MONITOR SPEAKERS AND STUDIO ACCESSORIES
This chapter looks at some studio items that are often taken for granted, but are actually quite significant. Monitor speakers (see Figure 7.1) are used to listen to sound in the studio. They convert the audio signal, stored on recording media like tape, computers, CDs, or digital recorders, back into sound that can be heard. The sound that comes from them is the final product, so they are very important in determining a production’s overall quality. What you hear on the monitor speakers should be the most accurate gauge of what you recorded and what the listener will hear.
Speakers are one of the various pieces of equipment used in the audio production studio. This chapter looks at various types of speakers and their cables and connectors.
You may want to review the sections on sound in Chapter 2, “The Studio Environment,” as they will help you understand how speakers work. Speakers are transducers, but they work in a manner opposite to that of microphones. Instead of converting sound waves into electrical energy, speakers produce sound from an electrical signal by converting it into mechanical energy that causes vibrations to produce sound waves or audible sound.
FIGURE 7.1 Studio monitor speakers help you judge the sound quality of your audio production. (Image courtesy of Behringer North America, Inc.)
The most common type of monitor speaker is a dynamic speaker. Also known as a moving coil or electromagnetic speaker, its transducing element (called a driver), produces sound by moving a flexible cone or diaphragm in and out very rapidly. The diaphragm, which may be made of paper, plastic, or metal, is suspended in a metal frame. Attached at the narrow end of the cone is a voice coil (a cylinder wound with a coil of wire), which is located between powerful circular magnets (see Figure 7.2). When an electrical current is generated in the voice coil, it creates another magnetic force that moves the coil and the cone back and forth, according to the electrical signal that is entering the coil. The cone vibration causes the surrounding air to move in a similar manner, which our ears pick up as sound.
Instead of a cone, some speakers use a dome, which is just another type of diaphragm that bulges out rather than tapers in. Other types of loudspeakers include electrostatic loudspeakers and planar-magnetic loudspeakers. However, these are considered to be fairly exotic and you aren’t likely to run across them in a typical production studio.
As the modern audio production facility is typically an all-digital environment, several manufacturers offer digital monitor speakers (see Figure 7.3). The speakers have either digital inputs or digital and analog inputs. Most digital inputs can identify up to a 24-bit digital signal with a sampling rate as high as 192 kHz. When a digital signal is detected in a speaker with both analog and digital inputs, the speaker’s internal digital-to-analog (D/A) converter becomes activated. There really is no monumental sound difference between an analog and a digital input; however, the convenience of attaching directly to the digital output of an audio console, digital audio workstation, or editing computer is a plus for the digital speaker. In addition, digital monitor speakers sometimes help eliminate line loss and possible hum that is associated with analog speakers.
FIGURE 7.2 The most common type of speaker driver is the dynamic cone driver.
FIGURE 7.3 Digital monitor speakers feature an input that allows for direct digital hookup from an audio console or workstation. (Images courtesy of Genelec, Inc., copyright 2012.)
7.3 BASIC SPEAKER SYSTEM COMPONENTS
The basic components of the typical speaker system are the woofer, tweeter, crossover, and speaker enclosure. “Woofer” and “tweeter” are names given to drivers or individual speakers used within a speaker system. Because no single speaker design can reproduce the entire frequency range of sound adequately, different speakers have been developed to handle different portions of it. A woofer is designed to move the large volume of air necessary to reproduce lower frequencies. The cone is usually larger in size (anywhere from 8 to 12 inches) and is able to make large movements. However, this bulk prevents the speaker from adequately reproducing the higher frequencies that require rapid cone movement. The tweeter uses a lighter and smaller design; often a convex dome (1 inch or less in diameter) replaces the cone. There are also midrange speakers with cones from 3 to 5 inches in diameter that are designed to reproduce midrange, higher-bass, and lower-treble frequencies.
An individual speaker is really a speaker system, in that many use at least a woofer and a tweeter driver. The crossover is used to divide the incoming electrical signal and send the proper frequencies to their respective driver. A crossover is a network of filters (mainly capacitors and inductors) between the input to the speaker and the individual speaker drivers. In a two-way system for example, an inductor would pass all audio below a certain frequency to the woofer. A capacitor in the same speaker would pass all audio above a certain frequency to the tweeter. Although there is no universal design for the crossover, most dividing points between the bass and treble frequencies are between 500 and 1,500 Hz. A speaker that has just a woofer, a tweeter, and a crossover is a two-way speaker system, like the one shown in Figure 7.4. A speaker that employs another driver (such as a midrange) is a three-way speaker system.
7.4 SPEAKER SYSTEM ENCLOSURE DESIGNS
Speaker drivers and crossover(s) are encased in a box (often called a speaker enclosure) that plays a role in how the speaker sounds. Every speaker produces sound both behind and in front of it: the back sound wave is exactly opposite of the one that goes into the forward listening space. If the two sound waves are allowed to combine naturally, they would be acoustically out of phase and cancel each other out. This would produce no sound at all or greatly diminished sound, especially in the bass part of the range.
The two most widely used speaker enclosure designs are the acoustic suspension and bass reflex systems shown in Figure 7.5. The acoustic suspension (also known as the sealed-box) design puts the speaker drivers and crossover(s) in a tightly sealed enclosure that produces an accurate, natural sound with a strong, tight bass. By containing and absorbing the back wave in the enclosure, the acoustic suspension design prevents the rear sound from radiating and disrupting the main sound coming from the front of the speaker. Because half the sound energy is trapped and absorbed in the box, acoustic suspension speakers require a more powerful amplifier to drive them. The acoustic suspension design also demands a rather large, sturdily built physical enclosure to ensure accurate reproduction of the lowest bass notes.
FIGURE 7.4 The basic two-way speaker system consists of a tweeter, a woofer, and a crossover housed within an enclosure.
On the other hand, the bass reflex (also known as the vented-box) design is quite efficient and produces a strong bass sound with less power required. The bass reflex speaker enclosure is designed with an opening (a vent, duct, or port) that is tuned to allow some of the rear sound (mainly the lower frequencies) to combine in phase and reinforce the main sound coming from the front of the speaker. Some bass reflex design speakers have been criticized for not having tonal accuracy that is quite as good as the acoustic suspension design, and for adding a “boomy” quality to the sound. These problems, however, are often the fault of a particular speaker’s tuning and construction and not of the bass reflex design itself. There are many different bass reflex designs, and most produce a clean, wide-ranging bass.
There is a wide variety of speaker systems to choose from, and as with some other audio equipment, the differences between various models may be minimal. One of the important qualities that a good monitor speaker must have is excellent frequency response. Remember, humans are able to hear frequencies in the range of 20 Hz to 20 kHz, although most of us don’t hear sounds quite that low or high. Top-line broadcast monitors often provide a frequency response range from 35 to 45 Hz at the low end, to 18 to 20 kHz at the high end. Increased use of digital equipment however, has made it necessary to have speakers that produce as much of this range as possible.
FIGURE 7.5 The most widely used speaker enclosure designs are the acoustic suspension and bass reflex systems.
Another important quality for the broadcast monitor speaker is its ability to produce a flat frequency response, which is the speaker’s ability to reproduce low, midrange, and high frequencies equally well while producing a natural sound. The speaker itself should not add anything to the audio signal that is heard. What is most important is merely how a speaker sounds. Among the combinations of driver types, speaker enclosure designs, and crossover frequencies, there is no one speaker configuration that produces the “best sound.” Keep in mind, however, that a good speaker sound does not depend only on the speaker itself. How well a speaker sounds is also dependent on the content being played through it, the dimensions and acoustic properties of the room in which the speakers are located, the location of the speakers in relation to the listener, and the listener.
In the audio studio, there may not be many options when it comes to placing monitor speakers. Usually they are positioned on each side of the audio console, but exactly how they are positioned is open to various schools of thought. At the very least, there should be an acoustically symmetrical layout. For example, don’t put one speaker in the corner next to a glass window and the other in the middle of a wall that’s covered with acoustic tiles. One thought is to mount the speakers in the wall. As long as the speakers are isolated from the wall structure—using rubber shock mounts, for example—this flush mount creates an infinite baffle that prevents rear wave problems. Large speakers can be built into the wall, providing a loud, clear sound with plenty of “heavy” bass. Unfortunately, this type of installation is often not practical for many studios.
Some production people feel the ideal sound is obtained when speakers are even with or a bit above ear level. This is called near-field or close-proximity monitoring and can be accomplished by putting smaller speakers, such as those shown in Figure 7.3, on the audio console “bridge” or on short stands to the left and right of the console, about 3 feet apart. Keeping the speakers a couple of feet from the back wall will prevent any excessive bass boost from the wall. Since the speakers are so close to the listener, mostly direct sound is heard and there is no need to worry much about other effects. “Toeing in” the speakers (or angling them toward the listener) or pointing them straight away from the wall will help control the treble, since speakers pointing toward the listener provide the greatest high-frequency response. Very clear detail and excellent stereo imaging are characteristics usually associated with near-field monitoring setups.
A greater concern with monitor speaker placement, especially in studios that employ near-field monitoring, has to do with the increased use of computer equipment in the studio. Unless the monitor speakers are magnetically shielded, they must be positioned far enough away from computer screens so that they don’t distort their pictures.
Perhaps the most practical monitor installation for many production studios is having the speakers hung from the ceiling or attached to the wall behind the audio console. For the best sound dispersion, the speakers should be hung from the upper corners of the production room. While putting speakers totally into the upper corners may result in too much bass boost, this is not an uncommon location. Usually there is enough space between the back of the speaker and the wall for heavy bass frequencies to be dispersed and the sound is not distorted. To maximize the amount of space between the back of a speaker and the wall, speakers mounted in upper corners should be toed-in toward the console or main listening area. Speakers that are hung from walls also keep counter space available for other production equipment, which is an important consideration in many settings.
Regardless of where the speakers are placed, the location of the operator in relation to the speakers also plays a role in how well they sound, especially with stereo programming. Ideally, the operator is located directly between the two speakers and far enough back from them so that an equilateral triangle is formed if a line were drawn from speaker to speaker and from operator to speaker (see Figure 7.6). If the layout of the production room positions the operator closer to one speaker than the other, the source of all the sound appears to shift toward that one speaker. As a production person, you may not have any control over speaker placement, so it’s important to realize the effects of speaker placement on the sound you hear.
FIGURE 7.6 The most basic rule of speaker placement dictates that the distance between the speakers equals the distance from speaker to listener.
7.7 PHASE AND CHANNEL ORIENTATION
The concept of phase was previously mentioned in Chapter 4, “Microphones.” Wiring monitor speakers incorrectly can cause phase problems. The sound signal is fed to each speaker from the audio console monitor amplifier (or sometimes an external amp) by a positive and negative wire. If the wires are reversed on one of the speakers (i.e., the positive wire is connected to the negative terminal), the two speakers will be out of phase. As the driver moves the cone of one speaker in and out, the driver on the other speaker is moving out and in, so that the two speaker sounds tend to cancel each other out and diminish the overall sound quality. This would be especially noticeable if the speakers were reproducing a monaural signal.
Another concern about speaker wiring is channel orientation. Most studio monitors are wired so that moving a balance control from left to right will shift the sound image from left to right as you face the speakers. In other words, while looking at the speakers, the left speaker is in line with your left hand. This setup is important for true stereo sound reproduction. For example, if you were listening to a classical music piece and the channel orientation was reversed, the violins would sound as if they were to the right of the sound stage, which would be contrary to normal symphony orchestra arrangement. However, since most speakers are wired by an engineer, phase and channel orientation should not be a problem in most audio studios.
Recall that most audio consoles have an internal monitor amplifier that provides the signal to drive the monitor speakers. Although this is adequate for many studio applications, some production rooms and control rooms are set up with external monitor amplifiers. These are merely more powerful amplifiers that provide higher volume levels and clearer reproduction of the sound signal. Remember, the volume of the monitor speakers is for the operator’s use only and has no relationship to the volume of the signal being broadcast or recorded.
A speaker’s sensitivity is the amount of sound (or output level) that can be produced from a given input level, much like the sensitivity of a microphone studied in Chapter 4. It is measured in decibels of sound-pressure level (db-SPL), and a good-quality broadcast monitor will usually have a sensitivity of more than 90 db-SPL measured at 1 meter with 1 watt of input level. There are speakers that range from low sensitivity to high sensitivity, but in reality, this characteristic of a speaker has little bearing on its quality. What it does mean is that a low-sensitivity speaker will need more power to drive it to any given volume level than a high-sensitivity speaker.
A speaker’s size, sensitivity, and bass response are all related. To increase a speaker’s low-frequency response, its enclosure can be made larger, or its sensitivity can be decreased. For many audio studio situations, a smaller speaker size offers a lot more flexibility in placement of the speaker and thus is preferred, even if it means using a low-sensitivity speaker that might require a more powerful monitor amplifier.
Headphones are tiny loudspeakers encased in a headset, which qualifies them as another type of monitor. Headphones are necessary in broadcast situations where studio monitor speakers are muted when a microphone is turned on, and the operator must be able to hear audio sources. For example, if a radio announcer was talking over the introduction of a song or a voice-over announcer was reading a commercial over the background of a music bed, headphones would allow him or her to hear both the other sound and the microphone sound so that he or she could balance the two or hit appropriate cues. Headphones are also portable, so sounds can be monitored when a standard monitor speaker might not be available.
Like regular monitor speakers, headphones come in a variety of designs and styles. The two main types of headphones found in the production studio are closed-cushion headphones and open-air or hear-through cushion headphones. Closed-cushion headphones, also known as circumaural headphones, have a ring-shaped muff that rests on the head around the ear and not actually on the ear. The enclosure around the muff is solid or closed, as shown in Figure 7.7. These headphones are probably the most common, as they usually provide a full bass sound and minimize outside noise better than other styles. Closed-cushion headphones are also less likely to leak sound into the studio, however they’re often heavier and more cumbersome than other styles.
FIGURE 7.7 Closed-cushion or circumaural headphones have a ring-shaped muff that rests on the head around the ear. (Image courtesy of Audio-Technica U.S., Inc.)
FIGURE 7.8 Hear-through or supra-aural headphones have a porous muff that rests directly on the ear. (Image courtesy of AKG Acoustics.)
Hear-through cushion headphones, also known as supra-aural or open-air, have a porous muff, instead of an ear cushion, that rests directly on the ear (see Figure 7.8). The enclosure around the muff typically has holes or other types of openings to give it the open-air design. Often made of very lightweight material, this design can be very comfortable for the wearer and provide superior sound reproduction. However, they are also more susceptible to feedback because the audio signal can leak out if driven at high volume levels.
Other headphone types include the tiny earbud, which is designed to fit in the ear; electrostatic headphones, which are extremely high-quality and require external amplification and special couplers to hook up; and wireless headphones, which operate similarly to wireless microphones by transmitting a radio frequency (RF) or infrared (IR) audio signal from the source to the headphones.
Unlike consumer headphones, many professional-quality headphones are purchased “barefoot,” meaning they have no end connector on them. Although most audio equipment requires a standard ¼-inch phone connector for headphones, there are situations where barefoot headphones allow an engineer to wire them specifically if necessary.
The most appropriate headphone style is often determined by the personal taste of the user. Professional-quality headphones should always feature large drivers and full (but comfortable) ear cushions and a headband. One note of caution for all headphone users: Listening at extremely high volume, especially for extended periods of time, can damage your hearing permanently. Be sure to practice “safe sound” and listen only at a moderate volume for short periods of time.
Audio equipment in the production studio is connected together by two methods: hardwiring and patching. Hardwired connections are usually permanent (such as a CD player connected directly to the audio console) and can be soldered or wired by the engineer. Equipment that may be moved from one production area to another (such as a portable recorder) is often connected through male and female connectors known as plugs and jacks. More will be said about the typical audio connectors in the next few sections of this chapter.
Many pieces of audio equipment, and even separate production studios, can be connected together through the use of a patch panel or patch bay. Most patch panels are configured as two rows of 24 phone jacks in a one- or two-unit rack space as shown in Figure 7.9. The patch panel is located near the equipment and the audio console so that the input and output of each piece of equipment can be quickly and easily connected.
There are several modes that patch bays can be set to; however, in a typical setup, the top row of sockets on the panel is where the audio signal is coming from, and the bottom row of sockets is where the signal is going to. Putting a patch cord into the correct jacks in the panel allows an operator to interconnect and reconfigure various pieces of equipment or even separate studios. Patch cords are available as either a single-plug cord or a double-plug cord. A double-plug cord works well for stereo patch bays since it has two plugs at each end. One side of the plug casing will be marked (usually with a colored or ribbed edge), so that you can keep left and right channels correctly aligned on both the input and output sockets of the patch panel. Of course, single cords work fine, too—just remember to always plug in one cord from the top-row right channel of the patch panel to the bottom-row right channel before plugging in the left channel, so you won’t cross channels. Crossing channels is easy to do if you plugged both left and right channels of the top row before plugging them in the bottom row.
Figure 7.10A shows a portion of a patch bay in which two CD players are linked to two channels on an audio console. With no patch cord put into the panel, CD 1 is linked to Channel 3 and CD 2 is linked to Channel 4. In patch panels, the top row is internally wired to the bottom row, and the audio signal flows in that manner. When it is unpatched like this, it’s known as a “normalled” condition. Figure 7.10B shows another portion of a patch panel that links the output of the audio console to audio recorders. When normalled, the PGM (or Program) output goes to CD-R 1, and the AUD (or Audition) output goes to the MiniDisc. The PGM signal could be sent to the MiniDisc (as shown) by putting a patch cord from the PGM position on the top row to the MiniDisc position on the bottom row. Now the signal flow has been changed, and that’s the purpose of a patch panel—to allow flexibility in configuring the audio studio.
An alternative to the patch panel is the audio routing switcher. The router (see Figure 7.11) operates just like a patch panel by allowing several input sources to be switched to a single output or sometimes multiple outputs. The switching is done electronically by selecting the appropriate switches or buttons, rather than by using patch cords. Most audio routers are centered around a matrix of “x” number of inputs times “x” number of outputs. Any one input can be sent to all the outputs, or all the outputs can be sent to one single input, or any combination can be configured.
FIGURE 7.9 A patch panel simplifies rewiring individual audio components into an audio console or studio. (Image courtesy of Gentner Broadcast Systems.)
There are primarily four types of audio connectors: RCA, XLR, phone, and miniphone. With each type, the female, or receiving, connectors are called jacks and the male connectors are called plugs, but often the terms “plugs,” “jacks,” and “connectors” are used interchangeably.
The RCA connector is sometimes referred to by its old time name, phono connector, and “pin connector.” Notice that it is “phono,” not “phone.” Most home stereo equipment and many professional-quality CD players use this type of connector. This connector is always a mono connector, so two of them are necessary for a stereo signal. Because of this, RCA connectors are often bundled in pairs and color-coded—red for right channel, and black or white for left channel. The male plug consists of a thin outer sleeve and a short center shaft that plugs into the female jack (see Figure 7.12). The female end is most often enclosed in a piece of equipment so that the male end will just plug directly into the equipment. RCA connectors are used for unbalanced connections and are prone to picking up extraneous electrical noises, such as switch noises or humming.
The XLR connector is also known as the Cannon connector or three-pin connector. It’s the most common microphone connector in audio production use and is often used as the input–output connection on audio recorders. By convention, male XLR connectors are outputs and female XLR connectors are inputs. The three pins of the male plug fit into the three conductor inputs of the female jack. The guide pin on the female end fits into the slot for the guide pin on the male end so that the connector can’t be put together improperly (see Figure 7.13). Like the RCA connector, the XLR connector is mono, so a stereo connection requires one XLR connector for the right channel and one for the left channel. The balanced three-conductor wiring of the XLR connector makes this a high-quality connection that is less likely to pick up noise through the cable.
FIGURE 7.10 A portion of a patch panel that is “normalled” (A) and a portion of a patch panel that has been “patched” (B).
FIGURE 7.11 An audio routing switcher operates in a manner similar to a patch panel. (Image courtesy of Lectrosonics.)
FIGURE 7.12 The RCA or phono plug is one of the common audio connectors. (Images courtesy of Switchcraft, Inc., a Raytheon Company; and Mackie Designs, Inc.)
FIGURE 7.13 XLR connectors feature a locking latch that prevents them from being accidentally disconnected. (Images courtesy of Switchcraft, Inc., a Raytheon Company; and Mackie Designs, Inc.)
FIGURE 7.14 Phone and miniphone connectors can be either stereo or mono. (Images courtesy of Switchcraft, Inc., a Raytheon Company; and Mackie Designs, Inc.)
The female XLR connection has a small spring lock on the outer casing that locks into the collar surrounding the male XLR connector. When connected properly, the XLR connection locks together and makes a snapping or clicking noise, letting you know your connection is strong. The connectors can only be unlocked by pressing the latch lock release.
The phone connector is also known as the ¼-inch phone. Notice that it is called “phone,” and not “phono.” Most pro-quality headphones use a phone plug to connect to the audio console, and most patch bays have female phone jacks which rely on phone plugs. The miniphone connector (also called a mini) is most often used to connect portable audio recorders to other pieces of production equipment. The output on many portable recorders is a female minijack. The miniphone is a smaller version of the phone connector, and although there are various sizes of miniphone connectors, the most common is the ⅛-inch. Phone and miniphone plugs each have a tip and a sleeve, which go into a female jack. Male mono plugs have one insulating ring that separates the tip from the sleeve, and stereo plugs have two insulating rings, which actually define the ring portion of the connector (see Figure 7.14). If the signal is stereo, both the female and male connectors should be stereo. The female end is often enclosed in a piece of equipment, but inline jacks are available if needed.
7.13 OTHER CONNECTORS AND CONNECTOR ADAPTERS
Most of the connectors mentioned so far are intended for analog inputs or outputs; however. more equipment in the audio studio today has digital connections. Some digital connections utilize standard broadcast connectors, such as the XLR and RCA plugs and jacks, and other digital inputs and outputs use different types of connectors. When XLR connectors are used for digital audio, you may see an input or output labeled AES/EBU. This means the equipment meets the digital standards set by the Audio Engineering Society and the European Broadcasting Union. Digital RCA connectors follow the S/PDIF (Sony-Philips Digital Interface Format) standards. If these audio connectors are used for a digital audio connection, the connecting cable should also be designed for digital audio.
FIGURE 7.15 Some digital connections require the use of connectors not normally associated with the wiring of audio equipment. (Image courtesy of Neutrik USA.)
Two other connectors that are still being used for digital hook-ups in some studios include the BNC and Toslink connectors. The Toslink connector was developed by Toshiba and is the most common optical connector for digital audio. The connectors are usually molded plastic with a fiber-optic glass cable. BNC connectors (see Figure 7.15) feature a locking design along the lines of the XLR and are designed for use with 75-ohm cable. Used extensively for years in video applications, BNC connectors have been used specifically for digital equipment.
Other connectors commonly found in audio studios are based on the increased use of computer equipment in audio production. Many production studios are designed around Ethernet and FireWire cables and connectors (see Figure 7.16). The Ethernet or RJ-45 connector looks and operates like a larger version of the standard modular telephone jack and is commonly wired with CAT-5 cable. Many audio console control surfaces are now connected to their input/output frames with this connector, greatly decreasing the amount of wiring necessary for a typical audio studio. Apple gave the IEEE 1394b digital interface the name “FireWire,” which is a tiny four- or six-pin jack or plug capable of very high speed digital data transfer. Although Apple has discontinued providing FireWire connections on its computers, some older editing machines using the technology are still in use.
A more common connector is the USB (Universal Serial Bus) which can link audio input/output equipment to computer recording and editing systems and has been used to directly connect microphones and loudspeakers to a computer. The increased practice of using USB flash drives for storage and playback of audio content has also helped solidify its use in the modern studio environment.
FIGURE 7.16 Connectors common to the computer industry are being used more and more in audio facilities and equipment: (A) Ethernet, (B) FireWire, (C) USB.
Something else that is very handy to have in any audio production studio is a supply of connector adapters, which enable you to change a connection hookup from one form to another. Let’s say, for example, that you need to connect an RCA output to a phone connector input, but the only cable you can find has an RCA connector at both ends. You can convert one of the RCA connectors to a phone connector with an adapter. This is a single piece of metal, which in this case houses a female RCA input at one end and a male phone output at the other. When the male RCA connector is inserted into the female end of the adapter, the signal is transferred from the RCA connector to the phone connector, and from there it can go to the phone input. Adapters usually come in handy in emergency situations when some connecting cable fails; therefore having a variety of them available is good production practice.
7.14 BALANCED AND UNBALANCED LINES
The standard monitor cable most often used in analog audio production consists of two stranded-wire conductors that are encased in plastic insulation along with a third uninsulated shield wire, all encased in a foil wrapping and another plastic sheathing (Figure 7.17). For most wiring practices, the inner wires are designated 1 (red) and 2 (black), and the uninsulated wire is the shield or ground wire. The audio signal is carried on the positive and negative conductors. This type of cable is referred to as three-wire, or balanced cable, and often requires the XLR connector, since that is the one best designed to connect three wires in addition to being the one most utilized by many types of audio equipment.
FIGURE 7.17 Typical audio cable is designed for a balanced wiring scheme. (Image courtesy of Cooper Industries, Belden Division.)
Another type of cable is two-wire, or unbalanced. In this configuration, the negative wire also acts as the ground. Since there is no plastic or foil shielding, an unbalanced cable is more susceptible to unwanted audio interference, such as that created by nearby electric sources. Unbalanced lines are also more likely to suffer from signal degradation and attenuation as they get longer. If that were not enough, equipment that utilizes unbalanced cable also generally outputs a lower level signal than equipment that employs balanced wiring. Because of these shortcomings, unbalanced cable is more often used in home stereo systems than production studios. Ideally, balanced and unbalanced cable should not be mixed in the same audio setup. However, sometimes this can’t be avoided, because different pieces of equipment require different cabling.
7.15 MICROPHONE, LINE, AND SPEAKER LEVELS
Equipment inputs and outputs can be considered in terms of one of three audio levels: microphone, line, or speaker. Think of these levels as very low for microphone (which usually must be preamplified), normal for line level (most equipment will use line levels), and very high for speaker levels (designed to drive a speaker only). Problems arise when various levels are mismatched. For example, if you tried to feed an audio recorder from a speaker-level source on a console or patch panel, you would probably distort the recording, because the speaker-level source would be too loud, and there is no control to turn it down. Another problem would occur if you fed a microphone-level signal into a line-level input. In this case, the signal would be too low because microphone levels must be preamplified to a usable level. Most audio equipment inputs and outputs are clearly designated as microphone, line, or speaker level, and good production practice dictates connecting them properly.
Although many audio consoles have built-in studio timers, it is not uncommon to find a separate timer in the audio production room (see Figure 7.18). Because the timing of production work is so important, an accurate timing device is crucial. Most studio timers are digital, showing minutes and seconds, and include at least start, stop, and reset controls. Many timers can be interfaced with other equipment (such as computers, recorders, and CD players) so that they automatically reset to zero when that piece of equipment is started. While shorter timers (10 minutes) are usually adequate for audio production work, 24-hour timers are also often found in the studio.
A simple telephone interface, or telephone coupler (see Figure 7.19), is a piece of equipment designed to connect telephone lines and cellular networks to broadcast or recording equipment. In a basic configuration, the telephone goes through the interface and comes into the audio console on its own channel. The caller volume is controlled with that channel’s fader, in addition to a caller volume control on the interface. Once a call is taken by the announcer and the interface is switched on, the announcer talks to the caller through the studio microphone and hears the caller through the headphones. The interface electronically maintains an isolation between the studio “send” signal and the caller “return” signal, providing a high-quality, clear telephone signal.
With the gradual upgrading of telephone lines and cell phone services across the country, many audio facilities have installed high-quality digital systems that give a clearer signal than the older analog systems. One such service is ISDN (Integrated Services Digital Network), which is a communications standard for sending voice or data over telephone lines. With the appropriate interface equipment, the telephone becomes just another audio input that can be easily recorded, edited, and mixed with other sound sources, and otherwise manipulated for production use.
Another telephone interface is a compact, handheld unit that allows for connection to a number of different wired and wireless data circuits. Although units like the one in Figure 7.20 can connect to standard telephone lines or POTS (Plain Old Telephone Service), it also can send audio over DSL, cable, Wi-Fi, 3G and 4G cellular, Internet, satellite, and other communication networks. This portable IP (Internet Protocol) audio codec makes field remotes possible in situations where setting up a rack of telephone interface equipment can’t happen.
Keep in mind that each of these interface devices can be used with cell phones as well as land lines. The biggest concern for a studio operator when it comes to recording or broadcasting cell phone calls is that the quality of the recording or broadcast relies on the quality of the cell phone connection. A poor connection will lead to a poor production.
FIGURE 7.18 An audio studio timer provides accurate timing for production work. (Image courtesy of Radio Systems.)
FIGURE 7.19 A telephone interface allows mixing an audio signal and a telephone signal. (Image courtesy of Comrex Corporation.)
FIGURE 7.20 This portable IP audio codec can interface with DSL, cable, Wi-Fi, 3G cellular, satellite, POTS, and other communication services. (Image courtesy of Comrex Corporation.)
Often, monitor speakers and connectors are given little or no thought. Some production people are concerned only with making sure sound comes out of the speakers and that some accessory items are available, but the purpose of the monitor speaker in audio production is not as minor as one might initially believe. Although much of the equipment mentioned in this chapter may never be installed or adjusted by the studio operator, it is critical to not take speakers, their connectors, and other interface equipment for granted. Always remember that loudspeakers in any form are the only tool you have to adequately determine the final quality of an audio production.
1. What components make up a two-way speaker system?
a) tweeter, woofer, and midrange speaker
b) tweeter, woofer, and crossover
c) tweeter and woofer
d) tweeter, woofer, and two crossovers
2. What is the transducing element of a speaker called?
a) tweeter
b) crossover
c) woofer
d) driver
3. Which speaker enclosure design utilizes a tuned port to provide a highly efficient system with a full bass sound?
a) acoustic suspension
b) bass reflex
c) bass boom
d) sealed box
4. Which individual speaker is designed to reproduce higher frequencies?
a) woofer
b) crossover
c) tweeter
d) bass reflex
5. For proper stereo sound, the listening angle formed between the speakers and the listener should be 90 degrees.
a) true
b) false
6. Which broadcast connector has a guide pin?
a) RCA
b) phone
c) XLR
d) phono
7. Which is the most practical place to locate monitor speakers in a production room?
a) near the upper corners, close to the wall
b) on the counter
c) not in the room at all, but in an adjoining room
d) in the middle of the wall, close together
8. Which is true if two speakers are out of phase?
a) The bass sounds will be generated at the rear of the cones.
b) Both negative wires will be connected to negative terminals.
c) Both positive wires will be connected to positive terminals.
d) The cone of one speaker will be moving out while the cone of the other speaker is moving in.
9. Which broadcast connector is always mono?
a) phone
b) miniphone
c) ¼-inch phone
d) RCA
10. Which type of monitor speaker will most likely be found in the audio production studio?
a) ribbon speaker
b) electrostatic loudspeaker
c) dynamic loudspeaker
d) condenser loudspeaker
11. Which component of a speaker system divides the incoming audio signal into different frequencies and sends the proper frequencies to the appropriate driver?
a) pigtail leads
b) tweeter
c) woofer
d) crossover
12. Which type of headphone is designed with a porous muff that rests directly on the ear?
a) closed-cushion headphone
b) circumaural headphone
c) earbud
d) supra-aural headphone
13. Unbalanced audio cables are more susceptible to interference than balanced cables.
a) true
b) false
14. Having a high-power, external monitor amplifier in your production studio will allow you to record or broadcast a louder signal than using the internal monitor amp in the audio console.
a) true
b) false
15. Small speakers set on short stands, placed left and right of the audio console so the listener hears mostly direct sound at ear level, are known as which type of monitors?
a) dynamic
b) near-field
c) acoustic suspension
d) out-of-phase
16. When a patch panel is normalled, a patch cord is used to link broadcast equipment assigned to the top row of the panel to the equipment assigned to the bottom row.
a) true
b) false
17. Which broadcast connector has a sleeve, ring, and tip?
a) RCA
b) Cannon
c) XLR
d) phone
18. Which connector is most likely to be used for a patch bay?
a) phone
b) miniphone
c) RCA
d) multipin connector
19. What is a connector adapter used for?
a) to transfer a signal in a patch bay
b) to change a connector from one form to another
c) to make a balanced line unbalanced
d) to change a telephone signal to an audio signal
20. Which configuration describes a balanced cable?
a) two wires
b) three wires
c) three ground wires
d) two ground wires
21. The normal outputs of a CD player produce which level of audio signal?
a) microphone
b) line
c) speaker
d) none of the above
22. Practically all consumer models of headphones can be purchased “barefoot.”
a) true
b) false
23. By convention, male XLR connectors are outputs and female XLR connectors are inputs.
a) true
b) false
24. Which production room accessory is used to connect telephone lines directly to broadcast equipment?
a) audio routing switcher
b) telephone coupler
c) patch panel
d) XLR connector
25. What would be the best type of monitor when you need to use a microphone in the production studio to record a voice over music?
a) headphones
b) tweeter
c) acoustic suspension
d) bass reflex
If you answered A to any of the questions:
1a. No. This speaker complement would be in a three-way system. (Reread 7.3.)
2a. No. A tweeter is a speaker designed to produce high frequencies. (Reread 7.2 and 7.3.)
3a. No. The acoustic suspension design is relatively inefficient. (Reread 7.4.)
4a. Wrong. The woofer is designed to reproduce the lower frequencies. (Reread 7.3.)
5a. No. This would put the listener directly in front of one of the speakers, and all the sound would appear to be coming out of that speaker. (Reread 7.6; check Figure 7.6.)
6a. No. (Review Figures 7.11 to 7.14; reread 7.12 and 7.13.)
7a. Correct. This gives the operator good sound and also leaves the counter clear for other equipment.
8a. No. You’re confusing this with speaker enclosures. (Reread 7.4 and 7.7.)
9a. No. The phone connector can be either stereo or mono. (Review Figures 7.12 to 7.14; reread 7.12 and 7.13.)
10a. No. Ribbon speakers are generally too exotic in design and too expensive for broadcast use. (Reread 7.2.)
11a. Wrong. You may be confused because this is a part of an individual speaker that receives an input signal, but after it has been divided into the proper frequencies. (Reread 7.3.)
12a. No. This is a headphone with a ring-shaped ear cushion designed to encircle the ear and rest on the head. (Reread 7.10.)
13a. Right. This is a true statement because one wire conducts the signal and also acts as a ground, so unbalanced cables are more likely to pick up unwanted noise.
14a. Wrong. A monitor amp has no relation to the broadcast or recorded signal; it only controls the volume of the monitor speakers. (Reread 7.8.)
15a. Although they may be dynamic speakers, this term usually refers to the speaker driver. There is a better answer. (Reread 7.2 and 7.6.)
16a. Wrong. A normalled patch panel is actually unpatched, so no patch cords are used. (Reread 7.11.)
17a. No. The phono connector only has an outer sleeve and tip. (Review Figures 7.12 to 7.14; reread 7.12 and 7.13.)
18a. Right. A male phone plug is the most likely connector to use with a patch bay.
19a. No. You would be very unlikely to use an adapter with a patch bay. (Reread 7.11 and 7.13.)
20a. No. Two wires would be unbalanced. (Reread 7.14.)
21a. Wrong. Microphone level is a low output level, which must be preamplified to be usable, and is primarily produced by microphones, as the name implies. (Reread 7.15.)
22a. Wrong. Most consumer headphones come with a plug already attached. Most professional headphones can be purchased “barefoot.” (Reread 7.10.)
23a. Correct. This is a true statement.
24a. Wrong. An audio router can be involved in selecting various inputs and outputs, but it can’t connect a telephone line by itself. (Reread 7.11 and 7.17.)
25a. Yes. Headphones would prevent feedback and allow the operator to hear the music when the speakers are muted because the microphone is on.
If you answered B to any of the questions:
1b. Correct. These are the basic components of a two-way speaker system.
2b. Wrong. The crossover divides the electrical signals and sends them to the speaker drivers. (Reread 7.2 and 7.3.)
3b. Right. This answer is correct.
4b. No. The crossover is not a speaker but an electronic device for sending various frequencies to different speaker drivers. (Reread 7.3.)
5b. Correct. This is false because an angle of about 60 degrees should be formed between the listener and the speakers for the best stereo sound.
6b. No. (Review Figures 7.11 to 7.14; reread 7.12 and 7.13.)
7b. No. The sound can be good, but the speaker takes up counter space that could be used for something else. (Reread 7.6.)
8b. No. One negative wire connected to a positive terminal would put them out of phase. (Reread 7.7.)
9b. No. The miniphone connector can be either stereo or mono. (Review Figures 7.12 to 7.14; reread 7.12 and 7.13.)
10b. No. Electrostatic loudspeakers are generally too exotic in design and too expensive for broadcast use. (Reread 7.2.)
11b. Wrong. This is a part of a speaker system that reproduces high frequencies. (Reread 7.3.)
12b. No. This is another name for the closed-cushion headphone, which has a ring-shaped ear cushion designed to encircle the ear and rest on the head. (Reread 7.10.)
13b. Wrong. This is a true statement. (Reread 7.14.)
14b. Correct. This is the right response, because monitor amps have no relation to the broadcast or recorded signal.
15b. Yes. Some production people think that the best sound is heard through near-field monitoring.
16b. Yes. When a patch cord is put into a patch panel, it is no longer normalled.
17b. Wrong. Cannon is just another name for the XLR connector. (Review Figures 7.12 to 7.14; reread 7.12 and 7.13.)
18b. No. You’re warm but not correct. (Reread 7.11 and 7.12.)
19b. Correct. It transfers the signal so that another form of connector can be used.
20b. Right. There are three wires: positive, negative, and ground.
21b. Right. Line-level outputs are standard for most broadcast production equipment, such as CD players and audio recorders.
22b. Correct. This is the best answer.
23b. No. This is a true statement. (Reread 7.12.)
24b. Correct. This is the best answer.
25b. No. This is only part of a monitor speaker. (Reread 7.3 and 7.10.)
If you answered C to any of the questions:
1c. No. You’re close though, but you’ve left out one component. (Reread 7.3.)
2c. No. A woofer is a speaker designed to reproduce low frequencies. (Reread 7.2 and 7.3.)
3c. Wrong. There’s no such enclosure design. (Reread 7.4.)
4c. Correct. The tweeter is the speaker designed to reproduce high frequencies.
6c. Right. The XLR jack has a guide pin that prevents it from being connected incorrectly.
7c. No. You couldn’t hear them if they were in another room. (Reread 7.6.)
8c. No. One positive wire connected to a negative terminal would put them out of phase. (Reread 7.7.)
9c. No. A ¼-inch phone or phone connector can be either stereo or mono. (Review Figures 7.12 to 7.14; reread 7.12 and 7.13.)
10c. Yes. The dynamic loudspeaker is found most often in the production studio.
11c. Wrong. This is a part of a speaker system that reproduces low frequencies. (Reread 7.3.)
12c. No. This is a type of headphone that is designed to fit into the ear. (Reread 7.10.)
15c. Wrong. Although they may be acoustic suspension speakers, this term is usually associated with the speaker enclosure. There is a better answer. (Reread 7.4 and 7.6.)
17c. No. (Review Figures 7.12 to 7.14; reread 7.12 and 7.13.)
18c. No. (Reread 7.11 and 7.12.)
19c. No. Adapters are not related to balance. (Reread 7.13 and 7.14.)
20c. No. Although there are three wires, they aren’t all ground wires. (Reread 7.14.)
21c. No. Speaker level is quite high and is designed to drive a monitor speaker. Most production equipment, like a CD player, would have to have its output signal amplified to reach speaker level. (Reread 7.15.)
24c. Wrong. A patch panel could be involved in wiring a telephone line to an audio console, but it can’t connect a telephone line by itself. (Reread 7.11 and 7.17.)
25c. No. You’re confusing monitors and enclosures. (Reread 7.4 and 7.10.)
If you answered D to any of the questions:
1d. Wrong. Only a single crossover is required in a speaker system. (Reread 7.3.)
2d. Yes. The driver transforms electrical signals into mechanical energy and thus audible sound.
3d. No. This is another name for an acoustic suspension speaker, which is relatively inefficient. (Reread 7.4.)
4d. No. Bass reflex describes a speaker enclosure design, not an individual speaker. (Reread 7.3 and 7.4.)
6d. No. Phono is just another name for the RCA connector. (Review Figures 7.11 to 7.14; reread 7.12 and 7.13.)
7d. Wrong. This would really limit sound dispersion and any stereo imaging. (Reread 7.6.)
8d. Right. The sounds will be fighting each other when this happens.
9d. Correct. You must use two RCA connectors for stereo, one for each channel.
10d. No. You might be thinking of a microphone; there is no such loudspeaker. (Reread 7.2.)
11d. Correct. A crossover is a network of filters that divides the audio signal into different frequencies and sends it to the proper individual speaker.
12d. Yes. Also known as open-air or hear-through cushion headphones, supra-aural headphones are designed to rest directly on the ear.
15d. No. Out-of-phase speakers are miswired, and this has nothing to do with speaker placement. (Reread 7.6 and 7.7.)
17d. Correct. The miniphone connectors also have them.
18d. No. (Reread 7.11 to 7.13.)
19d. No. There are devices to do this, but they are interfaces, not connector adapters. (Reread 7.13 and 7.17.)
20d. Wrong. (Reread 7.14.)
21d. No. There is a correct answer and this isn’t it. (Reread 7.15.)
24d. Wrong. You’re quite confused if you chose this answer. (Reread 7.12 and 7.17.)
25d. No. You’re confusing monitors with speaker enclosure designs. (Reread 7.4 and 7.10.)
Compare speaker/listener placement.
Purpose
To make you aware of how sound can change as the relationship between speaker and listener changes.
Notes
1. If your studio is too small for you to hear any differences, just indicate that this is the case.
2. The most important thing for your drawings will be to show the relative dimensions of the studio and the position of the speakers.
How to Do the Project
1. Make three sketches of your production room, showing where the speakers are located.
2. On the first drawing, put an X where the production person usually sits. On the second drawing, put an X at another spot in the control room where you can stand and listen to the monitors. Do the same for the third drawing.
3. Play some music through the monitor speakers, and position yourself in each of the three places where you have placed Xs. Listen for any differences in the way the music sounds at the three locations.
4. Write a short report detailing how the music sounded at each position.
5. Put your drawings and your report into a packet labeled with your name and the title, “Speaker/Listener Relationship.” Give the packet to your instructor to receive credit for this project.
Identify common connectors found in the audio production studio.
Purpose
To familiarize yourself with audio connectors and how they are used in the production studio.
Note
If you have trouble identifying them, review Figures 7.12 to 7.16.
How to Do the Project
1. Draw four columns on a sheet of paper and label them “A,” “B,” “C,” and “D.” On another sheet of paper, draw three or four more unlabeled columns.
2. Write the correct name for each connector beneath the appropriate letter. If the connector is also often called by another name, include both names.
3. Indicate whether this connector is mono, stereo, or can be both.
4. Now look around your studio and see how many instances you can find where each connector is used and note this on your list. Provide specifics on how the connector is being used. For example, “the output of the CD player uses RCA connectors for the left and right channels.”
5. Try to find at least one instance of use for each connecter, but be aware that some connectors may be used numerous times in the studio.
6. On the second sheet, list other types of connectors that you find in your audio studio.
7. You should be able to identify them from descriptions in the text. Remember to note how they are being used in the studio.
8. Label your forms with your name and the title, “Audio Connectors.” Turn it in to your instructor to receive credit for this project.