• Developed with Robbie O'Brien of O'Brien Guitars • Pioneering reseach by Trevor Gore Build Better Guitars Through Objective Measurement Every luthier has experienced it. You build two guitars using nearly identical materials, the same plans, and the same techniques—yet one instrument comes alive with remarkable responsiveness while the other is simply... good. What made the difference? One of the most important factors is monopole mobility—the ability of the guitar's soundboard to efficiently convert string energy into sound. The Cariko Guitar Top Deflection Measurement Tool was designed and manufactured by Cariko in collaboration with Robbie O'Brien for the O'Brien Guitars Lutherie Academy. It provides guitar builders with a precise, repeatable method for measuring top deflection—an important indicator of soundboard stiffness during the voicing process. Whether you're building your first guitar or your hundredth, this tool helps you replace guesswork with measurable data, allowing you to build with greater confidence and consistency. What Is Monopole Mobility? The strings of an acoustic guitar produce very little sound on their own. Nearly all of the instrument's volume, projection, and tonal character come from the soundboard. As the strings vibrate, energy is transferred through the bridge into the guitar top. The soundboard responds by moving air, creating the voice of the instrument. The primary vibration of the soundboard is known as the monopole mode. Monopole mobility describes how easily the top moves when energy is applied. A properly voiced top typically delivers: Exceptional responsiveness Increased projection Improved sustain Wider dynamic range Better note separation Balanced tonal response The objective isn't simply to build a lighter or more flexible top. The objective is finding the ideal balance between stiffness and mass for each individual instrument. Why Measure Top Deflection? For generations, master builders have relied on experience, tap tones, and feel to voice their instruments. Those skills remain invaluable. Objective measurement doesn't replace craftsmanship—it complements it. By applying a known load and measuring the resulting deflection, builders gain valuable insight into the stiffness of the complete top-and-brace system. Recording these measurements allows successful designs to be repeated with far greater consistency. Many builders measure top deflection: Before bracing After bracing During brace carving Before closing the guitar body Throughout multiple builds to establish proven targets Over time, these measurements become an invaluable record that connects construction methods with the tonal performance of completed instruments. Developed for the O'Brien Guitars Lutherie Academy For more than three decades, Robbie O'Brien has taught thousands of builders around the world how to build exceptional acoustic guitars. His teaching philosophy has always emphasized understanding why a guitar performs the way it does—not simply following a set of construction plans. The Guitar Top Deflection Measurement Tool was developed specifically to support that philosophy, providing students and experienced builders alike with a practical, repeatable way to evaluate guitar top stiffness during the voicing process. Designed for Serious Builders Whether you're a first-time builder or an experienced professional, the Guitar Top Deflection Measurement Tool helps you: Build more consistently Make informed voicing decisions Document successful builds Reduce guesswork Better understand the relationship between stiffness and tone Develop repeatable building processes What's Included Your Guitar Top Deflection Measurement Tool arrives ready to begin making accurate, repeatable top deflection measurements. Each component has been carefully built or selected to provide reliable, repeatable measurements, allowing you to confidently document and compare results from one instrument to the next. Included in the package: Guitar Top Deflection Measurement Jig – Precision-built to provide a stable, repeatable platform for measuring guitar top deflection during the voicing process. Digital Indicator – A high-precision digital indicator for accurately measuring top deflection. 1 kg Calibration Weight with Protective Storage Case – Precision 1 kilogram weight used to apply a consistent load during deflection testing. Supplied with its own protective storage case for safe handling and storage. Online Calculator Our browser-based calculator works on virtually any computer, tablet, or smartphone—no software installation required. Simply enter: Top deflection measurement Top resonance frequency Effective mass The calculator instantly determines your monopole mobility value, making it quick and easy to evaluate each guitar top as you build. Perfect for builders who want immediate results in the workshop. Microsoft Excel Calculator For builders who prefer to keep detailed records, we've also included a Microsoft Excel version of the calculator. The spreadsheet allows you to: Calculate monopole mobility Save measurements for every instrument Compare builds over time Create your own database of successful guitars Document your voicing process for future reference Many experienced builders find that maintaining historical measurements helps them develop repeatable construction methods and consistently produce outstanding instruments. Included at No Additional Cost Both the online calculator and the Microsoft Excel calculator are included with your purchase of the Cariko Guitar Top Deflection Measurement Tool. Together, the measurement tool and calculators provide a complete system for evaluating guitar top stiffness and documenting your journey toward building more responsive, consistent, and better-sounding guitars. 💡 Pro Tip: Save the measurements from every guitar you build. Over time you'll develop your own "recipe book" of successful tops, allowing you to confidently reproduce the responsiveness and tonal characteristics of your favorite instruments. Why Builders Choose Cariko At Cariko, our mission is to design innovative tools that help luthiers build with greater precision, confidence, and consistency. Working closely with Robbie O'Brien and the O'Brien Guitars Lutherie Academy, we engineered this tool to make accurate, repeatable deflection measurements simple and reliable. Our goal isn't to replace traditional craftsmanship. It's to provide builders with another valuable piece of information that helps transform experience into repeatable results. Because the finest guitars are built through a combination of craftsmanship, knowledge, and measurement. Acknowledgment The Guitar Top Deflection Measurement Tool was designed and manufactured by Cariko in collaboration with Robbie O'Brien for the O'Brien Guitars Lutherie Academy. The principles of monopole mobility and objective guitar analysis that this tool supports are based on the pioneering research of Trevor Gore, co-author of Contemporary Acoustic Guitar Design and Build. His groundbreaking work has transformed the understanding of acoustic guitar design by providing builders with a scientific framework for evaluating and voicing instruments through objective measurement. Builders interested in gaining a deeper understanding of guitar acoustics, monopole mobility, and objective design principles are encouraged to explore Trevor Gore's authoritative two-volume reference, Contemporary Acoustic Guitar Design and Build. More information about the books is available on Trevor Gore's official website. Cariko gratefully acknowledges Trevor Gore's significant contributions to the field of guitar acoustics and his dedication to advancing the craft of lutherie through research, education, and innovation. Measure with Confidence. Voice with Purpose. Build Exceptional Guitars.