A number of different types of cables have been used over the years for connecting speakers. These connections are usually specialised for particular types of equipment, such as CD players, MP3 players or television sets. In some cases, however, they may be specialised for high-end speaker systems. Often--though certainly not always--converters can be obtained to translate the signal from one type of connector to another.
Also known as stereo connectors, this type is most commonly used for small portable devices such as MP3 and CD players. It is also sometimes found on television sets and other devices. In most cases, headphone jacks are stereo, meaning they generate sound from both the left and right channels and have two rings on the plug. They measure 3.5 millimetres (mm) and offer connections for both the left and right plugs. Occasionally you find monophone headsets on which a single channel is used and connectors have only one ring.
5.1/6.1/7.1 Channel Connectors
Using the same 3.5mm connector as a standard headphone jack, 5.1, 6.1 and 7.1 channel systems all use a number of speakers designed to offer an experience similar to "surround sound." The connectors typically have only one ring, as opposed to the dual rings on headphone connectors.
Five-Way Binding Post
These kinds of connectors are commonly used in high-end speakers and receivers. They can accommodate five different styles of connections, hence the name.
Often paired with A/V (audio video, also known as RCA) cables, coaxial digital cables are commonly used for television sets and look similar to the RCA variety.
High-Definition Multimedia Interface (HDMI) is actually both an audio and a video connector. It is used for high-definition television signals and can also provide eight channels of audio content.
Mini Optical Jack
Similar in style to a standard headphone jack, this kind of connector is commonly used for MiniDisc players and recorders.
Toslink connectors are sometimes used for CD and DVD players. They are also found on some PC sound cards.
Similar in appearance to RCA cables, phono jacks were commonly used for record players, aka turntables that played vinyl records.
Speaker Wire and Spring Clips
This is actually two parts of the same kind of connection. Speaker wires are simply exposed edges of a wire with no connector. They go into a hole that has a kind of spring loaded clip to hold the wires in place. You typically push down on the clip and insert the wire, then release it. The clip then holds it in place. The hole is usually found in stereo systems and has an electric lead inside it to pick up the signal from the speaker wires.
Universal Serial Bus (USB) connectors are sometimes used as audio connectors for certain types of equipment, including headphone/microphone combinations and some high end PC speakers.
Commonly used for professional microphones, XLR connectors have three pins and are mostly used to connect to professional speaker systems.