Klipsch P-37F, P-39 RH, P-39F LH, F-20 User Manual

CABLE THEORY

Theory

Versus

Evidence

The following discussion is based on decades of evaluation experience. It is not the result of “ivory tower” isolation. Designing, whether

it be ampliers, speakers or cables, requires attention to all empirical data, whether derived from test equipment or from human eyes and ears. Solutions come from an open-minded acknowledgement of all

that is understood, and all that is not yet understood. Unfortunately, there is division in the audio/video community. At one extreme are those who only believe in their favorite measurements. At the opposite extreme are those who listen to or view a limited selection of

equipment and then develop pet theories that conform to their limited experience. A lack of a proper scientic approach often causes each

side to ridicule the beliefs of the other. The most effective audio and video designs come from those who take into account all the evidence, regardless of how measured or how well understood.

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Wire-Just Getting From Here To There

On the face of it, nothing could be easier than just getting an audio, video or digital signal from one place

to another-no amplication, no conversion of mechanical energy to electrical energy or vice versa. The

truth is, every cable must transfer a complex multi-octave signal without changing any of the information carried in that signal.

Damage Control

We all like to describe how a good component improves the performance of our system, a perfectly

legitimate comment. Unfortunately, buried in this statement is often the misunderstanding that the better component actually improved the signal in some way. There are certain areas of digital processing where this is possible, but in the analog world signals don’t get better, they only get worse. The substitution of a superior component improves a system only because it causes less damage.

Cables, like all components, should be chosen because they do the least damage. This “damage”

comes in two basic forms: a relatively benign loss of information, or a change to the character. A visual analogy might illustrate this distinction: consider “perfect” as a totally clear pane of glass. Since no component is perfect, the best we can strive for would be analogous to a pane of glass with a light gray

tint. Lower quality components would have a darker gray tint. These various densities of gray tint would

represent various amounts of lost information.

If the glass were tinted green or yellow or red, these colors would represent changes in character. We are

far more likely to notice, and be bothered by, a light colored tint than a denser gray tint. It is this mechanism of character versus quantity that causes much of the confusion in the pursuit of higher performance.

Chain Analogies, Synergy, Enhancement and Other Lies

We have all heard the truism that “a chain is only as strong as its weakest link.”Certainly this is true of a chain, but it becomes a misleading lie when applied to the world of audio and video. The quality of sound coming from your speakers and the quality of picture from your video monitor have both

been compromised by some degree of distortion in every component, starting with the microphone or

camera. No one actually believes that if you changed every piece of equipment except the proclaimed “weak link”-that there would not be any change in the sound or the picture. No matter how bad a CD player might be, no one would argue that you couldn’t hear the difference if you changed speakers. It is

worth noting that some components are more cost-effective to change than others, or that a particular

complaint will not be eliminated until a specic component has been changed. These truths might seem like an approximation of the chain analogy but the chain story has so much strength because it is an

absolute, and it absolutely doesn’t apply.

The logic of a good system is very simple: Every component matters!

The electronics, the speakers, the cables, even every solder joint, all cause damage. Each component is like one of the dirty panes of glass in this illustration. Each one blocks a bit of the view. The quality of the nal performance, or the clarity of the view, is the original signal minus

the damage done by all the pieces in-between. Improving any one of the components will improve the performance. Cleaning any one of the glass panes will allow a clearer view.

Recognizing that the challenge is to reduce negatives, to prevent distortion, makes it much easier to

understand “unexplainable” improvements. If the panes of glass are not only dirty, but also have a red tint, then as each pane is cleaned and the tint is eliminated, the “view” of the music will improve as expected. However, the red, and the awareness of the red, will not be eliminated until the last pane has been de-tinted.

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De-tinting this last pane will seem to make a bigger difference than de-tinting any of the previous panes.

We are naturally more impressed by the elimination of the red tint than by the previous reduction in the

tint’s density. If you didn’t want to hear trafc on the str eet, reducing the trafc from three cars per minute to none at all would be more impressive than reducing the ow from nine per minute to six. People are more sensitive to the presence of a phenomenon (the red or the cars) than to the quantity.

This type of surprise result, where we expected 1+1=2 and we think we got 1+1=3, is often called “syn-

ergy.” In truth, the “synergistic” aspect of this improvement would have been the same no matter which pane of glass happened to be the last one cleaned not much magic or synergy in that.

Sometimes we are faced with empirical data that we simply don’t understand. However, such a lack of

understanding doesn’t mean the phenomenon is magical or incomprehensible. A visual analogy might

be; just because something is too far away to see doesn’t mean that the distance in-between is innite. Our limitations might seem innite, but that doesn’t mean that a phenomenon we don’t understand takes place on the same scale. A more rigorous application of logic and scientic method might prevent all the

brouhaha we get about magical combinations.

Assembling or upgrading a system to cost-effectively maximize performance requires a broad perspective and a trustworthy evaluation methodology. Combined productively, these ingredients make the process predictable and enjoyable. (Please see “Evaluation Methodology” at the end of this booklet.)

The Challenge Of Speaker (High Current) Cable Design

While there are many physical, electrical and magnetic phenomena responsible for distortion in cables, there are really only a few basic mechanisms which account for the majority of the performance variations between cables. After considering the following information and evaluating even a small variety of

different cable types, you can acquire the ability to look at a cable’s design and know pretty well whether it deserves your further attention. Please don’t close your mind to new possibilities, just develop an educated skepticism.

Skin-Effect is one of the most fundamental problems in cables. It is useful to think of a metal conductor

as a rail-guide. Electric potential is transferred as current inside a metal conductor and as a magnetic

eld outside the conductor. One cannot exist without the other. The only place that both magnetic eld and current density are 100% is at the surface of a conductor. The magnetic eld outside a conductor

diminishes at distances away from the conductor, density is 100% only at the surface of the conduc-

tor. Something similar is true inside the conductor. Skin-effect means that current density diminishes at

distances away from the surface on the inside.

There is some disagreement as to whether skin-effect is relevant at audio frequencies. The argument concerns whether skin-effect causes damage other than simply power loss. Since the 3dB down point

(50% power loss) for a certain size strand might be at 50,000Hz, not everyone understands the mecha-

nism by which skin-effect is a problem at audio frequencies (20-20,000Hz). However, the problems are very real and very audible. This is because well before skin-effect causes a substantial power loss, it causes changes in resistance and inductance. Skin-effect causes different frequencies to encounter

different electrical values at different distances from the surface of a conductor.

If a single strand is too large, skin-effect will cause each frequency component of an audio signal to behave differently. Each frequency component will exhibit a unique current density prole. The result

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is that some of the delicate high frequency information, the upper harmonics, will be smeared. We hear sound that is dull, short on detail and has a at sound stage. The energy is there, the amplitude (frequency) response has not been changed, however the information content of the signal has been changed in a way that makes it sound as though the midrange notes have lost their upper harmonics.

There is a textbook equation which describes the reduction in current and power density at any depth from the surface of an electrical conductor. For copper the equation is: 6.61 divided by the square root of the frequency (Hz) equals the depth in mm at which the current density will be 1/e. Since 1/e is 37%, this equation tells us the depth at which the current density has been reduced by 63%. For 20,000Hz, current density is only 37% at a depth of 0.0467 mm, which is the center of a 0.934 mm (18 awg) conductor. Conventional use of the above formula falsely assumes that it is acceptable to have a 63% reduction in current ow and an 86% reduction in power density at the center of a conductor. However,

this formula does not by itself describe at what depth audible distortion begins. Listening (empirical evidence) shows that audible distortion begins at somewhat lesser depths.

There is a solution to skin-effect-using a single

strand of metal which is just small enough to push skin-effect induced audible distortion out of the audio range. Simple evaluation of multiple sizes re-

veals that audible skin-effect induced anomalies begin with a strand (or conductor) larger than 0.8 mm. A much smaller strand yields no benets but

encourages the problems discussed below.

A common misunderstanding of skin-effect results in the claim that “the bass goes down the fat strands

and the highs go down the little strands.” The surface of a fat strand is just as good a path as the surface of a thin strand, only the fat strands also have a core which conducts differently. In cables with fat

strands which are straight and little strands which take a longer route, the path of least resistance at higher frequencies is actually the surface of the fat strands. Since the lower frequencies are less subject to skin effect, they travel everywhere in all the strands.

Misunderstanding Resistance And Other Pitfalls

If a speaker cable used a single 0.8mm strand of copper, it would have too much resistance to do its job properly. Speaker sensitivity varies, but if the path between the speaker and amplier has too much resistance, the sound quality will suffer. Such degradation is not actually distortion in the cable, but is the result of using too small a cable. For this reason, even a short speaker cable should be at least 18 awg (.82 sq. mm) or larger.

Power loss due to resistance is not usually a signicant problem. If a very small cable were to cause a 10% power loss, the result would be like turning down the volume a fraction of one dB. If a signal

has been robbed of the information that allows you to perceive dynamic contrast, harmonic beauty and subtlety, we tend to refer to the loss as an “amplitude” loss. However, the signal sounds so dull and lifeless at the far end of a poor cable not because of lost power, but because of added distortion.

Unfortunately, the language of audio very often includes misleading terms. Many types of distortion are referred to as making the sound “bright” or “dull”, both of which imply a change in amplitude. “Bright” is

often used as a way of saying that harshness in the upper midrange has somewhat the same effect as

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turning up the treble. “Dull” is often thought of as turning the treble down, even though it is usually the result of distortions which obscure information. In most products, and certainly in cables, the amplitude

response (frequency response) is not the culprit.

Probably the biggest obstacle to predictably assembling a high performance audio or video system is too much thinking and not enough evaluating. It is tempting to follow some logical story as to why some key ingredient will make all the difference, when in fact, pursuing any one priority almost always means inadequate attention to dozens of other often more important concerns. Please be careful not to get

seduced by some common myths. Simplistic and ineffective solutions are often “sold” as cures for complicated problems. Dogma isn’t productive, results are what count. The best phono cartridges aren’t the

ones with the lowest tracking forces, S-video outputs are not necessarily better than composite, two way speakers are not necessarily better or worse than three way speakers, more powerful ampliers

are not etc. The most relevant fallacy in this discussion is the one about “the more strands, the bigger the cable, the better”.

Not Causing More Problems Than We Solve The Trouble With Strands: Since a good speaker cable needs to have more metal than a single 0.8mm (20 awg) strand, our challenge is to provide a larger electrical pathway without introducing new problems. If we take a group of strands and put them into a bundle, the entire bundle will suffer skin-effect. The strands on the outside present an ideal electrical

pathway, but the ones on the inside have different electrical values. This causes the same information to be distorted differently in different parts of the cable. The bigger the bundle of strands, the bigger the

problem. If resistance is to be lowered by using a bundle of strands, the bundle size must be kept small. Possibly several separate bundles will be needed.

There are many ways in which skin-effect

causes more distortion in a bundle than in a single over-sized strand. Strands are constantly changing positions over the length of a cable. Some leave the surface and go inside, others are “rising” to the surface. Since the current density distribution in a conductor cannot change, some of the current (particularly at

higher frequencies) must continually jump to a

new strand in order to stay at or near the surface. Unfortunately, the contact between strands is less than perfect. The point of contact between strands is actually a simple circuit that has capacitance,

inductance, diode rectication-a whole host of problems. This happens thousands of times in a cable,

and causes most of the hashy and gritty sound in many audio cables. This distortion mechanism is dynamic, extremely complex, and because of oxidation will become worse over time.

Magnetic Interaction is the other primary problem in cable design, both with a stranded conductor,

and between conductors. A strand carrying current is surrounded by a magnetic eld. In a bundle, each strand has its own magnetic eld. These magnetic elds interact dynamically as the signal in the

cable changes. On a microscopic level, a stranded cable is actually physically modulated by the cur-

rent going through the cable. The more powerful magnetic elds associated with the bass notes cause

the greatest magnetic interaction, which modulates the electrical characteristics of the cable, which in

turn modulates the higher frequencies. Because the music

signal modulates the contact pressure between adjacent strands, it also modulates the distortion caused by current jumping between strands.

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Reducing magnetic interaction is the primary reason speaker biwiring helps so much. Biwireable speakers have separate inputs for the bass and upper frequency ranges. These speakers simply allow separate access to the two halves of the “crossover”. A crossover is simply a low-pass lter which allows low frequency energy to pass to the woofer, and a high-pass lter which allows higher frequency current to pass to the tweeter, or midrange and tweeter. These lters block the undesired signal by causing the amplier to “see” an essentially innite impedance (resistance) at the frequencies which are to be blocked. Because there is no closed circuit at the blocked frequencies, current at these frequencies does not travel in the cable-just like a light bulb which does not light when the electric switch is turned

off, no matter how many megawatts are available.

Taking high frequency energy out of the cable feeding the bass does not signicantly affect bass performance. However, taking the bass energy out of the cable feeding the tweeter or midrange/tweeter causes a big improvement. The magnetic elds associated with the bass notes are mostly prevented from interacting with and distorting the elds associated with the higher frequencies. While the fundamental bass frequency is not affected, the

bass sounds better because the bass instrument’s harmonics are in the midrange. The harmonics dene the bass note and describe the instrument which created the note. Even if we could ensure absolute mechanical rigidity in a stranded cable, the interaction between magnetic

elds would still be a prime source of distortion. Current within a conductor is directly proportional to the magnetic eld outside the conductor. In most cables, the magnetic eld of any given strand encounters a complex and changing series of interactions as it travels through a constantly changing magnetic environment. As the magnetic eld

is modulated, the audio signal becomes confused and distorted.

Distortion due to both magnetic interaction and from bare strands touching can be dramatically reduced

by using Semi-Solid Concentric-Packing. In such a construction the strands are applied in a layer or layers spiraling around a central strand. Each layer is packed perfectly tight, exactly tting around the

strand or layer underneath. The strands in a given layer are uniform and never rise or fall to a different layer. This construction mimics many of the most important attributes of a solid conductor, while main-

taining most of the exibility of a stranded cable. The complete solution is solid conductors.

Magnetic interaction between conductors is also an area of major concern. This is discussed in the section following Material Quality.

Material Quality also dramatically affects the performance of cables and their terminations. By material quality we mean both the intrinsic quality of the metal, such as gold, nickel, brass, aluminum, copper or silver, and we mean the way the metal has been rened and processed. Pure silver is the very best per-

forming material for audio, video or digital. However, if silver is not carefully processed, even low grade copper will sound better. Silver has also earned a confused reputation because sometimes the term “silver” is used to describe silver-plated copper. When carrying an analog audio signal, silver-plated copper causes a very irritating sound, sort of a “tweeter in your face” effect. In a different application, such as video, RF or digital, good silver-plated copper becomes an extraordinary value, out-performing even the highest grades of pure copper.

Why no gold wire? Because gold has neither low distortion nor low resistance. Gold is used on connectors because it is a “noble” metal, it doesn’t corrode easily. Because gold is “noble” it is ideal for pro-

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tecting more vulnerable materials like copper and brass. The nature of gold’s distortion is mellow and pleasant, which makes it preferable to the irritating sonic signature of nickel. A bare copper or brass part will outperform a gold plated part, but only until the metal corrodes. In comparison, high quality thick silver plating actually improves performance. Silver is not noble like gold, but it does resist corrosion

and it enhances performance.

As for conducting materials, normal, high purity (tough pitch) copper has about 1500 grains in each foot (5000/m). The signal must cross the junctions between these grains 1500 times in order to travel through one foot of cable. These grain boundaries cause the same type of irritating distortion as current crossing from strand to strand.

The rst grade above normal high purity copper is called Oxygen-Free High-Conductivity (OFHC) copper. In fact, this copper is not Oxygen-Free, it should more properly be called Oxygen-Reduced. OFHC

is cast and drawn in a way that minimizes the oxygen content in the copper: approximately 40 PPM (parts per million) for OFHC compared to 235 PPM for normal copper. This drastically reduces the

formation of copper oxides within the copper, substantially reducing the distortion caused by the grain

boundaries. Additional improvement can be attributed to OFHC copper having longer grains (about 400

per foot), further reducing distortion. The sound of an OFHC copper cable is smoother, cleaner, and more dynamic than the same design made with standard high purity copper.

Not all OFHC is the same. If the poorest copper were given a value of one, and the best was a ten, then OFHC ranges from two to four-it is actually a range rather than a single performance level. Since

the most important audible attributes are due to the length of the grains, we use the name LGC (Long Grain Copper) to describe the very best OFHC.

The next higher grade is an elongated grain copper sometimes called “linear-crystal” (LC-OFC) or “mono-crystal”. These coppers have been carefully drawn in a process that results in only about 70 grains per foot. Cables using LC-OFC have an obvious audible advantage over cables using the same designs with

OFHC or LGC. From 1985 to 1987 several AudioQuest models benetted from this quality material.

In 1987 AudioQuest introduced FPC (Functionally Perfect Copper) in the higher models. FPC was

manufactured by a process called Ohno Continuous Casting (OCC).Through this process, the metal is very slowly cast as an almost perfect single crystal small diameter rod. This near-perfect rod is then carefully drawn to maximize grain length. However, OCC is a process, not a material. The metal (usu-

ally aluminum or copper), the purity, and the size of the cast rod all make a tremedous diference. FPC

copper was drawn from a smaller rod, causing less damage to the near perfect cast state, a single grain

was over 700 feet long. The audible benets were very obvious.

A couple of years later the “nines” race began. This refers to how many times the number “9” can be repeated when specifying a metal’s purity. In 1989 AudioQuest introduced FPC-6 in the highest models. FPC-6 had only 1% as many impurities as FPC. The prime contaminants in very high purity (99.997% pure, four nines) copper, like LGC and FPC, are silver, iron and sulfur, along with smaller amounts of antimony, aluminum and arsenic. FPC-6 was 99.99997% (six nines) pure with only 19 PPM of oxygen,

0.25 PPM of silver and fewer than 0.05 PPM of the other impurities. The improvement was dramatic. From 1989 to 1999, many of AudioQuest’s most famous models used FPC-6.

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As with OFHC and OCC, the nomenclature “six nines” or “eight nines” has almost no meaning. All else

being equal, higher purity is a straight forward benet. However, grain structure, softmess and surface nish can each make more difference than a “nine” or two. Then there is the matter of measurable purity. Due to contamination caused by the measuring process, there is a serious question as to whether any metal can be veried as having greater than six nines purity. Also, since “nines” became a selling point, some quite absurd and dubious claims have been made. Let the ears beware.

Once copper has been processed and rened to the Nth degree, the only improvement left is to go to a long-grain high-purity silver. AudioQuest FPS (Functionally Perfect Silver) is just such a superior

material. It was expensive, but the results were transparency, delicacy, dynamics and believability that

weren’t possible any other way... until PSC copper. FPS silver is still used to excellent effect in many CinemaQuest (from AudioQuest) wideband cable.

In the previous several paragraphs a number of important metallurgical concerns have been litsed,

such as purity, grain structure, softness and surface nish. Earlier in the discussion of skin-effect it was mentioned that the only place with 100% magnetic eld and current density is at the surface of a conductor. This means that the surface purity and smoothness does more to dene the sonic character, or hopefully lack of character, than any other part of a conductor. This is why AudioQuest’s recently introduced new range of metals are called “Perfect Surface.”

Perfect Surface Copper (PSC) is drawn and annealed though a novel proprietary integrated process

which creates an exceptionally soft copper conductor with an astonishingly smooth and uncontami-

nated surface. Ever since the beginning, AudioQuest cables have improved over time. Starting in 1987 with FPC copper, a foundation was created by four levels of superb conducting materials. On this foundation, renements such as SST continually provided further discrete improvements. With the introduction of PSC copper, a whole new foundation has been laid. For a price not much higher than FPC, PSC offers more natural and accurate performance than even FPS silver. AudioQuest’s CV-4 speaker cable is identical to Type 4 in every way, except for the use of PSC copper instead of LGC. Coral interconnect is identical to the previous Ruby and Quartz designs, except for using PSC instead of FPC (Ruby) and FPC-6 (Quartz).

Importance Of Overall Speaker Cable Geometry

We have been discussing problems within a single conductor, solid or stranded, regardless of polarity (+ or -). The relationship between conductors is also very important. If this relationship is not consistent, then the electrical parameters (such as capacitance and inductance) of the cable will be constantly changing and the signal will be distorted. Conductors can be parallel, spiraled (twisted), or braided.

These various geometries have certain inherent qualities. Parallel construction is inexpensive. Spirals have good RFI (radio frequency interference) rejection and usually lower inductance. Braids have good RFI rejection and low inductance, but suffer the consequences of a constantly changing electrical envi-

ronment for each conductor.

A cable may have two or more conductors. The arrangement of these conductors dictates the magnetic

interaction, the capacitance and the inductance of the cable. Both capacitance and inductance cause predictable and measurable ltering and progressively more phase shift at higher frequencies, though neither is a magic key leading to optimum performance. The effect of capacitance is somewhat like a

cliff, you can go near the edge as long as you don’t go over the edge. In a given application there is a value at which capacitance becomes a problem. At a lower value, away from the edge of the cliff, there

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is not much penalty. On the other hand, inductance is always a problem-a constantly accumulating problem. Capacitance and inductance are not the only important variables in cable design. However, it is productive to create cables whose capacitance doesn’t “go over the cliff” while also designing for minimum inductance.

One theory of cable design holds that the characteristic impedance of a cable should match the imped-

ance of the loudspeaker (When an antenna cable is referred to as 75 or 300, that is the characteristic

impedance). Impedance matching is a valid concept which only applies when the impedance of the source, the cable and the load are all the same, and when the cable is longer than the wavelengths

of the frequencies to be transmitted. Ampliers do not have 4 or 8 ohm output impedances, in fact amplier designers try to have as low an output impedance as possible. Speakers are all different and never have the same impedance at all audio frequencies. Since characteristic impedance equals the square root of the ratio of inductance to capacitance, very high (over the cliff) capacitance is a necessary corollary of a low characteristic impedance. Such high capacitance can severely affect amplier

performance and should be avoided.

Some of the rst generation of specialty speaker cables had a characteristic impedance of about 8.

These very high capacitance cables sounded better or worse because of their ability or inability to deal with the problems discussed earlier. However, many of these cables were accused of being extremely

bright and irritating. It was not the cables which were so bright, it was the sound of the amplier,which

had been encouraged into instability by the cables.

Such false conclusions could be avoided if products were judged on their merit and then methodically analyzed. Consumers, store buyers, and reviewers each need to discover what sounds good. Unfortunately the desire to understand “why” can cause more confusion than insight if not pursued empirically as well as theoretically.

The Challenge Of Interconnect (Low-Current) Cable Design

If you haven’t read the previous discussion of problems in speaker cables, then please read that rst. The following is meant to build

on that foundation. The same problems exist in both high-current

(speaker) and low-current (interconnect) applications. However, the

hierarchy among these problems differs.

In low-current cables; skin-effect, electrical interaction, magnetic interaction and conductor quality are still primary problems. The nega-

tive sonic effect of internal mechanical modulation due to magnetic

elds is greatly reduced.

The electrical behavior of the dielectric (insulating material) is much more important in low level cables. Dielectric involvement (the way in which a particular material absorbs and releases energy), has a

profound effect on an audio or video signal. Dielectric constant, the most often quoted specication for

insulating material, is actually not very helpful in understanding the audible attributes of different materi-

als. The coefcient of absorption value is more relevant, and the dissipation factor and the velocity of

propagation are even more useful.

The problem is that any insulating material next to a conductor acts like a capacitor which stores and

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