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November 2001
Enjoy the Music.com Review Magazine
Battle of the Noise Reducing Headphones!
Bose QuietComfort Headphones vs. The Etymotic Research ER-4P
& Headroom Total AirHead Combo
Review by Chris Boylan


  For audiophiles whose jobs or lifestyles require frequent travel on airplanes, trains, or subways, the big challenge is how to get good sound in a noisy environment. Several manufacturers offer solutions to this problem, with varying degrees of success. Two of the higher ticket portable audio solutions available today are the Bose QuietComfort headset, and the Etymotics ER4P earphones, which I decided to augment with the Headroom Total Airhead headphone amp. For the purposes of reference, I compared these 'phones with others in my arsenal, including the Sony MDR-V6, Grado SR-60 and KOSS ESP-950 electrostatic headphones. 

To give these headphones a fair sampling of music and source material, I included recordings from hard rock (Rush 2112 on MFSL Ultradisc), to classical (excerpts from Wagner's Ring cycle and Vivaldi's Four Seasons), to electronic (Kraftwerk's The Mix), to new age (several Enya CDs), as well as a few 24/96 DVD Audio discs, and several DVD movies. The source components included a cheapo Panasonic portable CD player, my Dell laptop, for DVDs and MP3s, as well as higher end sounds from my home CD and DVD units (Pioneer Elite components playing through a Sony ES preamp/DAC).


How To Kill Background Noise: Isolation Vs. Cancellation

The two basic approaches to producing good sound in a noisy environment are: a.) isolate the ears from external sound, or b.) cancel external noise before it reaches the ears. What's the difference, you may ask? Well, isolation means that you shield the ears from external noise via passive acoustic means - the headphones are designed to minimize the amount of external noise that leaks into your ears. Cancellation means that you reduce external noise via active electronic means - the headphones are designed to sample the external noise then cancel this noise by generating its inverse electronically.


Well, without getting too deep into acoustic theory, since sound travels in waves, you can cancel out any sound wave by generating a new sound wave that is exactly opposite in shape - or "out of phase" - to the original sound. Here's a simple graphic to illustrate.


Sine Waves

The first chart represents a simple 1 KHz test tone. The second chart depicts a new generated tone that is 180 degrees out of phase from the original sound. Where the original wave has a peak, this new tone has a trough, and vice versa. Now when you add the two sounds together, you get silence - the two tones cancel each other out completely. Now of course, most background noise is more complex than a simple 1 KHz test tone, but the basic principle is the same.

This technique has far-reaching applications. Using this basic premise, you can make helicopters that run whisper quiet, and you can allow two soldiers in a tank to hear each other at a regular speaking volume despite the 100 dB rumble of the tank engine. You can also make headphones that sound good in the noisy environment of an airplane cabin… at least theoretically.

Bose is one manufacturer that subscribes to the noise cancellation approach. They recently introduced the QuietComfort Acoustic Noise-Cancelling® headset as a solution for road heroes, sick of putting up with inferior sound while traveling. The QuietComfort headset retails for $299, and due to Bose's firm price fixing, you probably won't find them for less unless you buy them used. You can buy them online at the Bose web site - www.bose.com. For $299, you get pretty much everything you need to get started including a carrying bag, belt clip, airline output adapter, ¼" adapter, 36" extension cord and 2 AAA batteries you'll need to run the unit.


Bose QuietComfort Headset
The Bose QuietComfort headset come with everything you need to
enjoy music and movies on the road (or in the air).

In my experience, these headphones are a bit bulky for carry-on travel. They didn't fit in my laptop case, so I had to carry them separately, which was inconvenient. Of course, there is a good reason for their girth - the headphones are designed to completely surround the ears so they can offer an additional measure of isolation from external sound. Plus the sampling microphones and noise-cancellation electronics have to go somewhere so these too add to the bulk of the package.


The Comfort Factor

While they are bulky, the Bose headphones are certainly not heavy. The cushions on the earpieces are quite soft and plush and the pressure against the ears is firm but gentle. Overall, these headphones are very comfortable to wear, even for extended periods, such as a cross-country or transoceanic flight.


How about the Sound?

My experience with the sound of the Bose headphones was a bit mixed. Turning on the noise cancellation circuitry while on a plane in flight or in any noisy environment is a unique experience. It feels almost as if your ears are decompressing as the background noise is sucked out to form a near silent backdrop. With the ear-surrounding design and active noise-cancellation technology, the Bose 'phones are extremely effective at reducing intrusive background noise.

The bass response of the Bose phones is tight and punchy, and seems pretty extended. Kick drum and synthesized low bass notes come through loud and clear with good impact. It sounds as if there may be a slight hump around 100 to 120 Hz as male vocals were a little boomy, but not offensively so.

Above the bass notes, the sound didn't hold together quite as well. The upper midrange and treble had a tinny, slightly artificial quality that became fatiguing when listening for extended periods. Horns, strings and cymbals in particular sounded less natural than they did on the Etymotics and other headphones. I'm not sure if this is an artifact of the processing, or a limitation in the drivers themselves. I'd suspect the processing.

Also, there wasn't much in the way of imaging with these headphones. I know it's difficult to present a realistic soundstage with two speakers that are attached to your ears, but the impression I got of the Bose was always of two separate ear-speakers, not a cohesive seamless musical presentation.

In an airplane and on a noisy New York subway, the noise reduction and sonic insulation that these headphones provided was excellent, but the overall quality and precision of the sound was a bit lacking when compared with the Etymotics, the Grados and the Koss headphones.


Etymotic Research: An Isolationist's Dream?

A smaller, and certainly much less well-known company, Etymotic Research specializes in headphones with a very high degree of sonic accuracy and excellent acoustic isolation. They only make three models of headphones, which look identical and only vary in their sensitivity and in frequency response. The ER-4B is designed for listening to binaural sources (recordings made with a dummy head with microphones placed in the ears). The ER-4S is described as being the most neutral of the bunch, but these phones are relatively low in sensitivity, so they're best for home listening or higher powered sources. The ER-4P phones are designed with high sensitivity for lower output sources, so they're ideal for portable CD, DVD, cassette and (if you must) MP3 players.


Etymotic ER-4P and 4S
The Etymotic ER-4P and 4S come with extra foam and rubber earpieces, a ¼" adapter, a cord clip, a cleaning tool and a convenient soft carrying case.


I auditioned both the ER-4S and ER-4P, which each sell for $330 list, but can be found for less. In fact, you can get them for $269 online from the aficionados of portable sound Headroom - www.headphone.com. The Headroom web site is a wonderful source of information about the pleasures of headphone listening, and the staff is well informed, quite nice and accommodating. They also make several headphone amps that work well with the Etymotics and with any other set of headphones for that matter. I supplemented the Etymotic headphones with Headroom's ultra-portable Total AirHead amp. The Total AirHead runs on two AA batteries and sells for $159.

In terms of convenience, it would be hard to be more convenient than the Etymotic headphones. They are so small they'll fit easily in a shirt pocket, even in the soft (but sturdy) carrying case. The Headroom Total AirHead headphone amp is also quite slim - approximately 4 ½" X 2 ¾" X 1," or about the size of an audiocassette tape (anyone remember those?). It'll fit in the same shirt pocket as the headphones.

The amp only weighs a few ounces, even with its 2 AA batteries inside. According to the manufacturer, the batteries should last for around 15 hours of playback, but in my experience, it seemed longer. I do wish there was some kind of LED or other indicator of power and battery strength on the unit, so I could tell it was on visually, without groping for the switch. I frequently use it at home with my computer, and more often than not, I leave the thing on all night and come back to dead batteries the next day. There is an external input for an AC adaptor, but I haven't found one that fits it yet. Overall, this is a minor gripe. If the volume drops and you hear a bit of distortion, then you know it's time to change the batteries.


Headroom Total AirHead
The Headroom Total AirHead
runs for hours on two AA batteries.

The Etymotic Research headphones are unique in that they fit directly in the ear canal, rather than outside the ear. They are effectively a set of earplugs that have headphones built into them. This simple design makes for an extremely high degree of acoustic isolation - 23 dB of isolation in fact - which quiets even the roar of an aircraft engine to a dull whisper. Wearing them on a New York City subway provided a similarly insulated experience. As I walked along the platform, the only way I knew that a train was approaching was due to the vibration of the platform under my feet - I didn't hear the sound of the train over the music until it was right next to me.


The Comfort Factor

The Etymotics come with extra foam and rubber tips, so I was able to share these headphones with friends without totally grossing them out with the earwax deposits on my plugs (eeeeeeeewwwww!). In terms of the way they feel, well, folks either loved 'em or hated 'em. Most of the people who actually stuffed them in their ears loved 'em. They said they soon forgot they were wearing them. This is the way I felt. They fit so snugly that you just feel like the sound is magically appearing inside your head.

But a couple of folks just would not even put them on. I guess these are the folks who took their mothers seriously when they told them not to put anything inside their ear… except their elbow. So if you feel weird about wearing earplugs, then don't even consider the Etymotics. But if you are OK with this, then you're in for quite a treat!


How About the Sound?

I went back and forth between the ER4S and the ER4P, with and without the Headroom amp and the combination that clearly emerged the sonic winner for me was the ER4P with the Headroom amp. The ER4S definitely sounded smooth and accurate, but, when compared with the ER4P, the ER4S seemed a little thin; a little lacking in low-end impact. The ER4P, on the other hand, lacked nothing. Smooth treble, tight extended bass, without a hint of thump or tubbiness and a very solid and fairly wide sense of imaging, particularly with the Headroom processor on (more on this later).

The isolation, as mentioned above, was excellent. My previous boss brought them home to try them out, and he said they passed the "wife test" with flying colors. He was happily listening to tunes while his wife's lips were moving as she gesticulated at him in exasperation. He heard absolutely nothing. He bought a pair himself the next day. While I don't advocate aural evasion tactics such as these, it does help to demonstrate the level of isolation that these headphones will help you to achieve. You do have to be careful about volume level of course - with such a tight fit, there isn't much room for your ears to breathe - but because the isolation produces such a quiet background, you can keep your volume at a low level and still enjoy the music.

Upon this backdrop of silence, the Etymotics and Headroom combination produced a velvety smooth musical presentation. Cymbals and horns sounded natural without any stridency. Male vocals sounded full without any hint of throatiness or boom. There was a very slight touch of sibilance on some recordings with female voice such as the debut Enya album, but this may have been an artifact of the recording, as I did not notice it in the more recent Enya CD "A Day Without Rain".

Listening to the Wagner recordings, individual plucks of the harp strings stood out plainly and the intonation of the French horns was clear and liquid sounding. All the musical layers in the recordings combined to form a cohesive whole. "Natural," "full," and "cohesive" would be the best overall descriptions of the sound.

The Etymotics headphone cable is slightly microphonic - when you touch it the sound is amplified and transmitted to your ears. It's a little like the sound of tapping on the tube of a stethoscope, but far less pronounced. This was not distracting, and in fact, it has been improved recently with a design enhancement to the cable, but it is worth mentioning.


The AirHead Factor

I did a fair amount of listening of the Etymotics on their own, without supplementation with the Headroom headphone amp. But once I hooked the Headroom amp up, it just didn't want to take it out of the loop. It is not just an amp. An amp alone would be useful for boosting the levels of low output devices, and "in-flight entertainment systems." The Headroom also includes a built-in processor. I guess you could call it a spatial processor, because that's what it does - it gives the music inside your head a real sense of space and depth.

No matter which headphones I tried (the Sonys, the Grados, the Etymotics), connecting the Headroom amp in the signal chain just made things sound better. Without the headroom amp, music and movies sounded accurate through the Etymotics. With the headroom amp, music and movies sounded seductive. The Total AirHead literally draws you into the music. It makes you feel a part of it and this is really addictive! Do I think the ER4Ps sound good solo? Of course. They're a very nice set of headphones - very accurate, detailed and pleasant. Would I bring them along on a trip without the Headroom amp? No WAY! I love the synergy between these two and splitting them up would be like a messy divorce, so I'm just not going to do it.


And the Winner Is...

By now, it should be obvious what my personal favorite was, in this showdown. I did like the way the Bose headphones eliminated noise, and they sounded pleasant enough on certain material. They're certainly a huge improvement over the airline handout headphones or the 'phones that come standard with most portable gear. In fact, some airlines are providing the Bose headphones for their first class and business class passengers to use, as an extra little perk. But the Etymotics just worked better for me overall. They're smaller, more portable, provide even better acoustic isolation than the Bose, and they create a more pleasing, natural and less fatiguing sound overall. When you combine them with the wonderful Headroom amp, the combination is a slam-dunk - a one-two punch that knocks the Bose out of the ring.



Bose QuietComfort

Noise Cancelling: Reduces unwanted noise
QuietComfort Cushions: Maximizes noise reduction performance and comfort
Earcup Triport system: Greater noise reduction can be achieved in a smaller size earcup
Adjustable Headband: Provides comfortable settings
Hi / Lo switch: Volume levels adjustment
Airline stereo audio adapter: Included
Power: AAA batteries
Carry Bag: Included
Price: $299


Etymotic Research ER-4P

Frequency response re nominal: 20Hz to 16kHz (+/- 4dB)
1 kHz sensitivity: 109 dB SPL for .2 Volt Input; 107 dB SPL at 1mW 
Impedance: 27 Ohms nominal 
Maximum output: 122 dB SPL 
Maximum safe continuous input: .75 V RMS 
Acoustic polarity: + Electric = + Acoustic 
Weight: Less than 1 oz. (28 grams) 
Cord Supplied: 5 feet with 3.5mm (1/8") stereo phone plug 
Transducer Type: Dynamic

Accessories included:
Cable with 1/8" stereo plug for portables 
1/4" Stereo phone adapter plug 
White flanged eartips 
Foam eartips 
Shirt clip 
Fitted case 
Filter-changing tool with 4 filters 
Carrying pouch
Price: $330


Total AirHead

Type: Portable headphone amplifier
Input: 1/8" stereo, mini-headphone jack
Output: 1/8" stereo, mini-headphone jack
Batteries: two AA (15 hours of operation)
Price: $159


Company Information

Bose Corperation
Mountain Road
Framinging, MA 01701

Voice: (508) 766-1099
Website: www.bose.com


Etymotic Research
61 Martin Lane
Elk Grove Village, IL 60007

Voice: (847) 228-0006 
Fax: (847) 228-6836 
E-mail: customer-service@etymotic.com
Website: www.etymotic.com


HeadRoom Corporation 
521 East Peach Street 
Bozeman, MT 59715 

Voice: (406) 587-9466
Fax: (406) 587-9484. If
Website: www.headphone.com













































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