The main and most important element is the inner core. Here you have to distinguish between massive cores and strands. Massive cores use one massive wire as a conductor, whereas the stranded version of the conductor consists of several thin strands and achieves a higher flexibility.
In general: the thinner the strands are the more flexible the cable will be. Flexibility is most important in mobile use of microphone-, instrument-, loudspeaker- and multicore cables. Besides that, you have to pay special attention to the conductor cross section in case of long cable runs.
The common rule is: The bigger the conductor cross section, the lower the conductor resistance and the better the transmission. This is of utmost importance in the microphone cable field and so cross sections of 0.20 mm² or even better 0.22 mm² are common. For long distances we even recommend 0.50 mm². These values have to be evaluated as the case arises and the usage has to be decided on accordingly. When using loudspeaker cables, special attention has to be given to the conductor cross section due to modern power amplifiers which generate power of 2,000 Watts at 8 ohms respectively 4,000 Watts at 4 ohms in the bass range. Here, maximum values of 180 volts at 40 amperes are reached, which have to be transmitted by the loudspeaker cables. Conductor cross sections which are too small lead to considerable loss of power and in the end possibly to cable failures. Where speakers are concerned, cables with two, four and eight poles in the range of 1.5 mm² to 8 mm² are available according to the system specifications.