THE "TRUTH" ABOUT DIFFERENT SPEAKER CABLES
Many well-known Hi-Fi amplifier and speaker companies have praised us for having finally cleared the fog that surrounds connecting cables, which are being sold at astronomical prices and that in their practical aspect work in the same way as common cables found in wiring rooms.
It is a known fact that when a Hi-Fi enthusiast has read extolled articles from an editorial office, referred to cables that improve exaggeratedly the characteristics of any amplifier, has been consequently so influenced that after he uses them truly believes there is an improvement in sound. We share with you some parts from a letter we received from an American Hi-Fi amplifier industry:
“If it were true that cables could be able to improve the characteristics of a Hi-Fi system, we would be the first ones to advise it in the instructions guide, but as the connection between the amplifier’s output and the speakers input can be made with any cable, being only necessary that the copper cable is the adequate to the amplifiers power, we do not take it into account”
As a consequence of our article, a French Hi-Fi speaker company has send us a 30 page technical summary of the tests made on a laboratory with all the cables available in the market (tests that we had already done by our own), where it is proven that there is no type of cable that can modify the amplifier or speaker’s characteristics. In this report we emphasize that even if very long connections are made (20-30 meters) with very thin wires, the maximum (signal) you can obtain is only a tiny decrease of the acoustic power, that can be easily compensated by moving 1 mm the volume control of the source.
Being able to convince a music lover so influenced by the intensive advertising, that cables do not improve the characteristics of one’s music system, is not an easy task.
Therefore we start saying that a cable that works on LF serves the only purpose of transferring AC. The AC’s highest frequency does not go beyond 25.000 Hz.
Cable inductance can have influence on the signal only if this one reaches a wavelength of 1/4.
The formula to calculate wavelength in meters, when knowing the frequency in Hz is:
meter = 300.000 : KHz
Therefore, the inductance of a cable has a notable influence over the signal, only if its wavelength is higher than:
300.000 : 25 = 12.000 meter
12.000 : 4 = 3.000 meter
Consequently, if we use a 3 Km cable to connect the amplifier’s output to the speaker’s input, the cable would have some influence, but if the maximum length does not go beyond a dozen meters and the frequency range goes between the minimum of 10 Hz to a maximum of 20.000 Hz, the LF signal transferred between an amplifier and the speakers is not altered.
People who sell this cables at astronomical prices somehow convince buyers that their cables work better that others, and as Hi-Fi enthusiasts are not always engineers or technicians, listing parameters such as inductance – capacity – resonance – screening effect – absorption – copper purity, etc. that as a matter of fact do not have any influence on sound fidelity have some influence on costumer’s opinions.
For this reason we give a very simple example.
If someone would tell you that changing the telephone’s cable for another cable that has golden wires would clear the sound disturbances, you would not believe it, because you know that if the amplifier from the head office sends sound disturbances or if your earphone distorts, there is no cable that can clear the signal.
Therefore you will be asking yourself why all Hi-Fi magazines that advertise this type of cables do not say the truth, but what is really happening is that even if this cables are better quality, in practice those differences cannot be perceived by us.
The crowd, compelled by that strong advertising, buys the product and forces themselves to believe they obtain a superior result to what they obtain with cheaper products.
In the same way the music lover acts when he reads advertising about connection cables between an amplifier and the speakers.
Many are so influenced that after they have spent astronomical numbers to buy those cables they totally believe their Hi-Fi system has improved.
*Fig 1: There are many different types of speaker cables, and as we will explain, none can improve sound quality, and therefore, if you use a standard cable that has an adequate section to the power, you will obtain the same results as with an expensive cable, spending less money.
To those who have claimed those improvements we have asked them: “What equipment have you used to confirm the difference between a normal cable and a super cable? What advantages have you found?”
The answer we have received has always been the same: “I have not used any equipment to measure it; however I have heard that the contrast between highs and mids has improved, the soundstage has expanded, there is no bass roll-off, etc.”
These descriptions emphasize what the advertising articles say, and it can be concluded that the music lover, not being able to demonstrate the differences, has been influenced.
To our fortune, the cable neither has any influence in the characteristics of a Hi-Fi amplifier nor on a speaker, and even less modifies the wavelength of a LF signal. If it were that way think about all the problems amplifier and speaker companies would have to face.
To establish the existing differences between one cable and another, ear cannot be used as it cannot detect subtle differences, hence complex equipment that a music lover does not have at his disposal is needed.
The International Electrotechnical Commission recommends to the technicians that do not have at their disposal those means, to test it in real time, because only with that method it is possible to capture those nuances.
*Fig 2. Proof, with the adequate equipment, that a common copper cable of 1 mm thickness has a signal attenuation is of 3 dB at 120.000 Hz, that is, in non audible human frequencies.
*Fig 3. Proof that the signal of a common cable of 3,5 mm thickness diminishes 3 dB at 200.000 Hz. The second “green” line on the graph represents the feathery effect.
*Fig 4. On a SUPER cable we have a sound attenuation of 3 dB at 1MHz that does not interest us,
because frequencies higher than 20.000 Hz are included in the ultrasonic spectrum which is not audible to humans.
For example, if you have two Hi-Fi amplifiers and you want to test with your hearing which one has a better tone, you cannot listen one first and later listen to the other one, because our memory is not capable of making a comparison to a sound heard before.
To test in real time two amplifiers the output signal has to be leveled, therefore as shown in Fig. 5 a relay is applied on the input that can toggle the pick-up signal or the CD signal in both amplifiers, and on the output a second relay is applied that toggles the signal on the same speaker.
The two excited relays in cyclic mode allow listening alternatively to the signal of the two amplifiers for approximately 1 second.
With this method our hearing is able to detect immediately if there is any tone difference or not.
This type of test is also applied to different cables, connecting two relays as seen on Fig. 6; or to check the performance of two different speakers (Fig. 7) and also to tune to the same frequency two music instruments.
For example, to tune a guitar a tuning fork (which is tuned at 440 Hz, LA) is used, then almost immediately the LA from the guitar is played and using the ear, the sound from the guitar cord is leveled.
Unfortunately, this comparison on real time is not always used with the customer.
The sales agent usually shows first one speaker and then another.
The buyer, not able to remember the tone of both speakers, thinks that one set of speakers is better than the other for reasons such as esthetics, price, etc…
On the laboratory, to tests the differences between two cables, two Cross-Over filters, or two ends, oscilloscopes – spectrum analyzers – distortion analyzers – wobbulated receivers – audio tracers, etc are used because only with this equipment it is possible to measure very tiny differences that human hearing, for its nature, cannot grasp.
*Fig. 5: Without having the necessary equipment, the difference between the tone
of two amplifiers can be determined by using a “real time test”,
by rapidly toggling the inputs and outputs with two relays or switches.
Relé = relay; Amplificador = amplifier; Altavoz = Speaker
*Fig. 6: The same system used to test two amplifiers can be used to test the
differences between a “normal” cable and a “super cable”.
An inadequate cable can only “reduce” the voltage slightly, not the shape of the wave.
Cavo = cable
*Fig. 7: The “real time” system comparison is frequently used to compare
the different performance of two speakers. Apart from the cables
having some influence, good speakers or efficient Cross-Over filters of 18 dB have to be chosen.
SPEAKER CABLES AND LF SIGNAL
Many manufacturers state on their advertising that their speaker cables have low inductance and capacitance and are made of plated or golden copper wires with little amount of oxygen. We will refute all those arguments later, but to start with it is timely to know how a copper wire operates when transferring from an amplifier’s output to a speaker’s input, a voltage that varies from 0 to 40 Volts, with a variable frequency from 15 to 20.000 Hz.
1. The electrons are not perceived if the material is copper or silver. What is perceived is only a variable ohmnic resistance. Because no cable has zero resistance, there will always be a voltage drop more or less pronounced. This voltage drop increases when the length of the cable increases and is inversely proportional to the copper’s wire section. Due to Hi-Fi systems cable requirements being usually less than 20 meter cables, even if an inadequate thickness of the cable is used, the maximum power does not lessen over a 1%. That means that from 100 Watts, 1 Watt will be lost, but our hearing will not be able to detect that ridiculous sonic decrease.
2. The frequency that travels through the cable and the signal’s wave shape does not suffer any variation, therefore, applying 15 Hz or 20.000 Hz on the input, at the end of that cable the same frequency will arrive. If it were not that way, the voltage of 220 volts - 50 sinusoidal Hz, that travels various hundreds of kilometers, would arrive with a frequency of 46-48-49 Hz in a triangular or quadratic way, when in reality always 50 perfect sinusoidal Hz arrives. The only difference we can observe is the voltage’s amplitude, which can change between 215-210 volts due to the cable’s length and thickness.
3. For frequencies lower than 30.000 Hz, the cable’s inductance and parasitic capacitance is only influenced when the distance between a speaker and the amplifier is 100-200 meters.
INFLUENCE OF THE COPPER’S DIAMETER
In this paragraph we will only cover the pure resistive load of the cable and the reactive components.
The cable connected to the speakers has to have an adequate thickness so that the required ampere can cover all the distance with the minimum voltage drop.
If we use a cable with a diameter slightly inferior to the required, the maximum voltage will travel the wire only when the amplifier is working at maximum power.
To calculate the voltage that travels through a copper cable based on the power (watts), the following formula can be used:
On Table N. 1 the maximum voltage is based on the power of the amplifier and the speaker’s impedance.
*Table N. 1: Salida = output. Amperios = Ampere (8 Ohm ampere and 4 Ohm ampere respectively)
Knowing the maximum number of ampere that has to travel through the cable, you can choose the diameter of the copper’s wire or their thickness expressed in mm2.
This piece of data, together with the ohmnic resistance per meter, can be obtained through Table N. 2
*Table N. 2: amperios máximos = maximum ampere; diámetro filo = edge’s diameter; seccione filo mm.q = edge’s section mm2; ohm x metro = ohm per meter
Subsequently we use an amplifier of 80 watts and we check theoretically how the output power of an 8 ohm charge varies, using the adequate diameter, a thinner one and a thicker one.
For a power of 80 Watts, the maximum current that travels through the wire is 3,16 ampere (see Table N. 1)
Using Table N. 2 with that information we discover that for that current, a 1,5 mm cable that offers a 0,010 ohm per meter is required.
If we use a 5 meter length cable to connect the speakers, we introduce the cable’s resistance “in series” to the charge, which in this case will be:
(5 + 5) x 0,010 ohm = 0,1 ohm
Note: Using a 5 meter cable we have a total of 10 meters of wire, because we have to take in account 5 meters forward signal and 5 meters backward signal.
If the cable had zero resistance, and these cables do not exist, the speaker would reach a voltage of:
Volts = Watts : Ampere
80 : 3,16 = 25,316 volts
Using a copper wire of 1,5 mm thickness on the wire clamps of the speaker, the voltage can be calculated with the following formula:
Vc = [Va : (Rc + Z)] x Z
Meaning of the acronyms:
Vc = Volts on the speaker’s wire clamps
Va = Voltage supplied by the amplifier
Rc = ohmnic resistance of the cable
Z = speaker’s impedance
Therefore, an 8 ohm speaker will reach with the maximum power a voltage of:
[25,316 : (0,1 + 8)] x 8 = 25 Volts
Knowing the voltage and the resistance of the charge (from the speaker) we can calculate the real voltage transferred to the speaker with the formula:
Watts = (Volts x Volts) : Z
(25 x 25) : 8 = 78,125 Watts
We will proceed to check the difference between using a cable with bigger diameter, that is 1,7 mm instead of 1,5 mm.
Looking at Table N. 2 we will know that this cable has an ohmnic resistance of 0,008 ohm per meter, therefore if we use a cable of two wires of 5 meters long, we will obtain a total ohmnic resistance of:
(5 + 5) x 0,008 = 0,08 ohm
This minor ohmnic resistance will make that the speakers will reach a voltage of:
[25,316 : (0,08 + 8)] x 8 = 25,06 volts
And with this voltage we will obtain a normal power of:
(25,06 x 25,06) : 8 = 78,5 watts
If we use a cable of smaller diameter, for example, 1,1 mm with an ohmnic resistance of 0,018 ohm per meter, and a cable of a constant 5 meter length, we will get a total ohmnic resistance of:
(5 + 5) x 0,0018 = 0,18 ohm
This higher ohmnic resistance will make that the voltage that reaches the speaker is:
[25,316 : (0,18 + 8)] x 8 = 24,758 volts
That is equivalent to a power of:
(24,748 x 24,758) : 8 = 76,619 watts
In practice, with a theoretical power of 80 watts, we obtain the following power:
Cable 1,7 mm = 78,500 watts
Cable 1,5 mm = 78,125 watts
Cable 1,1 mm = 76,619 watts
Even if using three different diameters there are existing differences, you have to bear in mind this values have been calculated for the maximum input power and for a cable’s length of 5 meters.
Any way, you must not be fooled by this numbers, because these differences are not audible.
In fact, our hearing can capture a very small power decrease only when it drops to -3 dB, and captures average power when this one drops to -6 dB. Consequently, if we use an acoustic power of 78,5 watts, our hearing will have the sensation that that power has been slightly reduced when it descends to 39 watts and that it has been reduced to its half, when in reality it has dropped to 19 watts.
*Fig. 8: The attenuation indicated in every example is always calculated for the MAXIMUM power,
but as the volume control is never at the maximum, if you do a comparison
between two different cables, you will observe that the sinusoidal amplitude
does not suffer any variation.
Osciloscopio = oscilloscope
Therefore, even if we use a cable of an inadequate diameter the only effect will be a tinny reduction on the maximum power that can be counterbalanced by turning up the volume.
We have to add that even if special cables sold at astronomical prices have their own ohmnic resistance and supposing that it is minimal, no one has explained the fact that the signals before reaching the speaker get through the Cross-Over filters, which have an ohmnic resistance superior to the 5-6 meters of cable used.
We advice to use a copper cable with a slightly bigger diameter (see Table n. 3) for different output powers, not to reduce the resistance that, as we will see, is enough to decrease only the parasitic inductance that could diminish the highest frequencies.
Table N. 3: ADVICED COPPER WIRE
The indicated diameters on this table are the minimum advised, therefore, if you have an amplifier of 50 watts and 8 ohm speakers you could perfectly use a cable with a diameter of 1,60 – 1,70 – 2,10, but not 1,40 – 1,30 mm. In other words, do not use smaller diameter cables than the ones advised here.
INDUCTANCE AND CABLE CAPACITANCE
Convincing music lovers that the connection cable may have negative influence in the acoustic performance of an amplifier, can be done by saying that the cable has a low inductance and a low capacitance, therefore the cable can be represented as a bandpass filter (see Fig. 9)
However, no one stops to think on the real influence of the inductance and capacitance of the LF signal.
The inductance of a cable made by two parallel wires varies when the diameter of the wire changes, and stands between a minimum of 0,3 microHenry per meter to a maximum of 0,8 microHenry per meter.
The inductance is higher if the diameter of the cable is small and lower if the diameter is big.
The capacitance of the cable varies when the thickness of the cable varies from a minimum of 90 pF per meter to 250 pF per meter.
The capacitance is higher if the cable’s diameter is bigger, and lower if it is smaller. The correct way to illustrate a cable is shown on Fig. 10. Regarding capacitance and inductance it is spread through all the cable’s length.
If we increase the length of the cable, either the inductance or capacitance will increase; if we shorten it either the inductance or capacitance will decrease.
As we will see in the following lines, from these two parameters, only the inductance, if it is very high, will lessen the frequencies between 15.000 Hz - 20.000 Hz, whilst the capacitance does not alter the bass, nor the mids nor highs.
Everything mentioned above is applied if the distance between the amplifier and the speaker does not exceed 10-12 meters length.
Time ago we read on a Hi-Fi magazine a sentence that puzzled us:
“To reduce the parasitic capacitance our advice is to separate the bass plate conductors”
*Fig. 9: To convince music lovers that the inductance and capacitance of a cable
has an influence on the filter transmission band the cable is illustrated in an incorrect way as a bandpass filter.
*Fig. 10: In practice, capacitance and inductance is spread through all the cable’s length,
therefore, when varying the length of the cable, either the capacitance
or the inductance changes. Using a very “thin” wire you will obtain high
inductance and low capacitance, using a very “thick” cable you will obtain low inductance and high capacitance
In practice it is true that moving two cables apart will cause a reduction in the parasitic capacitance, but who has given this advice does not know that the parasitic inductance increases greatly.
As an example, a cable with both wires close to each other represents, on a 10 meter length, a parasitic inductance of 7-8 microHenry, but if we separate them the parasitic inductance will increase over 40 microHenry.
For that reason our advice is to never separate the speaker cables, as you will be increasing remarkably the parasitic inductance.
Do not worry if the parasitic capacitance reaches 20.000 pF when the conductors are close together because, as we will see, this capacitance does not decrease any frequency.
Only some people like us have shown the fact that the parasitic inductance of a cable can vary from 0,3 to 0,8 microHenry per meter, and the parasitic capacitance from 90 to 250 picoFarads per meter.
Therefore if these two parameters change between cables there will be some variations on the transmission band.
As a matter of fact, these variations only affect the super-high frequencies, and as no human ear is capable of sensing ultrasonic frequencies higher than 20.000 Hz, the attenuation of frequencies such as 30.000, 40.000 or 100.000 Hz does not matter.
INDUCTANCE - CAPACITANCE - FREQUENCY
Even if everyone compares a cable to a bandpass filter (see Fig. 9), as the latter has a unique inductance and capacitance, to calculate its cutoff frequency the same formulas used with the bandpass filter of a Cross-Over cannot be utilized, instead, a different method has to be used, and the time when the output frequency starts to decrease in a voltage of 3dB has to be known.
To calculate the reactance, product of that parasitic capacitance and inductance, the latter have to be substituted by two resistances named as XL and XC (see Fig. 11).
The ohmnic value of XL (inductance) and XC (capacitance) can be obtained using the following formulas:
XL ohm = 0,00628 x (KHz x microH)
XC ohm = 159.200 x (KHz x nanoF)
*Fig. 11: The cable’s inductance works as a XL resistance set “in series” to the speaker’s input.
While the cable’s capacitance works as a XC resistance set “in parallel” to the speaker’s input.
If we use different cables, 10 meters long each cable, with different parasitic capacitance:
300 – 1.000 – 2.000 – 3.000 – 4.000 pF
And go to Table N. 4, their resistance, equivalent to different audio frequencies, will rarely decrease beyond 1.900 ohm.
Since this XC resistance has been applied in parallel to the 8 ohms of the speaker, even if we take a cable with high parasitic capacitance, as 4.000 picoFarads, in the lower and medium frequencies we will not face any power decrease, whilst on the highs the decrease will be:
0,2% in 10.000 Hz
0,3% in 15.000 Hz
0,4% in 20.000 Hz
As the parasitic capacitance is always lower than 4.000 pF, we can deduce that a power decrease between 0,2% and 0,4% in the higher frequencies is insignificant and not noticeable, thus cannot be considered.
Table N. 4: CONDENSANCE
*Table N. 4: Capacidad para 10 metros = capacitance for 10 meters; resistencia ohmnica capacitiva XC en distintas frecuencias = ohmnic capacitive resistance XC type for different frequencies.
The parasitic inductance, when connected in series to the 8 ohms of the speaker, can diminish the medium and higher frequencies, based on its value.
If we use different cables of a length of 10 meters with different parasitic inductance such as:
3 – 5 – 8 – 10 microHenry
And we check on Table N. 5 the relation between different audio frequencies and resistance, we will eventually find out that from a minimum of 0,001 ohms it can reach a maximum of 1,25 ohms.
Table N. 5: INDUCTIVE REACTANCE
*Table N. 5: Inductancia para 10 metros = inductance for 10 meters; resistencia ohmnica inductiva XL en distintas frecuencias = ohmnic inductive resistance XL type for different frequencies.
To calculate the voltage reached by a speaker when using different cables with diverse reactance, the lag (cos-phi) has to be taken into account.
The formula that will give us the speaker’s voltage is:
Vc = [Va / (SQRT (XL^2 + Z^2))] x Z
Vc = Volts in the speaker’s wire clamps.
Va = Volts in the speaker’s output.
XL^2 = Squared cable’s reactance.
Z^2 = Squared speaker’s impedance.
Z = Speaker’s impedance
SQRT = Square Root
*Fig. 12: Even if we buy the best speaker cable, this will always have its ohmnic resistance per meter, its capacitance and its inductance. Even if at the cable’s end the signal has been ridiculously diminished, that cannot be captured by the human ear, the LF signal, once it has reached the speaker’s input and before reaching the drivers, gets pass a Cross-Over filter, which has an ohmnic resistance notably superior to the cables resistance, with supplementary capacitance and inductance..
Now with a special cable, of elevated price, and a normal cable with a parasitic inductance of 0,8 microHenry per meter, we look for, in Table N. 5, its XL value in the frequencies 1.000 – 10.000 – 20.000 Hz for a length of 10 meters.
1 Khz 10 KHz 20 KHz cable 3 microH = 0.018 0.19 0.38 ohm cable 8microH = 0.050 0.50 1.00 ohm
To calculate the voltage with the indicated formula we have to square those numbers and we will obtain:
cable 3 microH = 0.000324 0.361 0.1444 cable 8microH = 0.0025 0.25 1.0
When we square the 8 ohm impedance of the speaker, we will obtain 8 x 8 = 64.
With this data we can calculate the voltage of the speaker’s wire clamps on the different frequencies, taking as reference the voltage of 25,316 volts, provided on the output by an amplifier of 80 watts in a charge of 8 ohms and with a cable of zero resistance.
Special cable = 3 microHenry in 10 meters
Frequency 1.000 Hz --> 25.316
Frequency 10.000 Hz --> 25.308
Frequency 20.000 Hz --> 25.287
Common cable = 8 microHenry in 10 meters
Frequency 1.000 Hz --> 25.315
Frequency 10.000 Hz --> 25.266
Frequency 20.000 Hz --> 25.120
Studying all this voltage values we can conclude that cables do not have influence on the characteristics of a Hi-Fi system, being the only difference between an expensive cable and a cheaper cable the power attenuation in super-high frequencies.
In bass and mids there is no power reduction and the form of the wave for bass – mids - highs will not suffer any change.
Knowing the speaker’s input voltages on the 1.000 – 10.000 – 20.000 Hz frequencies, we will try to obtain the maximum output power using the formula:
Watts = (volts x volts) : Z
On Table. 6 we can see the ridiculous differences.
*Table N. 6: cable especial = special cable; cable comun = common cable; diferencia = difference.
NOTE: The reader will think that as at 1.000 Hz the power is superior to 80 Watts there is a miscalculation, well, there is not a mistake. That difference appears because for the calculations of voltage and current we have only taken 3 decimals, not the totality.
Even if the calculations show that the common cable at 10.000 Hz attenuates 0,27 watts and at 20.000 Hz, 1,05 watts less than the special cables, our ears cannot hear any decrease in power because the 20.000 Hz are not audible.
If you want to confirm that our ear cannot capture the difference between 80 and 79 watts, connect and oscilloscope to the speaker’s input, then play a tone of 10.000 Hz and with the amplifier’s volume control turn up the volume till the person listening tells you that he has heard a little sound reduction, and also when he hears the reduction at mid power.
Supposing that the amplifier’s power is 80 watts, the one listening will perceive a tiny sound reduction when the signal’s amplitude is 25 volts closer to 20 volts (50 watts power), and medium sound power when the amplitude’s signal is approximately 13 volts (20 watts power).
*Fig. 13: When using a super-cable, you can observe that it will begin to diminish all the frequencies beyond 80.000 Hz, but as our ear can capture 20.000 Hz as its maximum, you will not hear any difference.
*Fig. 14: A speaker cable built with normal copper, as seen on Fig. 16, will begin to diminish all the frequencies beyond 60.000 Hz, therefore at low cost you will have an excellent speaker cable.
*Fig. 15: The cheapest two wire cable, with a lower diameter than the required one, will begin to diminish the frequencies beyond 18.000 Hz, being super-high frequencies that cannot be heard by some people.
For this reason the dB logarithmic scale is used (voltage and power measures expressed in dB).
When our ear captures a power decrease of approximately 1/4, the truth is that it has decreased around 2 times (3 dB), and when it has decreased 1/2, it has actually decreased around 4 times (6dB).
Therefore, an amplifier of 100 watts power that provides:
50 watts = our hearing will tell us the power has decreased 1/4
25 watts = our hearing will tell us the power has decreased 1/2
Many will think this information is lame, when observing that big difference in voltage, but we will remind you that that voltage is equivalent to sound power for our hearing, not for an oscilloscope.
In practice it would be similar to using ones hand to measure weight.
*Fig. 16: If you want to build the best speaker cables, with similar features as the most expensive cables,
you can buy a normal copper cable with 4 wires, joining in parallel two wires.
You can also use two plates from two common cables, “joining” them together with some tape every 10 centimeters.
If we place in your hand three identical boxes with different mass inside, one 500 grams, other 450 grams, and 550 grams, and we ask you to tell us which one is heavier you could answer that the heaviest is the one that weights 450 grams, or that all of them weight the same.
These little differences can only be measured by a balance or weighing scale.
We have seen that the parasitic capacitance of cable produces a ridiculous power decrease in the entire audio spectrum that can be easily solved (compensated) by turning up slightly the volume control.
The parasitic inductance, on the contrary, only diminishes the super-high frequencies.
To know in which frequencies the cable starts to attenuate the 3dB signal, some precise instrumentation which a music lover does not have is needed; however it can be calculated using the following formula:
KHz = Z : (0,00628 x microHenry)
Z indicates the speaker’s impedance in parallel to the XC reactance of the cable’s stray inductance; the microHenry represents the parasitic inductance of the cable, that as we know, vary with the length of the cables.
To simplify the calculations, we can use Z as unfavorable values, in other words, a cable with a parasitic capacitance so high that will decrease:
an impedance of 8 ohms to 7,5 ohms
an impedance of 4 ohms to 3,5 ohms
Now using the value of the stray inductance for a 10 meter length cable:
3 microHenry = 10 meters of special cable
5 microHenry = 10 meters of medium quality cable
8 microHenry = 10 meters of standard cable
10 microHenry = 10 meters of low quality cable
Using the formulas from above, we can calculate the cutoff frequency of 3dB for a load of 8 ohms:
7,5 (0,00628 x 3) = 398 kilohertz
7,5 (0,00628 x 5) = 238 kilohertz
7,5 (0,00628 x 8) = 149 kilohertz
7,5 (0,00628 x 10) = 119 kilohertz
As you can see the low quality cable starts to diminish the ultrasonic frequencies beyond 119 kilohertz, in other words, the non audible frequencies.
If the formula gave us an error of approximately 10%,bwould not decrease beyond 107 kilohertz.
We have used the most unfavorable conditions, that is a parasitic capacitance higher than 4.000 picoFarads, and a cable of 5+5 = 10 meters.
As on a Hi-Fi system, the speakers are at a closer distance than 5 meters, the attenuation is notably decreased.
There is only one condition where the audio frequency between 15.000 and 20.000 Hz can be diminished by the cable, and that is when a cable with two separated wires is used.
Using two separate wires, the parasitic inductance can exceed 40 microHenry, and increasing the XL we can easily reduce the high frequencies.
Even if in theory we get data that confirms that the parasitic capacitance has influence on a LF signal, using sophisticated precision equipment we can see that it does not have any negative influence on the audio frequency.
Only the parasitic inductance has influence in a ridiculous way on frequencies over 15.000 Hz and usually cannot be detected by the human ear.
Even if a lot of salesmen advice through an intensive advertising to use their cables with Hi-Fi equipment due to their low inductance or capacitance, on the tests made on a laboratory, any normal cable works as good as the expensive ones.
The “skin effect” creates a tiny reduction in the ohmnic resistance.
Columnists who worry about 0,0005 ohms but do not take into account cross-over filters with a noticeably higher resistance can be compared to saying that throwing a kilogram of salt to a river can be dangerous for the fish, when it is more dangerous the dumping of toxic substances.
Maybe all of them do not take into consideration the most influential thing in sound, which is not the cables but the cross-over filter, that could not have an adequate cutoff frequency and could change the signal’s phase, the speaker’s quality or the dimensions of the speakers.
If your speakers have ordinary cross-over filters you can use super cables, but you will not improve the defects of the cross-over filter or the speaker.
In other words, super cables do not have any marvelous property.
We have made the cable a test connecting the equipment to the wire clamps of a speaker’s input, instead of connecting them to a common speaker or a resistive charge of 8 ohms because the frequency response varies a lot with the charges inserted directly on the cross-over filters.
FOR THE SKEPTICAL
For the ones who are still totally convinced that the super-cables improve sound quality because they have a lower parasitic inductance than any other common cable, we will teach you how to build a low inductance cable using a common cable.
Buy at any electronics shop a copper cable formed by 4 wires with an adequate diameter for the amplifier’s power (see Table N. 3), then connect “in parallel” two conductors as seen on Fig. 16.
If you do not find a cable with 4 wires, you can buy two plates, then you connect them in parallel as seen of Fig. 16 and you keep the wires joined with some insulating tape every 10 cm.
This way you will obtain a cable with a stray inductance from a minimum of 0,25 microHenry per meter to a maximum of 0,4 microHenry per meter. These are very similar characteristics to the expensive speaker cable’s characteristics.
Translated by: J. Ramírez
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