The propagation velocity of signals in cables decreases significantly at low audio frequencies, specifically slowing down to 5EE6 m/sec at 20Hz, as noted in a paper from Belden cable company. This reduction in velocity is attributed to the increased characteristic impedance of cables at low frequencies, where the skin depth becomes comparable to the conductor thickness. Calculations indicate that at 20Hz, the phase shift through a 1-meter cable is approximately 1.44 degrees, which is minimal for typical interconnect lengths. The discussion emphasizes that while the velocity reduction is notable, the practical implications on audio performance may be negligible.
PREREQUISITESAudio engineers, cable manufacturers, and anyone involved in the design and optimization of audio transmission systems will benefit from this discussion.
Yes, you catch the idea. In worst case, velocity is proportional to square root of frequency, while phase advance is linearly proportional to frequency. Therefore, at very low frequencies phase advance and phase dispersion are not significant. You should watch out for phase dispersion at around transition frequency of cable though.yungman said:Also, more importantly, even if it is true the velocity slow down to 5EE6m/s and phase delay is 1.44deg/m for 20Hz. This is compare to a PERFECT situation where the velocity of propagation is the same as all frequency.
BUT, this is a cable comparison, meaning it is compare one cable to another, not comparing a cable to perfect condition. The question remains how much one can improve the velocity on the best cable material. Say, if the best of the best cable only improved to say 1deg/m, that improvement is so minor that it won't matter in all do respect.