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Speaker Cable Faceoff 2 - Empirical Audio and Goertz

By

Empirical Audio Clarity 7 Speaker Cables

DC Resistance: 3.1 mohms/ft
Characteristic Impedance: 11-ohms
3dB bandwidth: 1MHz

Frequency

Ls

Cp

100 Hz

.033 uH/ft

117 pF/ft

1 kHz

.034 uH/ft

118 pF/ft

10 kHz

.033 uH/ft

118 pF/ft

100 kHz

.031 uH/ft

117 pF/ft

Empirical Audio Marketing Literature Excerpts
Bare Wire Technology
Unlike other designs, Empirical Audio cables utilize Bare Wire Technology (BWT) . BWT is a result of ten years of developing methods to process and suspend bare wires. Bare wires significantly reduce signal dispersion (smearing). Signal dispersion is caused by the dielectric absorption of solid insulating materials that are used in conventional cables, such as Teflon or PVC. Dispersion can cause:

  • Haze and lack of image focus
  • Bloated bass, not "tight"
  • Not enough impact from kickdrum and Bass
  • Lack of soundstage width and depth
  • Poor dialogue and lyric intelligibility
  • Acoustics, particularly guitar, harp and mandolin just don't sound live

If your audio system is suffering from the above symptoms, Empirical Audio is your solution. Our cable designs combine optimized electrical characteristics with BWT and smart metallurgy to bring you dynamics, inner detail and soundstaging beyond anything you have experienced.

Pursuing the Truth…
Of course most of these claims are purely subjective and cannot be backed up or verified, nor is it likely that the manufacturer can furnish any peer reviewed repeatable or measurable proofs to validate this. However, unlike many other exotic cable vendors, Empirical Audio at least makes an attempt to measure and simulate the benefits of their cables over ordinary 11 AWG Zip Cord. Of course, most of the illustrated benefits are either not based on the limitations of human hearing and resolution of audio equipment (particularly loudspeakers and the rooms they interact with), or taken out of context.

Their analysis starts out comparing bandwidth of 16 feet of 11AWG Zip Cord to the Clarity 7. They show that the 11AWG Zip Cord has a 3dB point of around 238kHz (over ten times past the limits of human hearing!) while the Clarity 7 has a 3dB point of 1MHz. Not sure what the advantage here is, especially when we have already proven in the original Speaker Cable Face Off that a 10 foot length of 12AWG Zip Cord is less than 0.1dB down at 20kHz into a 4 ohm load. In reality, most speakers have higher impedance at high frequencies due to increased tweeter inductance making this loss nearly vanish beyond measurable, let alone audible, limits. In addition, 11AWG wire has lower resistance and inductance and will likely attribute to even less losses. If anyone tells you that a normal human can discern a 0.1dB attenuation or associated phase change at 20kHz, beware - they may also have invaluable information on purchasing some Enron stock as well.

The manufacturer also fails to mention the inclusion of brickwall filters in digital playback devices limit frequency response extension past 20kHz to nothingness. In addition, no loudspeaker has any reasonable controlled dispersion past 20-30kHz, not to mention the limit of audibility for most non super humans is about 20kHz (again human brickwall filter). The 10kHz time domain measurements that Empirical Audio uses sells an interesting story. They tout that their cable introduces less high frequency noise because it is more damped. Yes this may be true, but again at frequencies decades past human audibility. If one wanted to achieve this with Zip Cord, it is an easy task with the addition of a Zobel termination RC network at the speaker end (see Figure 1 & 9). As we have seen in our simulations, this also restores the 10kHz square wave response to match the Clarity 7. Next Empirical Audio illustrates their cables have better phase response then 11AWG Zip Cord. They compare a 5 degree phase (or 694 nsec) shift at 20kHz to a 1.3 degree phase shift (or 181 nsec) to their Clarity 7 and imply that this is actually audible. 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. In addition, a slight turn of ones head or back and forth movement would yield a far greater change in phase than what a piece of speaker wire will ever do. More information on phase comparisons of the Clarity 7 vs the others in this review will be presented in the Analytical section of this article.

Empirical Audio illustrates the Clarity 7 cable as having a more damped resonance signature than normal Zip Cord. Again frequencies well beyond the unity gain crossing of most audio amplifiers and decades past the human hearing range and something again that can be resolved if need be by a simple insertion of a Zobel Network (see Figure 1 & 9) at the speaker side of the audio cable.

Rather than re-inventing the wheel, I have asked Rod Elliot permission to reprint an excerpt from his article about Zobel compensation and cable characteristic impedance, particularly on his analysis of 12AWG Zip Cord and the Goertz MI-2 Veracity cables featured in this review.

Excerpt from Rod Elliot Article on Loudspeaker Cable Characteristic Impedance
http://sound.westhost.com/cable-z.htm

3.2 12 Gauge "Zip" Cable

This seems to be the standard against which all other cables are judged, so it is next on the list. As you can see, there is a pronounced reflection at almost exactly the same frequency as before. This must be, since the cable (transmission line) is the same length, and the first reflection will occur at the same frequency. Small variations do occur, and are the result of differing velocity factors. Velocity factor refers to the speed at which an electrical signal passes through a cable. Typically, this is between 0.6 and 0.8 of the speed of light (3 x 10 8 metres per second.)

clip_image006_000.jpg
Figure 8 - 12 AWG Zip Cord, No Termination at Speaker Load

The response is relatively benign, despite the quite large peak at 10MHz. The reflection spike causes no change to the amplifier's phase response until it is above 40MHz and will have no effect. There is a very slight reduction of level at 100kHz (and down to 20kHz), but this is measured in fractions of a dB, so can safely be ignored. A greater disturbance to the in-room response will be experienced by moving the listening chair or a nearby coffee table.

clip_image008.jpg
Figure 9 - 12 AWG Zip Cord, Far End Terminated (100 ohms)

This is a perfect result. There are no spikes, no response anomalies, and the amp's phase margin is unchanged. For the cost of a 100 ohm resistor (close enough) and a 100nF ceramic capacitor, the cable is nicely terminated, and although virtually any amplifier will drive this cable with no ill effects even when unterminated, there is the potential to reduce RF pickup.

Another issue I have with Emperical Audio is their view on Skin Effect Relevance in speaker cables at audio frequencies.

Excerpt from Emperical Audio White Paper:

The effect is that the impedance (primarily inductance and capacitance) is different for low frequencies than high frequencies. This difference in impedance can cause attenuation and phase shifts in high-frequency passages relative to low-frequency passages, causing a smearing effect to the music. If a sufficiently small gauge is chosen for the conductors, all frequencies are "forced" to flow more uniformly in the conductors, effective eliminating skin-effect. Skin-effect is also a function of conductor material.

Pursuing the Truth
Many of the statements here are simply unfounded, at least by any objective provable science. Skin effect will not cause any measurable let alone audible phase shifts in audio frequencies for conventional speaker cables. In fact, we have already proven that Skin Effect will cause a slight decrease in inductance (minimization of internal inductance) with increasing frequency and an increase in AC resistance. However, this doesn't become significant until almost a decade past human hearing capabilities.

To further this point, let's take a look at the AC resistance of the Empirical Audio Clarity 7 and compare it to Zip Cord (which according to Empirical Audio suffers from problems with Skin Effect).

clip_image010_000.gif

Right off the bat it is obvious of that the 10AWG Zip Cord from AV Cable has lower DC resistance which is a significant advantage in long cable runs or terminations into low impedance speaker loads. What is interesting is both cables have about the same breaking point (about 100kHz) where skin effect causes a noticeable rise in AC resistance. As you can see the Empirical Audio cable has no advantage of resolving skin effect when compared to ordinary Zip cord and is in fact at a disadvantage with one of the primary concerns with speaker cables - DC resistance. The Clarity 7 is about on par with respect to DC and AC resistance as the much less expensive Axiom Audio cables.

In all fairness to Emperical Audio, much of their PSPICE analysis about cables is valid, though in my opinion, mostly inconsequential at audio frequencies for typical cable lengths that most consumers deal with. I found their established criteria on their website for defining maximum cable lengths for speaker wire and interconnects to be somewhat useful as well as their placement tips for loudspeakers. Most of the claims they make are based on opinion as seen in their verbiage in the above example with "can" as well the following example below:

Another possible benefit of biwiring is that the cable natural resonances will change and the reflections and standing waves seen by the amplifier may be reduced.

Goertz MI-2 Veracity

  • clip_image012.jpg High Purity
  • Oxygen Free Copper
  • .750 x .010"
  • 10 AWG 0.0022 ohms/ft
  • 0.95nF/ft
  • 6nH/ft
  • ~ 2.5 ohms Teflon/ Polyester Terepthalate/
  • Polycarbonate
  • 0.8 x 0.04"

Click Here for Detailed Pricing

10ft pair with Banana Plugs: $255

The Goertz cables stand out as a unique design in this face off. What makes them "different" is their geometry. Instead of a classic round conductor stranded or solid variant, they are a flat rectangular design. The advantage to this design is extremely low inductance due to the close proximity of the conductors. However, there is a price - ultra high capacitance. So high, in fact, that as the cable length increases, stability problems can arise, especially for esoteric tube amp designs with higher output impedance and lower unity gain crossing. It is possible for high capacitive loads of a cable to cause two related effects due to loss of the power amp gain and phase margin. Firstly, in the frequency domain, very significant gain peaking can occur. Secondly, in the time domain, the step response may have a much higher overshoot, and exhibit excessive ringing (at about the unity gain frequency) due to loss of power amp phase margin. However Goertz attempts to mitigate this problem by terminating the cable at the speaker side with a Zobel network. Their Zobel uses two 5.1 ohm resistors in series with a 0.1uF capacitor.

 

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