August 20, 1999 The Bose Aviation Headset X

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by	Joe Godfrey

About the Author ... Joe Godfrey mixes his love of flying with a love of music. He is an instrument-rated private pilot who flies a 1974 Bellanca Viking based at Palomar airport just north of San Diego, Calif. He composes music for commercials, films, broadcast and corporate media and has composed and produced thousands of music tracks for America's largest advertisers. In addition to writing for AVweb, Joe contributes to The Aviation Consumer and IFR Magazine. He is a director and pilot for Angel Flight West, a non-profit organization that uses private airplanes to fly indigent medical patients. He is married and lives in Leucadia, Calif. So far, Joe is the only AVweb staff member who has logged time with Ella Fitzgerald and conducted the London Symphony. JGodfrey@AVweb.com Angel Flight West Aviation Consumer IFR Magazine

Bose wasted no time introducing their eagerly-awaited Aviation Headset X at 1998's EAA AirVenture Oskhosh. It was the first product demo on the first morning of the event. You got the feeling they were just chomping at the bit to unleash their "LightSPEED Slayer."

Since August 1998, Bose has had to slay their own dragons. They had expected to begin shipping in late August. As September arrived and headsets didn't, those who had placed orders had to wonder if Bose might be an acronym for Blissfully Optimistic Shipping Expectation. As November arrived and headsets didn't, they had to wonder if Bose might be an acronym for Better Order Something Else. What happened is that Bose decided to make some changes to the design of the headset based on pilot feedback at the Oshkosh launch, and those changes took a lot longer than anticipated. Bose finally began shipping in early December 1998, and the caught up with the order backlog by March, 1999.

The Bose Series I introduced ten years ago was unique in several respects. The large see-thru earcups gave you a peek at the noise reduction circuitry inside. The see-thru Clear Comfort gel seals were a breakthrough in a world of foam and sponge. And the $995 price positioned it apart from the competition. The Series II came along in 1996 with essentially the same frame and the Clear Comfort gel seals, but with opaque earcups hiding the wires. Bose has never been reluctant to recall their products for modifications they thought would improve the product. Both Series I and Series II headsets were recalled for adjustments. This time Bose decided to make the mods first and ship later.

A Cursory EXam

Rather than re-tool the existing design of the I and II, Bose started the Headset X with a clean slate. The goal was to make a significant improvement in comfort without sacrificing Bose's reputation for noise reduction and audio quality. From the yokes that hold the earcups to the headband, they missed no opportunity to redesign the parts to be smaller and lighter.

The X doesn't look like a descendant of the I or the II, which is probably why it isn't called the III. Weighing in at only 12 ounces the X is just over half the weight of the old design. The familiar silicone gel-seals are gone, replaced by a more traditional foam cushion. The earcups are smaller with a more traditional oval shape. The magnesium headband is strong but light and is spring-loaded to keep clamping force to a minimum. Like previous Bose models, the X can be ordered as a battery-powered portable or for permanent installation using ship's power. What isn't new is the price range. MSRP for the X is still $995.

PNR/ANR ReduX

Chances are most AVweb readers are already familiar with the concept of active noise reduction and you're reading this hoping to figure out which ANR (active noise reduction) system to buy. But maybe you're like my Uncle George who used to say "Color TV's—I'll wait until they perfect them." If you're still flying with a passive noise reduction headset, or without a headset, you owe it to your only set of ears to try an ANR headset on your next cross-country trip. If you like scientific analysis, read LightSPEED's fascinating five-part tutorial on active noise reduction. Bottom line is that whether it's Bose, David Clark, LightSPEED, Pilot Avionics, Sigtronics, Telex or something else — whatever brand you choose — research proves you'll hear the radio calls and your passengers with greater clarity and arrive at your destination feeling less fatigued, which is more than color TV could ever promise to my Uncle George.

EXpanding on the New Features

The X's design is based on Bose's new Tri Port technology. Passive headsets need big earcups to put distance between the noise and your eardrum. Bigger cup = more noise reduction but less comfort. Many of the current ANR headset manufacturers took their most popular models of passive headset and added active noise reduction to them, replacing foam with circuit boards and adding weight. TriPort lets the headset think outside the box, or at least the earcup. The three external ports use the ambient air outside the cup, which means the X needs less space behind the speaker. The results are better active noise reduction and better passive attenuation. The ports aren't exactly fragile, but because they do figure into the sound pressure equation, Bose cautions against blowing on or vacuuming the ports.

Different airplanes have different noise patterns, and the aformentioned tutorial discusses noise components in molecular detail. For brevity's sake let's just say that there are two freqency ranges that make up typical cabin noise in a GA airplane: the whistle and the rumble (the whistle being highs and the rumble being the lows). In the past three weeks I've flown with the X in a Cessna 414A, a Cessna 182, a Bonanza F-33 and my Bellanca Viking. The X did a remarkable job of reducing both the whistle and the rumble in each of these airplanes.

I've been flying with a Bose Series II since 1996 and I had grown accustomed to its quality and level of noise reduction. The X beats it by a mile. The low frequencies disappeared to such a degree that I was able to hear previously hidden sounds, like the opening and closing of the relay for the rotating beacon. The engine sounds different, but it's a difference you get used to in short order.

When ANR headsets first came out I remember folks saying "No thanks. I want to be able to hear my engine in case there's something wrong." Knock wood it doesn't happen very often — in fact it has only happened once to me — but I had no problem detecting a rough running engine with the Series II. I knew what it was supposed to sound like and it didn't sound like that. Once I get used to the sound of a healthy IO-520 through the X, I'm confident that I'll be able to discern the audio cues of a sick one.

Contrary to the apprehensions of many pilots, an ANR headset actually let you hear mechanical anomalies better than you can with a passive headset (or, perish the thought, no headset at all). AVweb editor Mike Busch tells the story of the time — a couple of years back — when he upgraded to the LightSPEED 20K from his trusty old passive David Clarks.  With the new ANRs, he could hear a "funny noise" during ground operations that he'd never heard before. Soon he realized that the noise went away anytime the nosewheel was off the ground. He removed the nosewheel of his Cessna T310R from its strut and discovered one of the wheel bearings was galled and in need of replacement.

EXtolling Its Virtues

Bose engineers redesigned the electret microphone and the gooseneck that holds it. While taking another opportunity to make them both smaller and lighter, Bose also tightened the freqency response so when the squelch breaks, the mic looks for frequencies in the speech pattern range and eliminates more of the noise around it. The mic can be attached to either earcup and the cord moves with it. Two little screws hold the boom assembly in place so it's not the easy swap that Series II owners are used to.

The Clear Comfort gels seals had their fans, but I was never one of them. They retained heat and cold and never gave you a real solid seal if you were wearing glasses. Bose also suggested replacing them annually and they weren't cheap. The X uses a flat ear cushion that feels better and seals better.

The X is so light you can forget you have it on. A good steak weighs more than the X. The clamping force is about half of the industry average and comes from a spring which connects the two-piece headband. Springs being what they are, you have to wonder about how that will wear over time. But for now, it's doing the job of providing a snug fit without the head-in-a-vice feeling that pilots have gotten used to.

Music through the X is simply stunning and I'm not a big fan of music in the airplane. To support my flying habit I compose and produce music and soundtracks — mostly for commercials. Often that means I'm in a recording studio for about 26 hours a day. Between that and practicing to keep my "chops" in shape, it's not like I suffer from a lack of music in my life. And if there's anything more frustrating than hearing a piece of music you love through a 3" TV speaker, it's hearing it through a 2" aviation headset in a lousy listening enviroment.

Mostly though, since I fly in Southern California where 25% of the airplanes in the GA fleet are based, I'm almost always talking to ATC either under IFR or flight following. Trying to listen to the snippets of music that sneak in between radio calls is too frustrating for me, so I usually forego the experience of music when flying. But if you (or your passengers) are a fan of music in the airplane you should try the X. The stereo imaging and the frequency response are comparable to the pro-quality headsets we use in the studio. Bose lists the official frequency response as 15Hz to 15KHz.

The X I've been using is the portable model, powered by a single 9 volt battery in the control box. Bose estimates 20 hours of use per battery. That's a big improvement over the 6 AA powerpak of the Series II. Carrying around 6 extra AAs per headset was a pain, and if you're memory-challenged like me, it was only a matter of time before you'd need them after forgetting to power down. Give the X a demerit for not including LightSPEED's innovative auto-shutdown battery saving feature. But Bose did include a low battery warning light. A blinking green LED indicating power on changes to blinking red when remaining battery power drops below 5 hours. The control box has a clip that comes in handy for keeping the wires tidy.

Those that order the hardwired version of the X won't face these problems and will be happy to know that the X's power plug is compatible with already-installed plugs for the Bose Series II (but not the Series I). Bose offers other options for the X. If your aircraft is of the rotary wing persuasion you can order the X with a dynamic microphone and your choice of U-174 or NATO connectors. The X is available with a coil cord for all aircraft.

EXceptions to the EXcellence

There are other new features of the Bose Headset X that ... ahem ... take some getting used to. The volume control is one of them. It's a retracting knob that allows separate controls for each earcup. To adjust the volume you pop the knob out of its retracted position in the control box, and turn it to change the volume on only one earcup (the one the boom is attached to). It takes a pull on the control firmly (the knob will go through a "click" then reach a stop) so you can adjust the other earcup's volume. If you adjust only the first position, it will change the L/R balance as you change the level in one ear only. Once you get the balance and level set for your hearing and relative to the listening preferences of others you're flying with, you push it in and the setting won't accidentally get changed when you stow the headset. Overall volume adjustments are then made with the controls on your audio panel, intercom, or radio.

The X's sidetone (the sound of your own voice as you transmit) is thin compared to the rich sidetone of the Series II and other ANR headsets. Bose engineer Dan Gauger explains why:

"The subordinate objective in setting the audio input response of the X was to thread the needle between three requirements: (a) meeting the speech frequency requirements prescribed for TSO (given in RTCA DO-214) to ensure good communication, (b) a fairly simple circuit so that the earcup was not burdened with extra weight or battery drain (impacting comfort and ease of use), and (c) a good response to music inputs based on proprietary target curves developed by our research group. The response of the Bose X at 200-300 hertz is down a few dB relative to the higher frequencies, as a result of achieving these three constraints, and this is probably what you're hearing."

So I've given up on my Chuck Yeager imitation, and even Chuck Yeager doesn't sound like Chuck Yeager through the X. But that seems a small price to pay for being able to hear something more subtle than a sonic boom when you reach the General's age.

The X also seems to have some "interesting" compatibility issues. During the C-414A test flight, everybody but me was using Telex Airman 750s. When I plugged the Bose X into the PS Engineering intercom, everybody else's headsets went numb — their volumes dropped about 80%. We tried adjusting radio volumes and intercom settings, unplugging and re-plugging and finally gave up trying to find a setting that pleased everyone. I didn't try turning the radios and intercom up all the way and turning the X's volume down. That might have worked. But I can tell you that while I had the X on, the noise reduction and the quality of the music were still awesome.

In my Viking I moved the Series II to the copilot seat and piloted with the X. The listening levels were about the same but it took a bit of tweaking of radio and intercom (Telex ProCom 4) settings to find a squelch break that worked for both models. Dan Gauger adds:

"The need to do some tweaking of volume at the radio and intercom as well as squelch levels is built into the range of variation defined in the TSO microphone interface standard. The spec that the mic TSO refers to (RTCA DO-214) allows as much as 12 dB variation in mic sensitivity; the range is even greater when you factor in variation in the bias voltage and impedance from the radio or intercom and variation in how the individual pilot positions the mic (brushing the lips or half an inch away). This variation can add up to nearly the amount of volume control authority DO-214 allows in the headset as well as exceed the range of signal input needed to ensure good modulation of your radio. For best performance, the radio front end should be adjusted to match the headset."

Is that perfectly clear now? Suffice it to say that your mileage will vary according to your particular combination of radios and intercom and mix of headsets. Expect some tweaking.

I recently spoke with the owner of an A36 Bonanza who bought the Bose X and was convinced that they're noisier than the Series II on takeoff until the first power reduction. (He said in cruise they're quieter and more comfortable and he likes them.) When he called Bose, he talked to a senior tech guy who told him that Bose is getting a similar calls from many Bonanza and Baron owners. Apparently there's something peculiar to the frequency range in those airplanes. Bose is aware of the problem and is working on a fix. They're keeping a list of the people that call.

Mike Busch tried out my Bose X in his twin Cessna and also reported that he had some problems with them on takeoff. However, he attributed the difficulty to the fact that the clamping force of the Bose X is so low that the headset shifted on his head during the acceleration and vibration of the takeoff roll, giving the ANR system fits and creating all sorts of strange noises in his ears. He said that once he was off the ground with the wheels in the wells, the problem disappeared and the headset performed splendidly for the remainder of the flight.

Specs of the X

Is It Worth the EXtra EXpense?

In his product review of the LightSPEED 20K, Mike Busch suggested that the aviation headset consumer universe has a binary choice:

• A's say "I just can't believe how quiet and comfortable this headset is! I don't care what it costs."
   
• B's say "A thousand bucks??? No way that I'm going to spend a grand on any headset!"

If you're a card-carrying B the Bose X probably won't turn you into a rabid A. Personally, I have no plans to challenge Beethoven's claim to the title "greatest deaf musician" so I'd tend to vote A. But there's no point in voting A unless you're convinced you're getting some value for the extra expense. So I decided to do my own A/B scrimmage with the product of another loyal AVweb sponsor, the LightSPEED 20K, which sells for $439. Thses are my extremely subjective opinions and impressions after flying a few flights with both headsets in my exceptionally noisy Bellanca Viking.

Comfort ...

For my 7 & 3/8" hat-size head the Bose X beat the LightSPEED 20K hands down. The LightSPEED does a really good job of distributing the clamping force evenly throughout the fit. I wasn't really concious of it squeezing around the ears or the top of my head and the wide foam seals do a decent job of buffering and absorbing what pressure there is.

But the clamping force of the X is just a fraction of the force on the 20K so I didn't really feel much sensation of pressure at all. It's evident right away, and the longer I flew the more I noticed it. After a two hour flight there was no comparison in how my head felt when I removed the headset.

Here's another comfort issue for tall people or people with a vertical clearance problem. The Bose X's headband is thin so it's worth looking at if your height causes you to bump, scrape or rub your headliner.

Noise Reduction ...

For active noise reduction I give a slight edge to the Bose X with a couple of caveats. I'm still getting accustomed to the sidetone of the X. It sounds like they kept the basic speaking range and filtered out everything above and below it. My perception is that I sound a little muffled so I tend to speak a little louder than I'm used to. If it means listening to less whistle and rumble maybe I'll get used to it.

The LightSPEED 20K has excellent noise reduction characteristics and a nice rich sidetone. I detected a bit less rumble in the Bose X but I'd say both units were about the same for high frequency cancellation.

For passive noise reduction the LightSPEED wins decisively. The larger cups, the wide foam seals and the clamping force all become your new best friends when the power goes out. With the power switch off, the Bose X offers nothing between you and the noise but air. Turn the X's power on and the noise disappears with that "giant sucking sound" that Ross Perot made so famous, but it's all done with electronics. Bring spare batteries.

Music ...

Again it's a hands down win for Bose. It shouldn't be surprising that a company that's been designing large and small music speakers for 30 years developed an excellent small music speaker. It also shouldn't be surprising that Bose found a way to employ the porting technology they've been using in other speaker systems all these years. Music through the LightSPEED lacked the high-end crispness and clarity of the X.

It's probably a combination of better speaker technology and a much-improved listening environment, but whatever it is if you're a music lover you should try the X in your airplane.

Value ...

This is the most subjective one. It's tough because you introduce factors like how often you fly, how noisy your airplane is, if you use a stereo intercom, if you listen to music, how comfortably the less expensive models fit your head, how many headsets you need to buy, and how important $500 is to you. You'll need to make those calculations for yourself.

I'm still in the A camp. I fly a noisy airplane and my ears are my living. I figure if I fly 200 hours a year the $500 price difference costs me about the same as a gallon of gas per flying hour. If the headset lasts five years, that amortizes to about fifty cents per flying hour. That doesn't seem like such a terrible price to take a lot of the physical and mental fatigue out of flying.

After borrowing my Bose X and flying with them in his Cessna T310R, AVweb editor Mike Busch remains a defiant B. "I found the Bose X to be better than my LightSPEED 20K in a few areas — particularly the noise cancelling capability of the microphone — but it sure isn't two-and-a-half times better," he told me as I was nagging him for the third time to return my X-set. Of course, keep in mind that Mike makes his living with his fingers, not his ears, and that he's a world-class skinflint. (Owning a twin will do that to a person.)

If you're an A like me, you'll be happy that the X uses improved noise reduction technology. You'll be even happier that those improvements resulted in a remarkably comfortable headset.

EXperiment for Yourself

There's really only one way to find out if the Bose X — or any particular ANR headset model, for that matter— is right for you. You've got to try it. Comfort is a terribly subjective thing, and all the reviews, brochures and specs in the world won't tell you a fraction as much as actually putting on the headset and wearing it on a couple of actual flights. Luckily, Bose recognizes that and offers a 30-day no-risk test flight. Or order online from AVweb sponsor Avionics West who also offer a 30-day, no-questions-asked return policy.