RE:
My question -- at what point is a "system" too un-resolving for the cables to reveal a difference?
I am yet to hear a system that does not outperform most cables i.e. from a resolution perspective. In which case upgrading cables will most always result in sonic benefits. You just need the right cables
So here is what I have found about cable construction...
- Quality of the metal used in the wire i.e. UP-OCC copper or silver wire - this invariably helps with the speed and dynamics of a cable, whereas as OFC or a lesser grade will not perform to the same level
- the gauge of the wires used - for speaker cables, too thin and certain frequencies are impacted or in the case of power cables using a wire that is too thin can restrict dynamics
- Quality of the insulation i.e. Teflon, Foamed Teflon or Cotton - this reduces distortions created within in the cable. Better insulation improves clarity. The issue is the Dielectric Constant (Dk) of the insulation. Air is 1.1, cotton is 1.3, foamed teflon is 1.45 and Teflon is 2.2. The higher the valus the more disortions will be introduced in the cable
- Cable Geometry - this reduces distortions between the signal and neutral conductors and improves imaging. Also, if their capacitance is too high the cables becomes a filter and colours the sound e.g. a cable might sound bright.
Now also consider, there are two channels operating in an audio system i.e. two signals that must be perfectly "coordinated" in order to reproduce the recorded signal.
Anything less than perfect reproduction of those signals will impact the image, i.e. the size of the image, the position of the instruments within the image, how focused the artist appears, will be affected.
Also, when the two signals are not "perfectly aligned" then different instruments and voices can be "layered" on top of one another, which impacts clarity and details because those sounds all appear to come from the very same location and the signals become harder to distinguish, impacting clarity
Hearing the difference between most commercial grade cables can be a challenge, mainly because a great many of them adopt the same/similar geometry, so they inherit the same issues.
But once you hear very good cables you will understand more about what exactly to listen for.
As for the other question: will using a poor downstream cable impact using a good upstream cable - the answer to that is YES!
If you have a great interconnect that transfer the signal flawlessly, but your speaker cables introduces distortions in that signal, then your system will only sound as good as the speaker cables allow
So what’s the difference between cables?
Interconnects and speaker cables transmit the signal, so perfect transmission of that signal is the goal.
Whereas power cables conveys the current required by the attached component. Good power cables allow components to better handle the demand the component places on the power supply, in order to handle transient spikes in the signal it is processing, which improves dynamic performance, imaging and clarity. Also, if there is any noise in the cable then this can impact the neutral side of the component, which should be at ZERO volts. Noise on the neutral will impact the way the signal is processed/amplified and the overall sound is impacted.
In both cases, wire metallurgy, insulation, geometry present in really good cables, plays a key role in conveying the signal or power to the attached component without any noise.
Please note - this post is very much a summary of what is a very much more complicated topic
Hope that helps - Steve