Intro
You might be curious about the different audio cables that are needed to connect your speakers, receiver, and other devices. To ensure your system works as intended, it’s important to understand what each cable does and why it’s needed. Let’s delve into the various types of audio cables commonly used in home theater setups and their respective functions.
Analog vs Digital
Home theater audio cables are typically classified into two primary categories: analog and digital. Analog cables function by transmitting sound signals as continuous electrical waves, while digital cables convey sound signals as discrete binary data, consisting of 1s and 0s. Both analog and digital cables are used in modern home theater systems as they have their own respective purposes.
Analog Cables
Analog audio cables are wires that carry sound signals from one device to another using sine waves, such as from an AV Receiver to an external amplifier. They work by sending an electrical current that represent sound waves through the cable.
When the sound changes, the electric current flowing through the cable also changes in strength (amplitude) and speed (frequency). For instance, if the audio information consists of a 100 Hz sine wave, the voltage running through the analog cable will undergo 100 cycles of positive and negative changes per second.
Balanced v Unbalanced
Before delving into specific analog cable types, it is helpful to understand the distinction between balanced and unbalanced cables as knowing the difference can help to know what cable to pick.
Unbalanced analog cables have two wires: a signal and a ground. The signal wire carries the sound signal on one conductor and the ground wire acts as a shield against interference. Even though the ground wire protects from some interference, unbalanced cables are still susceptible to interference, especially over long distances. Unbalanced cables are typically used for consumer audio equipment and short-distance connections. For the majority of applications, unbalanced cables are generally sufficient to send high quality audio.
Image courtesy of SVS
Balanced analog cables, on the other hand, have three wires: a positive, a negative, and a ground. The positive and negative wires carry the same sound signal but with opposite polarity. This cancels out any interference that might affect both wires equally, creating a cable that is much less susceptible to interference. Balanced cables are typically used for professional audio equipment, high fidelity audio, and long-distance connections.
RCA
RCA cables are one of the most common types of unbalanced analog cables and will work for most home audio equipment. They have a round plug with a single pin in the center and a metal ring around it. RCA cables can be color-coded according to their function: red for the right channel, white for the left channel, etc.
In general, RCA plugs can only carry a single signal through one connector. That means for stereo sound, you need two RCA plugs: one for the left channel and one for the right channel. For surround sound, you need as many RCA plugs as there are channels. For a modern home theater, RCA plugs can be used as subwoofer cables, for two channel systems, and for connecting external amplifiers to your main sound processor or AVR.
XLR
XLR cables are one of the most common types of balanced analog cables. They have a cylindrical plug with three pins: one for positive, one for negative, and one for ground. XLR cables have a locking mechanism to prevent accidental unplugging. XLR cables are more common in professional audio gear where long cable runs are normally necessary, but are also used in home theater due to the ability to resist electrical noise that can cause distortion in the sound.
For most applications of XLR cables in home theater, only one channel of audio will be transmitted through the cable. This means that you will need an additional XLR cable for every channel of audio you wish to connect. An XLR cable is a good choice if your system has a lot of stray electrical noise or if you are concerned that it might. Be aware that XLR connectors are considerably larger than RCA connectors and not all equipment supports XLR connections, so it requires more planning when deciding on equipment.
Speaker Wire
Speaker wire is another type of unbalanced analog audio cable. Speaker wire has two strands: one for positive and one for negative. Speaker wire is usually color-coded according to polarity: red for positive and black for negative, but other colors can be used as well.
Image of a four conductor speaker wire, meaning it can be used for two speakers.
Speaker wire can vary in thickness or gauge depending on the power and impedance of the speakers. Thicker wire can handle more power and lower impedance than thinner wire. If you’re using passive speakers powered by an AV Receiver or amplifier, you’ll need a separate two conductor wire for each speaker. Understanding all the nuances of speaker wire can be challenging, but our article “Choosing the Right Speaker Wire” simplifies it for you.
Digital Cables
Instead of using a continuous electrical signal like analog cables, digital cables send encoded audio that has been converted into binary data by an Analog to Digital Converter (ADC), and then that binary data is sent through the cable to be decoded on the other side using a Digital to Analog Converter (DAC). This has the advantage of being less susceptible to electrical interference as well as being able to send multiple channels of audio through one wire, increasing the bandwidth per wire. There are three main types of digital audio cables: HDMI, optical, and digital coax.
HDMI
HDMI, an acronym for High-Definition Multimedia Interface, is a proprietary audio/video interface in a distinct D-shaped design. Its purpose is to facilitate the transmission of uncompressed video data and compressed or uncompressed digital audio data from a source device compliant with HDMI to a display device that is compatible, such as a monitor, projector, or TV.
Subsequently, HDMI has progressed through various iterations, each introducing fresh features and capabilities like higher resolutions, richer color depth, higher refresh rates, dynamic HDR, as well as enhanced audio functionalities like Audio Return Channel (ARC) and enhanced Audio Return Channel (eARC).
The advantage of using an HDMI cable is being able to send audio and video through one cable. This is quickly becoming the standard when it comes to source to sound device data transmission as it supports and uses the most advanced audio formats depending on the HDMI version.
Optical
Optical cables are also known as Toslink or SPDIF (Sony/Philips Digital Interface Format) cables. They are digital cables that use light pulses in binary to transmit sound signals through a thin fiber optic cable. Optical cables have a square plug with a small hole in the center..
Optical cables can support up to 2 channels of uncompressed PCM audio and up to 5.1 compressed audio using formats such as Dolby Digital, DTS, etc., but cannot support the latest ones such as Dolby TrueHD or DTS-HD Master Audio. This makes optical cables very limited in today’s climate, as more and more platforms and devices need the newer, more advanced audio formats. However, optical cables are still a viable option if you have a system that will not exceed the specs of cable.
Digital Coax
Digital Coax cables are designed for transmitting digital audio signals. They have a round plug with a center pin and a surrounding metal ring, similar to RCA cables. They send digital sound signals just like optical cables by sending it over a traditional wire rather than a fiber optic cable. However, this type of cable is able to transmit audio signals over longer distances than optical cables without significant signal degradation..
Digital Coax cables are similar to the optical cables in terms of capabilities as they can send up to 5.1 channels of audio using the SPDIF format. Therefore, we can draw the same conclusions as we did above with optical cables; that this type of cable is limited in today’s climate but will work well if you are within its capabilities.
Conversion Cables
When employing a cable that converts one type of connector to another, it is essential to consider that the overall signal quality will be limited by the lowest quality connector involved. For instance, if you intend to convert an RCA unbalanced input to an XLR balanced output, the resulting signal will only be as good as that of an RCA unbalanced input. It is crucial to recognize that the cable’s function is solely to facilitate the connection between connectors and does not possess the capability to alter or improve the signal itself.
What Cable to Use?
Choosing the right audio cable is a consideration when setting up your audio system. While price doesn’t always guarantee superior quality, it is essential to strike a balance between meeting your needs and staying within your budget. Opting for reasonably priced cables that offer decent quality can help you avoid overspending.
Understanding the requirements of your equipment and your room is key in making cable decisions. Different devices have varying inputs and outputs, and not all cables support the same audio formats. Therefore, it is crucial to ensure compatibility between your devices and the cables you choose.
It is important to note that the audio quality of your system is limited by the lowest quality component in the chain, and cables play a significant role in this. For instance, if your TV and AV Receiver can handle a 7.1 Dolby TrueHD signal, but you are using an optical cable to transmit the audio from the TV to the receiver, you will be limited to the 5.1 channel capability of the optical cable.
If you have any questions about how to wire up your home theater, feel free to leave a comment or book some time with us. See more about it here, or by clicking below.
Leave a Reply