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Speaker Cable Face Off 1 - Measurements

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10ft-resistance.JPG
Figure 2: Resistance vs Frequency Comparison

Summary

Once again the Stealth Fine Ribbon Cable had the highest Resistance out of all the cables in this face off. Its resistance was nearly 11 times greater than the lowest resistive cable in this face off. Incidentally the lowest resistance cable was the Stealth Premier II, followed by a very close second, the less expensive Cobalt Cables.

Notice again how Rs begins to increase significantly above 50 KHz to 100 KHz (depending on the wire gauge) and increases linearly with increasing frequency. Originally we predicted a 34% increase is AC Resistance (Rac) at 20 KHz due to skin effect for 12AWG wire (see Skin Effect Relevance in Speaker Cables), but this was assuming solid core wire as explicitly stated in the article. I suspect that in reality, employing stranded un-insulated wire further reduces skin effect in the audio band to result in a negligible change of resistance at 20kHz and merely a (4.14 / 3.1) = 33.5% at 50kHz with respect to 100Hz, which is well beyond the audible range. Although this is not true Litz wire (individually insulated stranded wire), this may indicate subtle, but apparent benefits of un-insulated stranded wire over solid core wire of similar gauge. John Escallier suspects " It is possible that oxide and chloride formation between strands interfere with eddy current formation, producing less of a skin effect ". These conclusions must be considered, with repeatable and verifiable measurements and analysis between un-insulated stranded and solid core wires. However for now we will defer this overall issue to further research as it goes beyond the scope of this article. Perhaps a future article may also consider the effects of PVC jacketed stranded wire, and how aging affects skin depth, and therefore, inductance between solid and stranded wires of similar gauge, including tracking of parameters after aging of the cables in an oven and/or cryogenically freezing.

Note, the analysis used for skin effect in the previously mentioned article only applied to round conductors utilized in all of these cables except the Stealth Fine Ribbon. The flat ribbon cable employed in the Stealth Fine Ribbon utilizes a different Bessel function. However these calculations are beyond the scope of this article, and since there is no significantly measurable skin effect problem with these cables in the audio bandwidth, the exercise is mostly academic.

10ft-capacitance.JPG
Figure 3: Capacitance vs Frequency Comparison

Summary

The Stealth Fine Ribbon cables had the lowest measured capacitance out of all the cables in this face off. This was due to the conductor spacing of the cable.

Note: It is likely that the manufacturer choose to minimize capacitance at the expense of a dramatic increase in cable inductance.

All of the other cables in this face off had appreciably higher capacitance, which should not represent any real world problems of amplifier stability or frequency peaking for moderately long runs (50ft or so).

Frequency Response Comparison

The measured RLC parameters of all the cables in this face off comparison must now be analyzed in the frequency domain to determine if any appreciable resultant attenuation or peaking is likely to occur in a typical high fidelity audio system. Before doing so, we must make a few basic assumptions for consistency in our comparisons.

Assumptions:

  • Speaker Load (RL) = 4 ohms
  • Ls - use typical Ls measurement within audio band measurements from Table 1.
  • Cp - use worst case measurement within audio band measurements from Table 1.

Using an ideal source and resistive load, we will now analyze the following cables based on the RLC metrics in Table 2.

Table 2: Measured Cable Metrics Comparison (typical)

Metric

Original Monster Cable

Monster Cable Navajo

Sound King 12AWG

Cobalt Cable

10AWG

Stealth

Fine Ribbon

Stealth

Premier II

Ls

.200 uH/ft

.187 uH/ft

.203 uH/ft

.176 uH/ft

.348 uH/ft

.176 uH/ft

Cp

21.9 pF/ft

17.6 pF/ft

15.8 pF/ft

19.1 pF/ft

3.3 pF/ft

8.8 pF/ft

Rdc (rt)

3.35 mohms/ft

3.88 mohms/ft

3.27 mohms/ft

2.01 mohms/ft

12.5 mohms/ft

1.23 mohms/ft

pspice-10ft-jpg.JPG
Figure 4: Graphical Frequency Response Comparison of 10ft Cable Lengths

Table 3: Frequency Response Comparison of 10 ft cable lengths

Manufacturer / Model / Key

Insertion Loss
(dB)

Total Loss

@ 20 kHz (dB)

Group Delay Change

(100Hz to 20kHz)
(nsec)

Original Monster Cable (omc)

-.072

-.089

1.9

Monster Cable Navajo (mcn)

-.083

-.098

1.6

Sound King 12AWG (sk)

-.071

-.088

2.0

Cobalt Cable 10AWG (co)

-.043

-.057

1.3

Stealth Fine Ribbon (sfr)

Closely Spaced

-.267

-.316

9.4

Stealth Fine Ribbon (sfr-D)

Dangling

-.267

-.461

72.6

Stealth Premier II (sp2)

Closely Spaced

-.027

-.040

1.3

Stealth Premier II (sp2-D)

Dangling

-.027

-.081

10.5

Table 3 illustrates comparative insertion loss, total loss at 20 kHz, and associated change in group delay within the audio band for 10ft lengths of cables based on their measured RLC parameters all terminated into 4 ohm loads. The yellow highlights represent the best performing cables while the red highlights represent the worst. As we can see by the results, the Stealth Fine Ribbon cables performance was dependent on conductor spacing. As conductor spacing increased, its performance decreased. Given the short cable lengths in this comparison, it is unlikely any of these cables would yield audible degraded performance with perhaps the exception to the Stealth Fine Ribbon cables. The excessive attenuation characteristics of the Stealth Fine Ribbon cables may yield a perceivable softening of the highs resulting in a commonly referred by audiophiles "warm" sonic signature.

Table 4: Frequency Response Comparison of 50 ft cable lengths

Manufacturer / Model

Insertion Loss
(dB)

Total Loss

@ 20 kHz (dB)

Group Delay Change

(100Hz to 20kHz)
(nsec)

Original Monster Cable

-.356

-.741

199

Monster Cable Navajo

-.411

-.745

162

Sound King 12AWG

-.347

-.745

209

Cobalt Cable 10AWG

-.215

-.534

145

Stealth Fine Ribbon

Closely Spaced

-1.26

-2.18

687

Dangling

-1.26

-4.08

3550

Stealth Premier II

Closely Spaced

-.132

-.449

149

Dangling

-.132

-1.28

991

Table 4 illustrates comparative insertion loss, total loss at 20 kHz, and associated change in group delay within the audio band for 50ft lengths of cables based on their measured RLC parameters all terminated into 4 ohm loads. The yellow highlights represent the best performing cables while the red highlights represent the worst.

Note that at 20 kHz, a phase shift of 36 degrees represents 5 microseconds, this delay being considered as close to the limit of human directionality perception. The worst performing cable in this respect (Stealth Fine Ribbon) phase shifts within the audio band close or at the threshold of humany hearing. With the exception of the Stealth Fine Ribbon cables, it is unlikely any effects due purely to phase shifting within the audio band would be audible for any of these cables.

As we can see by the results, the Stealth Fine Ribbon cables performance was dependent on conductor spacing. As conductor spacing increased, its performance decreased. Given the long cable lengths in this comparison, it is highly likely that audible degraded performance would be perceived if the Stealth Fine Ribbon cables are utilized. The excessive attenuation characteristics of the Stealth Fine Ribbon cables may likely yield a perceivable and excessive softening of the highs not dissimilar to attenuating a high frequency tone control in an audio system. It is interesting to note that that 50ft of the Stealth Premier 2 (closely spaced conductors) and Cobalt cables performed similarly to 10ft of the Stealth Fine Ribbon cables when loosely dangling.

 

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