IN A WAY, STEREO headphones are a throwback to the early days of radio and phonographs when the power from those devices wasn’t sufficient to drive loudspeakers. In fact, headphones were invented long before modern loudspeakers (telephones use a single headphone, and they date back to the 1870s). And, the first loudspeakers were nothing more than headphones with huge exponential horns attached to boost the sound output.
As a result, some scoffed, perhaps feeling that science was retrogressing, when John Koss exhibited his first pair of stereophones at a Milwaukee hi-fi show in 1958. Those early stereophones were pretty heavy and, after wearing them for a couple of hours, your head felt like it was going to sink into your neck. But what incredible sound they produced!
We had long been taught that to get good bass from a system you had to increase the diameter of the speaker cones. But then along came Koss, delivering supergood bass from vibrating diaphragms three inches or less in diameter. The trick, of course, was that headphones had to push around far less air than free-standing speakers. And, if you get a good seal between the phone’s earpiece and your ear cavity and eardrum, even tiny vibrating diaphragms can deliver good bass.
Today there are about 30 manufacturers of headphones, but Koss is still the undisputed leader with more models and the lion’s share of the business, both domestically and abroad. Koss products are manufactured in Europe as well as in Milwaukee and are sold in just about every country.
The first stereophones were really nothing more than miniature dynamic loudspeakers housed in earpieces. But new materials, lightweight designs and different physical approaches to sound reproduction have resulted in many advances. Koss and other companies have even developed phones that can remain slightly away from your head (suspended by soft foam plastics) and still give good sound reproduction without that closed-in feeling that cuts you off from the rest of the world.
Another new development comes from the giant Pioneer Electronic Corporation of Japan, which offers what it calls HPM (High Polymer Film) phones in two price categories. A signal voltage applied to a thin-film diaphragm, vacuum coated with conductive material, causes the film to expand and contract, pushing the air necessary to produce sound.
One of the greatest advantages of headphones is that you needn’t be bothered by poor room acoustics because the listening room plays no part in the sound quality. In that respect, headphones are a little easier to select than loudspeakers, which often sound different at home than at the store. But, like speakers, headphones must be carefully auditioned, because each model and style offers its own slight degree of coloration. Also like speakers, some headphones are now equipped with multiple drivers (woofers and tweeters) and even have controls to change the balance between the two drivers.
The increasing popularity of headphone listening has prompted one manufacturer, JVC America, Inc., to introduce a combination headphone-microphone. Two tiny microphones are embedded in the earpieces with a replica of the human outer ear molded around them. The idea is to record sounds while wearing the phones, using the self-contained microphones. When you play back the recording and listen via the phones, you are treated to a degree of spatial realism that is not to be believed. These unusual phones are called model HM-200E, and they’re quite a buy at $80.
A frequent complaint among headphone wearers is that once they don the phones, they’re pretty well tied to within a few feet of the amplifier or receiver. But already two companies, Sennheiser and Beyer, have developed phones that don’t require any cord at all. In the case of the Sennheiser models, one or more infrared light signal transmitters are positioned around the room. The music is sent out on invisible light beams, which are picked up by a light receiver mounted inside the phones. Imagine being able to walk almost anywhere in a room and pick up music— even while you dance. We’ve obviously come a long way since Koss was having a hard time convincing makers of amplifiers and receivers to add another hole on their front panels for headphones.