Harrelson Shim Kit to reduce gap: A Survey of Thirty-one Mouthpieces

4/1/2013

We have already taken several orders for the new Mouthpiece Gap Shim Kit, which includes 10 precision machined brass tubes designed to reduce gap. You could dramatically improve the playability of your current setup by doing the following:

1) Measure your current gap
2) Determine your target gap - usually .060 to .100 inches
3) Wide Gap: Insert appropriate gap shim inside the Mouthpiece Receiver of your trumpet
4) Narrow Gap: Reduce length of mouthpiece shank
Note: Installation is easier with the new Venturi Measurement Tool (VMT) and measuring gap with the new Gap Measurement Tool (GMT). You may also purchase the entire Gap Solution Set.

Example 1 - Monette B4S

Goal: Increase flexibility, lessen resistance

Original Gap: .138"

Gap Shim Size: .040"

New Gap: .098"

Expected Result: More open air flow, balanced flexibility & slotting

Example 2 - GR 64S

Goal: Decrease hard slotting, increase flexibility, lessen resistance

Original Gap: .167"

Gap Shim Size: .080"

New Gap: .087"

Expected Result: Hard slotting in upper register is replaced with even scale and arpeggio, flexibility when playing wide intervals is greatly improved, air flow is increased

Example 3 - Bach 1C

Goal: Achieve a gap of zero allowing the maximum flexibility & air flow

Original Gap: .020"

Gap Shim Size: .020"

New Gap: .000"

Expected Result: Zero gap is sometimes preferred by players accustomed to open air flow and extreme flexibility. This setting requires a very good ear as intonation on each note is determined more by the player.

Examples of Mouthpiece Gap variations by Manufacturer and Model
The following gallery shows 31 different mouthpieces inserted into a Harrelson trumpet receiver. This illustrates the corresponding gap variations present among various mouthpiece taper lengths.

The Harrelson Receiver taper and length was designed to minimize gap when used with most standard mouthpieces. When ordering a Harrelson Trumpet while using a Monette mouthpiece, the gap is almost always reduced by means of moving the leadpipe closer to the receiver taper to compensate for the extremely short shank length. The opposite is true if a client states they primarily use Schilke or various Bach mouthpieces. Bach mouthpieces typically vary in length by as much as .12 inches and are a major source of gap issues. Yamaha mouthpieces are not shown, but consistently measure slightly shorter than vintage Bach mouthpieces.

Bach (Gap: .005 - .02) Bach mouthpieces typically vary in length by as much as .12 inches and are a major source of gap issues.
Schilke (Gap: 0 - .08) Schilke mouthpieces commonly have a long shank creating very small gap.
Click on photo for gap measurements, make, model information

GR (Gap = .056 - .167) GR mouthpieces have the widest gap variance of any modern manufacturer I have measured.
Marcinkiewicz (Gap = .08 - .11) Marcinkiewicz mouthpieces are consistently within range of acceptable gap on most trumpets.
Reeves/Stomvi (Gap = varies) the Stomvi/Reeves Flex Sleeve 4.5 produces a .100" gap. Interchangeable shanks ensure a perfect fit.
Click on photo for gap measurements, make, model information

Harrelson (Gap = custom designed to your playing preferences and determined before the trumpet and/or mouthpiece are made)
Click on photo for gap measurements, make, model information

Monette (Gap = .112 - .143) Monette mouthpieces consistently have shorter shanks and larger gap translating to hard slotting.
Click on photo for gap measurements, make, model information

Warburton (Gap = .085 - .107) Warburton mouthpieces often produce gap close to the average target of .100".
Austin ACB (Gap = .076) Produced by Pickett, the ACB produces less gap increasing flexibility and airflow.
Stork (Gap = .109) Stork mouthpieces often produce gap close to the average target of .100".
Taylor (Gap = zero) Taylor mouthpieces do not always fit other brand receivers.
Callet (Gap = .075) Produced by Kanstul, this Superchops I offers the more desirable slightly smaller gap.
Curry (Gap = .048) Curry mouthpiece shank lengths vary by model, I suspect to achieve results related to their purpose.
Wick (Gap = .123) I have measured relatively few Wick mouthpieces. In this case, closing the gap with a .020 shim is advised.
Greg Black (Gap = .115) I have measured relatively few Black mouthpieces. In this case, closing the gap with a .020 shim is advised.
Click on photo for gap measurements, make, model information

Remember, the steps to measure and adjust gap:
1) Measure your current gap
2) Determine your target gap - usually .060 to .100 inches
3) Wide Gap: Insert appropriate gap shim inside the Mouthpiece Receiver of your trumpet
4) Narrow Gap: Reduce length of mouthpiece shank
Note: Installation is easier with the new Venturi Measurement Tool (VMT) and measuring gap with the new Gap Measurement Tool (GMT). You may also purchase the entire Gap Solution Set.

59 Comments

Rigoberto

4/1/2013 11:33:00 am

Question
1) once the shim is placed in the horn does it become a permanent fixture?
2) is it possible that its places incorrectly in to the horn.
3) out of the 5sets of rings are any comparable for a VB stad and a Monette MP

4/1/2013 12:39:22 pm

1) The shim is not permanent and it can be removed easily with the Venturi/Gap Tool, which is designed to measure the gap, the venturi and act as an installation and removal tool. The new Venturi/Gap Tool will be available next week.

2) It is possible to install incorrectly, but pressing the shims into the receiver with a pencil tip prevents this problem.

3) Yes, the Gap Shim Kit will work with a Bach Vindabonda and Monette mouthpiece.

Leo

4/2/2013 08:03:58 am

Do you think that there will be a video in the future showing how to install the shims correctly?

4/2/2013 10:51:53 am

Yes, there will be a video available on the website soon. Every Mouthpiece Gap Shim Kit includes instructions.

4/3/2013 11:16:44 am

Thanks!! One more thing what will he the cost on the Venturi/ gap tool?and when will it be available ?

Jason

4/4/2013 09:12:07 am

The Venturi/Gap tool is available now for $38 or you may purchase it with the Mouthpiece Gap Shim Kit for a discounted price of $50 total plus $5 shipping. We hope to have good photos and description on our website at the end of next week.

Adam

4/2/2013 08:26:00 am

1.) There are only 3 venturi sizes: .340, .345, and .350. What if my horn has a venturi of .343 or .348?

2.) These shims essentially lengthen the venturi section of the leadpipe. Doesn't this change the pipe's overall taper?

4/2/2013 11:04:53 am

Hello Adam,

We will offer every venturi size in the near future with other sizes being sold individually. However, there is no need to purchase the exact size Gap Shim as IMPROVEMENT is better than GAP. I find it interesting how so many people play on equipment with design and manufacturing flaws for many years. Then they learn that their instrument could be better, but get caught up on all the little pieces of the puzzle that they previously never knew existed. Trust me, I'm not spending all of my time developing products to make trumpet playing anything but easier!

You may use a Gap Shim that is slightly larger than your venturi to achieve great results. Using a Gap Shim that is smaller will be addressed in a future blog post as this also improves playability for a cross section of players. If you have a venturi of .348, I recommend a Gap Shim of at least .348 or larger IF your leadpipe + mouthpiece setup does not feel tight in the upper register. If things do feel constricted in the upper register, it is advisable to DECREASE the Venturi inside diameter by a few thousandths of an inch.

Concerning lengthening the leadpipe taper, this is physically impossible as the overall length of the mouthpiece backbore combined with the leadpipe IS essentially the leadpipe taper length. This would only change by reaming the mouthpiece receiver or pulling the mouthpiece out of the receiver. Mouthpiece Gap Shims do not change the length of the leadpipe taper in any way. They simply fill in a GAP within the taper length, thus decreases air flow turbulence.

I hope this helps!
Jason

Felix

4/2/2013 11:34:09 pm

What ventury size correspond to a Bach 25 Leadpipe?
Im Using Bach 5C and want to improve ease of register
Thanks

4/3/2013 02:56:40 am

Most Bach Stradivarius venturi sizes are in the .340-.345 range so you would order the .345 Mouthpiece Gap Shim Kit.

Terry link

4/4/2013 06:48:26 am

What venturi size would I need for the Yamaha Xeno 8335 RGS?

4/4/2013 09:13:09 am

Terry, You would most likely need the .345" Shim Kit as most Yamaha trumpets measure .341 to .345.

4/8/2013 12:26:26 am

Jason, Thanks for the quick reply. I have already done the o-ring trick and loving the way it plays. The shim kit sounds like a better long term fix.

Michael

4/7/2013 04:25:09 am

Hi Jason, what venturi size would I need for a Calicchio 1s/7 ML and a Marcinkiewicz Shew 1.25 or a yamaha 14b4? thank you!

4/15/2013 10:57:23 am

Hi Michael, most trumpet venturi sizes are around .341 to .345 so you would want the .345" set.

Blaine link

4/8/2013 02:29:13 am

Hi Jason, I get the 'gap' measurement, but don't know the proper way (or tool) to measure venturi size. I have a Romeo Adaci Referenz and an Adams A4 + a small collection of 'different' mouthpiece makes that I use on both, though I imagine it would be best to 'pick 1' mouthpiece per horn and stick with it to maximize the use of a shim (assuming each mouthpiece will have a different gap).

4/15/2013 11:00:24 am

Hello Blaine,
I have a new Venturil/Gap Measurement Tool that will soon be available on our website or you may order via phone or email. It allows you to measure the Venturi inside diameter and the Gap and it acts as a shim installation and removal tool. It is best to use mouthpieces of the same gap on one horn, but you don't necessarily need to just use only one mouthpiece. Often times, one brand will offer similar gap on various similarly sized mouthpieces.

4/15/2013 11:04:22 am

by the way, I like your web page! -Jason

Agustin

4/15/2013 10:19:19 am

Hi jason i play a callet jazz with a monette b4s wich rim i will have to use to make a beter gap

4/15/2013 11:01:33 am

Hi Agustin,

You will want the .345" gap shim kit. Let me know if you need help measuring your current gap. Jason

Mike Valichio

5/7/2013 05:21:25 pm

I have Selmer concept TT and Selmer 365 piccolo. What would be my venturi size?

5/9/2013 11:14:39 pm

The Concept TT is likely .343" so you would order the .345 shim kit. The Selmer piccolo may be smaller and the .345 kit will work with any smaller sized venturi. Jason

max

5/13/2013 09:19:57 pm

Great job Jason. It's time for flugelhorn gap?

6/5/2013 05:11:06 am

Yes, Flugel and Cornet gap kits will be next!

6/1/2013 08:00:25 am

Hi there Jason,
I have never truly experimented with gaps on my horns. That being said, will the effect be very noticeable? And is this a better system than reeves sleeves?
I play a schilke s32hd. Would that correspond to the .345" kit?
Thanks!

6/5/2013 05:13:40 am

Yes, adjusting gap is very noticeable. The Reeves system is the best option available right after the 5MM Modular Mouthpiece and I have recommended it for years. The S32 will work with the .345 shims even though the venturi may be closer to .340. We offer shim kits in .340, .345 and .350. -Jason

6/6/2013 01:01:32 am

Will you have this product at ITG? I tried my friends and it helped drasticly. Great work!

6/6/2013 02:38:51 am

Yes, I will be at the ITG Conference in Grand Rapids next week along with Jen, Jake and James Knabe. We will have a display in the main exhibit hall and a full service display in our private room (Ruby Room). Please stop in and check out the new 5MM Modular Mouthpiece line and the Gap Solution Kits! -Jason

Georg Steckler

8/4/2013 07:02:26 am

Very interesting! I play a Schilke B5 and Bobby Shew Lead. Also use Wick 4E and GR 64 SZ.

Can I use the same shim for all?

I'm eager to hear your advice.

12/19/2013 12:56:52 am

Hello Georg. The answer to your question really depends on the shank length of all four mouthpieces. I'm guessing that the Wick is shorter than the Schilke and GR. The Shew model has been produced by two different manufacturers so I cannot say for sure. However, you could trim the shank of the longest mouthpiece and compromise for a more consistent setup using all these mpcs. -Jason

Curt Peil

11/17/2013 07:32:05 am

I play a Holton 307S with 3.68 bore. Would it need a larger shim then the kit has in them. I also play a Selmer K-modified with a 3.59 bore. Can tou help me select what I need for shim's so I don't by something that won't work.Thanks

12/19/2013 12:58:43 am

Hi Curt, you may order a large inside diameter shim kit for your Holton 307S and a standard kit for your Selmer. Call us at 651.330.7774 and Christine or I will be happy to help you. -Jason

Al Moretti

12/16/2013 05:22:24 am

I have a Connstellation 1958 model 38B with a Marcinkiewicz Shew 2.
Do you have a shim size to fill that gap?
Thanks

12/19/2013 12:59:57 am

Hello Al, the standard shim kit should work fine with your 38B. Thanks! -Jason

Chuang Yee

1/15/2014 11:07:10 pm

Hi I play a Yamaha 8310z. Which shim kit should I get? Thanks

Leslie

1/21/2014 08:50:04 am

Hi, I have a 1946 Martin Committee that's tight in the upper register.. What shim size do you suggest?

1/24/2014 02:43:55 am

Hello Leslie, I recommend trying the .345 shim kit. The Committee was offered in several bore sizes and the most common problem with the ML and L (large) bore versions is stuffiness in the upper register. Thanks, Jason

Paul

1/25/2014 05:22:43 am

Your measure the gap page is missing. I don't think I'm gonna buy your shims if I don't know hoe to measure the gap!

1/26/2014 11:49:43 pm

Hello Paul,

The gap pages are complete and offered throughout our website. Directions for measuring gap are included with every Gap Solution product and here on our website. Thank, Jason

2/20/2014 11:59:02 pm

Need to know what shim kit that would work an Eclipse (removable lead pipe configuration) for both Bb and C, both are .470 bore horns. Can provide more measurements to figure this out. Just let me know what you need. Perhaps we can connect via email as I've tried the phone a few times. Or maybe a scheduled phone conference? Thanks!

Jason Harrelson link

5/22/2015 08:15:27 am

Hello Jason, You can email us at harrelsontrumpets@gmail.com or call 651.330.7774. There is always someone answering the phone Monday through Friday from 9am to 5pm CST. It is likely that your Eclipse trumpets would require the .345 shim size, but I don't believe I have measured the Eclipse horns I have owned in the past. We offer free exchanges if the outside diameter doesn't fit on the first try.

Mattias Coudron

4/29/2014 09:01:44 pm

Hi Jason.

Can i insert multiple shims in order to reduce a very large gap?

Thanks

4/30/2014 12:31:22 am

Hello Mattias,

You may insert multiple shims, but it may also be necessary to glue them together with rubber cement. I recommend purchasing one or two longer shims made custom to your needs. I have priced the custom inserts fairly and they really make a huge difference in situations where you need to close a lot of gap.

Orlando Calzada

5/2/2014 09:45:32 am

My current Trumpet is a Benge (Los Angeles) ML & and a Dennis Wick 4X MPC. Please tell me what kit to buy.

Christine

5/6/2014 02:55:40 am

Hi Orlando,

This is Christine in the Harrelson office. Most trumpet venturi sizes are around .341 to .345 so you would want the .345" set. Thanks and feel free to call if you have questions! 651-330-7774

Andy Wickstrom link

5/12/2014 06:06:04 am

I'm trying to understand the shim - so does it abut the end of the mouthpiece shank, or does it abut the end of the leadpipe inside the receiver? Or does it sit in the middle between the mouthpiece and the leadpipe? (If THAT is true, I don't understand how it would work) If it does touch the end of the mouthpiece shank, How do you get it to stop at the right spot inside the receiver?

5/12/2014 07:34:39 am

Hi Andy,
The shim can technically be anyplace between the end of the mouthpiece shank and the beginning of the leadpipe. Depending on the taper of any given receiver and the outside diameter of the shim, it may stop at the leadpipe or someplace closer to the mouthpiece shank. If the shim outside diameter is too large for your specific receiver, it may not seat far enough to insert your mouthpiece. In this case, we exchange shim kits at no charge. Since every receiver is different between brands and models, I have created three different outside diameters to accommodate for each with the standard size fitting the vast majority of horns. Having two small gaps simulates having one larger gap which is why the shim does not need to touch the leadpipe or mouthpiece shank. -Jason

Mark Bouyer

2/17/2015 06:27:43 am

I have been informed by Kanstul Sales that the venturi on my model 1503 Bb trumpet is 0.348 in. diameter. What size shim do you recommend?
.345 would be too tight and .350 would be too loose.
thanks,
Mark

5/22/2015 08:18:51 am

Hello Mark,
We do make the shims in every venturi size including .348. However, you may experience better results with .346 or .345 as most players discover that .347 and larger can be relatively difficult to be flexible in the upper register. Please email us at harrelsontrumpets@gmail.com or call us at 651.330.7774 and we will set you up with the correct size shim kit.

agustin

4/25/2015 01:31:32 am

I use the shims for my callet jazz trumpet with monetteb4s2prana and works great

chuck mackinnon link

5/16/2015 01:58:56 pm

Which shim kit would you recommend for a Kanstul 1500 Bb trumpet?
My repairman measured a .21'' gap with a GR 67M and think i'd like to get it to around .08 guessing.
Thanks,
Chuckj

5/22/2015 08:25:04 am

Chuck,
I would recommend any venturi size between .341 and .345 for a Kanstul 1500. You can easily close the gap to .11" with our largest standard shim in the kit or down to .07" by combining the .10 with the .04, which is close to your theoretical goal. Two shims can be held together by carefully putting a tiny dab of rubber cement between them before inserting into your mouthpiece receiver. I also make custom shims in any length so you could order a shim measuring .345 x .130" to achieve .08".

John

5/22/2015 07:38:33 am

What is the proper size shims for the Kanstul 991?

5/22/2015 08:28:05 am

John,

The Kanstul 991 is a special instrument much like the early Conn Connstellation with a .437" bore. The venturi is considerably smaller than normal so I would likely need to make a special set of inserts for this instrument. I'm happy to do this, but I would ask that you take some measurements for me before hand so I get it right the first time. Please email me at harrelsontrumpets@gmail.com and we'll discuss how to proceed.

Thanks,
Jason

David VAldez

6/23/2015 05:15:34 am

Hello,

I saw your video on youtube and i am quite interested in trying your product. I play Cannonball 789rl trumpet with a Bob Reeves 42s mouthpiece. Lately, I have been noticing some intonation issues in my playing. I got curious and i measured the gap on my horn Its about 1/4 inch gap! What would you recommend.

Thanks

Dave Banks link

1/28/2018 07:59:46 am

Hi Jason, I'm wondering if the concepts with the receiver gap might also apply to the gaps created with the tuning slide? Would response, openness and slotting be improved with those gaps being eliminated as well?

Jonathan Lipsky

4/9/2018 04:07:34 pm

Do you still sell the shim kits? Also, I saw a customer who used your .345" kit on his Callet Jazz to good effect. However, I thought my Callet Jazz has a wider Venturi .352 or .353 in part because Callet prefers less gap.

Brian Rowley

2/19/2020 12:01:57 am

Any thoughts on venturi size for 1964 Schilke E-flat (with unused slides for D)?
I love the buttery smooth sound of Schilke F2 (flugel hybrid in "symphonic series") mouthpiece, but note its spectacularly short backbore / shank. Gap is huge (estimated from mouthpiece insertion depth vs depth of bald q-tip insertion into leadpipe to stopping point ;o) Far, far bigger gap than bach 1C or usual Schilke mouthpieces. (And yes, slotting issues, upper register tightness etc syndrome with it).

Larry Moses

8/9/2020 09:15:09 am

Hi Jason; I usually play a Bach 43* with a Warburton 5sv..However I also enjoy playing on an Olds Super for certain gigs,but doing a rough gap measurment, seems like there is a large gap on that setup...I want to order the shimms, but what would you recommend? I think the bach/warb gap is ok..Thanks; Larry

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Harrelson Shim Kit to reduce gap: A Survey of Thirty-one Mouthpieces

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