Coaxial speakers
Encyclopedia
A coaxial loudspeaker is a loudspeaker
system in which the individual driver units radiate sound from the same point or axis. Two general types exist: one is a compact design using two or three speaker driver
s, usually in car audio
, and the other is a two-way high-power design for professional audio
, also known as single-source or dual-concentric loudspeakers.
, or the tweeter and a mid-range driver, are mounted in front of the woofer
, partially obscuring it. The advantage of this design is the ability to use a smaller area, hence their popularity in car audio. The low frequency sound waves from the woofer are not reduced too much by the drivers in their path. Without time-alignment correction, the sound from the tweeter may arrive slightly before the sound from the woofer; this misalignment is not generally addressed in automobile sound systems.
This design was popularized in the 1970s with Electronic Industries, Inc. of South Holland, Illinois
introducing the general concept in May 1973, and Jensen Loudspeakers
introducing a retail model the next month. This was followed by designs from Sparkomatic, Clarion
, Infinity
and others.
s containing physically separated drivers. As well, the pattern of response is symmetric around the axis of the loudspeaker.
Since the 1943 introduction of the Altec Lansing
601 "Duplex" coaxial driver, recording studio monitor
s have often been coaxial loudspeaker designs. In 1945 the improved Altec 604 was introduced, and it soon became the recording industry standard studio monitor in the U.S. First shown in 1947 in England, the Tannoy
Dual Concentric design assumed the same role across Europe from the 1950s onward. The Altec 604 combined a 15 inches (38.1 cm) woofer with a compression driver
attached to a horn to carry the high frequencies. The Tannoy also used a 15-inch woofer and a compression driver for high frequencies, but differed in that the woofer itself served as the final horn flare for the high frequency driver. Thus, its output pattern was radially symmetric, not just mirror-image symmetric as in the Altec. Both designs placed the high frequency driver behind the low frequency driver, and both were not initially time aligned. The high frequencies arrived at the listener's ear slightly later than the low frequencies.
One drawback of the design is the production line difficulty in mating the two drivers, and in replacing or reconing the woofer. Another drawback is that the low frequencies tend to modulate the high frequencies, causing greater intermodulation distortion. The Tannoy style of coaxial, with the woofer forming part of the high frequency horn, had greater intermodulation distortion. Designs similar to the Altec 604 have further problems with diffraction of the low frequencies around the central horn, and with rearward emanations from the horn body reflected forward by the woofer out of time with direct sound. All of the problems with sound waves tend to increase with sound pressure
level, causing significant shifts in tone as the loudspeaker changes volume.
In the late 1970s, Bill Putnam
of Universal Audio
worked with Ed Long
and his patented Time Alignment crossover design to fix the long-standing problem of the two bandpasses not being aligned in time at their crossover point. The Altec 604 was given this elaborate new crossover feature and incorporated into the UREI 813 studio monitor, which also had a second woofer physically separate from the coaxial pair. This design dominated recording studios of the 1980s, and time alignment became a feature of competing manufacturers. In the 2000s, digital signal processing
(DSP) was used by Fulcrum Acoustics to reduce some of the coaxial drawbacks such the diffraction of the woofer's upper range around the central horn, by filling in this "shadow" with low frequency sound from the compression driver, and by countering the out-of-time reflections bouncing off of the woofer.
Coaxial loudspeakers have been used in concerts for on-stage foldback
duties, giving musicians a more even sound field because of the single-source characteristic. As well, the enclosure may be made more compact. McCune Sound in San Francisco used Altec 604s in a large proprietary stage wedge in the 1980s, and at the same time Professional Audio Systems (PAS), using Time Alignment technology from Ed Long, sold the popular SW series of compact stage wedges; offered with a 12- or 15-inch woofer, and having a projecting high-frequency horn as in the 604. Other stage monitors using coaxial designs are made by Clair Brothers, L-Acoustics
, Radian Audio Engineering, RCF, Beyma, dB Technologies, Fulcrum Acoustics, and Rat Sound
in partnership with Eastern Acoustic Works.
Loudspeaker
A loudspeaker is an electroacoustic transducer that produces sound in response to an electrical audio signal input. Non-electrical loudspeakers were developed as accessories to telephone systems, but electronic amplification by vacuum tube made loudspeakers more generally useful...
system in which the individual driver units radiate sound from the same point or axis. Two general types exist: one is a compact design using two or three speaker driver
Speaker driver
A speaker driver is an individual transducer that converts electrical energy to sound waves, typically as part of a loudspeaker, television, or other electronics device. Sometimes the transducer is itself referred to as a speaker, particularly when a single one is mounted in an enclosure or as...
s, usually in car audio
Car audio
Car audio/video , auto radio, mobile audio, 12-volt and other terms are used to describe the sound or video system fitted in an automobile. While 12-volt audio and video systems are also used, marketed, or manufactured for marine, aviation, and buses, this article focuses on cars as the most common...
, and the other is a two-way high-power design for professional audio
Professional audio
Professional audio, also 'pro audio', refers to both an activity and a type of audio equipment. Typically it encompasses the production or reproduction of sound for an audience, by individuals who do such work as an occupation like live event support, using sound reinforcement systems designed for...
, also known as single-source or dual-concentric loudspeakers.
Car audio
Coaxial speakers in automobiles are 2- or 3-way loudspeakers in which the tweeterTweeter
A tweeter is a loudspeaker designed to produce high audio frequencies, typically from around 2,000 Hz to 20,000 Hz . Some tweeters can manage response up to 65 kHz...
, or the tweeter and a mid-range driver, are mounted in front of the woofer
Woofer
Woofer is the term commonly used for a loudspeaker driver designed to produce low frequency sounds, typically from around 40 hertz up to about a kilohertz or higher. The name is from the onomatopoeic English word for a dog's bark, "woof"...
, partially obscuring it. The advantage of this design is the ability to use a smaller area, hence their popularity in car audio. The low frequency sound waves from the woofer are not reduced too much by the drivers in their path. Without time-alignment correction, the sound from the tweeter may arrive slightly before the sound from the woofer; this misalignment is not generally addressed in automobile sound systems.
This design was popularized in the 1970s with Electronic Industries, Inc. of South Holland, Illinois
South Holland, Illinois
South Holland is a village in Cook County, Illinois, United States and serves as the seat of Thornton Township. The population was 22,147 at the 2000 census.-History:...
introducing the general concept in May 1973, and Jensen Loudspeakers
Jensen Loudspeakers
Jensen Loudspeakers is a company that manufactures speakers in many different models and sizes, originally located in Chicago, IL. They built a reputation during the 50's and 60's providing speakers used mainly in guitar and bass amplifiers. Though the American company is long gone, "reissue"...
introducing a retail model the next month. This was followed by designs from Sparkomatic, Clarion
Clarion (car audio)
is a Japanese manufacturer of car audio, automotive navigation systems, AutoPCs, visual equipment, bus equipment, and communication equipment.Up until the end of 2005, products in Japan were marketed under the brand name AddZest, while outside of Japan the same product typically carried the Clarion...
, Infinity
Infinity (audio)
Infinity Systems is an American manufacturer of loudspeakers founded by Arnie Nudell, John Ulrick and Cary Christie in 1968. Since 1983, Infinity has been part of the Harman International Industries group....
and others.
Professional audio
Coaxial loudspeakers in professional audio enable sound from two drivers to come from one source. This characteristic allows a wider field of listening to a synchronized summation of speaker drivers than loudspeaker enclosureLoudspeaker enclosure
A loudspeaker enclosure is a purpose-engineered cabinet in which speaker drivers and associated electronic hardware, such as crossover circuits and amplifiers, are mounted...
s containing physically separated drivers. As well, the pattern of response is symmetric around the axis of the loudspeaker.
Since the 1943 introduction of the Altec Lansing
Altec Lansing
Altec Lansing is a line of professional, home, automotive, computer, and multimedia audio products first developed in 1936. They were used in many studios as monitor speakers...
601 "Duplex" coaxial driver, recording studio monitor
Studio monitor
Studio monitors, also called reference monitors, are loudspeakers specifically designed for audio production applications such as recording studios, filmmaking, television studios and radio studios where accurate audio reproduction is crucial....
s have often been coaxial loudspeaker designs. In 1945 the improved Altec 604 was introduced, and it soon became the recording industry standard studio monitor in the U.S. First shown in 1947 in England, the Tannoy
Tannoy
Tannoy Ltd is a Scottish-based manufacturer of loudspeakers and public-address systems. The company was founded in London, England as Tulsemere Manufacturing Company in 1926, but has been based in Coatbridge, Scotland, since the 1970s...
Dual Concentric design assumed the same role across Europe from the 1950s onward. The Altec 604 combined a 15 inches (38.1 cm) woofer with a compression driver
Compression driver
A compression driver is a type of loudspeaker driver which uses the technique of "compression" to achieve high efficiencies. In this context compression refers to the fact that the area of the loudspeaker diaphragm is significantly larger than the aperture through which the sound is radiated....
attached to a horn to carry the high frequencies. The Tannoy also used a 15-inch woofer and a compression driver for high frequencies, but differed in that the woofer itself served as the final horn flare for the high frequency driver. Thus, its output pattern was radially symmetric, not just mirror-image symmetric as in the Altec. Both designs placed the high frequency driver behind the low frequency driver, and both were not initially time aligned. The high frequencies arrived at the listener's ear slightly later than the low frequencies.
One drawback of the design is the production line difficulty in mating the two drivers, and in replacing or reconing the woofer. Another drawback is that the low frequencies tend to modulate the high frequencies, causing greater intermodulation distortion. The Tannoy style of coaxial, with the woofer forming part of the high frequency horn, had greater intermodulation distortion. Designs similar to the Altec 604 have further problems with diffraction of the low frequencies around the central horn, and with rearward emanations from the horn body reflected forward by the woofer out of time with direct sound. All of the problems with sound waves tend to increase with sound pressure
Sound pressure
Sound pressure or acoustic pressure is the local pressure deviation from the ambient atmospheric pressure caused by a sound wave. Sound pressure can be measured using a microphone in air and a hydrophone in water...
level, causing significant shifts in tone as the loudspeaker changes volume.
In the late 1970s, Bill Putnam
Bill Putnam
Milton Tasker "Bill" Putnam was a renowned American audio engineer, songwriter, producer, studio designer and businessman who has been described as "the father of modern recording"...
of Universal Audio
Universal Audio
Universal Audio is the fifth and final studio album by Scottish indie rock band The Delgados, released September 20, 2004. The album is considered to showcase a more 'stripped down' sound than its predecessor Hate, featuring less orchestral themes....
worked with Ed Long
Ed Long (audio engineer)
Edward M. Long is an audio engineer known for introducing the first near-field studio monitors and the first time-aligned loudspeaker crossover. Long worked with Bag End and Ron Wickersham, and developed a method for extending low-frequency response in subwoofers.Long developed a passive crossover...
and his patented Time Alignment crossover design to fix the long-standing problem of the two bandpasses not being aligned in time at their crossover point. The Altec 604 was given this elaborate new crossover feature and incorporated into the UREI 813 studio monitor, which also had a second woofer physically separate from the coaxial pair. This design dominated recording studios of the 1980s, and time alignment became a feature of competing manufacturers. In the 2000s, digital signal processing
Digital signal processing
Digital signal processing is concerned with the representation of discrete time signals by a sequence of numbers or symbols and the processing of these signals. Digital signal processing and analog signal processing are subfields of signal processing...
(DSP) was used by Fulcrum Acoustics to reduce some of the coaxial drawbacks such the diffraction of the woofer's upper range around the central horn, by filling in this "shadow" with low frequency sound from the compression driver, and by countering the out-of-time reflections bouncing off of the woofer.
Coaxial loudspeakers have been used in concerts for on-stage foldback
Foldback (sound engineering)
Foldback is the use of rear-facing heavy-duty loudspeakers known as monitor speaker cabinets on stage during live music performances. The sound is amplified with power amplifiers or a public address system and the speakers are aimed at the on-stage performers rather than the audience...
duties, giving musicians a more even sound field because of the single-source characteristic. As well, the enclosure may be made more compact. McCune Sound in San Francisco used Altec 604s in a large proprietary stage wedge in the 1980s, and at the same time Professional Audio Systems (PAS), using Time Alignment technology from Ed Long, sold the popular SW series of compact stage wedges; offered with a 12- or 15-inch woofer, and having a projecting high-frequency horn as in the 604. Other stage monitors using coaxial designs are made by Clair Brothers, L-Acoustics
L-ACOUSTICS
L-ACOUSTICS is a French manufacturer of loudspeakers, amplifiers and signal processing devices for rental and installed sound markets. Headquartered in Marcoussis, just south of Paris, the company has satellite operations in the United States, United Kingdom and Germany, as well as a global Rental...
, Radian Audio Engineering, RCF, Beyma, dB Technologies, Fulcrum Acoustics, and Rat Sound
Rat Sound
Rat Sound Systems is a sound equipment provider of touring sound reinforcement equipment and services to the concert touring industry, based in Oxnard, California....
in partnership with Eastern Acoustic Works.