Solid state amplifier output stages become unstable due to capacitive reactance. The effects can be audible distortion caused by low level ringing up to the output devises overheating and in some cases destroyed.
To counter this all solid state power amplifiers have a Zobel network across the output stage to damp this oscillation; the conventional Zobel circuit consists of a series capacitor and resistor with values around 100nF and 10 Ohm. The capacitor begins to conduct as frequency rises and the 10 ohm resistor becomes the damping element shunting the circuit Q. With the variable capacitive reactance of the speaker load coupled to a length of speaker cable the Zobel circuit alone may not be enough. This is commonly solved by placing an inductor in series with the amplifier output downstream from the Zobel shunt circuit. The inductor value is set low enough to avoid high frequency roll-off in the audio range but high enough to provide the required damping at frequencies above that.
Amplifiers with a series inductor can use any type of speaker cable, however with a high inductance or excessive length of cable added to the amplifiers internal inductor it risks some roll-off at high frequencies.
Some manufacturers such as Naim do not have an internal inductor and choose instead to use only the speaker cable to provide inductance.