Martin J King Mathcad Worksheets -
On the right-hand margin, you will see vertical lines with little + or - symbols.
Note on Availability: Since PTC (the company that owns Mathcad) has moved to Prime and subscription models, the DIY audio community is slowly moving away from these worksheets because the software is hard to get. However, for understanding the physics of how transmission lines work, the visual layout of these worksheets is still unmatched.
Martin J. King's (MJK) Mathcad worksheets represent a landmark in high-fidelity DIY audio, providing the first accessible, scientifically rigorous tools for modeling Quarter-Wave (QW) Transmission Line (TL)
loudspeaker enclosures. Before these worksheets, TL design was largely a "guess-and-check" process using loosely defined rules of thumb; MJK's work transformed it into a predictable engineering discipline by solving equivalent electrical and acoustic circuits. Quarter-Wave.com Core Enclosure Models
MJK developed specialized worksheets for a wide range of sophisticated speaker geometries: = Ud + UcUo = UL SL ε Uo So
For decades, the name Martin J. King (MJK) has been synonymous with the gold standard of DIY speaker design, particularly in the realm of quarter-wave transmission lines. His work at Quarter-Wave.com
bridged the gap between complex acoustic theory and practical, accessible tools for hobbyists through his legendary Mathcad worksheets The Evolution of MJK Mathcad Worksheets
Martin J. King’s worksheets weren't just simple calculators; they were sophisticated mathematical models that evolved over 25 years. Initially focused on Transmission Line (TL) Tapered Quarter Wave Tube (TQWT) martin j king mathcad worksheets
designs, these models eventually expanded to simulate nearly any enclosure type, from open baffles to complex front-loaded horns. Key features of these worksheets included: Acoustic and Electrical Circuits
: The models solved equivalent circuits to predict real-world performance accurately. Baffle Step and Diffraction
: MJK was a pioneer in incorporating baffle geometry and edge diffraction into his simulations, helping builders understand why a "perfect" box might sound poor in a real room. Room Interaction
: Users could simulate the impact of floor, side wall, and rear wall reflections on the final sound pressure level (SPL). Driver Specifics
: The worksheets allowed for precise input of Thiele/Small parameters and even simulated multiple drivers wired in series or parallel. Why They Became a DIY Staple
The Martin J. King Mathcad Worksheets are the gold standard for high-level DIY loudspeaker design, specifically for those exploring transmission lines (TL) and quarter-wave resonators. Developed by engineer Martin J. King, these tools moved speaker design beyond simple "cookbook" formulas into precise, physics-based simulations. Key Features of the Worksheets Quarter Wavelength Loudspeaker Design
Martin J. King’s Mathcad worksheets are legendary tools in the DIY audio community, specifically designed for modeling quarter wavelength loudspeaker enclosures such as transmission lines and horns. Quarter-Wave.com Overview of Worksheets On the right-hand margin, you will see vertical
These worksheets allow designers to perform "what-if" analyses to predict how changes in enclosure geometry—like taper ratio, length, or stuffing density—impact the speaker's frequency response and impedance. www.coolcat.dk Key Capabilities Transmission Line (TL) Analysis
: Accurately models straight, tapered, or expanding transmission lines. Quarter Wave Theory
: Uses advanced algorithms to simulate standing waves within pipes to produce low-frequency bass response. Versatile Enclosure Types : While famous for TLs, the tools can also model sealed, bass-reflex, back-loaded horns, front-loaded horns Acoustic Modeling
: Accounts for the influence of the front baffle size, driver offset, and room boundary conditions (like floor and wall reflections) on the Sound Pressure Level (SPL). Electrical Simulation
: Incorporates Thiele/Small parameters, crossover networks (passive or active), and compensation circuits like Zobel or L-pads. Quarter-Wave.com Quarter Wavelength Loudspeaker Design
The power of martin j king mathcad worksheets is the "what if" analysis.
This is the holy grail. This worksheet allows you to model a straight, tapered, or expanding transmission line. Input parameters include: The power of martin j king mathcad worksheets
Outputs: The worksheet generates SPL (Sound Pressure Level) graphs, cone excursion, impedance curve, and group delay.
If you have the MJK archive, there are dozens of files. Focus on these three stages:
Stage 1: Quarter Wave (Transmission Line) Models
Stage 2: The Tables (Design Iteration)
Stage 3: Enclosure Design
Martin J. King is a retired mechanical engineer with a background in vibration analysis. In the early 2000s, he turned his analytical eye toward a long-standing problem in audio: the transmission line (TL) loudspeaker. Unlike ported boxes (bass reflex) or sealed enclosures, transmission lines were considered "black art"—tricky to model, difficult to build, and heavily reliant on trial and error.
King’s contribution was to apply transmission line theory (often used in RF engineering and telecommunications) to low-frequency acoustics. He wrote extensively in the Audio Engineering Society (AES) and, crucially, released his work via Mathcad—a engineering calculation software that allows for mathematical notation, live solving, and data visualization.
In a standard TL, the driver is at the closed end. King provided specific worksheets to model placing the driver 1/3 or 1/2 down the line, which helps smooth out standing wave ripples.
Further down, past the inputs, you will see the output graphs.