Headphones have enjoyed a diverse technological history, Paul Rigby looks at their past, present and future.
Headphones are one of the most personal items in anyone’s hi-fi. They generate some of the most intense, passionate and, sometimes, vitriolic fervour you’re likely to hear. We love speakers, obviously, but they lack a critical sensory link – touch. Speakers can look good and sound great but you don’t have to fit them to your body. Which is why a pair of headphones is often selected, partially at least, in the same way that you might choose a pair of shoes or, possibly more aptly, a hat.
Of course, comfort is not the only important aspect of buying a pair of headphones. Many people will not even class it as a deal breaker stating, for example, that sound quality is the most important factor. However, your individuality comes into play here too. Talking to Stuart Nevill, the engineer behind the new Bowers & Wilkins P5 headphones, how each headphone sounds depends on you, “You can’t really say exactly what any headphone will sound like because people have different shaped heads, different sized ears, some have hair, some wear glasses. It’s a bit like loudspeaker performance, the room type affects it. For every listener, each person’s brain is used to adapting to how the ear sounds like in free space. It’s not used to being enclosed, it perceives that sound differently.”
Headphones also affect us in drastically different, psychological, ways. Some people wear them to look good – as a sort of fashion accessory, others revel in a retro design adopted via some headphones which make you look like a Cyberman from Dr Who. Some hi-fi enthusiasts won’t blink about spending £10,000 on a new turntable but £500 for a pair of new headphones? Well, that’s a different matter. Headphones can even cause family strife. Triggering accusations of the user “cutting themselves off” from the rest of the household.
They might be quirky and they might trigger emotions but, when it comes down to it, headphones also offer a unique perspective on sound. There is, in fact, nothing quite like them.
Bowers & Wilkins’ Nevill agrees, “When I was younger and couldn’t afford a decent set of speakers and amplifier, the best sound I could get was out of headphones. In fact, they are a good entry point if you’re looking for audiophile music on a budget. Also, they have an innate portability and you can play them at any time of the day without annoying people. Big speakers are great but, in urban situations, for example, when the neighbours are close by, it’s not often that you have the ability to play a pair of 800s, say, at full blast.”
Aaron Kovics, an administrator on the highly respected, web-based, headphone-centric forum Head-Fi, was effusive, “For portability, a small pair of mobile headphones or custom-made IEMs (see below) are excellent for taking a walk in the park. I wouldn’t be bringing my large home-based headphones or a pair of electrostatics with its amp, for example! Portable headphones allow you to carry high quality sound with you, as long as you have a good player and a good amplifier. At home, I have the full-size headphones which give you more of a visceral feel, you can get some air moving on the diaphragm to give you that bass slam, a big sound stage and a sound that’s pretty close to speakers.”
Owner of the US-based jazz label, Chesky Records, David Chesky, has a slightly different take on why he felt headphones are special, “Because they make me so relaxed. I get so relaxed wearing headphones I fall asleep a lot! They close out the world and I get so immersed in the music like I can’t do with speakers. It isolates you, disconnects you from the world and there’s nothing to distract you from the music.”
Yet such lyrical waxing is done from a point of personal choice and there are many alternatives when choosing which is the right headphone for you. The core option is the type of technology the headphone utilises to produce its music in the first place. There are many varieties to choose from, all with their own pros and cons.
The most numerous and the most popular headphone type is the dynamic – sometimes referred to as the moving coil – headphone which works by producing an alternating magnetic field that reacts against a static magnetic field, causing the coil and attached diaphragm to move the air. Benefits of this form of technology are the production of meaty bass and a very musical, overall sound. They are not particularly known for their refined upper frequency response, however.
Electrostatic headphones are, however. But their problem is a lack of deep bass output. They normally consist of a thin, electrically charged diaphragm suspended between two perforated metal plates and require their own amplifier, “A good electrostatic and amp will give you incredible detail but also a wider, more true speaker-like head-stage: a soundstage on your head,” said Kovics. “So, you’ll hear the sound from just behind your ears to the tip of your nose with layers as you go outwards from your ears that you can peel away.”
Another technology type, which is making a big come-back, is the orthodynamic. Originally made in the eighties, they competed with electrostatics. In construction, they feature a kind of Mylar strip of the sort that you would see in a electrostatic but with the addition of tiny coils that act as capacitors. Instead of using scattered grids in the manner of an electrostatic design, the Orthodynamic uses magnets with opposing charges.
“There are a couple of companies making them and many people are now buying them, said Kovics, “There are pros and cons, however. They are extremely musical because of the magnets. However, they need a huge amount of power – you need around two volts per channel. Special amps are made for them. The upper frequencies are brilliant, the soundstage is excellent but they are heavy because they have magnets and they are expensive. At the moment, users of the new orthodynamic headphones are very happy with them and prefer them to everything else out there.”
Moving onto mobile technology, one of the most esoteric and aurally rewarding technologies out there is the IEM (In-Ear Monitor) headphone, an in-ear technology also described as Canalphones. Top quality IEM companies ask you to visit your local audiologist and ask them to take a mould of your inner-ear canal. The company then takes that to produce an in-ear headphone that will fit your ears and your ears alone. It also means that the IEM will be a perfect fit. In fact, you’ve seen these things in action on the TV as most top singing stars or bands use them so that they can hear themselves playing or singing. Offering superb upper frequency performance they do lack any real bass output because they cannot move the required air.
IEMs arrive in two flavours: balanced armatures, which many audiophiles swear by, and dynamic drivers which also have their followers, such as Bowers & Wilkins’ Nevill, “Balanced armatures are fancy hearing aids – they use modern hearing aid technology – they’re extremely expensive for what they are and, besides the lack of bass, because they’re based on levers, they have quite a lot of resonances in them. That’s why you see up to, say, 6-way balanced armature headphones. That’s not because you’ll get the advantage of six different drivers doing things well it’s because you need that many drivers to pump the bass. You can’t use the bass armatures for high-end frequencies because the have too many resonances. Some people say that balanced armatures sound exciting and lifelike. But that tends to mean that there’s a few resonances in there. In my opinion, they don’t sound any better than well designed dynamic drivers. In the meantime, there’s a lot you can do to change the sound on dynamic drivers.”
Of course, there are also much more simplified earphones such as the basic buds you might find bundled with a new MP3 player, for example, to the rather more expensive variants which you push directly into your ear, utilising replacement tips to obtain a ‘best fit’.
Associated with the above technologies is the relatively new enhancement: noise cancellation and, as in the case of the Bowers & Wilkins P5, noise isolation. In the majority of cases, a good noise isolation model, with a closed back and sealed earpads, will do the job, in a noisy environment, basically blocking outside ambient noise from entering the ear. It’s only when you get on a plane that noise isolation starts to fall over because of the very low frequencies produced. Noise cancelling is the only way to get around that: in fact the latter is around 10-15db better on a plane when compared to noise isolation.
There are two types of noise isolation: feed-forward and feed-back, “Those that use feed-back tend to have a microphone inside the ear cup that measures the sound that’s leaking into the ear cup and puts an anti-phase sound into the signal,” explained Nevill. However, that signal mixes with the music and degrades its quality. “The other option is feed-forward where microphones are placed outside the ear cup. The sound is measured on the outside and the transfer function is measured. That is, what the frequency response of the sound is after it has gone into the ear cup. Then an anti-phase signal is applied. There is no real sound degradation with feed-forward because you’re mixing the anti-phase signal afterwards. That’s why feed-back noise cancellation can sound artificial – because it’s been around a processing loop,” added Nevill.
The sheer breadth of headphone-related technologies is wide, weird and wonderful. We haven’t even had the time to mention those technologies that never made the grade. And that’s the fascinating thing about headphones, they are the embodiment of innovation and a reflection of great ideas, bad ideas and ideas that make you wonder about the sanity of the inventor. Whatever type of headphones you choose – and we’ll bet that it will ultimately depend on the type of music you enjoy – you will probably form a personal attachment with them. They’re like hi-fi’s equivalent of a big teddy bear.
IN THE STUDIO
Headphones may be useful for the home and as a mobile medium but they can be critical in the studio when music is being created, monitored, mastered and remastered. Andrew Thompson, mastering engineer for the company, Sound Performance, based in London, uses a pair of hard wearing, dynamic, closed-backed headphones for use in the studio, to give a balance of sound quality and noise isolation, “And also comfort,” he adds.
Currently, Thompson is working on a range of reissues for the quality reissue record label, BGO. Sound quality, on these projects is critical but standard monitor speakers are not enough, “Headphones are useful for detail work such as listening out for subtle clicks and noise during sound restoration which, perhaps, might pass you by if you are sat in front of the monitors. Such detail spotting can even depend on the angle your head is turned. In front of speakers you can often miss certain frequencies by turning your head a fraction. It’s a bit like colour blindness, where, for those people who have it, certain colours blend with other colours. Listening to the monitor speakers, certain details are lost – especially, if you’re not in the right position. Or, rather, the details are not noticeable enough.”
That said, for the overall image, it’s still best to listen to the main monitor speakers. As in many aspects of life, a balance is best and a combination of the two: headphones and speakers, form the best blend. But headphones allow you, with a good level of volume, to isolate certain frequencies.
David Chesky agreed, “For the record label, if we are editing we use a pair of electrostatic headphones to focus on specific details. If we’re in session then we’ll use a pair of dynamic headphones that we’ve been using for a long time for musicality reasons.”
Over the years, there have been plenty of test discs created for use with hi-fi systems. Such test discs play varying types of tones, noise patterns or music tracks with specific instructions on what to listen out for and how you tweak your hi-fi if you hear the wrong sort of noises. Widely available, they enable accuracy during the initial hi-fi set-up all the way through to monitoring your hi-fi for continued, efficient operation and can apply to just about every element within your system. Up until now, however, there hasn’t (at least, we don’t believe there has ever been) a test disc specifically created for use with headphones.
Now, David’s respected audiophile jazz record label, Chesky Records, has produced such a disc that can be downloaded as a 44.1Khz ($12) or 96Khz/24-bit FLAC ($18), called Open Your Ears. Both are currently on sale for $6 and $9 respectively, if you get in quick.
Tests include midrange tonality, transparency, visceral impact, spatial depth, bass and more. “I thought it would be a cool idea,” added Chesky, “it wasn’t planned, it was very much a spur of the moment. It took a few months to correct. First, it was a case of getting the ideas and how to test the headphones, what songs to include and so on. At least, now, you have a reference point so that, if you want to go out and buy a pair of headphones then you have a guide. You can test any type of headphones too.”
Don’t forget, although Chesky is offering a test disc, there are no absolutes in headphone technology, “Everyone looks for different things when buying a set of headphones,” agreed Chesky. “It’s an art-form. Buying headphones is like appreciating a painting, everyone gets something different from them. But at least were trying to define the parameters.”
When the Apple iPod first hit the streets, it was the height of chic to be seen wearing the associated white ear-buds. That is, until everyone realised that they didn’t produce the best quality sound. Now, of course, the streets are full of young people wearing varying mobile head-ware. Is this the result of a search for better quality music from the generation brought up on poor quality MP3s?
Bowers & Wilkins’ Stuart Nevill has his doubts and attributes the change to practical concerns, “Some people really don’t like to put things into their ears. They also drag on your ears. Also, bigger headphones give you a bigger sound but sound quality alone isn’t the only reason why people do it. Comfort is involved too. The most significant movement in the world of headphones of late has been cans that are treated like a fashion accessory and arrive in a million different designs – even though they don’t sound that hot.”
Head-Fi’s Aaron Kovics essentially agrees but also believes that the perceived change is rather more complicated, “ There’s only five or 10% of the population who want audiophile-like headphones and that’s the five or 10% of the people that I’m mixed up with but if you really look at people as a whole? I talk to them about my headphone equipment and they just have a blank stare on their faces. They have no idea what I’m talking about. So when you ask, is there a change? There really isn’t one. It’s an active niche.”
So, in effect most people couldn’t care less – whether they be younger or, for that matter, older. And then there’s the hi-fi enthusiasts who will always look for an improved sound. The same people who search out high quality vinyl or who download high-resolution music files. The good news is that those youngsters spotted wearing better quality headphones are, in fact, the new generation of enthusiasts!
The future of headphones is a moot point. Many believe that what we have will remain and just get better: more refined, better components and tweaked designs. Others see the development of innovative techniques such as Magnetostriction or bonephones which rely on bone conduction. Then there’s Sony’s Tokyo research lab which has discovered a method of connecting headphones to portable music and video players by feeding an audio signal straight through the listener’s body. The new system uses the human body as a capacitor. The idea is for the body to store a tiny electrostatic charge. Then the music player sends a signal to a conductive cloth pad – such as a wrist band – and this slightly charges the wearer’s body. A pair of conductive ear pads in the headphones pick-up the signal and rapidly converts it back into sound.
Then there’s Nintendo who want to combine advanced in-earphones with a new mind-controlled game that uses brainwaves to control characters. You press a single button on the slim remote and your brain does the rest.
Bowers & Wilkins’ Stuart Nevill even suggested an advanced surround sound system utilising clever phased arrays using wave field synthesis or, “A wireless system that would have no effect on sound quality, 3D goggles to have a GUI in front of your eyes, incorporating a brain wave selection system.” Farfetched? NTT Docomo, a Japanese mobile company, has taken the first step in such a device. Demonstrating eye-controlled earphones, the technology features electrodes embedded into the headphones that use the charge between your retina and cornea to initiate a command. Look to the right and then left will trigger a request to play the track. While right and right again will skip a track. You can imagine the funny looks you’d get on the train with that one.
Chesky Records – www.chesky.com
Sound Performance – www.soundperformance.co.uk
Head-Fi – www.head-fi.org
Headphone test disc: www.hdtracks.com/index.php?file=browse_music&type=label&id=158),