Exploring Common DIY Terminology (work in progress)

Preface

I started this article with the intention of offering a guide to DIYers, mostly those new to the field, that defines and explains the terminology you often see in discussions on the topic of DIY loudspeakers. Now, I have plenty of learning to do myself, and am under no illusion that what I do know is complete and correct. Because of this, I want these articles to be living documents. By that I mean, I'd like the DIY community to offer input on each definition to expand and clarify...

Planar Magnetic Transducers

A planar magnetic transducer, also known as a planar driver, is a type of loudspeaker driver that uses a thin and lightweight diaphragm with an embedded conductive coil to produce sound. It operates based on the principles of magnetic induction. A planar driver consists of the below:

• Diaphragm: The diaphragm of a planar magnetic driver is a thin, flat, and often rectangular or circular membrane made from a lightweight material such as mylar or a thin metal

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Xmech (Thiele/Small Parameter)

Xmech represents the maximum physical distance the diaphragm or cone can move before it encounters mechanical limitations. Exceeding the mechanical excursion limit can lead to high levels of distortion, increased nonlinearity, and potential physical damage to the driver. The mechanical excursion capability is a critical parameter for loudspeaker design as it directly affects the loudspeaker's ability to handle high power and reproduce low-frequency signals...

Cone

The cone of a loudspeaker driver refers to the diaphragm or membrane that moves air to produce sound. A cone is distinguished from a dome in that it is almost always a concave shape. It is a crucial component responsible for converting electrical signals into mechanical vibrations, resulting in the creation of sound waves. The cone typically consists of several layers and materials, each serving a specific purpose.

1. Cone Material:
   1. Paper: Paper cones have been widely used in

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Ferrofluid

Ferrofluid is a unique liquid that contains tiny magnetic particles suspended in a carrier fluid, typically a solvent. The particles are typically made of iron oxide or a similar magnetic material, and they are coated with a surfactant to prevent them from clumping together. Ferrofluid exhibits fascinating magnetic properties and finds various applications in audio, including loudspeaker design and optimization.

Applications in Audio:

• Loudspeaker Damping: Ferrofluid

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Pole Piece

The pole piece is a crucial component of the magnetic structure of a driver, especially in dynamic drivers (also known as moving-coil drivers). It is located at the center of the magnet assembly and plays a vital role in the driver's performance by focusing and guiding the magnetic flux. The pole piece typically consists of a cylindrical or conical metal structure that surrounds the center pole of the magnet. It creates a magnetic field that interacts with the voice coil,...

Cavity Resonance

Cavity resonance, also known as a Helmholtz resonance or Helmholtz cavity, is a phenomenon that occurs when air within a confined space vibrates at a specific frequency. This resonance is caused by the interaction between the volume of air in the cavity and the opening or port through which air can move in and out. The concept of cavity resonance was first described by German physicist Hermann von Helmholtz in the 19th century. It has since been widely studied and applied...

Sensitivity

Sensitivity measures how effectively a loudspeaker converts electrical power (input signal) into acoustic power (sound output). Sensitivity is typically expressed in decibels (dB) and is measured at a specific distance from the loudspeaker driver with a standardized input power level of one watt (1W) or other defined power levels. The sensitivity rating indicates the sound pressure level (SPL) produced by the loudspeaker at that distance and power level. For example, a speaker...

SPL (Sound Pressure Level)

SPL stands for sound pressure level, and it is a measure of the sound intensity or loudness at a specific location relative to a reference level. It is commonly used to quantify and describe the loudness of sound in various audio applications, including loudspeaker design, room acoustics, and sound engineering. Sound pressure level is expressed in decibels (dB) and is calculated using the following formula:

SPL (in dB) = 20 * log₁₀(P / P_ref)

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Sd (Thiele/Small Parameter)

Sd, also known as the effective piston area, plays a crucial role in loudspeaker design. It represents the effective surface area of a driver's diaphragm or cone that interacts with the air to generate sound waves. The importance of Sd in loudspeaker design can be understood in several ways:

• Efficiency and sensitivity: The diaphragm area, as represented by Sd, directly affects the loudspeaker's efficiency and sensitivity. A larger diaphragm area can move

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