[Puma Cat]

Here's what is going on from an systems engineering perspective: our stereo setups are a system that mediates a...transfer function, Y=f(x). Electrical signal energy (from the source) is amplified and ultimately tranposed into mechanical energy driving loudspeakers or headphones (in systems engineering, this is referred to as the "functional response")

The various components, including the source, amplification, are the control factors and "drive" the functional response heard by listening to the transducers, and their departure from "ideality" is due to...noise factors.

The cables in the system connect the various "energy sources" together, and the propogating signal is an EM wave, it is not a "flow of electrons" like water in hose or marbles in a tube. Source cables, e.g. digital cables, interconnects, etc, are susceptible to a whole class of noise factors. Just as one example, sources cable are susceptible to low- and high-source leakage impedance current, deterministic jitter, threshold jitter, phase noise, triboelectric noise, and longitudinal EM wave noise, as well as ground-plane noise.

Speaker cables are susceptible to current resonances and vibration imparted to the cable, and power cables are susceptible to noise from vibration, noise on the AC mains, and noise from the full-wave bridge rectifiers of the power supplies of the amplification components themselves (e.g. impulse noise, etc.)

All the cables tie the source, amplification, and transduction componentry together into a SYSTEM, as such, this system is susceptible to all these NOiSE factors combining together, and causing the transfer function to depart from IDEALITY, which results in the blur, slur, buzz, hash, grit, grain we all can hear. As well as the impact on transient response, neutrality, tonality, timbre, and dynamics.

Well-designed and engineered cables maximize their respective type of energy transfer (the control function) while miniminzing the impact of the all various noise factors that cause the control function to depart from its ideal functional response, add variance, or both.

So, from a system engineering perspective, that's why cables matter, because they are just as much a part of the system as the componenets themselves. Ultimately, at the end of the day, it always comes down to...PHYSICS.

Cheers.