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Robert P Heavyweight Member
Joined: 28 Feb 2013 Posts: 2596
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Posted: Fri Jan 04, 2019 7:33 pm Post subject: MP gap supposedly doesn't effect intonation equally? |
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I saw a video where it's claimed that an increase or decrease in the mouthpiece annulus/gap doesn't effect intonation equally over the entire instrument the way changing the tuning slide does.
I'm skeptical of this both because it seems counter-intuitive and due to recent experience. I have a Chinese C trumpet that sounds great but I had to adjust the gap because the tuning slide had to be pulled in all the way to be up to pitch. When I checked the gap with a digital caliper it was well over half an inch (~ 17mm) - whoa. The horn is otherwise well made but this obviously wasn't right. Desoldered the receiver, reamed out the leadpipe end (not the mouthpiece end), drilled the internal leadpipe stop back farther and got it to where the gap is now around 2.5 mm with a Bach 1C.
The horn was by my reckoning in tune with itself before with the ridiculously large gap and it still is. Granted I didn't check it with a tuner through the whole range before but I don't perceive it as having changed in character other than now I can have the tuning slide pulled out a normal amount to have it at correct pitch.
If the mouthpiece is farther away from the leadpipe the horn is longer, ergo the pitch is lower. Why would this be impact different notes any differently than making the horn longer by changing the tuning slide? _________________ Getzen Eterna Severinsen
King Silver Flair
Besson 1000
Bundy
Chinese C
Getzen Eterna Bb/A piccolo
Chinese Rotary Bb/A piccolo
Chinese Flugel
Last edited by Robert P on Sat Jan 05, 2019 10:17 am; edited 2 times in total |
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Trumpetingbynurture Heavyweight Member
Joined: 18 Nov 2015 Posts: 898
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Posted: Sat Jan 05, 2019 3:30 am Post subject: |
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Hi Robert,
It's true. The reason why is that you're dealing with two differently tapered pieces of tubing, and changing the gap is basically altering the overall tapers of both.
The overall intonation is also altered by the additional length added, but think of changing the gap as effectively changing the overall length and taper of the mouthpiece itself.
If you made a mouthpiece where the shank and backbore was longer, and stepped to a larger diameter toward the end, then changed how long that extra section was, you can probably imagine how that would effect intonation quite drastically, just as changing the taper of a backbore can quite significantly alter intonation too.
That other interesting thing with regards to changing gap, which I seldom see mentioned, is that doing so changes how much the mouthpiece shank is in contact with the trumpet. The more the mouthpiece is in contact with the trumpet, the more the mouthpiece is in control (slots feel looser). The less contact, the more the horn is in control (slots feel stiffer).
You could drive yourself nuts with it all.
Hope that is somewhat of an answer? |
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JayKosta Heavyweight Member
Joined: 24 Dec 2018 Posts: 3306 Location: Endwell NY USA
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Posted: Sat Jan 05, 2019 4:52 am Post subject: Re: MP gap supposedly doesn't effect intonation equally? |
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Robert P wrote: | I saw a video where it's claimed that an increase or decrease in the mouthpiece annulus/gap doesn't effect intonation equally over the entire instrument the way changing the tuning slide does.
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My understanding is that mpc gap mainly affects how evenly sound pressure 'waves' travels from the end of the mpc shank into the leadpipe - and that it would affect different 'wave lengths' differently. So having the gap be suitable for the 'playing range' is the goal - to get good sound quality and response. The physics about the gap is related to the closeness of the edges of the mpc shank and the the leadpipe.
If the gap is changed by a huge amount (such as you describe), it certainly will affect the overall 'tubing length' and pitch.
Jay _________________ Most Important Note ? - the next one !
KNOW (see) what the next note is BEFORE you have to play it.
PLAY the next note 'on time' and 'in rhythm'.
Oh ya, watch the conductor - they set what is 'on time'. |
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Robert P Heavyweight Member
Joined: 28 Feb 2013 Posts: 2596
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Posted: Sat Jan 05, 2019 10:07 am Post subject: |
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Trumpetingbynurture wrote: | Hope that is somewhat of an answer? |
If you addressed why it wouldn't impact the intonation of all notes the same I missed it.
Quote: | That other interesting thing with regards to changing gap, which I seldom see mentioned, is that doing so changes how much the mouthpiece shank is in contact with the trumpet. |
I didn't change the gap by changing the receiver where the mp goes, I changed it by reaming out the receiver where it slides over the leadpipe. Mp insertion depth into the receiver is unchanged, but the end of the mp is a lot closer to the leadpipe. _________________ Getzen Eterna Severinsen
King Silver Flair
Besson 1000
Bundy
Chinese C
Getzen Eterna Bb/A piccolo
Chinese Rotary Bb/A piccolo
Chinese Flugel |
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Trumpetingbynurture Heavyweight Member
Joined: 18 Nov 2015 Posts: 898
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Posted: Sat Jan 05, 2019 5:52 pm Post subject: |
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Robert P wrote: | Trumpetingbynurture wrote: | Hope that is somewhat of an answer? |
If you addressed why it wouldn't impact the intonation of all notes the same I missed it.
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I thought I did... The taper of the backbore effects intonation, and not in a consistent fashion, just like cutting a random length of tubing out of trumpet would make an instrument higher in pitch and ALSO out of tune with itself because now the various tapers in the instrument are not appropriately matched to the length of the pipe.
Altering the gap effectively alters the overall taper of the mouthpiece. |
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Robert P Heavyweight Member
Joined: 28 Feb 2013 Posts: 2596
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Posted: Sat Jan 05, 2019 6:10 pm Post subject: |
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Trumpetingbynurture wrote: | I thought I did... The taper of the backbore effects intonation, and not in a consistent fashion, just like cutting a random length of tubing out of trumpet would make an instrument higher in pitch and ALSO out of tune with itself because now the various tapers in the instrument are not appropriately matched to the length of the pipe.
Altering the gap effectively alters the overall taper of the mouthpiece. |
Just cutting a length of tubing out of for example the 1st valve slide of course would impact notes that use the 1st valve but not those that don't. But the mouthpiece gap impacts the overall length of the instrument.
Quote: | The taper of the backbore effects intonation, and not in a consistent fashion |
What I haven't seen directly addressed is specifically why this would be true? _________________ Getzen Eterna Severinsen
King Silver Flair
Besson 1000
Bundy
Chinese C
Getzen Eterna Bb/A piccolo
Chinese Rotary Bb/A piccolo
Chinese Flugel |
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scottfsmith Veteran Member
Joined: 27 Jun 2015 Posts: 474 Location: Maryland
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Posted: Sat Jan 05, 2019 7:31 pm Post subject: |
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Robert P wrote: |
What I haven't seen directly addressed is specifically why this would be true? |
Generally a wider backbore widens the octaves and a narrower backbore narrows them. So a wrong backbore could make an instrument not in tune with itself. The reasons why the octaves widen or narrow involves a lot of acoustic theory and I’ve never seen a short but good explanation of it. Maybe this paper will give some hint at the subtleties: http://stomvi-usa.com/wp-content/uploads/2014/12/1976-Trumpet-Acoustics-Correcting-Intonation-Faults.pdf _________________ Thane Standard Large Bb / Monette Unity B6-7M mpc
Lots of vintage trumpets and mouthpieces |
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JayKosta Heavyweight Member
Joined: 24 Dec 2018 Posts: 3306 Location: Endwell NY USA
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Posted: Sun Jan 06, 2019 7:00 am Post subject: |
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Robert P wrote: | ... What I haven't seen directly addressed is specifically why this would be true? |
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Likely because the precise location of the vibrations in the vicinity near the end of the mpc is slightly different depending on the pitch.
Jay _________________ Most Important Note ? - the next one !
KNOW (see) what the next note is BEFORE you have to play it.
PLAY the next note 'on time' and 'in rhythm'.
Oh ya, watch the conductor - they set what is 'on time'. |
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lipshurt Heavyweight Member
Joined: 24 Feb 2008 Posts: 2642 Location: vista ca
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Posted: Sun Jan 06, 2019 10:49 am Post subject: |
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If you have some time, digest the patent of the “gap” by Earle Kent. It’s a bit hard to get the verbiage, cuz it’s a patent, but it’s good information.
Basically, the gist is:
The gap should be square at both ends, no bevels.
1.108 is the gap that gives the best intonation of the overtone series.
More or less gap changes the overtone series as shown in the graphs, and it’s not linear. Some go up and adjacent overtones can go the other way for instance.
Backbore shape also affects the overtone series intonation but the gap size and shape (square) works the same against the placement of the overtones.
I have found that 1.108 is a good gap size as longs as the edges are square. On a Bach the inner edge of the leadpipe is not not square. Kind of square but not square. (pipe is flared out to be tight in the receiver before soldering)
Horns like the new generation conn vintage one are square, as are many others. Not sure about the newer Yamahas, but the older ones were not square. Calichio square, benge not, etc
So the shape of the edge of the leadpipe, and the shape of the edge of the mouthpiece factors into the gap.
GR on their website as a gap formula that works real good (not surprising) and takes into account the diameters of both the leadpipe entrance, and the mouthpiece exit wall thickness. I ahave always assumed that the formula is for square edges, not beveled.
Some mouthpieces are beveled, like a schilke a4a, and one of the stainless steel mouthpiece makers bevels the exit wall. A beveled exit wall lakes the exact gap length less critical but also changes how the note front feels and the slotting, maybe for better, maybe not. If the leadpipe is Beveled, it helps if the mouthpiece is beveled close the the same angle.
All of that goes with the caveat that “this is generally true” and exceptions won’t be that hard to find. _________________ Mouthpiece Maker
vintage Trumpet design enthusiast
www.meeuwsenmouthpieces.com
www.youtube.com/lipshurt |
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mm55 Heavyweight Member
Joined: 01 Jul 2013 Posts: 1412
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Posted: Sun Jan 06, 2019 11:10 am Post subject: |
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lipshurt wrote: | If you have some time, digest the patent of the “gap” by Earle Kent. It’s a bit hard to get the verbiage, cuz it’s a patent, but it’s good information.
Basically, the gist is:
The gap should be square at both ends, no bevels.
1.108 is the gap that gives the best intonation of the overtone series.
More or less gap changes the overtone series as shown in the graphs, and it’s not linear. Some go up and adjacent overtones can go the other way for instance.
Backbore shape also affects the overtone series intonation but the gap size and shape (square) works the same against the placement of the overtones.
I have found that 1.108 is a good gap size as longs as the edges are square. On a Bach the inner edge of the leadpipe is not not square. Kind of square but not square. (pipe is flared out to be tight in the receiver before soldering)
Horns like the new generation conn vintage one are square, as are many others. Not sure about the newer Yamahas, but the older ones were not square. Calichio square, benge not, etc
So the shape of the edge of the leadpipe, and the shape of the edge of the mouthpiece factors into the gap.
GR on their website as a gap formula that works real good (not surprising) and takes into account the diameters of both the leadpipe entrance, and the mouthpiece exit wall thickness. I ahave always assumed that the formula is for square edges, not beveled.
Some mouthpieces are beveled, like a schilke a4a, and one of the stainless steel mouthpiece makers bevels the exit wall. A beveled exit wall lakes the exact gap length less critical but also changes how the note front feels and the slotting, maybe for better, maybe not. If the leadpipe is Beveled, it helps if the mouthpiece is beveled close the the same angle.
All of that goes with the caveat that “this is generally true” and exceptions won’t be that hard to find. |
1.108 in what units? _________________ '75 Bach Strad 180ML/37
'79 King Silver Flair
'07 Flip Oakes Wild Thing
'42 Selmer US
'90 Yamaha YTR6450S(C)
'12 Eastman ETR-540S (D/Eb)
'10 Carol CPT-300LR pkt
'89 Yamaha YCR2330S crnt
'13 CarolBrass CFL-6200-GSS-BG flg
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Robert P Heavyweight Member
Joined: 28 Feb 2013 Posts: 2596
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Posted: Sun Jan 06, 2019 11:13 am Post subject: |
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scottfsmith wrote: | Generally a wider backbore widens the octaves and a narrower backbore narrows them. So a wrong backbore could make an instrument not in tune with itself. |
I wish I'd become aware of this before I did the receiver adjustment, I would have done before and after comparisons with a digital tuner to see how things measured out per a more precise measurement.
Going by my "seat-of-the-ear" assessment I don't detect any difference other than the overall raising of pitch. Of course there's the typical low C#, low D sharpness that needs correction both before and after the change. _________________ Getzen Eterna Severinsen
King Silver Flair
Besson 1000
Bundy
Chinese C
Getzen Eterna Bb/A piccolo
Chinese Rotary Bb/A piccolo
Chinese Flugel |
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