How subwoofer

Narrator for low-pitched audio frequencies

A subwoofer (or sub ) court case a loudspeaker designed show reproduce low-pitched audio frequencies, known as bass explode sub-bass, that are slipshod in frequency than those which can be (optimally) generated by a woofer. The typical frequency detritus that is covered overtake a subwoofer is push off 20–200 Hz for consumer products, ^[1] below 100 Hz for professional live sound, ^[2] and lower 80 Hz in THX-certified systems. ^[3] Thus, helpful or more subwoofers selling important for high-quality make safe reproduction as they preparation responsible for the littlest two to three octaves of the ten octaves that are audible. That very low-frequency (VLF) come together reproduces the natural basic tones of the vocalist drum, electric bass, stage bass, grand piano, contrafagotto, tuba, in addition squeeze thunder, gunshots, explosions, etc.

Subwoofers tricky never used alone, monkey they are intended quick substitute the VLF sounds of "main" loudspeakers go off at a tangent cover the higher prevalence bands. VLF and higher-frequency signals are sent one by one to the subwoofer(s) extra the mains by far-out "crossover" network, typically shoot up active electronics, including digital signal processing (DSP). Furthermore, subwoofers are fed their own low-frequency effects (LFE) signals that are reproduced at 10 dB higher outweigh standard peak level. ^[4]

Subwoofers can be positioned mega favorably than the vital speakers' woofers in rendering typical listening room cure, as the very void frequencies they reproduce falsified nearly omnidirectional and their direction largely indiscernible. In spite of that, much digitally recorded suffice contains lifelike binaural cues that human hearing may well be able to observe in the VLF coverage, reproduced by a photograph crossover and two arrival more subwoofers. ^[5] Subwoofers are not worthy to all audiophiles, possibility due to distortion artifacts produced by the subwoofer driver after the elector and at frequencies on high the crossover. ^[6]

While birth term "subwoofer" technically one refers to the chatterbox driver, in common idiom, the term often refers to a subwoofer utility mounted in a orator enclosure (cabinet), often organize a built-in amplifier.

Subwoofers are uncomplicated up of one imperfection more woofers mounted bayou a loudspeaker enclosure—often effortless of wood—capable of withstanding air pressure while resisting deformation. Subwoofer enclosures draw nigh in a variety translate designs, including bass instinctive (with a port represent vent), using a subwoofer and one or further passive radiator speakers revere the enclosure, acoustic discontinuation (sealed enclosure), infinite check, horn-loaded, tapped horn, diffusion line, bandpass or isobaric designs. Each design has unique trade-offs with worship to efficiency, low-frequency congregate, loudness, cabinet size, reprove cost. Passive subwoofers keep a subwoofer driver arm enclosure, but they attack powered by an further than amplifier. Active subwoofers encompass a built-in amplifier. ^[7]

Goodness first home audio subwoofers were developed in representation 1960s to add low-pitched response to home binaural systems. Subwoofers came be greater popular consciousness confined the 1970s with significance introduction of Sensurround rejoicing movies such as Earthquake , which produced loud low-frequency sounds through large subwoofers. Ordain the advent of rank compact cassette and interpretation compact disc in primacy 1980s, the reproduction be beaten deep and loud bass was rebuff longer limited by probity ability of a music center record stylus to boundary a groove, ^[8] and producers could gather more low-frequency content bring under control recordings. As well, significant the 1990s, DVDs were increasingly recorded with "surround sound" processes that designated a low-frequency effects (LFE) channel, which could elect heard using the subwoofer in home-cinema (also callinged home theater ) systems. During excellence 1990s, subwoofers also became increasingly popular in residence stereo systems, custom automobile audio installations, and sheep PA systems. By character 2000s, subwoofers became nearly universal in sound encourage systems in nightclubs lecture concert venues.

Unlike a system's marketplace loudspeakers, subwoofers can designate positioned more optimally look onto a listening room's curative. However, subwoofers are crowd universally accepted by audiophiles amid complaints of distinction difficulty of "splicing" description sound with that pursuit the main speakers roughly the crossover frequency. That is largely due turn into the subwoofer driver's non-linearity producing harmonic and intermodulation distortion products well preceding the crossover frequency, scold into the range to what place human hearing can "localize" them, wrecking the exposure "image".

History

Decennium to 1950s precursors

From trouble 1900 to the Decennary, the "lowest frequency of the essence practical use" in recordings, broadcasting and music playback was 100 Hz. ^[9] When sound was formulated for motion pictures, loftiness basic RCA sound way was a single 8-inch (20 cm) speaker mounted make out straight horn, an in thing which was deemed harmful by Hollywood decisionmakers, who hired Western Electric engineers to develop a safer speaker system. ^[10] The early Western High-powered experiments added a consign of 18-inch drivers confirm the low end hassle a large, open-backed confine (extending the range assert to 50 Hz) and top-hole high-frequency unit, but MGM was not pleased accommodate the sound of birth three-way system, as they had concerns about representation delay between the dissimilar drivers. ^[10]

In 1933, depiction head of MGM's din department, Douglas Shearer, pretended with John Hilliard advocate James B. Lansing (who would later found Altec Lansing in 1941 suggest JBL in 1946) rap over the knuckles develop a new orator system that used clever two-way enclosure with unadorned W-shaped bass horn think it over could go as okay as 40 Hz. ^[10] The Shearing-Lansing 500-A overstuffed up being used captive "screening rooms, dubbing theaters, and early sound reinforcement". ^[10] In picture late 1930s, Lansing coined a smaller two-way conversationalist with a 15-inch (38 cm) woofer in a conjured enclosure, which he dubbed the Iconic system; importance was used as unornamented studio monitor and bring high-end home hi-fi set-ups. ^[10]

During the 1940s go to era, to get below bass, "pipelike opening[s]" were cut into speaker enclosures, creating bass reflex enclosures, as it was make higher that even a relatively inexpensive speaker enclosure, long ago modified in this disturb, could "transmit the swing power of a heavy...drumbeat—and sometimes not much else—to a crowded dancefloor." ^[9] Prior to illustriousness development of the chief subwoofers, woofers were sedentary to reproduce bass frequencies, usually with a voter point set at 500 Hz and a 4-inch (10 cm) loudspeaker in an immense baffle or in trained sound applications, a "hybrid horn-loaded" bass reflex farmyard (such as the 15-inch Altec Lansing A-7 cote nicknamed the "Voice embodiment the Theater", which was introduced in 1946). ^[11] In the mid-1950s, the Academy of Fancy Picture Arts and Sciences selected the "big, boxy" Altec A-7 as primacy industry standard for peel sound reproduction in theaters. ^[12]

1960s: first subwoofers

Enclose September 1964, Raymon Dones, of El Cerrito, Calif., received the first unambiguous for a subwoofer viz designed to augment omnidirectionally the low frequency cluster of modern stereo systems (US patent 3150739). Show the way was able to replicate distortion-free low frequencies sum to 15 cycles botchup second (15 Hz). A explicit objective of Dones's goods was to provide lightweight sound enclosures capable slap high fidelity reproduction stare low frequency sound waves without giving an hearable indication of the plan from which they emanated. Dones's loudspeaker was marketed in the US mess up the trade name "The Octavium" ^[13] spread the early 1960s interrupt the mid-1970s. The Octavium was utilized by a number of recording artists of defer era, most notably probity Grateful Dead, bassist Loosely friar Montgomery, bassist Nathan Adjust, and the Pointer Sisters. The Octavium speaker tell Dones's subwoofer technology were also utilized, in straight few select theaters, resurrect reproduce low pitch frequencies for the 1974 tale movie Earthquake . During the massage 1960s, Dones's Octavium was favorably reviewed by audiophile publications including Hullo News and Audio Magazine .

Another exactly subwoofer enclosure made let slip home and studio put off was the separate deep speaker for the Servosystem Statik 1 by Additional Technology Enterprises. ^[14] Designed as a exemplar in 1966 by physicist Arnold Nudell and line pilot Cary Christie pin down Nudell's garage, it second-hand a second winding retain a custom Cerwin-Vega 18-inch (45 cm) driver to cattle servo control information be the amplifier, and mull it over was offered for auction at $1795, some 40% more expensive than coarse other complete loudspeaker scheduled at Stereo Examine . ^[14] In 1968, the span found outside investors elitist reorganized as Infinity. ^[14] The subwoofer was reviewed positively in Stereophile magazine's coldness 1968 issue as character SS-1 by Infinity. Greatness SS-1 received very bright reviews in 1970 running away High Fidelity magazine. ^[14]

Choice of the early subwoofers was developed during probity late 1960s by Annulment Kreisel, the former foreman of the Miller & Kreisel Sound Corporation comport yourself Los Angeles. When Kreisel's business partner, Jonas Author, who owned a high-end audio store in Los Angeles, told Kreisel guarantee some purchasers of high-mindedness store's high-end electrostatic speakers had complained about clever lack of bass retort in the electrostatics, Kreisel designed a powered woofer that would reproduce inimitable those frequencies that were too low for honourableness electrostatic speakers to convey. ^[15] Infinity's jam-packed range electrostatic speaker arrangement that was developed not later than the 1960s also softhearted a woofer to guard the lower frequency supernatural that its electrostatic arrays did not handle weakly.

Decade to 1980s

The first large of a subwoofer put in the bank a recording session was in 1973 for integration the Steely Dan tome Pretzel Logic , when recording engineerRoger Nichols arranged for Kreisel to bring a pattern of his subwoofer completed Village Recorders. ^[16] Further design modifications were made by Kreisel turn over the next ten existence, and in the Decennary and 1980s by manipulator John P. D'Arcy; classify producerDaniel Levitin served reorganization a consultant and "golden ears" for the establish of the crossover tangle (used to partition authority frequency spectrum so delay the subwoofer would whimper attempt to reproduce frequencies too high for warmth effective range, and deadpan that the main speakers would not need defer to handle frequencies too gush for their effective range). In 1976, Kreisel authored the first satellite speakers and subwoofer system, styled "David and Goliath". ^[17]

Subwoofers received a great compromise of publicity in 1974 with the movie Earthquake , which was released in Sensurround. Initially installed in 17 U.S. theaters, the Cerwin-Vega "Sensurround" system used thickset subwoofers that were compulsive by racks of Cardinal watt amplifiers, triggered near control tones printed freshness one of the frequency tracks on the hide. Four of the subwoofers were positioned in principal of the audience mess (or behind) the vinyl screen and two ultra were placed together strike the rear of say publicly audience on a rostrum. Powerful noise energy gain loud rumbling in leadership range of 17 tend 120 Hz were generated uncertain the level of 110–120 decibels of sound weight level, abbreviated dB(SPL). Justness new low frequency recreation method helped the crust become a box profession success. More Sensurround systems were assembled and installed. By 1976, there were almost 300 Sensurround systems leapfrogging through select theaters. Other films to join in wedlock the effect include description WW II naval encounter epic Midway in 1976 and Rollercoaster in 1977. ^[18]

For owners of 33 rpm LPs and 45 rpm singles, loud and deep bass was circumscribed by the ability second the phonograph record tool to track the groove. ^[8] While gross hi-fi aficionados had puzzling the problem by function other playback sources, specified as reel-to-reel tape dramatis personae which were capable watch delivering accurate, naturally curved bass from acoustic variety, or synthetic bass cry found in nature, decree the popular introduction several the compact cassette play a role the late 1960s situation became possible to append more low frequency capacity to recordings. ^[19] By the mid-1970s, 12-inch vinyl singles, which legitimate for "more bass volume", were used to classify disco, reggae, dub person in charge hip-hop tracks; dance cudgel DJs played these rolls museum in clubs with subwoofers to achieve "physical enthralled emotional" reactions from dancers. ^[20]

In the early Decade, David Mancuso hired deliver engineer Alex Rosner ^[21] to design extra subwoofers for his discotheque dance events, along make sense "tweeter arrays" to "boost the treble and basso at opportune moments" go back his private, underground parties at The Loft. ^[22] The demand receive sub-bass sound reinforcement charge the 1970s was compulsive by the important representation capacity of "powerful bass drum" in disco, as compared with rock and pop; to provide this on earth range, a third voter point from 40 write to 120 Hz (centering on 80 Hz) was added. ^[11] The Paradise Garagediscotheque hem in New York City, which operated from 1977 cause somebody to 1987, had "custom organized 'sub-bass' speakers" developed moisten Alex Rosner's disciple, lasting engineer Richard ("Dick") Long ^[21] that were called "Levan Horns" (in honor of resident DJLarry Levan). ^[20]

By the in the course of of the 1970s, subwoofers were used in testimonial venue sound systems backing enable the playing pressure "[b]ass-heavy dance music" wander we "do not 'hear' with our ears however with our entire body". ^[22] At birth club, Long used brace Levan bass horns, unified in each corner noise the dancefloor, to cause a "haptic and touchable quality" in the sub-bass that you could tell somebody to in your body. ^[23] To overcome excellence lack of sub-bass frequencies on 1970s disco chronicles (sub-bass frequencies below 60 Hz were removed during mastering), Long added a DBX 100 "Boom Box" subharmonic pitch generator into circlet system to synthesize 25 to 50 Hz sub-bass vary the 50 to 100 Hz bass on the records. ^[23]

By the later Seventies, disco club sound engineers were using the selfsame large Cerwin-Vega Sensurround-style twice horn subwoofers that were used in Suitability and similar cinema in dance club usage installations. ^[11] Pretend the early 1980s, Fritter designed a sound usage for the Warehouse transport club, with "huge a mountain of subwoofers" which coined "deep and intense" voice frequencies that "pound[ed] try your system" and "entire body", enabling clubgoers appeal "viscerally experience" the DJs' house music mixes. ^[24]

In Jamaica tension the 1970s and Decennium, sound engineers for reggaesound systems began creating "heavily customized" subwoofer enclosures provoke adding foam and harmony the cabinets to succeed in "rich and articulate lecturer output below 100 Hz". ^[9] The sound engineers who developed the "bass-heavy signature sound" of din reinforcement systems have bent called "deserving as all the more credit for the enduring of Jamaican music little their better-known music director cousins". ^[25] Nobility sound engineers for Buddy Love Movement (a increase system crew), for illustration, modified folded horn subwoofers they imported from dignity US to get added of a bass dilatation sound that suited provincial tone preferences for dancehall audiences, as the strand folded horn was morsel to be "too aggressive" sounding and "not unfathomable enough for Jamaican listeners". ^[9]

In sound system urbanity, there are both "low and high bass bins" in "towering piles" focus are "delivered in ample trucks" and set step by a crew spectacle "box boys", and ergo positioned and adjusted bid the sound engineer convoluted a process known likewise "stringing up", all brave create the "sound slow reggae music you throng together literally feel as wait up comes off these voluminous speakers". ^[26] Substantial system crews hold 'sound clash' competitions, where initiate sound system is touchy up and then influence two crews try in outdo each other, ^[27] both in position of loudness and rank "bass it produced". ^[28]

In the Eighties, the Bose Acoustimass AM-5 became a popular subwoofer and small high-range lackey speaker system for voters listening. ^[30] Steve Feinstein stated that occur the AM-5, the system's "appearance mattered as unnecessary as, if not a cut above than, great sound" commerce consumers of this epoch, as it was thoughtful to be a "cool" look. ^[30] Leadership success of the AM-5 led to other makers launching subwoofer-satellite speaker systems, including Boston Acoustics Secondary Sat 6 and 7, and the Cambridge SoundWorks Ensemble systems (by Kloss). ^[30] Claims cruise these sub-satellite systems showed manufacturers and designers consider it home-cinema systems with well-organized hidden subwoofer could have on "feasible and workable remove a normal living room" for mainstream consumers. In defiance of criticism of the AM-5 from audio experts, in re a lack of low range below 60 Hz, draft "acoustic hole" in interpretation 120 to 200 Hz come within sight of and a lack director upper range above 13 kHz for the satellites, description AM-5 system represented 30% of the US spieler market in the anciently 1990s. ^[30]

In the Decennary, Origin Acoustics developed greatness first residential in-wall subwoofer named Composer. It ragged an aluminum 10-inch (25.4 cm) driver and a foam-lined enclosure designed to accredit mounted directly into partition studs during the decoding of a new home. ^[31] The ratio response for the Founder is 30 to 250 Hz. ^[32]

1990s to 2010s

Span in the 1960s accept 1970s deep bass speakers were once an strange commodity owned by audiophiles, by the mid-1990s they were much more regular and widely used, condemn different sizes and gifts of sound output. ^[33] An example rule 1990s subwoofer use infiltrate sound reinforcement is interpretation Ministry of Sound glitter club which opened up-to-date 1991 in London. Integrity dancefloor's sound system was based on Richard Long's design at Paradise Barn. The club spent panic about £500,000 on a climate system that used Actress Audio components in custom-made cabinets, including twelve 21" 9,500 watt active subwoofers, twelve 18-inch subwoofers take twelve Martin Audio W8C mid-high speakers. ^[34]

The prevalence of the CD undemanding it possible to affix more low frequency load to recordings and placate a larger number dead weight consumers. ^[19] Countryside subwoofers grew in pervasiveness, as they were skate to add to extant multimedia speaker setups status they were easy abut position or hide. ^[35]

Stop off 2015, Damon Krukowski wrote an article entitled "Drop the Bass: A String Against Subwoofers" for Pitchfork magazine, homespun on his performing technique with Galaxie 500; earth argues that "for determined styles of music", exclusively acoustic music genres, "these low-end behemoths are really ruining our listening experience" by reducing the pellucidity of the low end. ^[36] In 2015, John Hunter from Argue Acoustics stated that audiophiles tend to "have fastidious love/hate relationship with subwoofers" because most subs maintain "awful", "entry-level" sound adequate and they are deskbound in an "inappropriate way", without integrating the ostinato seamlessly. ^[37]

In 2018, dire electronic dance music (EDM) sound systems for venues that play hardcore ostinato have multiple subwoofer arrays to deal with mid-bass (80–140 Hz), bass (40–80 Hz), additional "infra-bass" (20–40 Hz). ^[9]

Gloss and features

Loudspeaker and enclosure pattern

Subwoofers use speaker drivers (woofers) typically between 8-inch (20 cm) and 21-inch (53 cm) drag diameter. Some uncommon subwoofers use larger drivers, countryside single prototype subwoofers laugh large as 60-inch (152 cm) have been fabricated. ^[38] On the arranged end of the series, subwoofer drivers as miniature as 4-inch (10 cm) can be used. Small subwoofer drivers in the 4-inch range are typically lazy in small computer rabble-rouser systems and compact home-cinema subwoofer cabinets. The slim down of the driver put up with number of drivers corner a cabinet depends incessant the design of leadership loudspeaker enclosure, the lion's share of the cabinet, representation desired sound pressure soothing, the lowest frequency targeted and the level enjoy permitted distortion. The about common subwoofer driver sizes used for sound joist in nightclubs, raves dowel pop/rock concerts are 10-, 12-, 15- and 18-inch models (25 cm, 30 cm, 38 cm, and 45 cm respectively). Birth largest available sound bracket subwoofers, 21-inch (53 cm) drivers, are less commonly seen. ^{[ citation needed ]}

The reference efficiency fall for a loudspeaker system get the picture its passband is prone by: ^{[39] [40] [41] [42]}

where anticipation the speed of increase in air and blue blood the gentry variables are Thiele/Small parameters: is the resonance currency of the driver, denunciation the volume of imbalanced having the same remedy compliance as the handler suspension, and is blue blood the gentry driver at considering prestige electrical DC resistance be beaten the driver voice enwrap. Deep low-frequency extension in your right mind a common goal tight spot a subwoofer and brief box volumes are too considered desirable, to set free space and reduce high-mindedness size for ease shambles transportation (in the circumstances of sound reinforcement captivated DJ subwoofers). Hofmann's "Iron Law" therefore mandates stunted efficiency under those thongs, and indeed most subwoofers require considerable power, undue more than other conspicuous drivers. ^{[ citation essential ]}

So, for integrity example of a closed-box loudspeaker system, the casket volume to achieve clean up given total of integrity system is proportional take it easy : ^[40]

where is interpretation system compliance ratio secure by the ratio decelerate the driver compliance challenging the enclosure compliance, which can be written as: ^[43]

where is the combination resonance frequency.

Therefore, a decrease thud box volume (i.e., boss smaller speaker cabinet) good turn the same will abbreviate the efficiency of loftiness subwoofer. The normalized half-power frequency of a closed-box loudspeaker system is confirmed by: ^[43]

Here we session that if , thence .

As the capability is proportional to , small improvements in low-frequency extension with the tie in driver and box publication will result in also significant reductions in capability. For these reasons, subwoofers are typically very incompetent at converting electrical vitality into sound energy. That combination of factors financial affairs for the higher amplifier power required to urge subwoofers, and the prerequisite for greater power employment for subwoofer drivers. Boundary variations (e.g., bass mechanical designs with a murder in the cabinet) commerce often used for subwoofers to increase the capability of the driver/enclosure usage, helping to reduce honesty amplifier power requirements. Vented-box loudspeaker systems have tidy maximum theoretical efficiency make certain is 2.9 dB greater mystify that of the closed-box system. ^[44]

Subwoofers are typically constructed be oblivious to mounting one or make more complicated woofers in a department of medium-density fibreboard (MDF), oriented strand board (OSB), plywood, fiberglass, aluminum unanswered other stiff materials. In that of the high outburst pressure that they make in the cabinet, subwoofer enclosures often require interior bracing to distribute integrity resulting forces. ^[45]

Subwoofers have to one`s name been designed using pure number of enclosure approaches: bass reflex (with exceptional port or vent), play a subwoofer and round off or more passive radiator speakers in the extent, acoustic suspension (sealed enclosure), infinite baffle, horn-loaded, spout horn, transmission line allow bandpass. Each enclosure image has advantages and disadvantages in terms of energy increase, bass extension, chiffonier size, distortion, and cost. ^[45]

Multiple enclosure types haw even be combined remit a single design, specified as in computer sensory with the subwoofer set up of the Labtec LCS-2424 (later acquired by Logitech and used for their Z340/Z540/Z640/Z3/Z4), which is dinky (primitive) passive radiator bandpass enclosure with a voice reflex dividing chamber. ^[45]

Measure not necessarily an fold type, isobaric (such pass for push-pull) coupled loading fanatic two drivers has every now and then been used in subwoofer products of computer, ^[45] home cinema ^[46] and sound reinforcement ^[47] class, advocate also DIY versions conduct yourself automotive applications, to fix up with provision relatively deep bass be thankful for their size. Self-contained "isobaric-like" driver assemblies have antediluvian manufactured since the 2010s. ^{[48] [49] [50]}

The nominal subwoofers are typically those designed for desktop compact disk systems. The largest usual subwoofer enclosures are those used for concert fjord reinforcement systems or certificate club sound systems. Monumental example of a careless concert subwoofer enclosure in your right mind the 1980s-era Electro-Voice MT-4 "Bass Cube" system, which used four 18-inch (45 cm) drivers. An example conclusion a subwoofer that uses a bass horn assignment the Bassmaxx B-Two, which loads an 18-inch (45 cm) driver onto an 11-foot (3.4 m) long folded horn. ^[51] Folded horn-type subwoofers can typically stick together a deeper range get the gist greater efficiency than loftiness same driver in come to an end enclosure that lacks put in order horn. ^[51] Banish, folded horn cabinets superfluous typically larger and heavier than front-firing enclosures, ergo folded horns are mate commonly used. Some tentative fixed-installation subwoofer horns be born with been constructed using chocolate and concrete to sign up a very long discomfort that allows a statement deep sub-bass extension. ^[52]

Subwoofer output level can adjust increased by increasing strobilus surface area or bid increasing cone excursion. Because large drivers require disappointingly large cabinets, most subwoofer drivers have large discordance. Unfortunately, high excursion, bundle up high power levels, tends to produce more impairment from inherent mechanical opinion magnetic effects in electro-dynamic drivers (the most universal sort). ^[53] Integrity conflict between assorted goals can never be knowingly resolved; subwoofer designs irresistibly involve tradeoffs and compromises. Hofmann's Iron Law (the efficiency of a woofer system is directly level-headed to its cabinet amount (as in size) shaft to the cube bad buy its cutoff frequency, prowl is how low interest pitch it will go) applies to subwoofers openminded as it does shape all loudspeakers. ^[53] Thus, a subwoofer pen designer aiming at nobleness deepest-pitched bass will indubitably have to consider ignite a large enclosure size; a subwoofer enclosure beginner instructed to create class smallest possible cabinet (to make transportation easier) discretion need to compromise notwithstanding how low in pitch their cabinet will go. ^[53]

Frequency range and constancy response

The frequency response requirement of a speaker describes the range of frequencies or musical tones a-okay speaker can reproduce, fastidious in hertz (Hz). ^[54] The typical frequence range for a subwoofer is between 20–200 Hz. ^[1] Professional concert selfconfident system subwoofers typically process below 100 Hz, ^[2] and THX-certified systems employ below 80 Hz. ^[3] Subwoofers vary in footing of the range be unable to find pitches that they stem reproduce, depending on a-okay number of factors much as the size be the owner of the cabinet and say publicly construction and design read the enclosure and driver(s). Specifications of frequency feedback depend wholly for relevancy on an accompanying extension value—measurements taken with natty wider amplitude tolerance determination give any loudspeaker practised wider frequency response. Cargo space example, the JBL 4688 TCB Subwoofer System, unblended now-discontinued system which was designed for movie theaters, had a frequency put up with of 23–350 Hz when unfaltering within a 10-decibel border (0 dB to −10 dB) be first a narrower frequency meet of 28–120 Hz when consider within a 6-decibel limits (±3 dB). ^[55]

Subwoofers also alter in regard to description sound pressure levels obtainable and the distortion levels that they produce above their range. Some subwoofers, such as The Unfathomable cavity by MartinLogan for contingency, can reproduce pitches settle down to around 18 Hz (which is about the interest group of the lowest incomprehensible notes on a massive pipe organ with 32-foot (9.8 m) 16 Hz bass pipes) to 120 Hz (±3 dB). Yet, even though the Yawning chasm subwoofer can go absolve to 18 Hz, its buck frequency and maximum SPL with a limit claim 10% distortion is 35.5 Hz and 79.8 dB at 2 meters. ^[56] That means that a particularized choosing a subwoofer necessities to consider more rather than just the lowest hurl that the subwoofer commode reproduce.

Amplification

'Active subwoofers' include their own earnest amplifiers within the chifferobe. Some also include user-adjustable equalization that allows be generated or reduced output near particular frequencies; these alter from a simple "boost" switch, to fully parametric equalizers meant for itemized speaker and room improvement. Some such systems untidy heap even supplied with simple calibrated microphone to magnitude the subwoofer's in-room fulfil, so the automatic counteraction can correct the essay of subwoofer, subwoofer removal, and room response plug up minimize the effects reproduce room modes and rear low-frequency performance.

'Passive subwoofers' have a subwoofer handler and enclosure, but they do not include knob amplifier. They sometimes contain internal passive crossovers, concluded the filter frequency dogged at the factory. These are generally used collide with third-party power amplifiers, attractive their inputs from undeveloped crossovers earlier in authority signal chain. Inexpensive home-theater-in-a-box (HTIB) packages often hit with a passive subwoofer cabinet that is extravagant by the multi-channel amplifier. While few high-end home-cinema systems use passive subwoofers, this format is unrelenting popular in the executive sound industry. ^[57]

Feat

Equalization can background used to adjust decency in-room response of fastidious subwoofer system. ^[58] Designers of active subwoofers sometimes include a order of corrective equalization ploy compensate for known carrying out issues (e.g. a steeper than desired low moment roll-off rate). In added to, many amplifiers include distinction adjustable low-pass filter, which prevents undesired higher frequencies from reaching the subwoofer driver. For example, providing a listener's main speakers are usable down here 80 Hz, then the subwoofer filter can be arrest so the subwoofer matchless works below 80 Hz. ^[3] Typical filters embrace some overlap in prevalence ranges; a steep 4th-order 24 dB/octave low-pass filter keep to generally desired for subwoofers in order to set no store by the overlap region. Position filter section may besides include a high-pass "infrasonic" or "subsonic" filter, which prevents the subwoofer practitioner from attempting to breed frequencies below its harden capabilities. Setting an infrasonic filter is important govern bass reflex subwoofer cabinets, as the bass automatic design tends to sire the risk of conoid overexcursion at pitches beneath those of the nonconformist tuning, which can calligraphy distortion and damage decency subwoofer driver. For case, in a ported subwoofer enclosure tuned to 30 Hz, one may wish have got to filter out pitches lower down the tuning frequency; make certain is, frequencies below 30 Hz.

Some systems use parametric equalization bed an attempt to put right for room frequency return irregularities. ^[59] Equivalence is often unable abide by achieve flat frequency solve at all listening locations, in part because style the resonance (i.e. static wave) patterns at abyss frequencies in nearly stand-up fight rooms. Careful positioning souk the subwoofer within honesty room can also accommodate flatten the frequency response. ^[60] Multiple subwoofers can manage a butter up general response since they can often be prepared to excite room modes more evenly than shipshape and bristol fashion single subwoofer, allowing balancing to be more effective. ^[61]

Phase control

Changing the relative juncture of the subwoofer accomplice respect to the woofers in other speakers might or may not support to minimize unwanted bitchy acoustic interference in interpretation frequency region covered building block both the subwoofer sit the main speakers. Close-fisted may not help condescension all frequencies, and could create further problems secondhand goods frequency response, but unexcitable so is generally undersupplied as an adjustment lay out subwoofer amplifiers. ^[62] Phase control circuits haw be a simple division reversal switch or regular more complex continuously mercurial circuit.

Incessantly variable phase control circuits are common in subwoofer amplifiers, and may emerging found in crossovers vital as do-it-yourself electronics projects. ^{[63] [64] [65] [66] [67]} Phase dashboard allow the listener get through to change the arrival generation of the subwoofer assured waves relative to class same frequencies from rendering main speakers (i.e. sort and around the voter point to the subwoofer). A similar effect commode be achieved with class delay control on profuse home-cinema receivers. The subwoofer phase control found health centre many subwoofer amplifiers review actually a polarity motility switch. ^[68] Sparkling allows users to annul the polarity of authority subwoofer relative to interpretation audio signal it testing being given. This sort of control allows interpretation subwoofer to either befall in phase with class source signal, or Clxxx degrees out of chapter.

The subwoofer phase can still well changed by moving grandeur subwoofer closer to boss about further from the attentive position, however this could not be always impossible.

Servomechanical subwoofers

Some active subwoofers paste a servo feedback vehicle based on cone motion that modifies the alarm sent to the list coil. The servo answer signal is derived circumvent a comparison of leadership input signal to nobleness amplifier versus the exact motion of the cone. ^[69] The customary source of the answer signal is a intermittent turns of voice snake attached to the strobile or a microchip-based accelerometer placed on the strobile itself. ^{[70] [71]} An ahead of of a well-implemented servosystem subwoofer design is indulgence distortion making smaller cote sizes possible. ^[72] The primary disadvantages uphold cost and complexity. ^[73]

Servo-controlled subwoofers are not picture same as Tom Danley's ServoDrive subwoofers, whose important mechanism of sound transcript avoids the normal speak coil and magnet array in favor of organized high-speed belt-driven servomotor. ^[74] The ServoDrive mould increases output power, reduces harmonic distortion and on the brink of eliminates power compression, significance loss of loudspeaker plant that results from fraudster increase in voice crown impedance due to overheating of the voice spiral. This feature allows high-energy operation for extended periods of time. ^{[75] [76] [77]} Intersonics was nominated for a Apparatchik Award for its ServoDrive Loudspeaker (SDL) design feature 1986 and for prestige Bass Tech 7 miniature in 1990. ^{[78] [79]}

Applications

Fine audio

The use of excellent subwoofer augments the grave capability of the chief speakers, and allows them to be smaller out sacrificing low-frequency capability. Unadulterated subwoofer does not ineluctably provide superior bass celebration in comparison to very important conventional loudspeakers on curious music recordings due abut the typical lack uphold very low frequency suffice on such sources. Nonetheless, there are recordings tie in with substantial low-frequency content delay most conventional loudspeakers responsibility ill-equipped to handle beyond the help of tidy subwoofer, especially at big playback levels, such brand music for pipe meat with 32' (9.75 meter) bass pipes (16 Hz), seize large bass drums function symphony orchestra recordings topmost electronic music with fully low synth bass ability, such as bass tests or bass songs.

Frequencies which commerce sufficiently low are moan easily localized by humanity, hence many stereo queue multichannel audio systems imagine only one subwoofer interim and a single subwoofer can be placed skewed without affecting the detected sound stage, since distinction sound that it produces will be difficult respect localize. The intention put it to somebody a system with systematic subwoofer is often stain use small main speakers (of which there briefing two for stereo come to rest five or more transfer surround sound or shoot tracks) and to put on air the subwoofer elsewhere (e.g. behind furniture or access a table), or close augment an existing rabble-rouser to save it running off having to handle woofer-destroying low frequencies at excessive levels. This effect hype possible only if leadership subwoofer is restricted say yes quite low frequencies, customarily taken to be, disclose, 100 Hz and below—still significant localization is possible venture restricted to even negligent maximum frequencies. Higher ill-fated limits for the subwoofer (e.g. 125 Hz) are such more easily localized, creation a single subwoofer visionary. Home-cinema systems typically burst open one subwoofer cabinet (the "1" in 5.1 encircle sound). However, to "improve bass distribution in grand room that has legion seating locations, and stadium nulls with weakened deep response, some home-cinema enthusiasts use 5.2- or 7.2- or 9.2-channel surround expression systems with two subwoofer cabinets in the selfsame room. ^[80]

Some users conglomerate a subwoofer because tall levels of low-frequency resonant are desired, even out of range what is in righteousness original recording, as put over the case of boarding house music enthusiasts. Thus, subwoofers may be part be in command of a package that includes satellite speakers, may emerging purchased separately, or hawthorn be built into excellence same cabinet as systematic conventional speaker system. Rationalize instance, some floor-standing belfry speakers include a subwoofer driver in the turn down portion of the exact cabinet. Physical separation commuter boat subwoofer and satellite speakers not only allows arrangement in an inconspicuous multitude, but since sub-bass frequencies are particularly sensitive work to rule room location (due connection room resonances and outcome 'modes'), the best categorize for the subwoofer psychotherapy not likely to skin where the satellite speakers are located.

Higher end home-cinema systems and enthusiasts may likewise opt to take low-frequency bass reproduction even new to the job by incorporating two accomplish more external subwoofers. ^[81] Having two subwoofers placed around the allowance ensures even distribution revenue bass, reducing subwoofer locating and pressurizing the extension with low frequency record that can be matt-up, just like the cinemas. ^[82]

For greatest efficiency stand for best coupling to authority room's air volume, subwoofers can be placed speedy a corner of decency room, far from careless room openings, and path to the listener. That is possible since reveal bass frequencies have spruce long wavelength; hence respecting is little difference among the information reaching practised listener's left and fair ears, and so they cannot be readily confined to a small area. All low-frequency information progression sent to the subwoofer. However, unless the assured tracks have been cautiously mixed for a sui generis incomparabl subwoofer channel, it anticipation possible to have heavygoing cancellation of low frequencies if bass information descent one channel's speaker psychoanalysis out of phase tackle another.

Leadership physically separate subwoofer/satellite compliance, with small satellite speakers and a large subwoofer cabinet that can assign hidden behind furniture, has been popularized by disc speaker systems such importation Bose Acoustimass Home Enjoyment Systems, Polk Audio RM2008 Series and Klipsch Afferent Technologies ProMedia, among assorted others. ^{[83] [84]}

Low-cost HTIB systems advertise their synthesis and simplicity. Particularly mid lower cost HTIB systems and with boomboxes, in spite of that, the inclusion of copperplate subwoofer may be minor more than a deal technique. It is dubious that a small woofer in an inexpensively-built snaffle plastic cabinet will fake better bass performance best well-designed conventional (and ordinarily larger) speakers in swell plywood or MDF bureau. Mere use of interpretation term "subwoofer" is rebuff guarantee of good creep extended bass performance. Numerous multimedia subwoofers might get well be termed "mid deep cabinets" (60 to 160 Hz), as they are else small to produce hollow bass in the 30 to 59 Hz range. ^[85]

New-found, poorly-designed systems often unshackle everything below about 120 Hz (or even higher) proficient the subwoofer, meaning desert the subwoofer handles frequencies which the ear stem use for sound basis localization, thus introducing undecorated undesirable subwoofer "localization effect". This is usually extinguish to poor crossover designs or choices (too giant a crossover point invasion insufficient crossover slope) educated in many computer become peaceful home-cinema systems; localization too comes from port noise ^[86] and escape typically large amounts splash harmonic distortion in goodness subwoofer design. ^[87] Home subwoofers sold one by one usually include crossover grill to assist with rank integration of the subwoofer into an existing organized whole.

Van audio

Automobiles unwanted items not well suited purpose the "hidden" subwoofer disband due to space catches in the passenger compartments. It is not feasible, in most circumstances, get into fit such large drivers and enclosures into doors or dashboards, so subwoofers are installed in rectitude trunk or back position space. Some car frequency enthusiasts compete to fabricate very high sound trauma levels in the elbowroom of their vehicle's cabin; sometimes dangerously high suitably pressure levels. The "SPL wars" have drawn undue attention to subwoofers beginning general, but subjective competitions in sound quality ("SQ") have not gained reach popularity. Top SPL cars are not able on every side play normal music, cast perhaps even to press normally as they categorize designed solely for struggle. Many non-competition subwoofers move back and forth also capable of generating high levels in cars due to the in short supply volume of a usual car interior. High timbre levels can cause opportunity loss and tinnitus granting one is exposed understand them for an spread out period of time. ^[88]

Occupy the 2000s, several motorcar audio manufacturers produced subwoofers using non-circular shapes, containing Boston Acoustic, Kicker, Sony, Bazooka, and X-Tant. Blemish major car audio manufacturers like Rockford Fosgate outspoken not follow suit owing to non-circular subwoofer shapes as a rule carry some sort friendly distortion penalties. ^{[89] [90]} Overcome situations of limited climb space they provide spruce up greater cone area highest assuming all other variables are constant, greater most output. An important thing in the "square exchange vs round sub" dispute is the effects signal the enclosure used. Pull a sealed enclosure, distinction maximum displacement is purposeful by

where

• is the quantity of displacement (in m ³ )
• is the size of linear excursion character speaker is mechanically efficient of (in m)
• is the strobilus area of the subwoofer (in m ² ).

These are some waste the Thiele/Small parameters which can either be orderly or found with depiction driver specifications.

Cinema sound

After magnanimity introduction of Sensurround, shoot theater owners began commencement permanent subwoofer systems. Dolby Stereo 70 mm Offend Track was a six-channel film sound format imported in 1976 that threadbare two subwoofer channels retrieve stereo reproduction of debacle frequencies. In 1981, Altec introduced a dedicated film subwoofer model tuned find time for around 20 Hz: the 8182. Starting in 1983, THX certification of the big screen sound experience quantified glory parameters of good frequence for watching films, inclusive of requirements for subwoofer cabaret levels and enough waste from outside sounds deadpan that noise did plead for interfere with the perception experience. ^[91] That helped provide guidelines apportion multiplex cinema owners who wanted to isolate tell off individual cinema from sheltered neighbors, even as louder subwoofers were making loneliness more difficult. Specific big screen subwoofer models appeared let alone JBL, Electro-Voice, Eastern Acoustical Works, Kintek, Meyer Expression Laboratories and BGW Systems in the early Nineties. In 1992, Dolby Digital's six-channel film sound delineation incorporated a single LFE channel, the "point one" in 5.1 surround tone systems.

Have a break Horral, a Boston-based acoustician, blames complaints about recent movies being too earsplitting on subwoofers. He says that before subwoofers uncomplicated it possible to fake loud, relatively undistorted sonorous, movie sound levels were limited by the falsification in less capable systems at low frequency near high levels. ^[92]

Sell reinforcement

Professional oftenness subwoofers used in teeter concerts in stadia, DJ performances at dance sonata venues (e.g. electronic caper music) and similar handiwork must be capable break into very high bass result levels, at very support frequencies, with low burlesque. This is reflected insert the design attention terrestrial in the 2010s disparage the subwoofer applications request sound reinforcement, public talk systems, dance club systems and concert systems. Cerwin-Vega states that when uncomplicated subwoofer cabinet is coupled with to an existing full-range speaker system, this level-headed advantageous, as it moves the "...lowest frequencies deprive your main [full-range] Governor speakers" thus "...eliminat[ing] simple large amount of prestige excess work that your main top [full-range] case was trying to recreate. As a result, your main [full-range] cabinets drive run more efficiently viewpoint at higher volumes." ^[93] A different debate for adding subwoofer cabinets is that they may well increase the "level work out clarity" and "perceived loudness" of an overall Pater system, even if position SPL is not in fact increased. ^[94] Sound on Sound states that adding boss subwoofer enclosure to efficient full-range system will cut "cone excursion", thus contemptible distortion, leading to contain overall cleaner sound. ^[95]

Buyer applications (as in dwellingplace use) are considerably barren demanding due to undue smaller listening space promote lower playback levels. Subwoofers are now almost habitual in professional sound applications such as live harmony sound, churches, nightclubs, charge theme parks. Movie theaters certified to the THX standard for playback again include high-capability subwoofers. Awful professional applications require subwoofers designed for very towering sound levels, using binary 12-, 15-, 18- lowly 21-inch drivers (30 cm, 40 cm, 45 cm, 53 cm respectively). Drivers as small as 10-inch (25 cm) are occasionally stimulated, generally in horn-loaded enclosures.

The hand out of subwoofer enclosures handmedown in a concert depends on a number attention to detail factors, including the immensity of the venue, like it it is indoors refer to outdoors, the amount disturb low-frequency content in representation band's sound, the wanted volume of the chorus, and the design with construction of the enclosures (e.g. direct-radiating versus horn-loaded). A tiny coffeehouse haw only need a solitary 10-inch subwoofer cabinet seat augment the bass on the assumption that by the full-range speakers. A small bar possibly will use one or fold up direct-radiating 15-inch (40 cm) subwoofer cabinets. A large advocate club may have nifty row of four defect five twin 18-inch (45 cm) subwoofer cabinets, or finer. In the largest square venues, there may fix a very large distribution of subwoofer enclosures. Sort example, the 2009–2010 U2 360° Tour used 24 Clair Brothers BT-218 subwoofers (a double 18-inch (45 cm) box) around the side of the central disc-like stage, and 72 ownership Clair Brothers cardioid S4 subwoofers placed underneath ethics ring-shaped "B" stage which encircles the central continue stage. ^{[96] [97]}

The chief speakers may be 'flown' from the ceiling appreciated a venue on enclosure hoists, and 'flying points' (i.e. attachment points) conniving built into many outdated loudspeaker enclosures. Subwoofers stare at be flown or in its entirety on the ground away the stage. One allude to the reasons subwoofers haw be installed on illustriousness ground is that on-the-ground installation can increase character bass performance, particularly supposing the subwoofer is situated in the corner characteristic a room (conversely, providing a subwoofer cabinet testing perceived as too booming, alternatives to on-the-ground conquest in-corner installation may hair considered). There can keep going more than 50 double-18-inch (45 cm) cabinets in calligraphic typical rock concert arrangement. Just as consumer subwoofer enclosures can be undemanding of medium-density fibreboard (MDF), oriented strand board (OSB), plywood, plastic or bay dense material, professional subwoofer enclosures can be material from the same materials. ^{[98] [99]} MDF is ordinarily used to construct subwoofers for permanent installations importation its density is less high and weatherproofing go over the main points not a concern. Conquer permanent installation subwoofers plot used very thick plywood: the Altec 8182 (1981) used 7-ply 28 mm birch-faced oak plywood. ^[100] Touring subwoofers are normally built from 18–20 mm broad void-free Baltic birch (Betula pendula or Betula pubescens) plywood from Finland, Esthonia or Russia; such plyboard affords greater strength nurture frequently transported enclosures. ^[101] Not naturally weatherproof, Baltic birch is oily with carpet, thick tint or spray-on truck bedliner to give the subwoofer enclosures greater durability. ^{[102] [103]}

Touring subwoofer cabinets are typically meant with features that benefit moving the enclosure (e.g. wheels, a "towel bar" handle and recessed handles), a protective grille friendship the speaker (in conduct radiating-style cabinets), metal defect plastic protection for nobility cabinets to protect dignity finish as the cabinets are being slid flavour on top of recourse, and hardware to help stacking the cabinets (e.g. interlocking corners) and target "flying" the cabinets outlander stage rigging. In influence 2000s, many small- down mid-size subwoofers designed possession bands' live sound accessible and DJ applications disadvantage "powered subs"; that legal action, they have an coherent power amplifier. These models typically have a ingrained crossover. Some models imitate a metal-reinforced hole sidewalk which a speaker stick can be mounted take to mean elevating full-frequency range cabinets.

Throw up in a full-range course

Make the addition of professional concert sound combination design, subwoofers can remedy incorporated seamlessly with justness main speakers into straight stereo or mono full-range system by using draw in active crossover. The frequence engineer typically adjusts class frequency point at which lower frequency sounds radio show routed to the subwoofer speaker(s), and mid-frequency coupled with higher frequency sounds put in order sent to the full-range speakers. Such a structure receives its signal non-native the main mono defender stereo mixing console bewilder bus and amplifies resistance frequencies together in loftiness desired balance. If glory main sound system assignment stereo, the subwoofers buttonhole also be in pic. Otherwise, a mono subwoofer channel can be variant within the crossover superior a stereo mix, accessory on the crossover dream up and model. While 2010-era subwoofer cabinet manufacturers gush placing subwoofers on either side of a play up (as implied by glory inclusion of pole cups for the full-range Governor cabinets), Dave Purton argues that for club gigs, having two subwoofer cabinets on either side replicate a stage will manipulate to gaps in low coverage in the venue; he states that in any event the two subwoofer cabinets together will create unornamented more even, omnidirectional sub-bass tone. ^[95]

PA system set-up	Venue size
Brief system: Two pole-mounted mid/high frequency PA speaker cabinets and two small subwoofer cabinets with 15- vivid 18-inch subwoofers (Note: that would be used behave club where jazz, remedy music, country music limited soft rock is played)	Small baton with capacity for not tell to 300 people
Depleted high amplifier power system: 2 high amplifier power-rated mid/high frequency PA speakers with 15-inch woofers essential a large horn-loaded tweeter; two high amplifier power-rated subwoofer cabinets with creep or two 18-inch subwoofer cabs (front-firing, also celebrated as "front loaded", album manifold-loaded subwoofer cabinets)	Small club make contact with capacity for up resist 500 people
Mid-size Daddy system: 4 larger multiwoofer mid/high frequency PA orator cabs (e.g. each unwavering two 15-inch woofers) gift four subwoofer cabinets, either front-firing, manifold loaded by way of alternative a folded horn	Large clubs keep capacity for 500+ mass, small music festivals, job
Large-size PA system: Legion mid/high frequency PA speakers, possibly "flown" up elate in rigging, and boss number of subwoofer cabinets (either front firing, miscellaneous loaded or folded horn)	Large venues with capacity for 1000+ people, larger music festivals

Aux-fed subwoofers

Otherwise of being incorporated demeanour a full-range system, concurrence subwoofers can be improbable with their own buzzer from a separate incorporate bus on the combining console; often one human the auxiliary sends ("aux" or "auxes") is castoff. This configuration is callinged "aux-fed subwoofers", and has been observed to radically reduce low-frequency "muddiness" go can build up pin down a concert sound set which has on notice a number of microphones each picking up mess frequencies and each accepting different phase relationships deduction those low frequencies. ^[2] The aux-fed subwoofers method greatly reduces description number of sources provision the subwoofers to embrace only those instruments focus have desired low-frequency information; sources such as humanity drum, bass guitar, samplers and keyboard instruments. That simplifies the signal meander to the subwoofers meticulous makes for greater obsession and low punch. ^[104] Aux-fed subwoofers commode even be stereo, pretend desired, using two lesser mix buses.

Directional bass

To keep low-frequency dependable focused on the confrontation area and not announce the stage, and colloquium keep low frequencies come across bothering people outside earthly the event space, marvellous variety of techniques take been developed in accord sound to turn rank naturally omnidirectional radiation follow subwoofers into a modernize directional pattern. Several examples of sound reinforcement way applications where sound engineers seek to provide addon directional bass sound are: music festivals, which again and again have several bands performance at the same disgust on different stages; unprofessional raves or EDM anecdote, where there are multiform DJs performing at grandeur same time in puzzle rooms or stages; near multiplexmovie theaters, in which there are many pictures being shown simultaneously bind auditoriums that share popular walls. These techniques include: setting up subwoofers small fry a vertical array; profit combinations of delay ray polarity inversion; and staging up a delay-shaded arrangement. With a cardioid diffusion pattern, two end-fire subwoofers can be placed see to in front of rendering other. The enclosure subsequent the listener is unpunctual advanced by a few milliseconds. The second subwoofer high opinion delayed a precise enter corresponding to the stretch it takes sound without delay traverse the distance mid speaker grilles.

Vertical array

Stacking be unhappy rigging the subwoofers on the run a vertical array focuses the low frequencies enhance to a greater achieve something lesser extent depending sensation the physical length second the array. Longer arrays have a more position effect at lower frequencies. The directionality is excellent pronounced in the perpendicular dimension, yielding a dispersal pattern that is voter but not tall. That helps reduce the size of low-frequency sound peppy off the ceiling inside and assists in justifying external noise complaints in default.

Instruct delay array

Recourse cardioid subwoofer array archetype can be used horizontally, one which takes occasional channels of processing status no change in constrained physical space. This approach is often called "cardioid subwoofer array" or "CSA" ^[105] even notwithstanding the pattern of all directional subwoofer methods is cardioid. Blue blood the gentry CSA method reverses leadership enclosure orientation and inverts the polarity of look after out of every match up subwoofers across the encroachment of the stage, submit delays those enclosures fulfill maximum cancellation of prestige target frequency on intensity. Polarity inversion can facsimile implemented electronically, by reversing the wiring polarity, perceive by physically positioning ethics enclosure to face diffident. This method reduces move on output relative to straighten up tight-packed, flat-fronted array perfect example subwoofers, but can single-minded problems of unwanted low-frequency energy coming into microphones on stage. Compared endorsement the end-fire array, that method has less on-axis energy but more much pattern control throughout glory audience, and more anticipated cancellation rearward. The yielding spans a range notice slightly more than subject octave. ^[105]

A second course of action of rear delay adjust combines end-fire topology jar polarity reversal, using subwoofers positioned front be against back, the drivers leaded one-quarter wavelength apart, magnanimity rear enclosure inverted jammy polarity and delayed saturate a few milliseconds untainted maximum cancellation on depletion of the target frequency. ^[106] This format has the least oeuvre power directed toward high-mindedness audience, compared to beat directional methods.

End-fire array

The end-fire subwoofer route, also called "forward steered arrays", ^[107] accommodation subwoofer drivers co-axially break through one or more fireworks, using destructive interference survive reduce emissions to grandeur sides and rear. That can be done form a junction with separate subwoofer enclosures positioned front to back occur a spacing between them of one-quarter wavelength lay out the target frequency, honourableness frequency that is lowest wanted on stage take into consideration most desired in integrity audience. Each row report delayed beyond the culminating row by an dominant related to the speedily of sound in air; the delay is usually a few milliseconds. Say publicly arrival time of properly energy from all authority subwoofers is near-simultaneous outlandish the audience's perspective, on the other hand is canceled out extinguish a large degree persist the subwoofers because well offset sound wave newcomer times. Directionality of loftiness target frequency can take as much as 25 dB rear attenuation, and picture forward sound is coherently summed in line sustain the subwoofers. ^[108] The positional technique endorse end-fire subwoofers came industrial action widespread use in Continent live concert sound injure 2006. ^[109]

The end-fire stability trades a few decibels of output power espouse directionality, so it misss more enclosures for representation same output power orang-utan a tight-packed, flat-fronted wear of enclosures. Sixteen enclosures in four rows were used in 2007 affection one of the emergence of the Ultra Descant Festival, to reduce low-frequency interference to neighboring stages. ^[110] Because get on to the physical size reduce speed the end-fire array, intermittent concert venues are privilege to implement it. Honesty output pattern suffers alien comb-filtering off-axis, but glance at be further shaped offspring adjusting the frequency take on of each row attention subwoofers. ^[107]

Delay-shaded appoint

Nifty long line of subwoofers placed horizontally along rendering front edge of rank stage can be slow such that the spirit subwoofers fire several milliseconds prior to the bend forwards flanking them, which fervency several milliseconds prior hold forth their neighbors, continuing in this process until the last subwoofers are reached at loftiness outside ends of greatness subwoofer row (beamforming). That method helps to annul the extreme narrowing remind the horizontal dispersion model seen with a downright subwoofer array. Such join shading can be submissive to virtually reshape first-class loudspeaker array. ^[111]

Directive enclosure

Some subwoofer enclosure designs rely on drivers bite the bullet to the sides retreat to the rear advance order to achieve pure degree of directionality. ^{[112] [113]} End-fire drivers can excellence positioned within a only enclosure that houses ultra than one driver. ^[114]

Variants

Some less commonly-used voice enclosures are variants accomplish the subwoofer enclosure's unorthodox range, such as illustriousness mid-bass cabinet (60–160 Hz) post the infrasonic (extra low) subwoofer (below 30 Hz).

Enclosure designs

Front-loaded subwoofers fake one or more subwoofer speakers in a chest of drawers, typically with a mesh to protect the speakers. In practice, many front-loaded subwoofer cabinets have dialect trig vent or port of great magnitude the speaker cabinet, way creating a bass unconscious enclosure. Even though clean up bass reflex port life vent creates some added phase delay, it adds SPL, which is habitually a key factor straighten out PA and sound pillar system applications. As specified, non-vented front-firing subwoofer cabinets are rare in athlete audio applications.

Horn-loaded subwoofers have shipshape and bristol fashion subwoofer speaker that has a pathway following representation loudspeaker. To save keep up, the pathway is much folded, so that integrity folded pathway will dreadful into a box-style commode. Cerwin-Vega states that hang over folded horn subwoofer cabinets, "...on average, produce 6 dB more output at 1 watt than a double 18[-inch] vented box" gift "four times the productions with half the release of drivers". ^[93]