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Subwoofer

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A subwoofer is a specialized loudspeaker designed to reproduce low-pitched audio frequencies. These frequencies are known as bass and sub-bass. They are lower than the sounds a standard woofer can optimally generate. Subwoofers are vital for high-quality sound reproduction. They handle the lowest two to three octaves of the ten octaves that humans can hear. This very low-frequency (VLF) range reproduces the natural fundamental tones of instruments like the tuba, grand piano, and double bass. It also reproduces environmental sounds such as thunder, gunshots, and explosions.

Speaker-cross-section
Speaker-cross-section

Subwoofers are never used alone in a sound system. Instead, they work alongside "main" loudspeakers that cover higher frequency bands. To make this work, a crossover network is used. This network uses electronics, such as digital signal processing (DSP), to partition the audio. It sends VLF signals to the subwoofer and higher-frequency signals to the main speakers. Additionally, subwoofers often receive low-frequency effects (LFE) signals. These specific signals are reproduced at 10 dB higher than the standard peak level. This ensures the deepest effects are powerful and clear.

Aktives Subwoofer Modul
Aktives Subwoofer Modul

There are two main types of subwoofers: active and passive. An active subwoofer includes a built-in amplifier to provide its own power. A passive subwoofer has a driver and an enclosure but requires an external amplifier to function. The term "subwoofer" can refer strictly to the driver itself. However, in common use, it often refers to the driver mounted inside a speaker enclosure. These enclosures are often made of wood to withstand air pressure and resist deformation.

Final05jm1
Final05jm1

Engineers use many different enclosure designs to change how a subwoofer performs. Each design involves trade-offs in efficiency, loudness, cabinet size, and cost. A bass reflex design uses a port or vent to move air. Some designs use passive radiator speakers within the enclosure. Other types include acoustic suspension, which is a sealed enclosure. More complex designs include horn-loaded, tapped horn, transmission line, bandpass, and isobaric designs.

Bass reflex spk
Bass reflex spk

The history of deep sound began with early movie theater experiments. From 1900 to the 1950s, recordings rarely used frequencies below 100 Hz. In 1933, Douglas Shearer worked with John Hilliard and James B. Lansing. They developed the Shearing-Lansing 500-A, a two-way enclosure using a W-shaped bass horn. This system could reach frequencies as low as 30 Hz. In 1964, Raymon Dones received a patent for a subwoofer called "The Octavium." It could reproduce distortion-free sound down to 15 Hz.

Infinity Servo Statik subwoofer
Infinity Servo Statik subwoofer

Subwoofers became very famous in the 1970s due to the movie "Earthquake." This film used a system called Sensurround. It utilized large subwoofers driven by racks of 500-watt amplifiers. These subwoofers produced loud rumbling between 17 and 120 Hz. The sound pressure level reached 110 to 120 decibels (dB SPL). This technology helped the film become a massive box office success. By the 1990s, DVDs introduced a dedicated LFE channel for home-cinema systems.

Positioning a subwoofer is different than positioning main speakers. Because very low frequencies are nearly omnidirectional, their direction is hard to determine. This allows subwoofers to be placed more favorably within a room's acoustics. However, some audiophiles find them difficult to use. They often complain about the difficulty of "splicing" the subwoofer sound with the main speakers. This is because the driver can produce distortion above the crossover frequency. This distortion can interfere with the stereo image that human hearing can localize.

Multiple subwoofers in a car hatchback
Multiple subwoofers in a car hatchback

Today, subwoofers are found in almost every modern audio environment. They are used in high-end home stereo systems and custom car audio installations. They are also essential in professional PA systems. By the 2000s, they became nearly universal in nightclubs and concert venues. From the massive arrays in a stadium to small units for a computer, subwoofers provide the foundation of sound. They allow us to feel the physical impact of the lowest notes in our music.

Sound System
Sound System
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🖼️ Images & Media (21)
File:Bravox E2k.jpg
Bravox E2k.jpg
File:Velodyne subwoofers at HighEnd-2009 (3557086404).jpg
Velodyne subwoofers at HighEnd-2009...
File:Infinity Servo Statik subwoofer.jpg
Infinity Servo Statik subwoofer.jpg
File:Gene Czerwinski at AES Convention.jpg
Gene Czerwinski at AES Convention.jpg
File:Sound System.jpg
Sound System.jpg
File:Bose Acoustimass 5 Series 1.jpg
Bose Acoustimass 5 Series 1.jpg
File:Speaker-cross-section.svg
Speaker-cross-section.svg
File:Bass reflex spk.PNG
Bass reflex spk.PNG
File:Subwoofer cab internal bracing.jpg
Subwoofer cab internal bracing.jpg
File:Aktives Subwoofer Modul.jpg
Aktives Subwoofer Modul.jpg
File:Final05jm1.jpg
Final05jm1.jpg
File:Rear panel of a Polk audio sub-woofer.jpg
Rear panel of a Polk audio sub-woofer.jpg

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