Power cables for active speakers - do they matter?

[mhardy6647]

The magnetic core absorbs RF and they are usually in a metal case so not a great antenna either.
Unless your close to a powerful RF transmitter RF is not a problem for home audio.

Perhaps you've never encountered an AM (MW) ferrite rod antenna...

 

[Timcognito]

Perhaps you've never encountered an AM (MW) ferrite rod antenna...

When we remodeled our home (2005) our electrician used an AM radio to test the transformers in the low voltage light fixtures before the wallboard went up. I trick I've impressed a couple of friends* with.

*My standards are necessarily low.

 

[egellings]

Power cords are definitely directional, that's all I can say.

They are. The go from the outlet to the amplifier. Never the other way around.

 

[Speedskater]

So the last 6' of power cord eliminates all the RF picked up by the 300' of cable running to the transformer? Do cables look like antennas? Antennas act as antennas and cables act as cables, to do what there designed to do. Sure cables will pick up some RF but the levels are very low and easily dealt with with a RF filter on the device............

Well no!
To quote retired Audio Engineering Society interference expert:

Antenna Action The most fundamental cause of radio interference to other systems is the fact that
the wiring for those systems, both inside and outside the box, are antennas. We may call them
"patch cables" or "speaker cables" or "video cables" or "Ethernet cables," or printed circuit traces,
but Mother Nature knows that they are antennas! And Mother Nature always wins the argument.

More likely the cord is acting as a transmitting interference antenna of noise generated by the audio component.

 

[kyuu]

More likely the cord is acting as a transmitting interference antenna of noise generated by the audio component.

Hm, I thought that SMPS were typically the culprits for RF noise of any magnitude. And in any case, is the power cabling from the component to the wall where the RF radiation typically happens?

 

[ckernel8]

Hm, I thought that SMPS were typically the culprits for RF noise of any magnitude. And in any case, is the power cabling from the component to the wall where the RF radiation typically happens?

They used to be. Not really anymore.

 

[Timcognito]

Hm, I thought that SMPS were typically the culprits for RF noise of any magnitude. And in any case, is the power cabling from the component to the wall where the RF radiation typically happens?

I know from my work with medical devices where highly sensitive sensors can be affected. RF that we know travels through the air usually comes from a near by device not the power cord or in wall wiring. The irony is very robust med grade power cables that meet ISO standards for use in ICUs, Cath Labs and Surgical Suites are ubiquitous and can be had for less than $20. No need for a $200 one.

 

[HalSF]

My expectation was NOT to hear any difference

Seeing this point after reading the account in your OP post about devoting a fairly tremendous amount of time and effort to exploring the possibility of hearing consistently noticeable sonic differences caused by different power cables makes me seriously doubt this self-reported claim of firm skeptical disbelief. The plunge into the deep end of extensive subjective cable-swapping tests says much more about expectation bias and willingness to believe than any denial.

My hypothesis is that if the testing had been both blind and had included numerous steps where no change in cables had occurred and no listener was aware of this non-switching, obvious and noticeable changes would have been perceived in those cases as well. Even more stupendous and embarrassing results would be likely if the person running a blind test lied about swapping out cables, but used only one cable in all stages of the test, and participants discerned and reported differences anyway.

 

[DSJR]

I always was skeptical about influence of power cables on sound from well designed audio equipment. My EE education background also made me to believe that all things can be measured. Recently I attended a listening session where we - five members of local audiophile club, compared sound of several "high end audio" power cables. System where we tested them was what I would call mid-range audiophile class setup. All cables (with one exception) were from major brands which are usually advertised in audio related publications. We listened five tracks - each was selected by attending person. What surprised me was that I did hear the difference in sound in all of them. The fact that 4 out of 5 people explained what they heard exactly with the same words surprised me even more. This was not a dealer presentation, so there was no push to choose a specific cable. Actually Chinese knock off version of one of major brands purchased from Ali Express came second and most expensive cable came the dead last.

After that experience, I decided to do my own testing. I use active speakers - ATC SCM100A, where amplifier is located inside each speaker. ATC is a well respected brand and I honestly thought that I would not experience anything similar to what I heard at session described above where audiophile kind amplifiers were in play. Also unlike host of the session, I have a dedicated 30A power line from distribution box to my music room, which should reduce any power related differences even more.

I did not want to spend a lot of money: I needed two cables - one for each speaker. I also wanted to make sure that cable does not have something that may intentionally degrade its performance. Thus I decided to make cables myself from parts I could buy individually. From quick search I found wire and connectors made by Supra Cables - company in Sweden, which specializes on all kind of cable products. They advertise their power cables as the only "audio grade" ones which are UL listed to confirm their safety. I ordered 20 feet of Lorad mains wire plus 5-15P and C13 connectors made by the same company. I did assembly myself, which was rather easy and saved me $30 per cable in cost.

When I finished that assembly work late evening, I replaced my standard 15A rated cables used for ATC speakers before with this newly made ones. I did a quick listen and I felt that there was some difference, but I was not sure if this is a real thing or imagination. I did listen few tracks and went to sleep.

Next day I decided to test if what I hear is a real thing or not. I invited my wife, who does not really into audio hobby but did have some formal music education, to join me for a test session. I selected 5 tracks which I know relatively well, and which represent different kind of sound for this testing. I played track for 3 minutes, then swapped cables, played track again. Then played another track, swap cables again and repeat that tracks. This protocol reduced number of cable swaps and randomized experience a bit since same cable was used for two tracks without swapping.

Both me an my wife agreed that there was a difference between two cables. That difference was consistent throughout all tracks we played and we had the same words to explain what we heard: New cable made sound a bit more transparent, like the scene you see when you clear your glasses. Spacial details like reverb tails were better heard with new cables. This is not what I expected from ATC speakers, but that was real and confirmed by someone who has no stakes in that game.

Tell me: how to quantify that? This is a serious question.

You could have saved yourself a shed-load of time, money and effort, simply by clipping a ferrite on each existing mains cable... VERY cheap to buy and when I had these speakers, easily shown if 'bass tunes' are to be followed. My cables weren't long, 1m for one and 3m or so for the other I remember. Still got 'em too, stored away...

Where I lived back then, the mains seemed to vary a lot and if the perceived bass quality wasn't there, the rest just didn't 'sound' as good to me. yes, a subjective impression and no, I have no objective proof at all, especially as the mains seems so much better here. I still use ferrites everywhere on mains cables feeding our tellies, laptop power supplies and so on and every audio component I can. No idea if they make any difference, but they cost me little, I've used them for years and I'm happy

 

[solderdude]

(clamp-on) ferrites only increase the impedance of the entire cable for common mode signals and thus lowers emission or induced common mode (RF) signals.
They don't do anything for differential 'crap' on the mains.
If possible wrap the cable 2 to 3 times around the ferrite for better attenuation of common mode RF.

Mount them as close as possible to the device in question.

 

[Cbdb2]

Well no!
To quote retired Audio Engineering Society interference expert:

Antenna Action The most fundamental cause of radio interference to other systems is the fact that
the wiring for those systems, both inside and outside the box, are antennas. We may call them
"patch cables" or "speaker cables" or "video cables" or "Ethernet cables," or printed circuit traces,
but Mother Nature knows that they are antennas! And Mother Nature always wins the argument.

More likely the cord is acting as a transmitting interference antenna of noise generated by the audio component.

So a shielded cable picks up as much RF as an RF antenna? That was my point.

 

[Cbdb2]

Perhaps you've never encountered an AM (MW) ferrite rod antenna...

No I havent. And I took an EE antennas course back in the day. Looks likes a very specific design.

"primarily, a ferrite rod antenna is used to receive lower frequency signals between 50hz to 50khz."
"To work efficiently, the circuit must have a high Q at frequencies over which the antenna is going to operate.
If the frequency is at a few hundred kHz, a medium permeability material will be placed in the ferrite rod antenna that would help to maintain a Q value of 1000 approximately."
"In terms of performance & frequency response, it is compromised because of the losses in the ferrite core."
"It is designed with a rod or bar made of ferrites and includes a coil wound around the ferrite rod with the help of a variable tuning capacitor in the radio circuitry."

To be efficient the circuit needs high Q, to get that you need a capacitor. So an inductor would need a parallel cap (parasitic C is probabky to small for those low freqs.) to make the tuned circuit. And it would only pick up a very narrow range of low f RF. If this was a problem we would have heard about it.

And transformers have a closed magnetic circuit so I dont think this applies.

 

[Speedskater]

So a shielded cable picks up as much RF as an RF antenna? That was my point.

Well no.
In 1995 Neil Muncy (RIP) in his AES paper wrote that all shields should be attached to the metal chassis at their connector (or entry point).

 

[Speedskater]

Hm, I thought that SMPS were typically the culprits for RF noise of any magnitude.

In past decades yes. Back then printers and desk top PCs sometimes had shielded power cables or ferrite filters, so they could pass the interference tests.
Now days power cords seldom act as interference antennas.

 

[Avp1]

You could have saved yourself a shed-load of time, money and effort, simply by clipping a ferrite on each existing mains cable... VERY cheap to buy and when I had these speakers, easily shown if 'bass tunes' are to be followed. My cables weren't long, 1m for one and 3m or so for the other I remember. Still got 'em too, stored away...

Where I lived back then, the mains seemed to vary a lot and if the perceived bass quality wasn't there, the rest just didn't 'sound' as good to me. yes, a subjective impression and no, I have no objective proof at all, especially as the mains seems so much better here. I still use ferrites everywhere on mains cables feeding our tellies, laptop power supplies and so on and every audio component I can. No idea if they make any difference, but they cost me little, I've used them for years and I'm happy

When I made new cables which I wrote about above, I did add ferrite bead at each side, just in case. My listening was WITH these beads in place.

 

[olds1959special]

I almost had a heart attack when I realized the right power cord to my active speaker was half a foot longer than the left one.

 

[Rick63]

I almost had a heart attack when I realized the right power cord to my active speaker was half a foot longer than the left one.

Man, would that ever trigger my OCD! LOL.

 

[solderdude]

I almost had a heart attack when I realized the right power cord to my active speaker was half a foot longer than the left one.

Even when the power cables are very different in length then still they aren't that different in 'actual length'.
You see ... those power cords are in series with all the wiring in the house + wiring from the house to the street transformer.
This means that even when the last stretch by those power cords is substantially different in length they aren't in reality, they only differ a small percentage in total length to the actual power supply (mains transformer your house is connected to).

Now... if they were speaker cables and they were thin then cable length could matter.

 

[solderdude]

When I made new cables which I wrote about above, I did add ferrite bead at each side, just in case. My listening was WITH these beads in place.

As said .... ferrites can only lower common mode currents, they don't change (filter) anything on the mains.

A big-ass power transformer usually (depends on how it is build) usually conducts common mode crap or only attenuates it just a little.
Cables don't 'filter' any of it.
When you need filtering one should use an actual mains filter that has common mode and differential filtering.
Again... cables don't filter, also not when they are shielded.
And no... a little extra capacitance (even when it is double) don't 'filter' anything.
Shielding can lower emission and improve immunity for 'crap' present on mains when is is properly connected on both sides (so connected directly to chassis).

 

[olds1959special]

Even when the power cables are very different in length then still they aren't that different in 'actual length'.
You see ... those power cords are in series with all the wiring in the house + wiring from the house to the street transformer.
This means that even when the last stretch by those power cords is substantially different in length they aren't in reality, they only differ a small percentage in total length to the actual power supply (mains transformer your house is connected to).

Now... if they were speaker cables and they were thin then cable length could matter.

Ha! I was joking.