Measurements of speaker cables in frequency and time domain

[pma]

Measurements of 6m zip-cord speaker cable in frequency and time domain

A controversial theme and I would like to contribute with facts only. I have made measurements on my 6m 2x4mm2 speaker cable and wanted to show the effect of the cable in isolation, however with the cable connected in the real audio chain as used in my listening room. The test schematics is as follows:

V1 is either a notebook with soundcard to generate sine sweep or an analog square generator GAG-810, depending on measurement of frequency response or square wave response. A and B are measuring points, A is behind the cable at speaker terminals and B is at amplifier output before the cable. R1 is a 47 ohm / 10W terminating resistor that I routinely use connected at speaker terminals. This resistor prevents from HF cable reflections and considerably reduces RFI induced voltage into the cable. SP1 is the CNO-T25 speaker built according to Troels Gravesen project

http://www.troelsgravesen.dk/CNO-T25.htm

The impedance plot looks like this:

X2 is my class AB 2x250W amplifier

https://www.audiosciencereview.com/...on-blameless-topology-and-measurements.21542/

1. Measuring cable effect on frequency response

This is IMO the most important measurement. The system is driven with a sine sweep and frequency responses at points A and B are measured. The ratio A/B is then plotted and it shows frequency response of the cable itself when loaded with the real speaker used. This is the result with my cable and speaker:

We may see the effect of finite resistance at low frequencies and the effect of cable inductance as a HF roll-off above 5kHz. Overall, the deviation is below 0.15 dB. V(A)/V(B) = Zsp/(Zsp + Zcab), Zsp is speaker complex impedance and Zcab is cable complex impedance.


2. Measuring cable effect on square wave transfer

The setup was driven by square waves with 1kHz and 10kHz repetition frequencies. Again, responses at points A and B were measured, with an oscilloscope with 10Mohm probe and the oscilloscope was supplied from 1:1 isolation transformer to eliminate measuring ground loops that would devalue the measurements.

This is the 1kHz square wave response at amplifier output, point B, before the speaker cable

This is the 1kHz square response at point A behind the speaker cable

This is the 10kHz square wave response at amplifier output, point B, before the speaker cable

This is the 10kHz square response at point A behind the speaker cable


Conclusion
We can see some modulation of frequency response due to the cable itself that is a result of ratio of cable complex impedance to speaker complex impedance, V(A)/V(B) = Zsp/(Zsp + Zcab), Zsp is speaker complex impedance and Zcab is cable complex impedance. This would be reduced if shorter cable was used.
In time domain, comparing square wave responses before and behind the cable we can see very small, almost negligible differences. I have to remind to the terminating 47 ohm resistor used. The result in time domain seems to be in contrast with observations described in

https://www.eetimes.com/loudspeakers-effects-of-amplifiers-and-cables-part-5/?page_number=2#

 

[MarkS]

"I have made measurements on my 6m 2x4mm2 speaker cable"

For Americans, a cross-sectional area of 4 square millimeters corresponds to AWG 11.18 (if I have done the math correctly).

https://en.wikipedia.org/wiki/American_wire_gauge

 

[jokan]

Interesting read, and you've done well to include a frequency sweep.
I am not being a critic or critiquing you and methodology but have you tried physically placing wooden blocks about 25mm cubed squares under your cables and tried remeasuring? An awful lot of interference comes from the floor of many buildings with hidden pipes and electrical wires under the floors. I noticed no zobel circuit on your circuit design, is that intentional if so that's ok and totally fine it doesn't change the data you have collected.

I use Nordost Speaker wires for my primary listening system. Why, they use the speed of light as a measurement, capacitance and inductance. As well as the FEP insulation and being a flat, evenly spaced wire. I also have vintage late 60's, early 70's 16 gauge Western Electric twisted speaker cable that is not soldered, or have ends on it, it is bare. Cotton/Wax, twisted pair wires. Highly sought after and next to impossible to find new old stock of. I have a 3m pair of them. They offer a very different sound. Solder alters the sound to such an extent that you need to cut off the area that has absorbed the solder. The original Tin coating is very thick and acts as 02 inhibitor, or rust inhibitor. The Nordost is clear sounding, fast and detailed. Very good match with digital sources and amplification. The Western Electric vintage wire is laid back, full and robust. Instruments have a better sense of size. I have many other speaker cables also. They all sound different. But what you've done is great. Evidence!

Please try using some wooden blocks to raise the speaker cables off the ground to see what if any effect that has. I see these wooden squares with notches cut out for speaker cable, and mains cable and haven't purchased or made my own because I've not seen anybody with measurements. I would assume that there would be an impact to the sound heard from the speakers. Almost everything changes the sound of speakers. Even room temperature does so...

Thanks for the tests, and the data. Well done! Please do try suspending the cables!

 

[DHT 845]

I used to have 1 feet speaker cables and in that short lenght there were no differences between cables, pure copper, tinned copper sounded equal. Now I use 3 feet cables and that gives also extremely small differences so I use cheap (under 1$/m) electric wires made of copper, 10 AWG. In my case there is no need for nordost, siltech or other expensive speaker wires (as far as Nordost concerned I use, among others custom made (on good XLR plugs) replicas of Odin Supreme Reference, 2 feet only, and like them very much). In my experience the shortest cables - the better. And speaker wires do not touch the floor I also try not to cross various cables (esp. with power cords) by using foam "spacers"...

 

[pma]

Interesting read, and you've done well to include a frequency sweep.
I am not being a critic or critiquing you and methodology but have you tried physically placing wooden blocks about 25mm cubed squares under your cables and tried remeasuring? An awful lot of interference comes from the floor of many buildings with hidden pipes and electrical wires under the floors. I noticed no zobel circuit on your circuit design, is that intentional if so that's ok and totally fine it doesn't change the data you have collected.

I will not comment on wooden blocks.

There is no Zobel, however there is a terminating resistor R1 (I hope you have seen it in the schematics) which is more effective than the Zobel against reflections and EMI coupled voltage into the cable.

If there was any interference or reflections, you would see it in the 10kHz square plots. They are clean, both before and behind the cable, so your suspect is incorrect. I will not bother anymore to communicate on wooden blocks and similar purely marketing aids. If you have any measured results, please go on and post it. With proper description of the test and calibrated X and Y axis of the plots.

 

[Ismapics]

Pardon my ignorance, why do you need to test this? Or maybe, is it better than the test that @amirm did? Why not KIS? It looks like a thorough and somewhat complex test for a subject that has been beaten to a pulp already,

We know that expensive cables don't make a difference. That any difference received its is all in our brains and that the only controversy about cables is created by the profits the brands make from gullible consumers.

 

[MarkS]

I found it interesting, and I have accepted that cables are irrelevant to sound since 1979 (and hence use 16 gauge zipcord for speaker cables).

 

[DHT 845]

I found it interesting, and I have accepted that cables are irrelevant to sound since 1979 (and hence use 16 gauge zipcord for speaker cables).

Have you tried 10 gauge belden or other inexpensive cables? 16 AWG is pretty thin, but if it works for you....

 

[MarkS]

I'm quite confident that I would not be able to hear a difference.

 

[FrantzM]

I'm quite confident that I would not be able to hear a difference.

+1
and allowing myself to edit your reply:

Science says: no Human on planet Earth is able to hear a difference ...

 

[LTig]

Interesting read, and you've done well to include a frequency sweep.
I am not being a critic or critiquing you and methodology but have you tried physically placing wooden blocks about 25mm cubed squares under your cables and tried remeasuring? An awful lot of interference comes from the floor of many buildings with hidden pipes and electrical wires under the floors. I noticed no zobel circuit on your circuit design, is that intentional if so that's ok and totally fine it doesn't change the data you have collected.

I use Nordost Speaker wires for my primary listening system. Why, they use the speed of light as a measurement, capacitance and inductance. As well as the FEP insulation and being a flat, evenly spaced wire. I also have vintage late 60's, early 70's 16 gauge Western Electric twisted speaker cable that is not soldered, or have ends on it, it is bare. Cotton/Wax, twisted pair wires. Highly sought after and next to impossible to find new old stock of. I have a 3m pair of them. They offer a very different sound. Solder alters the sound to such an extent that you need to cut off the area that has absorbed the solder. The original Tin coating is very thick and acts as 02 inhibitor, or rust inhibitor. The Nordost is clear sounding, fast and detailed. Very good match with digital sources and amplification. The Western Electric vintage wire is laid back, full and robust. Instruments have a better sense of size. I have many other speaker cables also. They all sound different. But what you've done is great. Evidence!

Please try using some wooden blocks to raise the speaker cables off the ground to see what if any effect that has. I see these wooden squares with notches cut out for speaker cable, and mains cable and haven't purchased or made my own because I've not seen anybody with measurements. I would assume that there would be an impact to the sound heard from the speakers. Almost everything changes the sound of speakers. Even room temperature does so...

Thanks for the tests, and the data. Well done! Please do try suspending the cables!

Are you the late Richard Feynman? Surely you're joking ...

 

[Beave]

Interesting read, and you've done well to include a frequency sweep.
I am not being a critic or critiquing you and methodology but have you tried physically placing wooden blocks about 25mm cubed squares under your cables and tried remeasuring? An awful lot of interference comes from the floor of many buildings with hidden pipes and electrical wires under the floors. I noticed no zobel circuit on your circuit design, is that intentional if so that's ok and totally fine it doesn't change the data you have collected.

I use Nordost Speaker wires for my primary listening system. Why, they use the speed of light as a measurement, capacitance and inductance. As well as the FEP insulation and being a flat, evenly spaced wire. I also have vintage late 60's, early 70's 16 gauge Western Electric twisted speaker cable that is not soldered, or have ends on it, it is bare. Cotton/Wax, twisted pair wires. Highly sought after and next to impossible to find new old stock of. I have a 3m pair of them. They offer a very different sound. Solder alters the sound to such an extent that you need to cut off the area that has absorbed the solder. The original Tin coating is very thick and acts as 02 inhibitor, or rust inhibitor. The Nordost is clear sounding, fast and detailed. Very good match with digital sources and amplification. The Western Electric vintage wire is laid back, full and robust. Instruments have a better sense of size. I have many other speaker cables also. They all sound different. But what you've done is great. Evidence!

Please try using some wooden blocks to raise the speaker cables off the ground to see what if any effect that has. I see these wooden squares with notches cut out for speaker cable, and mains cable and haven't purchased or made my own because I've not seen anybody with measurements. I would assume that there would be an impact to the sound heard from the speakers. Almost everything changes the sound of speakers. Even room temperature does so...

Thanks for the tests, and the data. Well done! Please do try suspending the cables!

Baahahahahahahahaha.

You're funny.

 

[MarkS]

I use Nordost Speaker wires for my primary listening system. … I also have vintage late 60's, early 70's 16 gauge Western Electric twisted speaker cable ... They offer a very different sound.

Here's an idea: lay out both of these, in position to connect up your speakers and amp. Have a friend hook up one or the other, in such a way that you cannot tell which by sight. Then listen, and decide which is hooked up. Repeat several times (the time between switches can be minutes or hours or days or weeks, whatever is convenient), with your friend flipping a coin to determine which cable to hook up. See how well you do at identifying the cable in use without being able to see which is which.

 

[pma]

More measurements

I have just measured the effect of 2 speaker cables on frequency response, with my speaker dummy load. The dummy load simulates behaviour of a 2-way closed box speaker. It should be understood that the effect of a speaker cable on frequency response depends on complex impedance of the speaker (load) as was explained, with formulas, in post #1.

This is the dummy load impedance

We can see that the impedance is capacitive at high frequencies and this will have interesting consequences.

Two speakers cables were tested:
1) a flat cable, length 2m
2) a zip-cord, cross section 2x1.5mm2, length 5m

The flat cable looks like this:

It has bigger distance between the wires (than a zip-cord) and this increases inductance and reduces capacitance of the cable.

Again, a voltage transfer ratio of voltages behind the cable / before the cable as a function of frequency was measured, which shows the frequency response of the cable in isolation, with the load used.

This is the result:

Please see the rise of frequency response above 5kHz due to capacitive character of the load at high frequencies. Also see the 0.2dB dip in zipcord FR at 150Hz due to high resistance of the 2x1.5mm2 zipcord with 5m length.

Conclusion
It is impossible to say that "cables make no difference". It is not true. The cables depending on length, construction and speaker used may make an audible difference, even if they are as short as 2m. 5m of 2x1.5mm2 zipcord makes 0.2dB deviation at higher bass, into quite standard speaker load. This starts to be audible. The speaker cable should be as short as possible and monoblocks placed near the speaker are the best option in case of passive speakers.

Edit: the zipcord used was 2x1.5mm2, length 5m.

 

[pma]

Measurement into 4ohm resistive load

Now I would like to show a measurement into 4ohm resistor load. The cable used was the zipcord 2x1.5mm2 of 5m length, same as in the previous post. The frequency response of this cable into 4ohm resistor is exactly as would be predicted, with high frequency roll-off due to cable inductance and resistive drop at lower frequencies. The technically oriented guys may easily calculate R and L of the cable based on 4ohm load knowledge. This measurements confirm that we need to know the speaker complex load to be able to speak about cable effects. And we also need to know cable R, L, (and C) parameters.

 

[BluesDaddy]

Have you tried 10 gauge belden or other inexpensive cables? 16 AWG is pretty thin, but if it works for you....

I wouldn't call 16 AWG "pretty thin" over any distance less than 25 feet.

 

[BluesDaddy]

More measurements


Conclusion
It is impossible to say that "cables make no difference". It is not true. The cables depending on length, construction and speaker used may make an audible difference, even if they are as short as 2m. 5m of 2x1.5mm2 zipcord makes 0.2dB deviation at higher bass, into quite standard speaker load. This starts to be audible. The speaker cable should be as short as possible and monoblocks placed near the speaker are the best option in case of passive speakers.

Edit: the zipcord used was 2x1.5mm2, length 5m.

I don't know that any knowledgeable person has ever claimed "cables make no difference". Generally there are many caveats, but that all things being equal, different cables won't "sound" differently. The "cables make no difference" assertion is a strawman subjectivists often trot. It's like driving amps to clip or distort in some way - sure, they certainly sound "different" then.

 

[DerRoland]

This resistor prevents from HF cable reflections and considerably reduces RFI induced voltage into the cable.

I have only low electronic skills, please can you explain why a resistor with 5 times higher value parallel to a loudspeaker can do any termination (4/5 of the electric power is going thru the speakercoil) ?

 

[Matias]

This is very interesting, thanks for sharing!
I wonder if you could do the same for different types of cables with the same termination and length, say a common 2m zip cable and some high-endish speaker cable, and measure their differences.

 

[preload]

Baahahahahahahahaha.

You're funny.

I was trying to figure out if he was serious or not. If he wasn’t then that was some very subtlely disguised satire.