouthpiece throat (venturi) and the leadpipe venturi. That doesn’t change the way the horn/leadpipe plays?

[JohnL]

I still don’t follow. In this case, you’ve changed the distance between the mouthpiece throat (venturi) and the leadpipe venturi. That doesn’t change the way the horn/leadpipe plays?

Imagine if he'd done the cut with the mouthpiece in the leadpipe. Chuck the whole thing up, make a cut about 1/4" from the top of the lead pipe (being careful not to cut into the shank, of course). The mouthpiece would still be firmly seated in what remains of the leadpipe, with the distance from mouthpiece venturi to leadpipe venturi unchanged. You could make a longitudinal cut in the 1/4" ring and remove it, then attach a new ring at the new end of the leadpipe, all without removing the mouthpiece from the leadpipe.

[harrisonreed]

Yes it's just limited by the .546" exit on a tenor, and the notional .546" spot inside the larger bass tube where the mouthpiece is supposed to mate (but doesn't have to). Extending the leadpipe past that point would just be cosmetic. But that point still exists on both types of pipes.

[boneagain]

McCracken convinced me of the wisdom of what Matt asserts above.
He felt the effects become more pronounced as the bore near the mouthpiece decrease.
The key bit can be seen in Harrison's diagrams above.

There is a taper INSIDE the mouthpiece.
McCracken's goal was to avoid any acoustically significant discontinuity between that taper and the taper of the leadpipe.

Acoustical significance was proportional to the normal range played on the horn.

The stumbling block was there there would always be some kind of step at the end of the mouthpiece.
The trick was to arrange that step and the narrow point of the following leadpipe taper so that, to the vibrating air column, it APPEARED as if the path from the throat of the mouthpiece down the lead pipe was one continuous path.

Duo Gravis did this with an actual step in the leadpipe, as noted above.
This is similar to most (all?) modern trumpets.

... and the length of the gap is half as critical for trombone as for trumpet, and less so at bass trombone "money range."

So, yeah, it's "what's after the end of the mouthpiece."

I don't know how George found the "magic spot" between his mouthpiece backbores and lead pipe tapers. I DO know that his pipe/mouthpiece matches were appreciated in orchestras around the globe.

Dave

[harrisonreed]

I still don’t follow. In this case, you’ve changed the distance between the mouthpiece throat (venturi) and the leadpipe venturi. That doesn’t change the way the horn/leadpipe plays?

No, it sounds like he just cut off the excess leadpipe above where it mates to the slide tube. Nothing changed with the distances.

[Doldom]

one different question here. If a specific mouthpiece and a leadpipe combination feels good with one instrument but not so good with other instrument(imagine both are 0.547 tenor.) can I be benefitted with different insertion depth(different gap)? or ultimately do I need other mouthpiece-leadpipe combination because it already have "perfect gap" but still not feels good with other instrument ?
In other words, Is a "perfect gap" for a specific mouthpiece and leadpipe is not a constant thing but changes with different instruments?

[harrisonreed]

You'd be assuming that the leadpipe you're moving over to the other horn would be good for that horn to begin with.

Maybe it would be the best setup for that leadpipe on that horn, but making a change from a Bach to a Conn, for example ... I probably wouldn't use the same pipe on both of those.

[GabrielRice]

Gabe,
The thing I'm getting at is, there are plenty of people who only look at the insertion depth as the guide as to how a mouthpiece may play. Or, will use insertion depth as a deciding factor on if the leadpipe is good or not. When in fact it is what happens "after" the end of the mouthpiece shank that matters.

Case in point. The first Shires pipe I ever played swallowed my mouthpiece by almost 1/4" more than the pipe I had been playing on. So I decided to do some experimenting with it. I removed the threaded collar, and reattached it lower down on the pipe, then cut off the excess. It didn't change in how it played in any way, because I did not alter the relationship between the shank end and the rest of the leadpipe. Externally, it "looked" very different! But internally, it had not changed

More to add, bit have to come back later..

OK, I get it now. As I suspected, we don't disagree at all. As I've been saying, the operative dimension is the distance between the two venturi, which, in some modular instrument systems you can get a gauge on by how far the mouthpiece goes in.

At the risk of irritating some of my friends at S. E. Shires, one of my constant frustrations when I worked there was that the leadpipes were not as consistent as I thought they should be. The way they were made was that the main taper was drawn on a mandrel for each bore size and then they were cut at different points for the different number pipes. Then the mouthpiece receiver taper was stretched by hand before the collar was soldered on, and this was the point of inconsistency. So I could go to a bin with a couple of dozen copies of the same leadpipe and see variations of 1/16" or so on either side of the 1" standard Morse taper mouthpiece insertion depth (earlier in the company's history the standard was deeper than that, but that was changed in the mid 2000s). The playing differences were obvious and dramatic, at least to me.

One argument was that there were players who preferred a depth other than the standard, and there was truth to that. And in defense of current Shires production, the last time I was there the leadpipes seemed to be more consistent than in the past.

And FWIW, I've seen the same inconsistency in Bach and some of the aftermarket leadpipes. Can't speak to Edwards or Rath or others.

[Doldom]

You'd be assuming that the leadpipe you're moving over to the other horn would be good for that horn to begin with.

Maybe it would be the best setup for that leadpipe on that horn, but making a change from a Bach to a Conn, for example ... I probably wouldn't use the same pipe on both of those.

I also thinks there is such thing as leadpipe-instrument match. I also switch leadpipe according to the instruments. But what I haven't done before is experimenting different gaps with same leadpipe for different instruments so I was questioning about that.

[elmsandr]

To Gabe’s point on the manufacturing process… there are good ways to gauge and control the Venturi diameter and position relative to the mouthpiece receiver taper when you add that to the pipe…. I have been to a LOT of brass manufacturing facilities. I have never seen those process controls in place at any location.

Cheers,
Andy

[timothy42b]

<large snips>

McCracken's goal was to avoid any acoustically significant discontinuity between that taper and the taper of the leadpipe.

The stumbling block was there there would always be some kind of step at the end of the mouthpiece.
The trick was to arrange that step and the narrow point of the following leadpipe taper so that, to the vibrating air column, it APPEARED as if the path from the throat of the mouthpiece down the lead pipe was one continuous path.

Duo Gravis did this with an actual step in the leadpipe, as noted above.


Dave

This always made sense to me. You have an actual venturi at the throat of the mouthpiece. Why would you want another one further downstream?

But I had not realized until reading a few versions of this thread that if the leadpipe taper is too long, you can in effect get that second venturi to some extent.

I probably don't understand what a venturi does in a trombone. In engineering, in subsonic flow, it is a constriction to get a short faster flow rate usually for measurement purposes, followed by an expansion to get the exit pressure back up to inlet pressure.

In a mouthpiece you need a tight throat section presumably to create a Helmholtz resonance condition in the cup of the mouthpiece. Then we need to get pressure back to normal gradually without introducing turbulence.
My speculation anyway.

[harrisonreed]

<large snips>

McCracken's goal was to avoid any acoustically significant discontinuity between that taper and the taper of the leadpipe.

The stumbling block was there there would always be some kind of step at the end of the mouthpiece.
The trick was to arrange that step and the narrow point of the following leadpipe taper so that, to the vibrating air column, it APPEARED as if the path from the throat of the mouthpiece down the lead pipe was one continuous path.

Duo Gravis did this with an actual step in the leadpipe, as noted above.


Dave

This always made sense to me. You have an actual venturi at the throat of the mouthpiece. Why would you want another one further downstream?

But I had not realized until reading a few versions of this thread that if the leadpipe taper is too long, you can in effect get that second venturi to some extent.

I probably don't understand what a venturi does in a trombone. In engineering, in subsonic flow, it is a constriction to get a short faster flow rate usually for measurement purposes, followed by an expansion to get the exit pressure back up to inlet pressure.

In a mouthpiece you need a tight throat section presumably to create a Helmholtz resonance condition in the cup of the mouthpiece. Then we need to get pressure back to normal gradually without introducing turbulence.
My speculation anyway.

I believe almost all leadpipes will extend past the end of the mouthpiece, so nearly all leadpipes will have a "second venturi" that happens after the mouthpiece ends. That isn't a design flaw. Otherwise, why would some people prefer the T1 pipes and others prefer the T3? These both effectively increase or decrease the gap distance, unless the receiver taper significantly changes leading into the venturi, past the end of the mouthpiece. There is no "one size fits all" for this stuff, and I don't think the goal is ever to completely eliminate the gap between the end of the mouthpiece and the venturi in the leadpipe. It's just a matter of how much distance.

Shaving down the shank makes some mouthpieces better but you hit a point and then they stop being better, and get worse really fast. I don't believe you ever actually get the shank tip up against the venturi (eliminating it), at least not before it goes from "wow!" To "oh no!". And that is only possible on those really open pipes, if at all.

I've gotten close to that point on my 36H with my alto mouthpieces, but even those hit a point where it goes bad.

[tbonesullivan]

I wonder if ADAMS can put one of the Adjustable Gap Receivers from their Euphoniums onto a trombone somehow... They haven't put it on their trumpets though, where I think there would be more of a demand.

Another option is the Reeves sleeve system.

I seem to recall some designs where the leadpipe and mouthpiece were one long piece?

[Doug Elliott]

In effect, when assembled, the backbone and leadpipe IS one long piece. Mechanically the "2nd venturi" is inevitable but in my opinion has no other significance acoustically. Changing the insertion distance has a tightening or opening effect, but as Maximillien pointed out (but everybody is ignoring) the same effect occurs even without a leadpipe.

[Doldom]

Another question.. Why are the trumpet's leadpipes almost always 2-piece construction? What is downside if one builds trumpets with 1-piece leadpipe..?

[Doug Elliott]

Tradition

[boneagain]

Tim,

But I had not realized until reading a few versions of this thread that if the leadpipe taper is too long, you can in effect get that second venturi to some extent.

In the horn shop we called the first taper the mouthpiece receiver.

I probably don't understand what a venturi does in a trombone. In engineering, in subsonic flow, it is a constriction to get a short faster flow rate usually for measurement purposes, followed by an expansion to get the exit pressure back up to inlet pressure.

In a mouthpiece you need a tight throat section presumably to create a Helmholtz resonance condition in the cup of the mouthpiece. Then we need to get pressure back to normal gradually without introducing turbulence.
My speculation anyway.

My speculation is that the real venturi is the throat of the mouthpiece.
I further speculate that it has more than one function.
It needs to allow the air passing the lips to dump effectively.
This is a fluidic challenge like what you mention above.

Frequency stuff varies with air density and humidity.
I'll speculate that aside from the fluidic dumping that there are acoustic results of those factors.

Intuitively I suspect some sort of Helmholz effect as you do.

But I also suspect a non-Helmholz effect. Benade did interesting tests going from straight tube to straight tube with bell to straight tube with mouthpiece with cup and throat.

The only combination that gave our supposedly natural overtone series was cup and bell.
The straight pipe yielded every OTHER member of the natural series.
Somehow the combination of cup and bell squashes the alternates until they present as "natural."

Seems to me that messing with "the gap" has great possibilities for causing or resolving discontinuities in the cup end of things to have related effects on the squashing of the alternate overtone series.

But I haven't seen acoustical studies to back that up anywhere.

Dave

[timothy42b]

In effect, when assembled, the backbone and leadpipe IS one long piece.

A modular mouthpiece could have three parts: Rim, cup, and a combined shank and leadpipe where the expansion is continuous, no second venturi.

Someone makes one. He had a table at the ATW last year. I can't remember his name, but he seemed to have some interesting ideas.

Monette made trumpets with integral mouthpieces long ago. I think they screwed in?

[Doldom]

Someone makes one. He had a table at the ATW last year. I can't remember his name, but he seemed to have some interesting ideas.

Madpipe or Madbone? Am I right?
Anyway I want to hear some review of his products, but cannot find any useful reviews on the internet.

[harrisonreed]

In effect, when assembled, the backbone and leadpipe IS one long piece.

A modular mouthpiece could have three parts: Rim, cup, and a combined shank and leadpipe where the expansion is continuous, no second venturi.

Someone makes one. He had a table at the ATW last year. I can't remember his name, but he seemed to have some interesting ideas.

Monette made trumpets with integral mouthpieces long ago. I think they screwed in?

The Madpipe. I've never seen one in the wild. The deal with that one, though, wasn't just that it was like one long mouthpiece shank without the leadpipe venturi -- that thing was also miles long. It effectively changed the top bore of your entire slide...

Integral mouthpiece Monnettes and Monette trumpets in general are extremely rare.

The venturi in the leadpipe past the end of the mouthpiece shank is a design feature, not a design flaw. It's possible to make leadpipes all with venturi nearly equal to the standard tip diameter of a mouthpiece shank and put that venturi within a few thousands or hundredths of an inch from where the shank generally should end, as a standard. But they don't typically make them that way.

I don't think it's because it's too hard to do, I think it's because that would cause them to play far too open for most people.

[brassmedic]

Apologies if I missed it, but I haven't seen anyone mention that there is another factor besides insertion depth, and that is the location of the narrowest part of the leadpipe. You can have exactly the same insertion depth for 2 different leadpipes, but if the venturi is further down on one of them, the "gap" is bigger. For one piece leadpipes, I would define the "gap" as the distance between the end of the mouthpiece and the narrowest part of the leadpipe. When I measured vintage leadpipes to design my replicas, I found that there is quite a bit of variation in the location of the venturi. And I absolutely believe that affects how it blows. The diameter of the venturi probably affects the blow even more.

A sackbut does not have a leadpipe, but it does have a receiver. If the mouthpiece does not insert all the way down to the end of the receiver, then you have a sudden expansion in bore size where the mouthpiece ends, and then a contraction where the receiver continues to taper down to the bore of the slide tube. So if you change the insertion depth, you are either elongating or shortening this area of expansion and contraction. So I definitely believe that would have an effect on how it blows.

[hornbuilder]

Brad.
In your measuring of pipes, did you notice a change in taper in the receiver side of the pipe, "after" the end of the mouthpiece shank?

I've not seen any pipes where there was a change in taper after the point where the shank ends, but have not measured nearly as many/as exotic pipes as you have!!

In regards the placement of the venturi. Assuming everything else is "identical", moving the venturi point closer to the end of the mouthpiece will make the venturi dia. larger. Moving it further away will make the dia. smaller. Both due to the fact we're dealing with a taper of constant rate (generally speaking) so yes, it will absolutely make a difference in how the pipe plays.

[harrisonreed]

I was trying to show that in the diagrams above, but I suppose the venturi isn't really a single well defined point, like in my diagrams. That might be what Brad is talking about. So the taper rate would change after the receiver and could be different on leadpipes with the same narrowest diameter. Not necessarily a cylindrical section, but certainly not like two cones with the tips cut off and grafted together, either.

[brassmedic]

Brad.
In your measuring of pipes, did you notice a change in taper in the receiver side of the pipe, "after" the end of the mouthpiece shank?

I've not seen any pipes where there was a change in taper after the point where the shank ends, but have not measured nearly as many/as exotic pipes as you have!!

In regards the placement of the venturi. Assuming everything else is "identical", moving the venturi point closer to the end of the mouthpiece will make the venturi dia. larger. Moving it further away will make the dia. smaller. Both due to the fact we're dealing with a taper of constant rate (generally speaking) so yes, it will absolutely make a difference in how the pipe plays.

I haven't methodically checked that. I guess I could put a straight edge on the receiver and see if it is a constant taper. After I posted I did think of what you're saying; if the taper is constant, then "smaller venturi" and "venturi further down" are the same thing.

[LeTromboniste]

A sackbut does not have a leadpipe, but it does have a receiver. If the mouthpiece does not insert all the way down to the end of the receiver, then you have a sudden expansion in bore size where the mouthpiece ends, and then a contraction where the receiver continues to taper down to the bore of the slide tube. So if you change the insertion depth, you are either elongating or shortening this area of expansion and contraction. So I definitely believe that would have an effect on how it blows.

Right you still get contraction after the mouthpiece ends (just not to a smaller dimaneter than the main bore size followed by re-expansion into the slide the way a leapipe does). That would explain why I felt the same effect. But of course the geometry of historical mouthpieces is also fundamentally different (with rapid expansion after the throat, then a sudden step in bore, followed by slow contraction in the shank, then followed by a small amount of expansion and contraction again after the end of the mouthpiece), so it's hard to say what causes what.