Mouthpiece gap on C trumpet

Robert P · Heavyweight Member Joined: 28 Feb 2013 Posts: 2596

Is there any reason why the mp gap on a C trumpet would be typically different than on a Bb or should they be in the same approximate range?
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lipshurt · Posted: Tue Apr 18, 2017 9:50 am Post subject:

i say generally the same
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lipshurt · Posted: Tue Apr 18, 2017 9:52 am Post subject:

unless one horn has a significantly different venturi shape. Like if its beveled at the end of the pipe etc.

But comparing a bach Bb to Bach C, i say same gap
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Tpt_Guy · Posted: Tue Apr 18, 2017 9:56 am Post subject: Re: Mouthpiece gap on C trumpet

James Becker · Posted: Tue Apr 18, 2017 10:02 am Post subject:

Generally I default to the 1/8" (.125") gap on Bach C trumpets, same as Bb. However we've had a few customers express their preference for less gap in the .090" to .100" range which provides a wider slot allowing for greater ability to correct pitch with less change of timbre. Generally these players are stronger to begin with, requiring less slotting and blow resistance.

I hope this is helpful
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rufflicks · Posted: Tue Apr 18, 2017 10:58 am Post subject:

Some good info here... check out the videos.

http://stomvi-usa.com/learn-about-the-annulus-gap/

Best, Jon
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James Becker · Posted: Tue Apr 18, 2017 12:18 pm Post subject:

FWIW the Yamaha Artist Series C trumpets are set very near .100".

Just remember that gap can be a very personal thing, not everyone likes the same amount of slot.

For those interested in Reeves Sleeves, we can convert any mouthpeice same day with an appointment (see link) http://www.osmun.com/convert-to-reeves-sleeves.html

And we have the entire range of sizes in stock, available here: http://www.osmun.com/accessories/reeves-sleeve.html

I hope this is helpful.
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Klastos · Regular Member Joined: 15 Aug 2004 Posts: 51

Do you (Jim, or anyone) have any sense for why the Bach Chicago C was designed to have a larger gap than the standard 0.125" of other Bachs? This is particularly curious to me since it also has a venturi somewhat on the small side.

James Becker · Posted: Wed Apr 19, 2017 4:36 am Post subject:

ScottA · Posted: Wed Apr 19, 2017 6:57 am Post subject:

Although I don't have the exact info in front of me at the moment I know that one change made between the series I and II of the Yamaha Artist series was in the mouthpiece receiver and the gap. To get the best gap for me on my GR pieces I needed a slightly larger shank than standard on the series I horns. On the series II it was a slightly smaller shank than the standard GR. So that was a fairly significant change.
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Dan in Sydney · Posted: Wed Apr 19, 2017 7:36 am Post subject:

I haven't an answer as to why the Bach Chicago/Philly receivers gap as much as 3/16" (.1875") but they do share a different part number than the stock receiver used on all Stradivarius trumpets listed in the Conn-Selmer parts catalog. Occasionally we've run across vintage Stradivarius trumpets with gaps that run that large, so that might be the era they've chosen to replicate.

As for venturi size you're right, on average these measure .345".

So if one wanted to reduce resistance on a Bach Chicago or Philly C trumpet there's some room to either reduce the gap or increase the venturi size. We've addressed both for our customers that requested it.

FWIW we've had very positive feedback by reducing the venturi size on 25H pipes from the standard .351".

I hope this is helpful.
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Jim--now you've got my curiousity going--how do you in fact reduce the venturi on a 25H--does that not imply that you're putting the metal back?
Funny, I had an older 25H pipe horn that they measured at the factory years ago as having a .345 Venturi--I really liked the horn and didn't want to make a drastic change, so we set it around .347-8. It works very well on this particular instrument.
I've also noticed particularly with the work I've done with Bach in Europe that the receivers on many Philly's and Chicagos were a little tight, thereby making the gap too large. The combination of this and the slightly tighter tuning slide wrap of these instruments make them feel very tight in the upper register in particular.
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lipshurt · Posted: Wed Apr 19, 2017 9:32 am Post subject:

If the Chicago has a smaller venturi, it would beg a slightly longer gap. If you do the GR formula for gap, you will see that the thickness of the wall of the lead pipe means a longer gap "required". I'm nt sure if the smaller venturi would actually need a whole 1/16th extra gap though.

The conn patent describes a .110 gap as best. That is with a venturi of .330, which is small ("normal" is about 345) so the yamaha gap is very much in line with the conn patent and also the GR formula as far as i understand it.

The"standard" gap of 125 is on the long side i think and allows for wear.

on a side note, i have not seen an adjustable receiver (other than the harrelson system with the rings) that does not mess things up more that it helps. That is because they always make the actual gap way bigger in diameter. That makes it whole thing more exaggerated. It means that the difference between the right gap and the wrong gap is super obvious. It gets you find the right gap, but the horn would be better off without that exaggerated bulging gap chamber. Then you can't even measure that gap and apply it to other horns because the geometry of the gap is so much different with the adjustable receiver.

The other thing that is not a good idea is sliding the receiver back form the end of the lead pipe to increase the gap. It also increases the diameter of the chamber so no you have a situation similar to an adjustable receiver with a whacked gap geometry. if you slide the receiver back there need to be a ring inserted to fill that area. Making the ring is fairly easy but its delicate if you only need a ring of .015 or so.
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James Becker · Posted: Thu Apr 20, 2017 9:41 am Post subject:

Steve Hollahan · Posted: Mon Apr 24, 2017 8:06 am Post subject: Bach leadpipes

To my knowledge C pipes are cutdown Bb pipes. So gap should be the same. Some early Mt Vernons had different receivers. Not sure when that was changed.
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Paladin53 · Regular Member Joined: 27 Sep 2015 Posts: 34

James,
Is setting the receiver gap to 0.125 part of your Blueprinting service?

Floyd

James Becker · Posted: Mon Apr 24, 2017 9:50 am Post subject:

Thanks Floyd for asking. We measure and record mouthpiece receiver gap as part of the blueprinting service. When we find deviations greater than + or - .030" either side of .125" we'll advise the customer. The majority of the time it's the result of excessive wear requiring a replacement receiver to restore to .125" target. Receiver replacement is not included in the flat rate blue printing service, but are additional line items.

Keep in mind there was a time in the late 50's and Early 60's when some Bach trumpets were built with greater receiver gap. The Current production Bach Chicago and Philly C trumpets are made with 3/16" gap, perhaps a throw back to this earlier time. As a rule of thumb if a vintage trumpet has greater than .125" it's best to leave things be, especially if the player has grown accustom to the blow.

I'm in agreement with Bob Reeves when he suggests it's better to have too much gap than not enough.

I hope this is helpful.
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Osmun Music Inc.
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Acton, MA 01720
www.osmun.com

Our workshop is as close as your nearest UPS store https://www.ups.com/dropoff?loc=en_US

croyal · Posted: Mon May 22, 2017 5:49 am Post subject:

My Chicago C also has a much larger gap, requiring a 6 sleeve to equal the 4 sleeve distance on my Bach Bb. I was considering getting the throat on my C mouthpiece enlarged ( currently a 1c 26/24) to make a 24/24.

To Jim or anyone that knows,
Would the larger throat offer any advantage over simply switching to a higher numbered sleeve?

Chris