In audio there is 3 camps : the audiophiles that believe in some fancy designs and this permits to hundred of manufacturers to advertise and sale average to bad products. The opposite camp is the electrician camp that believe only to Maxwell theories and others things that they learned when the were at University or Engineer School. They design and sell quite good electronics with 10€ cables etc... (see sometimes surprising discussions on some forums, all based on traditional mesures that mesured absolutely nothing interesting). The 3rd camp is audiophiles, musicians, engineers that listen, believe in what they heard and try sometimes to understand why this happens. I'm engineer, I was teacher in an high regarded French Engineers university in mechanical vibrations also in fondamental mechanics. During those years, we spend endless time to understand or begin to understand about phenomenons that are not completely related to theory or not enough detailed by theories.It all depends on what you call the signal. In audio cables the propagation speed of the free electrons, the things that carry the charge, is only about one meter per hour, whereas the electromagnetic wave that pushes the electrons travels at near lightspeed. furthermore, since these are AC circuits we‘re talking about, the net velocity of electrons is zero. The same goes for the electromagnetic wave.
When I see some crazy designs in cables, they are really trying to sale expensive cables that change the sound, not improve them. When I see reference DACs, Preamp, amplifiers with steel thin enclosures with absorbing feet, I am sure that it is from camp 2. Then there are few designers that designs in real world, with EMI ambiant, amplifier design with real speaker charge, and in dynamic situation. Their products are awesome.