Asian Academy of Film and Television

Thesis project on

Loudspeaker and Audio Monitors

Guided by – Submitted by -

Mr. Rajinder Gandhi Name – Vaisakh S. Kurup

Mr. Avneet Grewal Roll no. – DPP/ I-1

Batch – Diploma in Post Production

INDEX

Acknowledgement …… 3

Loudspeaker …… 4

Types of Enclosure …… 5

Subwoofer …… 7

Woofer …… 8

Tweeter ……8

Loudspeaker System Design ……8

Studio Monitors (Audio Monitors) ……11

History ……12

Monitor v/s hi-fi speakers ……14

Conclusion ……18

ACKNOWLEDGEMENT

I wish to express my sincere gratitude to Mr. Rajinder Gandhi (senior faculty for

sound recording and radio production), for providing me with all the necessary

material and timely encouragement, required for the completion of my thesis.

I place on record, my sincere gratitude to Mr. Avneet Grewal for providing all

necessary practical knowledge regarding the thesis work.

I also place on record my sense of gratitude to one and all who directly, or

indirectly have lent their helping hand in this venture.

LOUDSPEAKER

A loudspeaker is an electro-acoustic transducer; a device which converts an

electrical audio signal into a corresponding sound. The loudspeaker serves four

primary purposes of Communication, Sound Reinforcement, Sound Production and

Sound Reproduction.

Dynamic Loudspeaker Principle

A current-carrying wire in a magnetic field experiences a magnetic force

perpendicular to the wire.

An audio signal source such as a microphone or recording produces an electrical

image of the sound. That is, it produces an electrical signal that has the same

frequency and harmonic content, and a size that reflects the relative intensity of the

sound as it changes. The job of the amplifier is to take that electrical image and

make it larger large enough in power to drive the coils of a loudspeaker. Having a

"high fidelity" amplifier means that you make it larger without changing any of its

properties. Any changes would be perceived as distortions of the sound since the

human ear is amazingly sensitive to such changes. Once the amplifier has made the

electrical image large enough, it applies it to the voice coils of the loudspeaker,

making them vibrate with a pattern that follows the variations of the original

signal. The voice coil is attached to and drives the cone of the loudspeaker, which

in turn drives the air. This action on the air produces sound that more-or-less

reproduces the sound pressure variations of the original signal.

Types of EnclosureThe production of a good high-fidelity loudspeaker requires that the speakers be

enclosed because of a number of basic properties of loudspeakers. Just putting a

single dynamic loudspeaker in a closed box will improve its sound quality

dramatically. Modern loudspeaker enclosures typically involve multiple

loudspeakers with across over network to provide a more nearly uniform frequency

response across the audio frequency range. Other techniques such as those used in

bass reflex enclosures may be used to extend the useful bass range of the

loudspeakers.

Speakers are typically housed in an enclosure which is often a rectangular or

square box made of wood or sometimes plastic where high quality reproduction of

sound is required. Multiple loudspeakers may be mounted in the same enclosure,

each reproducing a part of the audible frequency range. In this case the individual

speakers are referred to as "drivers" and the entire unit is called a loudspeaker.

Miniature loudspeakers are found in devices such as radio and TV receivers, and

many forms of music players. Larger loudspeaker systems are used for music, live

shows, in theatres and concerts, and in public address systems. The term

"loudspeaker" may refer to individual transducers (known as "drivers") or to

complete speaker systems consisting of an enclosure including one or more

drivers. To adequately reproduce a wide range of frequencies with even coverage,

most loudspeaker systems employ more than one driver, particularly for

higher sound pressure level or maximum accuracy. Individual drivers are used to

reproduce different frequency ranges. The drivers are named subwoofers (for very

low frequencies); woofers (low frequencies); mid-range speakers (middle

frequencies); tweeters (high frequencies); and sometimes super-tweeters, optimized

for the highest audible frequencies

Subwoofer

A subwoofer is a woofer driver used only for the lowest part of the audio spectrum:

typically below 200 Hz for consumer systems, below 100 Hz for professional live

sound, and below 80 Hz in THX-approved systems. To accurately reproduce very

low bass notes without unwanted resonances, subwoofer systems must be solidly

constructed and properly braced; good speakers are typically quite heavy. Many

subwoofer systems include power amplifiers and electronic sub-filters, with

additional controls relevant to low-frequency reproduction.

Woofer

A woofer is a driver that reproduces low frequencies. The driver combines with the

enclosure design to produce suitable low frequencies. Some loudspeaker systems

use a woofer for the lowest frequencies, sometimes well enough that a subwoofer

is not needed. Additionally, some loudspeakers use the woofer to handle middle

frequencies, eliminating the mid-range driver. This can be accomplished with the

selection of a tweeter that can work low enough that, combined with a woofer that

responds high enough, the two drivers add coherently in the middle frequencies.

Tweeter

A tweeter is a high-frequency driver that reproduces the highest frequencies in a

speaker system. Since high frequency sound tends to leave the speaker in narrow

beams. Soft-dome tweeters are widely found in home stereo systems.

Loudspeaker System Design

Used in multi-driver speaker systems, the crossover is a subsystem that separates

the input signal into different frequency ranges suited to each driver. The drivers

receive power only in their usable frequency range thereby, reducing distortion in

the drivers and interference between them.

Crossovers can be passive or active. A passive crossover is an electronic circuit

that uses a combination of one or more resistors, inductors, or non-polar capacitors.

These parts are formed into carefully designed networks and are most often placed

between the full frequency-range power amplifier and the loudspeaker drivers to

divide the amplifier's signal into the necessary frequency bands before being

delivered to the individual drivers.

Passive crossover circuits need no external power beyond the audio signal itself.

Passive crossovers are commonly installed inside speaker boxes and are by far the

most usual type of crossover for home and low-power use. In car audio systems,

passive crossovers may be in a separate box, necessary to accommodate the size of

the components used. 

An active crossover is an electronic filter circuit that divides the signal into

individual frequency bands before power amplification, thus requiring at least one

power amplifier for each band-pass. Passive filtering may also be used in this way

before power amplification, but it is an uncommon solution, being less flexible

than active filtering. Any technique that uses crossover filtering followed by

amplification is commonly known as bi-amping, tri-amping, quad-amping, and so

on, depending on the minimum number of amplifier channels. Some loudspeaker

designs use a combination of passive and active crossover filtering, such as a

passive crossover between the mid- and high-frequency drivers and an active

crossover between the low-frequency driver and the combined mid- and high

frequencies.

Enclosures

Most loudspeaker systems consist of drivers mounted in an enclosure, or cabinet.

The role of the enclosure is to prevent sound waves emanating from the back of a

driver from interfering destructively with those from the front. Hence, without an

enclosure they typically cause cancellations which significantly degrade the level

and quality of sound at low frequencies. A sealed enclosure prevents transmission

of the sound emitted from the rear of the loudspeaker by confining the sound in a

rigid and airtight box. Techniques used to reduce transmission of sound through

the walls of the cabinet include thicker cabinet walls, lossy wall material, internal

bracing, curved cabinet walls.

However, a rigid enclosure reflects sound internally, which can then be transmitted

back through the loudspeaker diaphragm—again resulting in degradation of sound

quality. This can be reduced by internal absorption using absorptive materials.

Such as glass wool, wool, or synthetic fiber batting, within the enclosure. The

internal shape of the enclosure can also be designed to reduce this by reflecting

sounds away from the loudspeaker diaphragm, where they may then be absorbed.

One of the most common uses of loudspeakers in the home environment is

as home theater speakers. These speakers often are synchronized so they produce

a surround sound effect and are often referred to as surround speakers. This is

especially useful when watching movies, where the audio is often meant to be

played on a surround sound system.

The quality of the loudspeaker greatly depends on the weight, and therefore the

size, of the magnet inside the speaker. The larger the magnet, the more powerful

the speaker will be. The weight of the magnet should be listed on the specifications

of any good loudspeakers. However, it should be noted that some weigh the entire

magnet system and not just the magnet itself. This could affect the power and

quality of the speaker and deceive some into buying something other than what

they thought they were purchasing.

STUDIO MONITORS (AUDIO MONITORS)

Studio 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. Whereas reference monitors

refer to loudspeakers generally used to gage what a recording will sound like on

consumer-grade speakers. Studio monitors are made in a more physically robust

manner than home hi-fi loudspeakers; whereas home hi-fi loudspeakers often only

have to reproduce compressed commercial recordings, studio monitors have to

cope with the high volumes and sudden sound bursts that may happen in the studio

when playing back unmastered mixes.

Among audio engineers, the term monitor usually implies that the speaker is

designed to produce relatively flat (linear) phase and frequency responses. Beyond

stereo sound-stage requirements, a linear phase response helps impulse

response remain true to source without encountering "smearing". An unqualified

reference to a monitor often refers to a near-field (compact or close-field) design.

This is a speaker small enough to sit on a stand or desk in proximity to the listener,

so that most of the sound that the listener hears is coming directly from the

speaker, rather than reflecting off of walls and ceilings. Also, studio monitors are

made in a more physically robust manner than home hi-fi loudspeakers; whereas

home hi-fi loudspeakers often only have to reproduce compressed commercial

recordings, studio monitors have to cope with the high volumes and sudden sound

bursts that may happen in the studio when playing back unmastered mixes.

The Yamaha NS-10, one of the most influential studio monitors of all time.

HistoryIn the early years of the recording industry in the 1920s and 1930s, studio monitors

were used primarily to check for noise interference and obvious technical problems

rather than for making artistic evaluations of the performance and recording.

Musicians were recorded live and the producer judged the performance on this

basis, relying on simple tried-and-true microphone techniques to ensure that it had

been adequately captured; playback through monitors was used simply to check

that no obvious technical flaws had spoiled the original recording.

The first high-quality loudspeaker developed expressly as a studio monitor was

the Altec Lansing Duplex 604 in 1944. The 604 was a relatively

compact coaxial design and within a few years it became the industry standard in

the United States, a position it maintained in its various incarnations over the next

25 years. It was common in US studios throughout the 1950s and 60s and remained

in continuous production until 1998. However, in 1959, at the height of its industry

dominance, Altec made the mistake of replacing the 604 with the 605A Duplex, a

design widely regarded as inferior to its predecessor. There was a backlash from

some record companies and studios and this allowed Altec’s competitor, JBL (a

company originally started by 604 designer James B. Lansing), to make inroads

into the pro monitor market.

In a BBC white paper published in January 1963, the authors explored 2-channel

stereophony, and remarked that it was at a disadvantage compared with multi-

channel stereophony that was already available in cinemas in that "the full intended

effects is apparent only to observers located within in a restricted area in front of

the loudspeakers". The authors expressed reservations about dispersion and

directionality in 2-channel systems, noting that the "face-to-face listening

arrangement" was not able to give an acceptable presentation for a centrally-

located observer in a domestic setting. In the late 1960s JBL introduced two

monitors which helped secure them pre-eminence in the industry. The 4320 was a

direct competitor to the Altec 604 but was a more accurate and powerful speaker

and it quickly made inroads against the industry standard. However, it was the

more compact 4310 that revolutionized monitoring by introducing the idea of close

or "near-field" monitoring.

However, a backlash against the behemoth monitor was soon to take place. With

the advent of punk, new wave, indie, and lo-fi, a reaction to high-tech recording

and large corporate-style studios set in and do-it-yourself recording methods

became the vogue. Smaller, less expensive, recording studios needed smaller, less

expensive monitors and the Yamaha NS-10, a design introduced in 1978 ironically

for the home audio market, became the monitor of choice for many studios in the

1980s. While its sound-quality has often been derided, even by those who monitor

through it, the NS-10 continues in use to this day and many more successful

recordings have been produced with its aid over the past twenty five years than

with any other monitor.

Monitor v/s hi-fi speakers

No speaker, monitor or hi-fi, regardless of the design principle, has a completely

flat frequency response; all speakers color the sound to some degree. Monitor

speakers are assumed to be as free as possible from coloration. While no rigid

distinction exists between consumer speakers and studio monitors, manufacturers

more and more accent the difference in their marketing material. Generally, studio

monitors are physically robust, to cope with the high volumes and physical knocks

that may happen in the studio, and are used for listening at shorter distance than hi-

fi speakers, though nothing precludes them from being used in a home-sized

environment. Studio monitors are increasingly self-amplified (active), although not

exclusively so, while hi-fi speakers usually require external amplification.

Whereas in the 1970s the JBL 4311’s domestic equivalent, the L-100, was used in

a large number of homes, and the Yamaha NS-10 also served both domestically

and professionally during the 1980s. Despite not being a "commercial product" at

the outset, the BBC licensed production of the LS3/5A monitor, which it used

internally. It was commercially successful in its twenty-something-year life.

The archetypal studio near-field monitor, Yamaha's NS10M, is well known to have

(put politely) a characterful tonal balance. The general consensus seems to be that

it is uneven through the mid-range and too bright at the top (hence the commonly

employed trick of hanging tissue paper over the tweeters to calm it down).

In two words, we should be looking for the 'neutral average' neither too bright nor

too dull. If the aspirations we have for our work are that it should sound tonally

acceptable on the widest range of systems out there, from hi-fi systems costing

many thousands to AM radio (or its low-bit-rate MP3 equivalent), then the

perceived tonal balance of our near-field monitor, which will be used up close and

probably with its back to the wall, should be as close to the 'population average' as

possible. The same is probably true of a hi-fi speaker, because in balance terms, the

hi-fi speaker is nothing but a monitor that's used a few stages down the line (ie. by

the consumer of the music you're mixing).

A neutral tonal balance, however, is not the same thing as a flat axial frequency

response. The perceived tonal balance of a speaker is the combination of the direct

sound from the drivers and reflected sound from nearby surfaces, and, as speakers

are directional devices (especially at high frequencies), a flat axial frequency

response doesn't mean that a loudspeaker will necessarily sound that way. But we

can work backwards, and predict generally how the axial response might look for

different types of loudspeakers if they are to sound neutral. Firstly, a hi-fi speaker

that's positioned perhaps four meters away from the listener and is mounted a little

away from the wall on a floor stand should have a subtly different response shape

compared to a near-field monitor that's maybe one to two meters away and

mounted on a wall. Where the near-field should demonstrate a slightly up-shelved

response at a few hundred Hertz combined with a slow roll-off at either frequency

extreme, the hi-fi speaker, unless it has been specifically balanced for use against a

wall, should probably be closer to flat.

Secondly, if a near-field monitor is to be used in a small room, where strong

reflections from the side walls will reach the ear within a few milliseconds, the

shape of the horizontal off-axis response is vital too. Wild variations between on

and off-axis responses are well-known to result in perceived tonal imbalances, so if

the monitor is not to sound unnaturally colored, its off-axis response should be as

close to a gently down-tilted version of the axial response as possible. This is one

very good reason why landscape-mounted near-field monitors tend to be a bad idea

the horizontal off-axis response from laterally adjacent drivers will almost

certainly display major discontinuities through the region where the drivers'

outputs overlap.

Yamaha HS80m

The Yamaha HS80m studio monitor is the successor to the NS10, and tries to

replicate the philosophy behind the NS line. Featuring the same iconic white

woofer cones as the NS10, the Yamaha HS80m produces an accurate and pleasant

sound. Consistent and smooth audio make the Yamaha HS80m a no-brainer when

it comes to deciding which studio monitors to buy.

M-Audio Studiophile BS5 D2

M-Audio are famous for their music production equipment, but they also make

some great speakers. The M-Audio Studiophile monitor series are loved and

trusted by musicians and recording professionals all over the world. There is a

reason that the Studiophile series is one of the best selling monitor studios in the

world. M-Audio is a trusted brand and you won’t regret purchasing a set of

Studiophile speakers.

JBL LSR 2325P

JBL has been in the loudspeaker industry for a long time and they know how to

create great audio equipment while still being affordable. The JBL LSR series is a

great range to look at when considering studio monitors. LSR stands for Linear

Spatial Reference, this technology takes your room shape and size into account to

produce the most accurate sound possible.

KRK Rokit 8

The KRK Rokit 8 is latest version of the very popular Rokit series. Instantly

recognizable with its yellow woofer, the KRK Rokit is the new-age standard for

studio monitors. Perfect for electronic dance music and acoustic productions, you

can’t go wrong with the Rokit series.

CONCLUSION

Studio monitors are designed to reproduce audio signals that are as flat as possible

across the audible frequency spectrum. Unlike consumer stereo speakers that may

be tweaked to produce a strong bass response and sound punchy, good studio

monitors don’t emphasize particular frequencies over others. A good monitor will

give you accurate, consistent response no matter the volume level. This allows you

to listen critically to how certain elements of the mix sound at different volumes.

They also capture fleeting musical transients that add subtlety and nuance to the

sounds they reproduce.