Headphone Cable Measurements Wrap-Up

Tyll Hertsens's picture

A Tangled Mess
I've spent the last couple of weeks listening to various cables on my Sennheiser HD 600, and while I think I've noticed some differences between the cables, I'm certain I wouldn't be able to tell them apart in blind tests. Well...I might be able to pick out the stock HD 600 cable from the others---it sounded just a bit confused---but otherwise, the differences I think I might have heard are too small to reliably identify.

To put a finer point on the sonic characteristics I heard, it sometimes seemed that certain instruments or sounds in the mix were slightly more obvious on some cables than others. Sometimes I'd hear the high-hat more clearly with one particular cable, sometimes I'd hear the vocals a bit more forward or back, but the cables wouldn't act the same way with different music, and it seemed the harder I listened for the effect, the more it would disappear. (Sort of like when you stare at an image without moving your eyes for long enough and the image starts to disappear.)

I've also spent quite a bit of time reading about people's experiences with cables. Not just anybody though, people for whom I've got a great deal of respect. I found a good deal of commonality in their opinion: Cables may make a small difference in some cases, but for the most part it's the last thing you should worry about.

It seems the most common reason cables made marked differences when installed was when there was something wrong with the stock cable. Maybe it had become intermittent over time, or oxidation had corroded the connectors, but replacing the cable made the headphones usable again.

Of course, there were also many comments ranging away from this middle ground, but it always seemed to me that confirmation bias was playing a big role in the opinion. Either the listener was wowed by the huge changes made, or was ever more convinced that cables made no difference at all. No doubt a self-fulfilling prophecy in most cases.

Untangling the Issue
Still, I remain convinced that there are good reasons to purchase aftermarket cables. For starters, I'm certain I've heard differences, and after reading and talking to some trusted sources, it appears they too have all experienced small differences in the sound of cables. There's just too much anecdotal evidence to believe anything other than sometimes something is happening with cable swaps that is apparent to the listener. Additionally, most have a hard time expressing exactly what they're perceiving. It doesn't seem like it's as simple as tonal changes that might be seen in frequency response measurements.

I'd like to caution objectivists to understand that there are a lot of things that could account for a small audible difference that doesn't show up as a change in frequency response. For example, back in the early days of the CD, "perfect sound forever" was the rallying cry. Objectivists claimed CD players should be indistinguishable, but subjectivists heard differences. Later, the discovery of jitter timing errors would clarify the source of the differences heard. Objectivists should always bear in mind that you don't know what you don't know, and skepticism should target both subjective experience and objective evaluation.

I'd like to point out this recently published scientific paper, "Human Time-Frequency Acuity Beats the Fourier Uncertainty Principle." The paper's abstract states:

The time-frequency uncertainty principle states that the product of the temporal and frequency extents of a signal cannot be smaller than 1=(4pi). We study human ability to simultaneously judge the frequency and the timing of a sound. Our subjects often exceeded the uncertainty limit, sometimes by more than tenfold, mostly through remarkable timing acuity. Our results establish a lower bound for the nonlinearity and complexity of the algorithms employed by our brains in parsing transient sounds, rule out simple "linear filter" models of early auditory processing, and highlight timing acuity as a central feature in auditory object processing.

While I'm not capable of delving into the fine details of this paper, the gist of it is readily apparent: Our listening system is far more complex than we're currently able to understand, and is much more focused on the time-domain than previously thought. Here's an excerpt:

Early last century a number of auditory phenomena, such as residue pitch and missing fundamentals, started to indicate that the traditional view of the hearing process as a form of spectral analysis had to be revised. In 1951, Licklider [25] set the foundation for the temporal theories of pitch perception, in which the detailed pattern of action potentials in the auditory nerve is used [26, 28], as opposed to spectral or place theories, in which the overall amplitude of the activity pattern is evaluated without detailed access to phase information. The groundbreaking work of Ronken [22] and Moore [23] found violations of uncertainty-like products and argued for them to be evidence in favor of temporal models. However this line of work was hampered fourfold, by lack of the formal foundation in time-frequency distributions we have today, by concentrating on frequency discrimination alone, by technical difficulties in the generation of the stimuli, and not the least by lack of understanding of cochlear dynamics, since the active cochlear processes had not yet been discovered. Perhaps because of these reasons this groundbreaking work did not percolate into the community at large, and as a result most sound analysis and processing tools today continue to use models based on spectral theories. We believe it is time to revisit this issue.

Additionally, training and expertise in the art of listening has an effect on our hearing acuity. From the paper:

We further found that composers and conductors achieved the best results in task 5, consistently beating the uncertainty principle by factors of 2 or more, whereas performers were more likely to beat it only by a few percentage points. After debriefing subjects, it appears that the necessity of hearing multi-voiced music (both in frequency and in time) in one's head and coaching others to perform it led to the improved performance of conductors and composers.

The take-away points here are: The human hearing system is exquisite and evidently capable of beating what we think of as objective theoretical limits---we need to learn much more about the human hearing system in order to identify things to measure for evaluative purposes. There are aspects of hearing that require training and long experience---just because we don't perceive something doesn't mean there isn't something there to be perceived. Some people will be far more sensitive than others. And lastly, though not addressed in the paper, it seems to me that these subtle effects and our experience of them will not yield easily to definition, and each individuals experience of them will vary somewhat. When it comes to cables, YMMV (your milage may vary).

An Avenue for Exploration
I did manage to stumble into what seems to me as a particularly interesting avenue for further exploration and development. I had a discussion with Dr. Kevin Gilmore (who many of you know from his terrific work designing commercial and DIY electrostatic headphone amplifiers) in which he stated that the effectes of impedance matching with headphone cables could be of an order strong enough to influence the listening experience.

All cables have a characteristic impedance. For example, I use Canare 4E5C cable for my cable building needs. This cable has a 40 Ohm characteristic impedance. If I were to build a headphone cable for a Sennheiser HD 600, which has a 300 Ohm impedance, there would be a point at the headphones where the signal went from the 40 Ohm impedance in the cable to the 300 Ohm impedance of the driver. This impedance mismatch would cause a point of reflection for the signal. There is an instrument call a Time Domain Reflectometer that is able to send a signal down a cable and see the various points of reflection caused by impedance mismatches (and other things). The reflected signal from the impedance mismatch can, depending on the topology of the amplifier in use, have an effect on the signal from the amp. To properly impedance match the cable to the headphones in this example case, you would have to put a 40 Ohm resistor between the signal and ground at the headphone end of the cable. This would dramatically reduce the reflected signal.

A further twist on cable impedance matching is to impedance match the output of the amp to the cable. This works better for interconnects where the damping factor between the source and load isn't as important. For further information on this topic see this Headcase thread.

It seems to me this is a readily available avenue for further development by custom headphone cable makers.

Other Good Reasons for Aftermarket Headphone Cables
While the sonic improvements of headphone cables may be a contentious subject, there are a number of other good reasons to consider an aftermarket headphone cable.

  • Balanced Drive - There are many balanced drive headphone amplifiers available today. Using one of these amps requires headphones to be re-cabled.
  • Ergonomics - Your particular habits of use may be aided by a cable that is longer (for home and office) or shorter (for use with mobile devices) than the one supplied with your headphones.
  • Cable Born Noise - Often improperly called "microphonic" noise, a stiff cable will transmit mechanical vibration up the cable to the ear pieces, which can often be heard. (The term "microphonic noise" is aplicable to active components, like tubes, which will create electrical noise through mechanical vibration of the tube.) Replacing stiff cables with softer more pliable cable will reduce cable-born mechanical noise.
  • Esthetics - Styling has become more important to headphone users these days, and replacing stock cables with cooler looking aftermarket cables having nicer connectors can bolster pride of ownership. Sorry, I dont see anything wrong with this.
  • Ridding Headphones of Extraneous internal Connections - Many headphones have multiple solder joints within the headphone that can be bypassed when rewired. This is especially true of single-sided entry designs where the incoming cable is often soldered to a small circuit board to split the left and right channel. An additional cable will go to the driver on that side, and another cable will go up through the headband to the driver on the opposite side. Custom headphone re-cablers will often re-cable this type of headphone with a "Y" cable to go directly into each earpiece, and internally connect the new conductors directly to the driver wire terminals thereby bypassing a number of previously existing solder joints.
  • DIY Opportunity - Recabling headphones is a great way to express your DIY skills. I would strongly recommend spending quite a bit of time building interconnects and headphone extension cables before attempting to re-cable a pair of headphones, but re-wiring your cans is a really fun mid-level DIY project for those interested and properly skilled.

Summary
To say that headphone cables make a significant difference, or no difference at all, is, to my mind, an overly-simplistic view. Objectivists will claim no one has ever identified differences in cable in double-blind tests, ignoring the possibility of subtle effects that don't lend themselves to that type of observation. And enthusiastic subjectivists often want to contribute to the evolution of their rig by swapping cable around, naively ignoring the fact that there are hundreds of solder joints and conductors inside their gear that will have a combined effect much stronger than that of any particular interconnect between the various pieces of gear. The truth, as always, lies in some middle ground where the gear you choose is of primary importance, and once you find a system to your taste, some slight tweaks may be achieved with careful cable selection.

Further development is possible both in our understanding of the human hearing system and how it perceives sound, and in understanding what factors may come into play with cable construction that might yield a better listening experience. Easier to achieve improvements may also be available though fairly simple impedance matching techniques in the design of aftermarket headphone cables.

Aftermarket cables can also provide improvements in ergonomics, styling, cable-born noise control, and connector changes for your particular use.

My suggestion? The diminishing returns curve is steep with cables, don't over buy. I like the Cardas Headphone Cable and the Moon Audio Blue Dragon. There are numerous cable makers out there, many are good, but many more are just hobbyists with a soldering iron and a yen to be in business. With cables, the devil is in the details, I strongly suggest using cable makers with long years of experience and a good reputation. If you have headphones with a hard wired stock cable and would like to have them replaced, again, it is very important to find a reputable supplier who is very familiar and competent with this type of work. I'll happily recommend Moon Audio as one such supplier.

Disclaimer - Many of you may have noticed Moon Audio as a recent advertiser at InnerFidelity. I've been planning to do this article for a long time and had requested cables from Moon (and Cardas) long before they began advertising here. My desire to do this article and my conclusions have nothing to do with who advertises here.

Resources
If you have any cable questions I suggest searching for answers in the Head-Fi.org Cable and Accessories forum area.
I couldn't find a particular thread for full-size headphone recabling vendors (please feel free to provide a link in the comments if you know of one) but I did find a thread for IEM recabling suggestions here and here.

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Comments
NA BLur's picture
Cable Differences

I have seen quite a few professional posts about cable differences and the only ones that seem credible are the ones regarding possible slew rate differences in the current draw.  To this end the differences appear to be only tens of microseconds and I have not way of telling if it would be audible.  That I leave for the blind tests.

As Tyll's initial tests show there is a high probability that there are no audible differences showing up in the measurements.  This is not to say there are not audible differences, but the equipment which we place a lot of faith into has not shown any audible difference.

Anyone who thinks there are audible difference better be ready to defend that statement with a little more than just "I hear it."  That is possibly the most subjective statement to make in the audible world.  Companies claiming that their cables improve the sound should provide great detail about what exactly is being "improved" and show some definitive graphs or A/B/X tests that support such claims.

Tyll,

I would be more than glad to take some time to do some A/B/X testing.  We can both do the cable swapping / switching and both do the listening.  We should choose the cables at random right before the test as not to bias the results prior to even starting the test.

Thoughts?

Tyll Hertsens's picture
Not for a while yet.

I see no reason to subject myself to blind tests until I think I can readily identify something during subjective listening...which, at the moment, seems not to be the case. But I'm going to continue to do listening with some other headphones to see if I can find something readily identifiable.

tdockweiler's picture
DBT

Tyll you could easily pass a double blind test and here's how you do it without fail.

Make an HD-650 cable with a high capacitance wire such as Canare. Highest you can find. Then make one with silver or the lowest capacitance wire you can find. Maybe ALO SXC or Belden 1192A.

I guarantee you will pass the double blind test without many errors. If not I'll send you a check for $50,000 and retire from all this nonsense.

In my experience, the higher capacitance the "warmer" and fuller sounding it will be. This is why I like the stock HD-650 cable. Low capacitance wire sucks out all the warmth. Obviously it will still be there somewhat if it's in the recording. Higher capacitance wire seems to add a little warmth.

The most dramatic difference between cables is when you switch from an ultra high to low capacitance wire. I've used dozens of different DIY wire brands and this has always been the case for me.

Oh and as much as I love the HD-650, it's not the best for testing out cables. Try the Q701 since it's cheaper for DIY cable versions and fairly revealing.

 

Also..strangely enough I could not hear an ounce of difference between cables until I  got a nice DAC. It seems I notice the difference less with my ODAC than my old HRT MSII. Not sure why!

Limp's picture
The 24AWG Canare star quad

The 24AWG Canare star quad has lower nominal capacitance than the 24AWG Belden star quad. I'm sorry, but your reasoning falls flat. 

tdockweiler's picture
capacitance

Sorry, I didn't look up capacitance ratings of wires just to troll someone like you have. Canare is the highest capacitance wire i've heard of. It's pretty close to a stock HD-650 cable. Feel free to look that up too. My reasoning doesn't fall flat. The whole point was that the greatest difference in sound between cables (IMO) is when they have a very low capacitance and high. When it's nearly the same they generally sound quite similar in tone. I'm not here to prove anything.

Limp's picture
Just pointing out a logic

Just pointing out a logic fault.

29.6, 46 and 57.4pF/ft is the numbers given by Mogami, Canare and Belden, respectively, for their 24AWG star quads wired in quad configuration.

It is true that shunt capacitance works as a simple low pass filter, the problem is that you'd need a cable run of houndreds of feet for this to be audible, and even then the Canare would be 'brighter' than Belden. 

donunus's picture
I passed a blind test using

I passed a blind test using an hd650 cable/hd600 stock cable and an equinox cable on my hd600s.I found the stock hd600 cable less V-shaped in its delivery vs the hd650 cable and the equinox sounded more bold with bigger mids vs the stock hd600 cable sounding less airy and more distinct/bold. I could between them tell 9/10 times. I only got slightly confused when 3 cables were mixed together since I would get confused with the musical passages sometimes but I think I still got a 7/10. I made sure the person holding the cans would lift the cable up a little so that I couldn't tell the weight of the cables too because that would be a giveaway. I also made sure that they didn't rub the cables together too because the equinox in particularly microphonic.

Jazz Casual's picture
It seems to me that blind

It seems to me that blind testing is the most effective way to overcome the confirmation bias variable that dogs subjective impressions in this hobby and audio generally. As far as cables are concerned, any future purchasing decisions will be subject to my stock cables going kaput and how cool the replacements are going to look.      

Tyll Hertsens's picture
Just like...

Just like frequency response measurements don't reveal the effects of jitter, blind testing may not be the way to reveal some listening experiences.

However, I do think blind testing is a powerful and important tool in audio.

Please don't use blind testing to pick which cable is the coolest looking though. :)

Jazz Casual's picture
There are several aspects of

There are several aspects of the listening experience that frequency response measurements do not show. However, I do think that blind testing is a very effective BS detector. And thanks for the tip. :) 

KikassAssassin's picture
Blind testing
Tyll Hertsens's picture
Paywall!?

Really!? Bummer, I didn't encounter a paywall getting to the paper. Try going to this page first and hit the download pdf link, that's how I got there.

KikassAssassin's picture
Other paper

Sorry, I meant the paper NwAvGuy linked to, not the one you linked to. Smile

FHC's picture
regardless

The picture was worth it.  

Tyll Hertsens's picture
Couldn't remember my

Couldn't remember my safe-word. Had a bit of panic there for a while.

MacedonianHero's picture
Great write up Tyll and

Great write up Tyll and definitely one of the most fair I've seen on the subject that can be so very controversial.  I find small differences in cables and make cable changes the "final" tweak when my headphones permit it (I won't spend $ for recabling). Headphones like the HD800s or LCD-3s make this easy.

BTW, I love the photo! Classic and appropriate.

Thanks for this!

br777's picture
the best

this was the best article on cables i've ever read.   Most of them just make me want to shake my head and face palm.   

Great job as always Tyll

Seth195208's picture
When it comes right down to it...

All else being equal, I'll take a great headphone with a crappy cable over an OK headphone with a glitzy cable every time. High end aftermarket cables are a horrible value, even if by chance they do make a slight difference. Monoprice? Now were talkin'..

Tyll Hertsens's picture
Value

Givent the cost of good connectors, cable, and most especially the cost of the labor and running a company, I don't think a $200-$400 headphone cable is out of line.  Whether it's a good value or not is dependent on the values of the customer. On sonic benefits alone, I might tend to agree personally (remember, if it were me I'd build my own), but given all the other potential benefits I enumerated I don't think it's disproportionate.

Seth195208's picture
I'm also a DIY guy..

I guess DIY guys see things from a different perspective. Typically, audio jewelry is the last thing on our minds. Rolex watches are a good analogy. They don't tell time any better than a Casio..

Tyll Hertsens's picture
Indeed...

I've got a $250 Weller and a $300 Fluke so I can solder and Ohm out my nice cheap cables. surprise

Our DIY values are just different than most. yes

Willakan's picture
A number of questions

A number of questions arise.

Why is blind testing described as less sensitive for detecting differences? I see this claim everywhere, but as I've mentioned before, blind testing is just like sighted testing - but blind! If it's suddenly harder to hear the difference under blind conditions, that suggests that the difference has "extra-auditory" components, not that blind testing is somehow hiding the differences!

Indeed, the short switching times often adopted (but by no means obligatory to adopt) with a blind protocol makes it exquisitely sensitive to differences, by virtue of accounting for the extreme fragility of auditory memory.

As for measureable differences between cables, null testing removes any doubt here. What could escape such a test? If you listen to the difference signal between two cables (you can even do this all in the analog domain if A/D conversion is somehow going to mask the differences) and there's nothing there, where exactly are these differences hiding? Do audiophile electrons bugger off when a skeptic is looking Laughing out loud?

As for jitter, just no! Jitter was not why people heard differences between early CD players - they heard differences between early CD players because a lot of them were a bit crap! I mean, the Phillips equipment could only muster 14 bits of resolution initially, and it took a little while for people to cotton on to oversampling for decent digital filtering. It sure as hell wasn't jitter: that bandwagon, as I understand it, was largely started by a certain Robert Harley, who couldn't even measure it properly, and has yet to present any evidence whatsoever for its increasingly ridiculous claims. The idea that jitter has now been proved to be far more important than initially thought *thanks to what the audiophiles heard* appears to be largely mythological.

Finally, presenting that article about the uncertainty principle/Gabor limit as some sort of general proof that "Hearing is complicated mkay? (implied: therefore anything goes!)" is a little disingenous. As various articles on this have noted, we've known that the human ear could go beyond the time/frequency resolution trade-off necessitated by the Fourier transform since the 1970s. It's not really relevant to audiophile claims  - it certainly hasn't shaken the foundations of psychacoustics or anything like that. It also doesn't invalidate the huge quantities of experimental data we have on the human auditory system.

It's a subtle discovery, that deserves an equally subtle interpretation. It shows that the crudest models of the human ears are, well, crude. However, the more sophisticated ones have been sidestepping the whole Gabor limit issue for some time.

Jazz Casual's picture
What he said! Excellent post.

What he said! Excellent post.

Tyll Hertsens's picture
Nice post...

I appreciate a good counter point. 

" Do audiophile electrons bugger off when a skeptic is looking Laughing out loud?"

Possibly yes, if the skepticism is deeply held enough it can creat just another type of confirmation bias.

Willakan's picture
True, but that doesn't apply

True, but that doesn't apply to null testing, and ideally you have the skeptics simply administering the experimental conditions rather than doing the listening.

And as others have said, great picture Laughing out loud

Limp's picture
Aha! but anyone conducting a

Aha! but anyone conducting a blind test is by definition a sceptic, and thereby makes the whole methodology moot.

Perfectly logical!

Tyll Hertsens's picture
Now, now....

...there's healthy scepticism, and then there's "deeply held" scepticism. Two different things.

I strongly believe blind testing is an important part of doing audio science. Folks like Floyd Toole and Sean Olive do outstanding research with it. 

 

ednaz's picture
confirmation bias

This has been proven in much more difficult and what you'd think would be highly objective situations.

The placebo effect was shown to be heightened in double blind clinical trials of drugs if those getting the placebo picked up hints (that were planted for the purposes of the experiment) that they were getting the real drug. Similarly, those getting the real drug seemed to not show as much improvement compared to other double blind trials if they believed they were getting the placebo. Confirmation bias can go both ways. 

We are fascinating creatures.

dan.gheorghe's picture
Measurable differences?

Hey Tyll,

Thank you for the article. I've been eagerly waiting for this. Very nice article and well said!

I have some questions here.

     Let's say you have the measurements of HD800 and LCD2 in front of you. Where can you see that HD800 has better instrument separation, better soundstage, or has more details? In my opinion if a cable changes the freq response of a headphone, it ruins the way the producers meant you to hear it.

Thank you,

Dan

P.S. Love your work and what you made of this hobby Laughing out loud

Tyll Hertsens's picture
Imaging

I think I see the ability for a headphone to image in a clear initial leading edge of the 300Hz square wave response without a second significant rising edge...which the LCD2/3 has.