Isolation cabinet (guitar)
Encyclopedia
The characteristic sound of a tube
guitar amplifier
as heard on the majority of professional recordings is achieved by playing the amplifier at high volumes, and using one or more microphones to capture the sound. Turning the volume up causes the pre-amplifier to drive the power amplifier into distortion
and the loudspeaker
to "break up", adding crunch and grit to the amplified tone. The speaker cone
also generates more sound pressure
, delivering more dynamic range
and detail to the microphone.
However, an amplifier at full volume is extremely loud, posing a risk to hearing
and an annoyance to neighbors, and will often drown out other instruments in a mix. A guitar speaker isolation cabinet is a sound-proof enclosure that surrounds, at minimum, the speaker and microphone and prevents sound leakage into the outside environment, enabling the amplifier to be turned up without excessive listening volume.
to prevent blowing the speaker.
A guitar speaker isolation box is large enough to contain a standard guitar speaker cabinet such as a 1x12" or 2x12" cabinet and a couple of compact microphone stands. Inexpensive but less effective implementations of this approach are to bury a guitar speaker and microphone in a closet, place gobo partitions around a speaker cabinet to somewhat deflect the sound, or form a tent with multiple layers of heavy blankets over a guitar speaker cabinet and microphone.
An isolation booth is a small room large enough to contain a single performer along with a rig, enabling the instrument to interact with the amplifier while isolating the rest of the band from the extreme volume.
Finally, the live room of a recording studio
provides sound isolation between an entire band and the control room
, allowing the studio engineers to work at manageable volumes and prevent ear fatigue
.
The frequency response
of an isolation system depends on the number of microphones, the type of microphones, microphone positioning, cabinet dimensions, speaker size, speaker model, and the amount of sound-absorption material inside the speaker cabinet. To control the resulting response, a dedicated equalizer
can be used to enhance or reduce specific frequency ranges. The small room of an isolation cabinet does not
produce audible room reverb, so that for recordings in general the "flannelly" sound has to be enhanced with an electronic reverb.
To reduce volume on stage while staying near to a traditional guitar amp setup, a guitar amp can drive two parallel loads: a power attenuator driving a conventional guitar speaker cabinet (with no microphone), and a speaker isolation cabinet providing the signal for the mixer board and sound reinforcement system
.
A speaker isolation cabinet can be combined with a Direct Inject signal. A DI signal is run from the guitar amplifier or from a guitar amp power attenuator to one channel of the mixing console. A miked guitar speaker in an isolation cabinet is run into another channel of the mixing console. The DI signal and miked guitar speaker can then be selectively blended, with the DI providing a more immediate, present, bright sound, and the microphone and guitar speaker providing a colored, distant, darker sound.
"Cranking an amp" means turning up a guitar power amplifier well into the region at which power-tube distortion is produced, generating as much as twice the amplifier's rated non-distorting wattage. Pushing a guitar amp to such an extent can destroy components of an amplifier whether using an isolation cabinet, dummy load, power attenuator, or conventional guitar speaker cabinet. In particular, tubes wear more quickly when they are consistently pushed into saturation.
Vacuum tube
In electronics, a vacuum tube, electron tube , or thermionic valve , reduced to simply "tube" or "valve" in everyday parlance, is a device that relies on the flow of electric current through a vacuum...
guitar amplifier
Guitar amplifier
A guitar amplifier is an electronic amplifier designed to make the signal of an electric or acoustic guitar louder so that it will produce sound through a loudspeaker...
as heard on the majority of professional recordings is achieved by playing the amplifier at high volumes, and using one or more microphones to capture the sound. Turning the volume up causes the pre-amplifier to drive the power amplifier into distortion
Distortion
A distortion is the alteration of the original shape of an object, image, sound, waveform or other form of information or representation. Distortion is usually unwanted, and often many methods are employed to minimize it in practice...
and the loudspeaker
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...
to "break up", adding crunch and grit to the amplified tone. The speaker cone
Speaker cone
A speaker cone, loudspeaker cone or diaphram can be manufactured from various materials depending on driver implementation , desired frequency response for each driver, and cost....
also generates more 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...
, delivering more dynamic range
Dynamic range
Dynamic range, abbreviated DR or DNR, is the ratio between the largest and smallest possible values of a changeable quantity, such as in sound and light. It is measured as a ratio, or as a base-10 or base-2 logarithmic value.-Dynamic range and human perception:The human senses of sight and...
and detail to the microphone.
However, an amplifier at full volume is extremely loud, posing a risk to hearing
Noise health effects
Noise health effects are the health consequences of elevated sound levels. Elevated workplace or other noise can cause hearing impairment, hypertension, ischemic heart disease, annoyance and sleep disturbance. Changes in the immune system and birth defects have been attributed to noise exposure...
and an annoyance to neighbors, and will often drown out other instruments in a mix. A guitar speaker isolation cabinet is a sound-proof enclosure that surrounds, at minimum, the speaker and microphone and prevents sound leakage into the outside environment, enabling the amplifier to be turned up without excessive listening volume.
Sizes and types
A guitar speaker isolation cabinet has a built-in mounting baffle for a guitar speaker and a permanently mounted microphone clip. A compact isolation cabinet contains a small guitar speaker such as 6½" diameter and sometimes an attached power attenuatorPower attenuator (guitar)
In conjunction with an electric guitar amplifier, a power attenuator is used to divert and dissipate some or all of the amplifier's excess or unneeded power in order to reduce the volume of sound produced by the speaker.- Explanation :...
to prevent blowing the speaker.
A guitar speaker isolation box is large enough to contain a standard guitar speaker cabinet such as a 1x12" or 2x12" cabinet and a couple of compact microphone stands. Inexpensive but less effective implementations of this approach are to bury a guitar speaker and microphone in a closet, place gobo partitions around a speaker cabinet to somewhat deflect the sound, or form a tent with multiple layers of heavy blankets over a guitar speaker cabinet and microphone.
An isolation booth is a small room large enough to contain a single performer along with a rig, enabling the instrument to interact with the amplifier while isolating the rest of the band from the extreme volume.
Finally, the live room of a recording studio
Recording studio
A recording studio is a facility for sound recording and mixing. Ideally both the recording and monitoring spaces are specially designed by an acoustician to achieve optimum acoustic properties...
provides sound isolation between an entire band and the control room
Control room
A control room is a room serving as an operations centre where a facility or service can be monitored and controlled. Examples include:*in television production, the master control is the technical hub of a broadcast operation common among most over-the-air television stations, television networks...
, allowing the studio engineers to work at manageable volumes and prevent ear fatigue
Noise health effects
Noise health effects are the health consequences of elevated sound levels. Elevated workplace or other noise can cause hearing impairment, hypertension, ischemic heart disease, annoyance and sleep disturbance. Changes in the immune system and birth defects have been attributed to noise exposure...
.
The frequency response
Frequency response
Frequency response is the quantitative measure of the output spectrum of a system or device in response to a stimulus, and is used to characterize the dynamics of the system. It is a measure of magnitude and phase of the output as a function of frequency, in comparison to the input...
of an isolation system depends on the number of microphones, the type of microphones, microphone positioning, cabinet dimensions, speaker size, speaker model, and the amount of sound-absorption material inside the speaker cabinet. To control the resulting response, a dedicated equalizer
Equalizer
Equalizer or equaliser may refer to:*Equalization, the process of adjusting the strength of certain frequencies within a signal*An equalization filter for used audio and similar signals...
can be used to enhance or reduce specific frequency ranges. The small room of an isolation cabinet does not
produce audible room reverb, so that for recordings in general the "flannelly" sound has to be enhanced with an electronic reverb.
Degree of sound isolation
A single-layer isolation cabinet or isolation box reduces the sound but does not make the speaker silent; significant bass leaks out. A double-layer box with dead space between the layers still leaks audible bass, if typical plywood thickness is used. Getting closer to silencing would require two very massive layers of plywood, MDF board, or soundproofing board such as Homasote or Wonderboard. An additional layer may be needed, such as for a 100-watt guitar amp with multiple efficient guitar speakers inside the box.Combined approaches
To reduce the volume leakage or to prevent blowing the speaker or microphone, a power attenuator is sometimes used between the tube power amp and the guitar speaker in the isolation box. This reduces the power delivered to the speaker and thus the volume, but has some effect on speaker and microphone response.To reduce volume on stage while staying near to a traditional guitar amp setup, a guitar amp can drive two parallel loads: a power attenuator driving a conventional guitar speaker cabinet (with no microphone), and a speaker isolation cabinet providing the signal for the mixer board and sound reinforcement system
Sound reinforcement system
A sound reinforcement system is the combination of microphones, signal processors, amplifiers, and loudspeakers that makes live or pre-recorded sounds louder and may also distribute those sounds to a larger or more distant audience...
.
A speaker isolation cabinet can be combined with a Direct Inject signal. A DI signal is run from the guitar amplifier or from a guitar amp power attenuator to one channel of the mixing console. A miked guitar speaker in an isolation cabinet is run into another channel of the mixing console. The DI signal and miked guitar speaker can then be selectively blended, with the DI providing a more immediate, present, bright sound, and the microphone and guitar speaker providing a colored, distant, darker sound.
Over stressing components
Blowing a speaker is a significant possibility when using an isolation cabinet. A blown speaker usually has a broken wire in the coil and would need to be reconed. A blown speaker appears as an open or infinite resistance to the tube power amplifier and can "fry" expensive components in the amp, such as the output transformer or power tubes, which would then need to be replaced."Cranking an amp" means turning up a guitar power amplifier well into the region at which power-tube distortion is produced, generating as much as twice the amplifier's rated non-distorting wattage. Pushing a guitar amp to such an extent can destroy components of an amplifier whether using an isolation cabinet, dummy load, power attenuator, or conventional guitar speaker cabinet. In particular, tubes wear more quickly when they are consistently pushed into saturation.
See also
- Spill (audio)Spill (audio)Spill is the occurrence in sound recording and live sound mixing whereby sound is picked up by a microphone from a source other than that which is intended. Spill is usually seen as a problem, and various steps are taken to avoid it or reduce it...
- Guitar amplifierGuitar amplifierA guitar amplifier is an electronic amplifier designed to make the signal of an electric or acoustic guitar louder so that it will produce sound through a loudspeaker...
- Power attenuator (guitar)Power attenuator (guitar)In conjunction with an electric guitar amplifier, a power attenuator is used to divert and dissipate some or all of the amplifier's excess or unneeded power in order to reduce the volume of sound produced by the speaker.- Explanation :...
- DI unitDI unitA DI unit, DI box, Direct Box, or simply DI , is a device typically used in recording studios to connect a high-impedance, line level, unbalanced output signal to a low-impedance microphone level balanced input, usually via XLR connector...
- SoundproofingSoundproofingSoundproofing is any means of reducing the sound pressure with respect to a specified sound source and receptor. There are several basic approaches to reducing sound: increasing the distance between source and receiver, using noise barriers to reflect or absorb the energy of the sound waves, using...
- Sound baffleSound baffleA sound baffle is a construction or device which reduces the strength of airborne sound. Sound baffles are a fundamental tool of noise mitigation, the practice of minimizing noise pollution or reverberation. An important type of sound baffle is the noise barrier constructed along highways to...
External links
- Grendel Sound - Manufacturers of the Dead Room speaker isolation cabinet.
- StudioIsolation.de - Manufacturers of the IsoCab, Guitar Recording Cab und Hatari Isolation Cabinet.
- Box of Doom Isocabinets Manufacturer of "Box of Doom" IsoCabs. Unique because of speaker cassette system.