THE Bose A20 has the same magnesium headband as its X model, but the ear cups and control module are different.
The two biggest additions is the ability to use Bluetooth, the addition of a 3.5mm auxiliary audio input (MP3 player, GPS unit etc.) and priority audio switch - all things the X lacked. Bose also claim that two normal alkaline AA batteries will last for up to 45 hours.
IT was big news in 2010 when Bose announced the launch of its first new AN headset in just over 12 years. Just when the Bose X was starting to look a tad dated they released the A20. As soon as it was revealed Dave Caiderwood got his hands on one to see if the best got better.
His summary? "With the ANR off the sound quality is OK and there's a definite improvement in the passive noise reduction, through built-in insulation. However, once you've tried the ANR, you won't go back - the difference is outstanding."
"The new ear cushions contribute hugely to the A20's overall comfort level which is nothing short of extraordinary. The new bigger ear cups/cushions seem to embrace the ears with just the right amount of pressure, which is claimed to be one-third of the pressure of other leading headsets."
"The new headband is a very clean redesign of the X, though the family resemblance is kept and it sits on the head so lightly you forget it's there."
Ever since the beginnings of aviation, one of the major problems for pilots Eand passengers alike has been that of noise.
Early aviators, of course, had more important things on their mind, like staying alive, so they simply disregarded the racket made by their usually unmuffled engines.
Through the Thirties, the design of aircraft — even airliners, including such silver-winged behemoths as the Ford AT-5 TriMotor or the Douglas DC series — paid only scant attention to soundproofing.
It's no wonder that disembarking passengers, when asked how they'd liked their flight, often simply answered, "What?" This regrettable trend continued during World War Two — after sitting behind the twelve stacks of a Merlin or between two or four big radials for a few hours, the intrepid Mustang, Spitfire, or bomber pilot not only said, "What?" after a flight, but often continued to say, "What?" in response to most questions well into the 1960s. It wasn't really until after WWII that much attention was paid to soundproofing — and then primarily in larger aircraft that could afford the cost and not insignificant weight of soundproofing materials.
Thus, the airliners were the prime beneficiaries, and even today, in even the best of produc-tion lightplanes, it's noisier than you think — while, back on the ground, the occupants of an auto costing a tenth as much enjoy relative silence.
No wonder that the pilots of many lightplanes — from homebuilts to turboprops and even some jets — choose to wear heavy, bulky headsets for noise attenuation.
During the last couple of years, however, one firm — The Bose Corporation, of Framingham, Massachusetts — has been tackling the issue of aircraft noise from a different direction.
Rather than attempting to limit the amount of noise to which the pilot is exposed by soundproofing the cabin, or even keep the noise out of the headset's earcups by tight-fitting ear cushions and high clamping pressure, the Bose scientists and engineers took the position that some noise entering the earcup is inevitable — but that it can be dealt with electronically.
In fact, the basic idea of negative feedback is not new: If a signal is combined with another signal of exactly opposite polarity — in other words, a mirror image of itself — the result should be zero.
Any sound wave can be graphed as a series of peaks and valleys; if you were to superimpose an inverted version of the same signal, so that the peak of the original signal would correspond to a like-sized valley in the inverted signal and vice versa, the resulting graph should be a straight, flat line.
In feet, this phenomenon is the basis of a classic (and hilarious) science fiction story by the great Arthur C. Clarke, who in his spare time invented the concept of communications satellites; next time you're at the library, pick up his Tales from the White Hart and read the one called "The Fenton Silencer"
Once the Bose folks had done the basic research and had a handle on implementation, they found the ideal test bed: Dick Rutan and Jeana Yeager's Voyager.
Here was an aircraft that was not only intensely noisy, but also could not spare an ounce for soundproofing; and its crew would be exposed to noise for nine days straight, resulting not only in increased fatigue and impaired performance but the very real possibility of significant permanent hearing loss.
Traditional headsets had been tried, and indeed were originally planned for the trip — but the prospect of spending nine days with one's head clamped in the viselike grip necessary for a good ear seal was not pleasant either.
Dick and Jeana were issued the first experimental pairs of Bose headsets for the trip, and have stated that they made a very significant contribution to their ultimate success. (In fact, even without active noise cancellation the headsets helped; on one, noise suppression failed partway into the trip since no one had ever had to design circuitry to withstand nine days' worth of ear sweat before).
Even so, the Bose people seem somewhat perfectionist, since it was not until about July of this year that the production version of the Bose Aviation Headset finally became available to the general public.
I've been using one ever since then, and its performance has been, frankly, almost unbelievable. I devoutly hope that I'll never have to go back to conventional headsets, excellent though some of them are, except in the very quietest of airplanes — in which I wouldn't really need a headset at all!
The basic function of the Bose headset is far easier to explain than it was for the Bose engineers to get to work reliably under all conditions: A tiny microphone in- side each earcup picks up the total sound presented to the pilot's ear — that is, both desired sounds such as radio communica- tions and undesired ambient noise.
The circuitry in the earcup then electronically subtracts the desired sounds (ie the signal input to the headset) from the microphone input, inverts the resulting signal, and feeds it back into the earphone driver.
Thus, the final mix presented to the pilot's ear consists of the original desired signal plus a mirror image of the noise, so the noise is effectively cancelled.
Sounds simple — but building microphones, inverting amplifiers, signal processors, and drivers fast and stable enough to repeat the process thousands of times per second took even Bose a firm with a long and proud reputation for advanced sound reproduction equipment — several years.
I mentioned earlier that conventional headsets are comparatively heavy and bulky.
The Bose headset, on the other hand, is light and bulky — in fact, somewhat bulkier than some of its competitors (although considering conventional headsets' competitors at this point is something of an apples vs oranges situation).
The earcups, built from dark-gray plastic, are large and somewhat angular; a clear plastic section at the rear of each reveals the mass of circuitry that performs the noise-canceling function.
The headband is also fairly large, primarily because of a very thick and squashy cushion for the top of your head. On the other hand, the whole assemblage is remarkably light, weighing in at just under 20 ounces.
The ear cushions merit special mention; Bose calls them Gel/Foam, and each includes a base of foam rubber and a double ring — the part that actually rests against the side of your head — of clear plastic filled with a viscous silicon gel.
I believe Bose farms out the manufacture of these cushions, which they recommend be replaced once a year for about $20, to an outside subcontractor — and having had an acquaintance who was a Southern California plastic surgeon specializing in the silicon augmentation of natural female endowments, and having seen examples of his stock in trade, I believe I know what kind of subcontractor they're using.
Suffice it to say that donning the headset can be a delightfully sensual experience — and the extremely compliant nature of the cushions lets them snuggle up to the side of your head and make a good seal, even around glasses frames, without exerting much actual pressure on your skull.
The boom mike, which can be mounted on either earcup, is a noise-canceling electret type which can be articulated at the mike itself, halfway back along the boom, and at its mounting on the earcup.
If you drop the headset, the mike just pops off and can be snapped back on. The headset cable — unfortunately not the self-retracting curly kind — terminates in a unique multipin plug that attaches to the other major unit in the system, the Headset Interface.
This is a little aluminum box, about the size of a couple of packs of chewing gum, which contains an on-off switch and volume control.
A cable extends from this box and ends in standard aircraft phone and mike plugs, while a receptacle accepts a power lead: For noise cancellation, the system requires DC from 11 to 32 volts, normally provided by a cigarette lighter plug, with built-in fuse, that's supplied with the system.
The system is fail-safe; when its switch is turned off, or if power fails regardless of switch position, it reverts to conventional or non-noise- canceling operation.
The proof of the system comes in using it, and as far as I'm concerned, it's proven: While Bose provides various graphs showing how much noise it reduces, the subjective impression is even more startling. Even with noise-canceling turned off, the headset does a pretty good job attenuating both low- and high-frequency noise.
Throw the switch, however, and there's a strange momentary sensation of very slight pressure against your ears, following which the vasdy greatest part of the external noise simply fades quietly away.
You can still hear your engine or engines, but what was a roar is now a very muted hum; oddly enough, you can also hear slight high-frequency changes — someone talking to you, for example — reasonably well.
ATC communications come through crystal clear, and you can hear them very comfortably at much lower volume than what you're probably used to.
Thus far, I've had the chance to experiment with the headset in various aircraft ranging from what are supposed to be hushed executive turboprops through standard Spam cans all the way to high-noise ships like homebuilts, helicopters, and Warbirds.
In every case the noise cancelation worked like a charm, leaving me much more relaxed yet less tired after a flight. At the same time, I've worn the headset for up to six hours at a time on a couple of flights and have found it completely comfortable.
I've found that I tend to get so used to the noise cancellation that I take it for granted; every now and then I'm tempted to switch it off for a moment just as a reminder, at which point the aircraft noise comes crashing back in.
The ultimate system, if you were going to use the headset primarily in one particular aircraft, would involve permanently mounting the headset interface in some convenient spot and providing a full-time power lead to free up your cigarette lighter.
The final fillip would be to add a stereo music system or intercom switcher; the headset can be converted to stereo by simply clipping one jumper in the interface box, and instructions for doing so are included with the system.
If this all seems too good to be true, there's one thing that can bring us back to earth with a thud: If the performance of the Bose Aviation Headset is breathtaking, so is its list price, at $965.
For the present, too, Bose is selling them factory direct, so it may be a while before the big discounters like American Avionics get their hands on them; moreover, they've got the works of the thing patented about six ways from Sunday, so it may be awhile before another firm can compete directly against them
On the other hand, Bose was selling the headsets at Oshkosh as fast as they could get them shipped in from the factory, so there are obviously people out there who are willing to pay that kind of money for a unique level of quiet and comfort — and, very significantly, for long-term protection against hearing loss.
I was a pretty hotshot recording engineer myself 20 years ago, and I doubt that I could be as good today — 25 years and 12,000 hours of aircraft noise have taken their inevitable toll. If a headset like this had been available back then, I'd have scrounged up the funds to buy it immediately.
If you fly more than a few hours a year, particularly in noisier aircraft such as light trainers, homebuilts, Warbirds, or helicopters, I'd suggest that you try a pair, at which point it may well sell itself; even at close to $1000, it's cheaper than the only pair of ears you'll ever have.