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...

Cms (Thiele/Small Parameter)

Cms refers to the mechanical compliance of a driver's suspension system. Cms represents the stiffness or flexibility of the driver's surround and spider, which are responsible for centering and controlling the motion of the driver's diaphragm. It quantifies the ability of the suspension to move in response to changes in force.

The compliance of the suspension affects the resonant frequency, low-frequency response, and overall behavior of the...

Re (Thiele/Small Parameter)

Re refers to the DC resistance of the driver. It represents the electrical resistance encountered by the audio signal as it passes through the voice coil. This has important implications in loudspeaker design:

• Power handling: Re affects the power handling capabilities of the loudspeaker. As the audio signal passes through the voice coil, it encounters electrical resistance, causing a voltage drop and generating heat. A lower resistance value (lower Re)

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Decibel (dB)

The decibel (dB) is a unit of measurement used to quantify the level or intensity of sound. In the context of loudspeaker audio, the decibel is used to express the sound pressure level (SPL) or the power level of audio signals. The decibel scale is used to measure and compare sound pressure levels. It helps in determining the efficiency, output capability, and distortion characteristics of loudspeakers, as well as assessing their suitability for different applications....

Harmonic Distortion

Harmonic distortion refers to the presence of additional frequency components in the output audio that are multiples (harmonics) of the input signal frequency. It occurs when a loudspeaker driver introduces unintended changes to the original signal, resulting in the generation of harmonic frequencies that were not present in the source material. Harmonic distortion can degrade sound quality, introduce coloration, and affect the accuracy of sound reproduction. There...

Overhung Voice Coil

An overhung voice coil is a type of loudspeaker driver design where the winding height of the voice coil is longer than the height of the magnetic gap in which it operates. In this design, the coil extends beyond the magnetic gap, giving it a longer excursion capability than a standard driver.

Pros of Overhung Voice Coils:

• Greater Excursion Capability: Overhung voice coils have a longer excursion range, allowing them to move the speaker cone farther

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Vd (Thiele/Small Parameter)

Vd (Volume Displacement) quantifies a speaker driver's ability to move air and generate sound. Vd is an important consideration for determining the driver's power handling capacity, efficiency, and maximum output level. Volume displacement is defined as the maximum volume of air displaced by the diaphragm of the loudspeaker driver when it moves back and forth. It is typically measured in cubic meters (m³) or liters (L). Vd is calculated using the following...

Spider

In the context of loudspeaker drivers, the spider refers to a component that plays an important role in the suspension system of the driver. The spider is an essential part of the driver's overall mechanical structure, helping to center and control the movement of the voice coil and diaphragm within the magnetic gap. The spider is typically located between the voice coil and the frame (basket) of the loudspeaker driver. It is made of a flexible material, such as cloth or treated...

Vas (Thiele/Small Parameter)

Vas stands for "equivalent compliance volume" or "effective volume of compliance". Vas represents the volume of air that has the same compliance (springiness) as a driver's suspension system. In other words, it measures the air volume that would produce the same acoustic compliance as the driver's mechanical suspension. Vas is typically expressed in liters (L) or cubic feet (ft³) and is an important parameter when designing loudspeaker...

Qes (Thiele/Small Parameter)

Qes (Electrical Q-factor) is a parameter used in loudspeaker design to quantify the electrical losses within the driver's voice coil and magnetic circuit. It provides insights into the efficiency and electrical characteristics of the loudspeaker. Qes is an important parameter and carries the following implications:

• Efficiency: Qes is an indicator of the driver's electrical efficiency. It represents the ratio of electrical energy stored in the voice coil

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