The headphones

There is no Amateur Radio that don't have headphones! Why? Because with them we got a better sign to noise relation, because we avoided to disturb the family , and finally, because XYL considers them the best invention of the world.

I am not different from the others radio operators, my first headphones was a Telex Explorer. It was a bad experience, they have a bad sound, a terrible isolation, and they are uncomfortable after one hour of use. I put them, definitively, in the shelf forever.

This bad first experience alert me to take care in the future headphones acquisitions. I have collected more than a half dozen always demanding more from the available technology.

Some Amateur Radios choose Heil Sound as the best headphones option because they have included the best microphone not caring with the sound quality of the headphones. However, unhappily, the Heil after one hour becomed displeased, hot ,and sweated, being incredibly poor with noise isolation, in other words, a bad choice! Which will the best heaphones option then?

fig.1 - Heil ProSet Plus the favorite in the contests

The parameters that make the difference

What we have to do first is to verify the basic characteristics of the output device, like the impedance, the maximum voltage, and the Bandwidth of the audio equipment. The Yaesu 1000mp out earphones impedance is 35 ohms but in other radios can be any other value. The closer is the input impedance from the source of the radio, better is the link and consequently we got the best sound! Most of us already have verified, that with some headphones, it is necessary to increase too much the amplifier audio level (higher impedance) but in others ones it is necessary to lower too much (low impedance). Well its obvious that not only the impedance limits our choice. Other factors like the sensibility, the comfort, the noise isolation, the bandwidth, and of course, the price, will limit our preference.

Let's put the price away because is not a technical choice.The fast conclusion is that more we maximize the others factors, best are the headphones. It is known, that a better sensibility (gain) implicates less audio amplifier level in the circuit reducing the noise source (amplifier hiss noise). It is easy to find headphones with excellent values of sensibility (115dB/mW), however it is much more difficult to find ones that satisfy comfort and isolation simultaneously. Usually the closed headphones ( theoretically more isolated ) have a comfort problem because they need to be closest to the ear through an exaggerating mechanical pressure on the head.

This dilemma isolation/comfort begans a war between the manufacturers that develop the technology of the active noise cancellation. This new headphones have microphones that capture the external noise and using complex algorithms generates an inverse external sound inside the headphones. Theoretically it's easy to understand the technology but, unfortunately, they revealed excellent only in the reduction of the specific noises, like computers fans and motors noises.

In practice. the claimed 10dB of isolation only works between 20 to 300Hz without perceptible results in voice noise, resulting sometimes in more added noise. There are some available models in the market, like the expensive Bose Quiet Planet, the amazing Solitude, the amateur prefered heilsound Proset QuietSound, and the accessible Sony. I have made a test with a Sony MDRNC6 that have an excellent sensibility (106dB/mW) and also an excellent sound. They are comfortable (until when they turn hot and sweat) but they lose in the inefficacy of the noise cancellation of the external noises, as it is the case of the voice.

Noise Isolation

We know that the noise is part of the communication and today the great effort of the technology is centralized in the noise war. All of the elements of the communication, the atmosphere, the antenna, the coaxial cable and the receiver add some noise dBs to the communication link, and that's why we use the DSP (Digital Signals Processors) technology , best narrow filters, and coldest components (MosFet, GasFets), to get intelligible communication from the interior of our ears into the brain.

But, if noise exists close to the ear? Did you already try to listen a very weak signal with your son singing at your side? And the smallf PC fan noise? Turn up the volume solve the problem? Sometimes we think it does, but the increase of the sound's level , increases the pressure inside the ear channel and it can, in extreme cases, to cause irreparable damages in the Human auditive system.

The sound of the silence

After all, which are the best headphones of the world? No matter how strange it seems, the best headphones are not headphones. The EIM(Ear in Monitor) or In-the-ear phones are not headphones, or anything that it seems like, but they are, without a doubt, the best devices of sound of the moment.

EIMs are small high fidelity earphones that works into the ear channel blocking, with a silicon membrane, the external sounds. We should not mislead these small marvels of the sound with the vulgar ears bugs that are used in the MP3 and CD players, because EIMs have a sound quality and fabulous acoustic isolation.

Of course in these cases the size is inverse of the price. The E5C from SHURE with 122dB and 20-30dB of isolation cost about $US500. Anyway, they still below the US$1000 of the exorbitant Ultimate Ears UE-10 Pro.

SHURE and Ultimate Ears UE-10 Pro prices were unthinkable, so I have acquired the better priced etymotic, with less sensibility, but with much better isolation (30-40dB). What can I say about them? Initially they are a little tiring but after a play time they become very comfortable. When we put them without sound, we have the doubt if we are deaf, but when we powers on the sound, we have the sensation that we are in an silent auditorium. If you like big headphones this is not for you, Etymotic are ridiculously small. For me, they are the biggest invention of the world because when I'm using them in the radio, no longer listen to XYL. It's the sound of the silence!

Fig. 3- The Etymotic ER6