Guitar speaker
A guitar speaker is a
The cones of these drivers typically range in size from 6.5 to 15 inches (170 to 380 mm) with 10 inches (250 mm) and 12 inches (300 mm) models being the most popular for electric guitar and electric bass combo amps and speaker cabinets. As with all loudspeaker drivers, the magnets are usually made from
Guitar speakers are designed differently from
Cabinet
A guitar speaker cabinet is typically a wooden box that contains one or more guitar speakers. The smallest guitar cabinets have one 6.5" or 8" speaker; these are usually practice amplifier units designed for private practice. Some cabinets designed for rehearsals and small- to mid-size venues contain two 10" or 12" speakers. Another popular format is four 10" or four 12" speakers. Some performers use two 4x10" or 4x12" cabinets. The largest guitar speaker cabinets have eight 10" or 12" speakers. A 4x12" ("four by twelve") is a guitar speaker cabinet containing four 12" speakers. Less commonly, some bass amp cabinets have multiple 8" speakers (e.g., the 8x8" cabinet).
Cabinets with mixed-size speakers are less common, but they are used (e.g., a bass amplifier cabinet with a 15" loudspeaker for lower frequencies and a smaller speaker for mid- to high-range frequencies. A cabinet is usually
Many cabinets contain parallel input/outputs on the rear panel, so that one speaker cab can be plugged into the amp head, and then a second cabinet can be plugged into the first cabinet; as this "daisy-chaining" approach is wired in parallel, plugging in a second cabinet lowers the impedance seen by the amplifier. Cabinets typically have an impedance rating printed on the rear panel, such as "8 ohm minimum" or "4 ohms minimum". These warnings mean that the user should not connect an amplifier requiring a higher impedance; tube amps in particular are designed to work with speakers having some particular impedance. Since speaker impedances as seen by the amplifier vary with frequency, with voice coil construction, and with the cabinet's acoustical loading (which also varies with frequency) there can be no exact match under all conditions. When users daisy-chain a second cabinet with paralleled speakers, they must ensure the amplifier can handle the lower impedance it will see.
Bass guitar cabinets may include a single speaker (typically 12" or 15"), multiple speakers of the same type (common formats include 2x10", 4x10" and 8x10"). Some bass cabinets use multiple different-sized speakers, such as a mixture of 12" and 15" speakers. In rare cases, some large bass cabinets (known as "bass bins") incorporate folded horns to boost the bass response. Bass amp cabinets may have a horn or tweeter built into a speaker cabinet which contains one or more woofer drivers. When a cabinet includes such a horn, the enclosure may also have an attenuator knob, for turning the horn volume up or down. Some more expensive bass cabinets with a woofer/horn approach may have additional features, such as circuitry to protect the speakers or horn from overloads or a biamplification option.
Biamplification enables a bassist to use a
Often what is referred to as a "guitar amp" is in fact a combo amplifier: a cabinet with speakers and a built-in amplifier. Combo amplifiers may be referred to by their speaker cabinet configuration plus the word "combo", so that "4x10 combo" means a guitar amplifier built into a 4x10" speaker cabinet. Since the popular configurations are limited in variety, cabinet configurations are often written abbreviated without ambiguity: For example, 4x10" may be written 410, and 112 refers to a single cabinet housing a 12" speaker.
The speaker cabinets, which hold these drivers can be closed-back or open-back, along with variations such as a semi-open back 4x12 in cabinet, which may have a baffle deflecting two of the four speakers. Closed back cabinets may be acoustic suspension or bass reflex. Bass cabinets are usually closed-back or use a bass reflex port or vent to boost low frequency response. The purpose of the cabinet is match the acoustic impedance seen by the driver to the driver's own electrical/mechanical impedance. Cabinets are best used when they are matched to the driver(s) being used; casual substitution of another driver which can be mounted in a cabinet will only accidentally make changes in a beneficial direction.
The sound of the speaker and cabinet is crucial to the sound of the electric guitar, so much so that it needs to be considered part of the instrument's tone. If the clean signal from a guitar amplifier or pre-amplifier is captured directly (i.e., before it is sent to a speaker cabinet) it will very often be rather brittle and thin, with no "resonant" depth, particularly if the guitar signal is from a string pickup (i.e., the type used in a solid-body electric guitar). Vibration pickups, or microphone pickups, as used in many hollow body electro-acoustic guitars, aren't as strongly affected. The result can sound excessively shrill, scratchy and fizzy, completely different from the smooth tones that listeners hear in recordings or live performances.
When driven hard, guitar speakers produce complex behavior, which affects the sound of the instrument. There will be some power compression, several kinds of distortion, even mechanical limiting as one or more drivers approach their physical limits (e.g. cone excursion). A guitar speaker shows a nonlinear frequency response depending on the speaker's load, e.g. the frequency response, and various distortions, at small amplitudes is different from those at large amplitudes.
Isolation cabinets and emulation devices
A guitar speaker
As an alternative to the isolation cabinet, there are guitar speaker cabinet emulating circuits or signal processors (also known as
Digital cabinet emulation is the treatment of a signal with the simulation of the sound of a speaker and a cabinet. It is available in software, "
See also
- Isolation cabinet (guitar)
- Guitar amplifier
- Instrument amplifier
- Loudspeaker
- Bass instrument amplification
- Electric guitar
- Re-amp