Pros: AirHead can enhance old recordings slightly. ER-6 has excellent isolation from unwanted ambient noise. Compact carry case for iPod and accessories.
Cons: AirHead is pointless for contemporary recordings. ER-6 has poor bass and too shrill medium-to-high response. Carry case too big for just an iPod and earphones.
Hoping to hear something as good as the Etymotic ER-4earphones I’ve just tried the $139 (sold by HeadRoom Corp. for $129) ER-6 ‘Isolator’ earphones, from Etymotic Research.
And I tried them with the HeadRoom Corporation’s $119 AirHead portable headphone amplifier, to hear what kind of boost it gave to iPod’s audio output.
Both the Etymotic earphones and the AirHead pocket amp are also available together as a ‘Packaged System’ by HeadRoom (for $$239.00) in a neat two-compartment weatherproof, clip-on, zipped pouch, so that you can carry everything as one unit.
Airhead Headphone Amp
You plug the AirHead into the iPod’s audio port with a little patch-lead (supplied) and then plug your earphones into the AirHead. HeadRoom says that the amp – a plastic box a bit bigger than an iPod, using three AAA batteries – adds a slightly delayed (300 millisecond) ‘copy’ of the left earphone channel into the right earphone channel, and vice versa, to simulate the spacial information you’d get when listening to real stereo speakers while in the ‘sweet spot’ where the sound converges in a real room. (see illustration)
They say “This is the acoustic information your mind needs to create a believable audio image in your head.” And they also say “This added information eases the burden on your brain by spreading out the clumped image in your head.”
Having tried the $119 device, I disagree.
Bass Boost and Center Smear
The AirHead amp makes a very, very faint difference to the sounds you hear through headphones, and this minimal effect just makes sounds slightly blurry and adds a faint touch of bass. The crisp positioning of audio across a broad horizontal ‘sound stage’ – which album producers strive so hard to achieve – is smeared away by this add-on box which just smudges the sound layout.
I compared the AirHead amp with a miniature Sennheiser headphone processor, which supposedly provides ‘Virtual Dolby Surround’ from recordings which have surround-info encoded into the music. But, the Sennheiser module’s no better: it just squirts everything from the edges into the center of the sound stage, and the AirHead then blurs it.
Unsatisfying Thump
The guts of the AirHead are two five-dollar SSM2475 decoder chips, which extract the ‘surround-sound’ information from an iPod’s left and right audio channels. This is mixed into the output to your headphones via the four transistor-amplifier chips.
Staff at HeadRoom said this works great with old Beatles recordings, which had extreme left and right stereo leaving a ‘hole’ in the middle of the sound.
I tried it with ‘Penny Lane’, and it did blend the left and right channels into a ‘warmer’ center channel, boosting bass slightly.
With the Etymotic headphones there was slight improved bass. But the Sony EX-70 earphones provided extra bass, and this extra bass was unsatisfying, as though the AirHead couldn’t reach down as far as the Sony earphones could and were just supplying a low-level muddy ‘thump’. The slight extra bass was completely unnoticeable with the iPod’s original earphones.
I asked the HeadRoom Corporation about the frequency response and output of the AirHead, and they “guessed” it ranged from 10Hz (bass) up to 20kHz (treble), but couldn’t say for sure because “…the guy who designed the circuit has left, and he didn’t provide us with those details.”
If there’s no ‘surround-encoded’ information present on audio tracks – and usually there isn’t – then the AirHead just smears the sound with no added benefit. For iPod tracks of old Beatles recordings: fine – the AirHead may enhance them a touch. But for most contemporary tracks it’s pointless.
Etymotic ER-6 Earphones
The Etymotic ER-6 earphones are in-ear phones which you push into your ear canal. The Etymotic documentation shows that the soft silicone ‘plugs’ that holds the phones inside your ears block almost all external sound, and this seems to be the major selling point, leaving you in a world of your own with your music.
