Variable Length Trumpet Backbore

Wedge Adjustable Backbores (VLB) – Overview & Use

Backbore length has a major influence on how a mouthpiece slots. Most noticeably, it affects the pitch of the 5th partial, which in turn impacts the tuning of 4th space E and related notes such as Eb and D. These notes tend to run flat on Bb trumpets—and often even flatter on C or higher-pitched instruments.

This is why many manufacturers offer shorter backbores, particularly for C trumpet, though they are also used on Bb horns.

Cup depth also influences pitch relationships between notes. To compensate, some designs pair deeper cups with shorter backbores to maintain balance.

The Challenge

Shortening the backbore raises the pitch of the 5th partial—but it can also affect the 6th partial, pushing top-of-staff G sharp if the backbore is too short or not well matched to the cup.

• A slightly flat E can usually be adjusted
• A sharp G is much harder to manage

This trade-off has traditionally forced players to compromise.

The Solution

Now you don’t have to.

The Wedge Adjustable Backbore (VLB) allows you to precisely fine-tune backbore length—so you can optimize 5th partial pitch without making G uncomfortably sharp.

How It Works

• The backbore features a central core that determines size (Small → Large)
• The threaded shank adjusts length across a wide range—from longer than typical Bb backbores to shorter than most C backbores
• A knurled locking collar secures the setting at repeatable reference points

Setup Instructions

1. Assemble your mouthpiece with your chosen top and VLB backbore
2. Play and evaluate pitch and slotting
3. Focus on key notes:
• 4th space E
• Top-of-staff G
4. Adjust backbore length incrementally
5. Lock in the position once you find the best balance

After adjustment, install your chosen sleeve (regular or heavy) over the mechanism before attaching the top.

Backbore Sizes

Small Backbore

• Best with: ES, LV, S cups
• Feel: Focused, efficient, strong upper register support
• Comparable to: Slightly larger than Schilke A; similar to Warburton 4–5 or Pickett 10-4

Medium Backbore

• Best with: MV, MDV
• Feel: Balanced response, versatile across registers
• Comparable to: Warburton 6–7 or Pickett 10-3

Medium Large (ML)

• Best with: MDV, RT (also works well with MV)
• Feel: Broader sound, slightly less upper register support
• Ideal for: Orchestral playing
• Comparable to: Bach 10, Warburton 8–10, Pickett 10-2

Large Backbore

• Best with: MDV, RT
• Feel: Broadest sound, most open response

Throat Options

• Available with #27 or #25 throats

Note:
At the shortest settings, the VLB can feel tighter than a fixed C backbore.
If you plan to use shorter settings regularly, consider choosing one size larger than your usual backbore.

Sleeve Options

• Heavy Sleeve
• Slightly reduces bright overtones
• Improves slotting stability
• Designed for Wedge tops
• Regular Sleeve
• Compatible with Wedge tops and most standard 3/8-40 threaded tops
• (Warburton, ACB, Pickett, etc.)

Shank Options

Standard Shank

• OD: 0.385" (industry standard, ±0.001 variation typical)

Variable Gap Shanks (optional)
Fine-tune response and feel by adjusting mouthpiece gap:

• Available individually or in sets of three (10% discount)

Why It Matters

Combining adjustable backbore length with variable gap shanks gives you unprecedented control:

• Dial in pitch accuracy across partials
• Optimize slotting for your specific horn
• Match performance precisely to your cup and playing style

Result: A mouthpiece that is truly customized to you—not a compromise.