Audio data carried on speaker cables runs approximately 20 – 20,000 Hz. EMI and RFI noise has a very minimal effect at this frequency range. Hence, shielded and/or twisted speaker cables are not necessary unless they are running close to power lines or their length is greater than 50 feet.
Using the correct speaker interconnect is more important than a properly shielded cable. The smaller the contact resistance, the better. See the speaker interconnect section for more information.
The most important quality in a speaker cable is the gauge thickness. A large amount of current is transmitted over speaker wires, and a small gauge can clip the necessary amount of current needed to drive a speaker. The larger the gauge, the larger amount of current a cable can carry. Remember that larger gauge sizes have smaller numbers using the American Wire Gauge (AWG) standard
The amount of current required by a speaker is also determined by speaker impedance. A 4 Ohm speaker impedance will require double the current (or power) when compared to a 8 Ohm speaker. The table below shows what gauge thickness is required for specific speaker cable lengths.
|Speaker Cable Length||4 Ohm Impedence Minimum Size||8 Ohm Impedence Minimum Size|
|10 feet||18 AWG||20 AWG|
|20 feet||16 AWG||20 AWG|
|30 feet||14 AWG||18 AWG|
|40 feet||12 AWG||16 AWG|
|50 feet||12 AWG||14 AWG|
|100 feet||10 AWG||12 AWG|
|200 feet||--||10 AWG|
Maximum Cable Lengths
Video, audio, and data cables all lose signal strength as the cable length increases. Longer cable lengths cause signal degradation by:
- Having longer exposure to EMI radiation
- Increased signal absorption
- Increased chances of an impedance mismatch.
A set maximum cable length for each video, audio, and data signal is not available due to the many variables in a cable’s build quality. A cable with increased shielding and a higher gauge conductor will have less signal degradation than a cable with lower build quality. See the build quality section for more information on what to look for in longer cable lengths.
Besides build quality, the frequency of the signal is another factor in determining the maximum cable length. Lower frequency signals will have less degradation than higher frequency signals. This is why speaker cables running at 20 kHz do not need the same shielding as a HD video signal running at 30 MHz (1 MHz = 1000 kHz).
Coax and fiber optic cables are ideal when longer cable lengths are desired. Light is not affected by EMI radiation, which allow fiber optic cables to go for miles without loss. Coax cables are commonly seen connecting to our cable boxes. Coax can be in the RG-59 form factor or the higher quality RG-11 form factor. Adaptors can be used to convert video, audio, or data signals into coax or fiber optics.