Custom Shop Build Overview

The Martin Custom Shop GJ-18 Burst Grand Jumbo is a bold, powerful acoustic guitar that brings the classic mahogany tone of a Style 18 into a larger, more commanding body shape.

This Custom Shop build pairs a premium spruce top with mahogany back and sides, delivering the dry, woody fundamental tone that has made mahogany Martins a staple of American acoustic music. The larger Grand Jumbo body adds increased air volume, resulting in greater projection, deeper bass response, and a wider dynamic range.

Finished in a striking vintage-inspired burst, this guitar blends traditional Martin tone with a visually rich aesthetic that stands out both on stage and in the studio.

Why the Grand Jumbo Body Matters

The Grand Jumbo body shape expands on the familiar dreadnought concept by increasing internal air volume and surface area, creating a more expansive tonal footprint.

Enhanced bass response and low-end depth
Greater overall volume and projection
Wide dynamic range for aggressive strumming
Full, room-filling sound ideal for live performance

Combined with mahogany back and sides, the result is a guitar that delivers powerful fundamentals with excellent clarity and control.

Custom Shop Craftsmanship

Handcrafted in Nazareth, Pennsylvania, this Custom Shop instrument features Martin’s traditional dovetail neck joint and solid tonewood construction to maximize resonance and long-term stability.

The guitar is built to deliver both strength and responsiveness, allowing the top to move freely while maintaining structural integrity under heavy playing.

The elegant burst finish complements the classic Style 18 aesthetic, giving the instrument a timeless yet distinctive appearance.

Tone & Performance

The GJ-18 delivers a strong, focused voice with the warmth and punch that players expect from a mahogany-bodied Martin. The larger body adds depth and authority while maintaining the clarity needed for articulate playing.