Martin: J King Mathcad Worksheets

King’s worksheets are not point-and-click apps. They are living documents. When you open a worksheet, you don’t just see a result; you see the entire chain of physics:

Because it’s Mathcad, the user can change any variable (e.g., “What if I stuff the first 12 inches with 0.5 lb/ft³ of polyfill?”), and the entire worksheet recalculates instantly. There is no black box.

Numerous DIY builds (e.g., on diyAudio, Parts Express Tech Talk) confirm MJK simulations match measured impedance and near-field SPL within ~1–2 dB and 5 Hz in tuning. It correctly predicts the ripple and extended bass of a well-damped TL – something simple models miss.

For those determined to try, search for the “MJK worksheets” archive on the Internet Archive or diyAudio threads – and expect to spend a weekend reading the accompanying PDFs before simulating your first line. martin j king mathcad worksheets

Martin J. King’s Mathcad worksheets represent a landmark in high-fidelity loudspeaker design, particularly for enthusiasts of quarter-wave and transmission line (TL) enclosures. Before King's work, TL design was often a process of trial and error; however, his mathematical models provided a rigorous framework for predicting how sound waves interact with enclosure geometry. The Significance of MJK's Work

Martin J. King (often referred to as MJK in the DIY community) developed these worksheets to bridge the gap between complex acoustic theory and practical speaker building. Key contributions include:

Transmission Line Theory: His models moved beyond basic "lumped parameter" models (like Thiele/Small) to account for the physical dimensions and standing waves within a pipe or enclosure. King’s worksheets are not point-and-click apps

Mass-Loaded Transmission Lines (MLTL): King is credited with popularizing the MLTL, which uses a port (or "mass loading") at the end of a transmission line to allow for a smaller enclosure while maintaining deep bass.

Baffle Step Compensation: His worksheets often included calculations for baffle diffraction, helping designers account for how the cabinet's front face affects frequency response. How the Worksheets Function

The worksheets are built for PTC Mathcad, a software platform for engineering calculations. Unlike a "black box" program, the worksheets allow users to see the underlying equations and perform "what-if" analyses. Quarter Wavelength Loudspeaker Design Because it’s Mathcad, the user can change any variable (e

"Why is the graph red/blank?"

"What is the 'Acoustic Resistance' variable?"

"How do I interpret the Impedance graph?"