Gap - Adjustable Gap Receiver - No Gap

[Art Lewis]

I´ve just read an article about Adams´ adjustable gap receiver and checked my Sterling Virtuoso (built 2008). From what I see with a torch: There is a smooth transition from the mouthpiece receiver into the leadpipe. No gap intended. How are your horns constructed? Among trumpeters there seems to be a lot of discussion about "the gap". Adams even put an adjustable gap receiver on their Euphoniums and leave musicians with lots of choices. Why don´t they make Euphoniums with a smooth transition? Are there different philosophies of the makers regarding gap or no gap? I wonder what´s it all about.

[ghmerrill]

You won't really have a smooth transition unless the end of your shank abuts the end of the receiver (actually, the lead pipe -- see below) so that there is no "step" between the end of the shank and the receiver wall. So I'm highly skeptical that your Sterling has a smooth transition -- or that you would be able to see this by looking with aid of a torch (which I take it to be British for "flashlight" and not something like a Butane torch ). So my guess is that you didn't look down through the mouthpiece as it was inserted in the receiver and determine that the transition from end of shank to receiver/lead pipe was smooth.

There's no way to construct a universal receiver so that it would provide a smooth transition of this sort for every mouthpiece shank (because of differences in diameter and wall thickness). (I seem to recall that some Monette instruments are made with an integral -- non-removeable -- mouthpiece?) So there WILL be some sort of step or abrupt transition from the shank to the lead pipe. Unless your Sterling has it's receiver as an integral part of the lead pipe? Try very carefully inserting something like a small dowel or plastic straw or rod down your receiver and you will probably feel a lip where it joins the lead pipe.

In addition, every receiver I know of on euphoniums and tubas, etc. is soldered onto the end of the lead pipe. So the end of the lead pipe fits INTO the receiver and is then soldered. This means that there are (at least generally) TWO non-smooth transitions: shank end to receiver, and receiver to lead pipe. Thus a "gap".

The adjustable gap receiver ... er ... adjusts this gap. (Trombones are a little different since the receiver is -- generally, modulo some King ones -- integral with the rest of the lead pipe, but there's then a step transition from the end of the lead pipe to the inner slide.)

[RickF]

From what I understand, it's better to have a bit of a gap between the mpc shank and the lead-pipe. It helps with response and a little bit with tone. For more information, check out Dave Werden's video on the Adams euphonium. Slide the playback forward to just past 4 mins to see the discussion on the AGR.

Discussing the Adams Custom Euphonium

[davewerden]

As I recall from my own Sterling, there is a "bump" in there, but it is probably more subtle than you are expecting. The bump is only caused by the thickness of the leadpipe tubing, so it is no greater than the thickness of the end of the tuning slide tubes.

[Art Lewis]

Allow me to try to explain....
In my Sterling, the inner diameter at the end of the receiver and the inner diameter of the mouthpipe where it meets the receiver without a gap are the same. The receiver-and-pipe unit is tapered to meet the taper of the mouthpiece. My mouthpiece rests in the receiver just beyond the place where leadpipe and receiver is soldered together. No rattle, no fuzzy tone, normal position. Much like a Cornet receiver. No Gap!?

[davewerden]

OK, so I think you are saying that without the mouthpiece inserted there is a bump, roughly where the end of the shank would be, correct? And that the end of the shank and end of the leadpipe mate virtually perfectly?

If so, they you have a zero-gap setup...with the current mouthpiece.

Did you read this article?
http://www.dwerden.com/forum/entry.p...e-Gap-Receiver

In my tests I found that there was a difference of 3.6mm between two of the mouthpieces' insertion depth. If your gap is zero now, it's possible that a different mp would either bottom out and rock in the receiver or that it would create a gap. That's partly why the AGR is there. At the bottom of the linked article above are some links to Harrelson's blog, which talks more about the gap and its effects. It has a little summary, which I will reformat here:

Wide Gap (mouthpiece shank may be shorter)

• More Air Resistance
• Less Intonation Control
• Hard Slotting
• Less Flexibility
• Need Less Aperture Control

Medium Gap (Recommended)

• Medium Air Resistance
• Balanced Slotting & Flexibility

Small or Zero Gap (mouthpiece shank may be long)

• Less or No Air Resistance
• Considerable Intonation Control
• Loose Slotting
• Incredible Flexibility
• Need More Aperture Control

[bbocaner]

It is possible to machine a groove in the end of the receiver so that the leadpipe fits perfectly in. My besson Prestige baritone is built this way. It's also possible to put a taper for the mouthpiece directly into the leadpipe and just reinforce this with the receiver itself fitting over the leadpipe. Most trombones are made this way.

I think the gap itself matters less than the overall taper you get connecting the backbore of the mouthpiece to the taper of the leadpipe. Having the mouthpiece end fit perfectly against the beginning of the leadpipe so there is no gap at all usually means that there's a large jump in the taper you get from the mouthpiece as compared to the taper at the start of the leadpipe. This is more harmful than the actual gap.

I'm not a big fan of AGRs, though, I would prefer just to experiment with having the mouthpiece stem modified so it works optimally.

[bbocaner]

Check out this link from GR mouthpieces: http://www.grmouthpieces.com/gap.html

My thought is that the ideal starting point is where you can draw a dotted line connecting the taper of the mouthpiece backbore and meet perfectly the start of the leadpipe. This is almost certainly not where there is zero gap. And then you can move it a little in or a little out from there to fine tune slotting and resistance.

[davewerden]

I think the gap itself matters less than the overall taper you get connecting the backbore of the mouthpiece to the taper of the leadpipe. Having the mouthpiece end fit perfectly against the beginning of the leadpipe so there is no gap at all usually means that there's a large jump in the taper you get from the mouthpiece as compared to the taper at the start of the leadpipe. This is more harmful than the actual gap.

Right. If the end of the shank were made as thin as the leadpipe tubing, it would be very subject to deformation. So even with the AGR there is still a thickness jump.

I'm not a big fan of AGRs, though, I would prefer just to experiment with having the mouthpiece stem modified so it works optimally.

Different strokes! Normally I'm all for a simpler design where practical. For example, I don't have a trigger on my Adams even though it would be handy every now and then. But it's not necessary and it is an extra point of maintenance or failure (an airline proved that concept on my Sterling with a trigger). I would typically feel the same about something like the AGR, but I have found it useful enough to justify the extra mechanism.

[ghmerrill]

It is possible to machine a groove in the end of the receiver so that the leadpipe fits perfectly in.

Fits perfectly in, in the sense that the transition between receiver and leadpipe is smooth?

But then you still don't have a smooth transition between the end of the shank and the leadpipe. You don't actually have a "gap", but there might be similar turbulence effects.

I have no idea how important these miniscule differences may be. But I've seen some people express concern that on Schilke mouthpieces, the inside of shank end is chamfered.

Not sure how much of this is empirically based or just speculative.

[bbocaner]

Fits perfectly in, in the sense that the transition between receiver and leadpipe is smooth?

correct

But then you still don't have a smooth transition between the end of the shank and the leadpipe. You don't actually have a "gap", but there might be similar turbulence effects.

Yep. It's not necessarily better.

[Art Lewis]

Trying to summarize in short the MP/receiver/leadpipe situation on my Sterling:
- transition between receiver and leadpipe is smooth. Same diameter of both where they meet for the eye inside the receiver. I assume the above mentioned "grove".
- the end of the shank (SM4X) rises up into the leadpipe about 5 mm / 0.2 inch
- no wobble, snug fit of the MP, not too far in
- looks like the leadpipe takes over and continues the taper of the receiver for around 13 mm / 0.5 inch
- conclusion: there is no gap, but a small "step" to the leadpipe due to the thickness of the mp rim at the end of the shank

Why not ask Paul Riggett about the receiver design? Who could help me with a working email-address of Paul? (I´m not on facebook nor twitter)

[carbogast]

Here's my take on this after reading all the interesting comments: there are two tapers coming together; the AGR provides an opportunity to fine tune the acoustical impedance at the interface (which may be frequency dependent) to personal preferences. Most equipment packages provide a very good match right out of the box. As Barry points out, there are a variety of ways to mate a mouthpiece to a lead pipe; good quality equipment should have negligible problems caused by fit or machining artifacts. An alternative to the AGR is a custom shank such as Doug Elliot offers... making me think this might be my next mouthpiece experiment.

- Carroll

[Paco Blasco]

Hi all!
I was with Miel Adams past summer and I've asked the reason of the receiver and how to use it. He tolds me that each mouthpiece requires a different distance to the lead pipe, and he was helping to to adjust my horn with my mouthpiece. What I found is that with a specific mouthpiece, there is a setup where the articulation seems much more easy. You feel that "it is the point", because everything seems easier.

[Art Lewis]

My B&S CC Tuba too has no "bump" at the end of the receiver and beginning of the mouthpipe tube. Instead there is a counterbore in the mouthpiece receiver which allows for the wall thickness of the leadpipe and a flush transition.

So there is not a physical „gap“ but a point where the taper in the receiver converges with the taper of the leadpipe. Unquestionably there must be a point where the taper stops getting smaller and where the tube starts getting larger. (I presume that we have a conical bore in the leadpipe of our Euphoniums. too. Of course(?) this is not the case on a trumpet because of the cylindrical shape of the leadpipe. But on a trumpet too there are two tapers - conical and cylindrical, gap in between - that meet.)

Dealing with a gap on the tubas and euphoniums without a „bump“ at the transition of receiver and leadpipe in my opinion means:
Setting a mouthpiece farer back or closer to that point of the smallest diameter in the receiver/leadpipe unit.

On my horn my mouthpiece seems to be pretty close to this point where the two tapers meet. I tested my mouthpiece with layers of scotch tape to get it farer back from this point. I don´t like it. The response of the euphonium actually is different. It feels like a bad embouchure day. Perhaps this is not because of the changed position but because of the Scoth tape and/or the now thicker wall in the back end of the mouthpiece and a more significant bump in the bore? Or is it a reverse-venturi-effect? Or is it just because I am not accustomed to this mouthpiece position? Lots of questions to be answered. Do you know of somebody who has written a dissertation on the issue?