AUDIO 101

A loudspeaker is a device which converts an electrical audio signal into a corresponding sound.  When an alternating current electrical audio signal is applied to its voice coil, a coil of wire suspended in a circular gap between the poles of a permanent magnet, the coil is forced to move rapidly back and forth due to Faraday's law of induction, which causes a diaphragm (usually conically shaped) attached to the coil to move back and forth, pushing on the air to create sound waves.  

• Audio frequency - the acoustic spectrum of human hearing, generally regarded to be between 20 Hz and 20 kHz.
• Highs (or High end, Top end, Treble, or Air) – The section of the frequency spectrum above 8kHz. 
• Lows (or Low end, Bass, or Sub-bass) – The section of the frequency spectrum between 60Hz-200Hz.
• Mids – The section of the frequency spectrum between 600Hz-3kHz.

• Cone - the conical diaphragm of a speaker attached to the voice coil which produces pulsation's of air that the ear detects as sound.
• Crossover Network (Filter) - an electric circuit or network that splits the audio frequencies into different bands for application to individual speakers.
• Diaphragm - the part of a dynamic loudspeaker attached to the voice coil that moves and produces the sound. It usually has the shape of a cone or dome.
• Driver - a loudspeaker unit, consisting of the electromagnetic components of a speaker, typically a magnet and voice coil.

• Dome Tweeter - a high frequency speaker driver with a dome-shaped diaphragm usually made of metal or silk.
• Spider - the flexible material that supports the former, voice coil, and inside portion of the cone within the speaker frame.
• Surround (suspension) - the outer suspension of a speaker cone; holds the diaphragm in place but allows it to move when activated. Usually made of foam or rubber.
• Voice coil - the wire wound around the speaker former. The former is mechanically connected to the speaker cone and causes the cone to vibrate in response to the audio current in the voice coil.

• Dispersion - the spreading of sound waves as it leaves a speaker.
• Efficiency: Another very important characteristic, it is the ratio between the output power and power consumed.
• Efficiency rating - the loudspeaker parameter that shows the level of sound output when measured at a prescribed distance with a standard level of electrical energy fed into the speaker. However, a driver with a high efficiency rating needs a larger box to play a lower frequency than a driver with a lower efficiency rating.

• Electronic Crossover - uses active circuitry in addition to passive to filter unwanted signals for each driver. Usually active filters are employed as LPF(Low Pass Filters) for subwoofers or for the sub out of a preamp / receiver.
• Enclosure - a box that contains the driver(s).
• Full-range - a speaker designed to reproduce all or most of the sound spectrum within human hearing (20Hz - 20KHz)

• Treble (highs) - the upper end of the audio spectrum reproduced by tweeters, usually 3 - 4 kHz and up.
• Tweeter - a speaker designed to reproduce the high or treble range of the sound spectrum.
• Subwoofer - a loudspeaker designed to reproduce bass frequencies.
• Woofer - a loudspeaker transducer designed to reproduce low-frequency sounds.

SPEAKER DESIGNS:

• Two-way - a type of speaker system composed of two ranges of speakers, usually a woofer and tweeter.
• Three-way - a type of speaker system composed of three ranges of speakers, specifically a woofer, midrange, and tweeter.

• Monitors – This refers to speakers that are used for mixing.
• Standing wave - a buildup of sound level at a particular frequency that is dependent upon the dimensions of a resonant room, car interior, or enclosure. It occurs when the rate of energy loss equals the rate of energy input into the system. This is what you hear when you listen into a sea shell.

• Horn - a speaker design using its own funnel shaped conduit to amplify, disperse, or modify the sounds generated by the internal diaphragm of the speaker.
• Imaging - it is the speakers ability to localize different instruments playing simultaneously
• Timbre - The quality of a sound related to its harmonic structure. Timbre is what gives a voice or instrument its sonic signature -- why a trumpet and a saxophone sound different when they play the same note.

Sound Stage - the sound systems ability recreate an imaginary stage. A good speaker will faithfully make the stage seem close to the actual height, width and depth of the actual performance stage where recorded. Imaging is similar, but the speaker must be able to place each instrument or voice in the correct location on the soundstage. The reproduction of the way the music would sound if you were actually watching the musicians play in front of you. The stage should always appear to be in front of you, with a proper "image" of where each musician is playing on the imaginary soundstage.

Audio encompasses a large number of interfaces including digital and  analog. These are used in a number of applications from home theater and  portable use to the pro audio mixing boards that DJ's and other audio  professionals use. 

Audio cables are often referred to as accessories. However, an audio system cannot make sound without cables installed which implies that they are essential components. 

Much like the other components in the system, cables must be chosen with the  same research that one would perform in choosing an amplifier, a speaker or a turntable. 

Characteristics such as colouration, distortion and  other anomalies must be minimized in order for the system to perform at  its optimum. 

Too often, audiophiles and music lovers treat these  essential components as after thoughts and end up compromising the  performance of their carefully chosen audio gear.    

The RCA connector is used in several audio applications. Stereo RCA Cables connect two analog audio components together. They are found on most  types of A/V gear. 

S/PDIF (Sony®/Philips  Digital Interface) is the "red book" standard for digital audio signal  transfer. A S/PDIF coaxial cable can carry linear PCM or multi-channel  Dolby® AC-3/DTS® digital content. 

For dual channel stereo audio, two RCA connectors deliver the analog composite audio  signal to the left and right channels of audio. In home theater, RCA can be used as a powered sub-woofer connection.

LFE (Low Frequency Effects)

Home  theater receivers use a single RCA output for the sub-woofer connection -  that's the ".1" in a 5.1 system. This output is often labeled LFE. It  sends bass information to a powered sub-woofer. 

 Headphone connections (1/4" and 1/8")

Stereo  headphone connections come in two sizes: full-size (1/4") and mini (1/8"). 

Home A/V components like CD players, receivers, and headphone  amplifiers use the 1/4" connection. 

Smartphones, tablets, and computers  use the smaller 1/8" jack.

Headphones with 1/4" plugs can be stepped down to 1/8" to plug into a mobile device. 

Headphones that use a 1/8" plug can be stepped up to 1/4" to fit equipment that uses a full-sized connection.

Speaker Wire:

Speaker Wire connects a non-powered speaker to an amplifier or receiver. Speaker wire has two leads: one for the positive signal, and one for the  negative. Usually speaker wire is marked (+) and (-) to help distinguish  between the two.

Wire thickness is identified by its American Wire Gauge (AWG) number. The lower the gauge number, the  thicker the wire.  Thicker wire presents less resistance to current flow.

Thick wire (12 or 14 gauge) is recommended for long wire runs, high power applications, and low-impedance speakers (4 or 6 ohms).

What gauge do you need?

For  relatively short runs (less than 50 feet) to 8 ohm speakers, 16 gauge  wire will usually do just fine. It’s cost-effective and easy to work  with.

Speaker Wire Connectors:

Add speaker wire connectors to bare wire for additional connection options. 

Banana Plugs:

If  you have binding post terminals on your speakers and/or receiver,  banana plugs are a great choice. The flexible metal collar of a banana  plug is slightly wider than the center hole of a binding post.  It compresses to fit when you plug it in, resulting in a very solid connection.

Spade Connectors:

Spade connectors feature a forked piece of metal that hugs the collar of a  5-way binding post terminal. The spade is then secured by tightening the  binding post's cap.  Spade connectors give you very secure contact.

Pin connectors:

Pin connectors may either be straight or angled. They work with spring clip speaker terminals, as well as with binding posts.

XLR – primarily found on professional audio equipment.  XLR Cables pass an analog signal between compatible audio components.  They're  commonly used with high-performance two-channel systems, as well as with microphones.

An  XLR connector has three pins - a positive conductor, a negative  conductor, and a ground. The presence of the ground wire makes XLR  cables known as "balanced" cables. It helps reduce electronic noise throughout the cable. 

A clasp built into the round XLR plug locks it  tightly into the receiving socket, ensuring a secure connection.

Digital Cables:

USB (Universal Serial Bus)

USB is a digital interface that  connects compatible devices together. It's used to transfer audio,  video, and other digital information. Originally designed for computers, USB cables are now used for data transfer and charging in a wide range of components.  USB inputs can be  found on computers, TVs, home theater receivers and car stereos. 

The  standard USB connection is considered Type A - that's the one that plugs into your computer. Type B USB plugs are commonly used with  printers. 

Micro USB plugs are found on smartphones and other portable  devices.

HDMI (High Definition Multimedia Interface) - This digital video interface allows high definition video and audio to be transmitted over a single cable. 

Cables can be made of copper (limited to ~30 feet without  electronic signal boost and equalization) or fiber optic, with the  latter able to reach almost unlimited distances.

An HDMI cable is today's go-to connection for high-definition audio  and video transmission. It's used with TVs, gaming systems, home theater  receivers, computers, and HD monitors. 

The standard HDMI cable has an  identical plug on each end. Inside there are 19 individual wires. They  carry audio and video data along with control signals, low-voltage  power, Ethernet, and copy protection.

Standard-size HDMI cables are called Type A. Compact devices like smartphones, cameras, and  camcorders use mini HDMI (Type C), or micro HDMI (type D) because of  their small form factor.

TOSLINK is the name of an optical interface for digital audio signals.  The interface was developed by Toshiba, and TOSLINK is their registered  trademark. The TOSLINK (also known as EIAJ optical) connector is a  small, round optical conductor housed in a squarish connector body.  Originally intended for use solely with Toshiba CD players, it has been  adopted by many other manufacturers and is standard equipment on many  A/V sources, receivers and surround sound equipment. Even though TOSLINK  uses fiber optic cable, it is limited to a maximum cable length of  about 5 meters, due to the low power of the LEDs used in transceivers.

Coaxial digital cable

A coaxial digital cable transmits a digital audio signal between two devices. It's commonly  used with home theater receivers, music streaming devices, and disc players.  Coaxial digital cables look virtually identical to single analog RCA cables. But they are specially designed to handle the wide frequency bandwidth of digital signals. 

A single cable is used to transmit the entire  digital signal.  Coaxial digital connection ports are typically orange.