nor fully correct. lumped circuit theory doesn't only depend on the frequency but also the cable length. EM waves travel at around 0.6C in solids (copper). wavelength = V/f where V=0.6C, and frequency is say 20kHz, which is 9km. If you have an audio cable of hundreds of meters you would need impedance matching.
Rule of thumb for RF is that you can ignore impedance matching for <=1/10 WL. So for 20kHz you could ignore impedance matching if your cables are less than 900 meters long. How many audiophiles use cables 900m long? Or anyone else for that matter?
