Cables from the perspective of measurements
An evaluation of cables, based on tests and measurements:
There are cables between the individual Hi-Fi components
and to the speakers even more so. Basically, the following rule always applies
to music reproduction: the dynamic range is very wide, so the contacts must have
perfectly electrically conductive transitions. This means: plug and screw
contacts must be metallically bright and fit tightly.
With cables before the power amplifiers it is therefore often super sufficient
to use products for the studio application.
There is another factor in loudspeaker cabling and that is bi-wire cabling. Here
the objective is that the back inductions of the low-mid speakers from their
membrane resonances in the tweeter should not influence the tweeter via the
electrical path, or that their influence should be minimized via the damping of
the amplifier. However, bi-wire is not a fundamental must. If bi-wire is used,
the following applies as a rule: for the bass you need a loudspeaker cable with
low resistance - i.e. a high cross section of well-conducting material (e.g.
2x4mm² OFC cable), for the tweeter a cable for small signals in a shielded
version is ideal for the optimal sound (e.g. microphone cable such as CMTOP 222
with inner conductors used together in a chamfer). Usually, the tweeter is
reduced in level by means of series resistors or voltage dividers. In addition,
the tweeter is "quiet" relative to the bass, i.e. the electrical voltages are
small and the AC voltage of details of the music is well below one millivolt.
This means that a loss of sound due to electrical interference is definitely
within the audible range, and shielded cables are an ideal solution.
In addition to this, there is the insight gained from comparing coils with
identical electrical values, but once wound from thick stranded wire and once
wound from 7 twisted (thin) strands. Measurements show that in the low and
mid-range the coils have identical electrical behaviour, in the high frequency
range the electrical properties change with the thick wire (show electrical
non-linear behaviour - the ohmic resistance increases with frequency), with the
other coil this effect cannot be measured. Acoustically the same effect can be
heard (in A-B comparison and only to a small extent), the overtones are
reproduced less cleanly with the coil with thick wire than with the comparison
coil. Occasionally you can find references to this topic in publications under
the term "skin effect". The conclusion is that coils with an effect in the high
frequencies, as well as longer cables (to and in the loudspeaker), should be
made of thin conductors (electrically insulated from each other) in order to
work in an ideal physical way.
These findings make it possible to understand why many loudspeaker cables rated
as good (regardless of their price) are made of many thin individual conductors
interwoven together. On the one hand there is the factor that with increasing
frequency thin single conductors (meaning electrically isolated from each other)
behave physically neutral and the multitude is necessary for the low resistance
required in the bass and the braiding has a shielding effect. The capacitive or
inductive effect of cables still plays a subordinate role here - this is my
state of knowledge.
According to my experiments, woven cables made of silver-plated copper leads can
be used as a reference for loudspeaker cables. Here, the silver layer on the
surface of the copper cores reduces the ohmic resistance without having to
increase the cross-sections. This is the technically ideal approximation to the
physical optimum.
