| by |
Mike Busch |
When Bose introduced the
first active noise reduction (ANR) headset to the aviation community at Oshkosh
in 1989, pilots who visited Bose's big black trailer and tried the headset
had two distinct reactions to it:
Reaction A: "I just can't believe how quiet and comfortable this headset
is! I've simply gotta have one!!! I don't care what it costs."
Reaction B: "How much did you say this headset costs?
A thousand bucks??? Be serious! They'll never get away
with pricing it that high! The price has got to come down!
I'll just wait until it does. No way that I'm going to spend a grand on any
headset!"
AVweb's publisher Carl Marbach and I make a good case study. He's
an "A" and I'm a "B". Carl bought his first Bose headset at that 1989 Oshkosh
trailer and has simply refused to use any lesser headset since. I, on the
other hand, have lots of hours wearing other peoples' Bose headsets and I
agree that they're absolutely marvelous — but I simply have never been able
to bring myself to spend a kilobuck on a headset. For eight years, I've been
waiting for the price to come down. And for eight years, Bose has stubbornly
held it firm. The nerve of those people!
Where's the competition?
Meanwhile, the other major players in the aviation headset business introduced
their own ANR headsets, all at prices somewhat lower than Bose. And I've
tried them all. Telex was the first to field a competitive active headset.
I flew with it but didn't like it at all, which didn't surprise me because
I've never much cared for Telex headsets.
Next, David Clark entered the ANR competition. This time, I really had my
hopes up because I've always been a big-time DC fan and my headsets have
always been green (as opposed to my wallet). But again I was disappointed:
DC's ANR offerings were just DC passives with some ANR circuitry added...and
not terribly good ANR circuitry at that. They didn't come close to offering
the comfort of the Bose, and I still couldn't wait to get the darned things
off toward the end of a long flight. Okay, they're incrementally better than
my faithful old DC passive headsets...but they sure aren't worth $700 in
my book!
Call me frugal. Call me a cheapskate. I'm guilty as charged...and I've been
called a lot worse.
I tried the Peltors and the Sennheisers and a couple of the off-brand ANRs
too. But none of them were comfortable enough or quiet enough or cheap enough
to persuade me to forsake my trusty DC green-earcup head-in-a-vise passives.
But that just changed! A small audio company in Oregon that nobody ever heard
of is about to stand the aviation headset market right on its proverbial
ear. The comfortable, quiet and cheap ANR headset that I've
been waiting eight years to purchase is now here! Good things
do come to those who wait...but sometimes you've got to be
incredibly patient.
So who the heck is LightSPEED?
LightSPEED Technologies in Lake Oswego, Oregon, was founded a few
years back by some engineering, manufacturing and marketing people who formerly
worked for Tektronix, the giant electronics and instrumentation company.
LightSPEED manufactures a variety of precision audio products including wireless
microphones, hearing aids, and classroom amplification systems. About a year
ago, they stuck their corporate toe into the aviation headset market by
introducing the LightSPEED model "15K" ANR headset at Oshkosh '96, priced
at $299. (More about the "15K" later in this article.)
Recently, LightSPEED introduced their second-generation "20K" aviation headset,
priced at $439. That's the one I'm all excited about. They're showing the
"20K" for the first time at Oshkosh '97, and my guess is that once the word's
out they'll have trouble keeping up with the demand. I've already ordered
two of the 20K's for my airplane...just to make sure I beat the rush.
Look and feel
The LightSPEED headset looks, well, different. It appears to be made entirely
of gray plastic, and has a sort of extra-terrestrial look (as if designed
by aliens from Roswell, NM). It turns out that the headband actually has
a metal core, but it's totally sheathed in plastic. The yokes, earcups, and
adjusting mechanism are all plastic, too. So I imagine that this headset
won't take the kind of physical abuse that a David Clark headset will. But
then neither will a Bose.
The earcups have a distinctive triangular shape, and
are fitted with ultra-deep (inch-and-a-half thick) earseals that contain
three layers of temperature-sensitive foam, each layer having a different
density than its neighbor. The earseals remind me of the aftermarket Oregon
Aero "Soft-Seal" cushions that I use on my DCs for increased comfort; they
use the same sort of temperature-sensitive foam construction. (Hmm, LightSPEED
is in Oregon, too.) The foam softens where it touches warm skin, making it
capable of accomodating the head shape perfectly with minimal clamping force.
It also seals exceptionally well around the temple pieces of eyeglasses or
sunglasses. (But don't leave this headset in the plane overnight when it's
below freezing outside, or the earseals will be rock-hard when you first
try to don the headset.)
The headband is also padded with one-inch-thick soft foam pillows, and is
adjustable over a wide range by means of "ratchety" sliding rails that connect
the headband to the earcup yokes. Unlike my DCs, there are no tools required
to loosen the headband adjustment (which is good) and no way to lock the
adjustment in place (which could be a disadvantage if you carry the headset
around in a carrying bag rather than leaving it in the airplane like I do).
I have a wide head (some say swelled) and the headset fit me fine without
going to max extension. LightSPEED claims that the low end of the adjustment
range accomodates children, and it certainly looked that way to me although
I didn't actually try it out on a kid.
The microphone uses an electret element (the best kind) with an integral
foam blast shield. It mounts on a thin flexible "gooseneck" boom with a
ratcheting plastic elevation adjustment where it attaches to the left earcup.
It seems like a good arrangement. My only complaint is that the headset is
permanently a "lefty." When I'm flying in the right seat, I usually like
to turn my headset around so that the mic boom is on the right side. I can
do this with my DC, but not with the LightSPEED because its triangular earcups
are canted for optimum fit and distinctively left- and right-handed. This
is only a minor drawback, though..
Comfort is a very subjective thing, but I found the LightSPEED to be every
bit as comfortable as the Bose. In some ways, I liked it better: it weighs
less (16 ounces) and the earseals don't have that strange "breast-implant
feel" of the Bose gel-filled seals. Certainly, the LightSPEED is as comfortable
as any headset I've tried.
ANR performance
Let's cut to the chase. The active
noise reduction capabilities of the LightSPEED "20K" are simply outstanding.
Flip on the switch and it "sucks the noise right out of your head" just like
the Bose does.
Lab tests indicate that the LightSPEED "20K" ANR system provides exactly
the same number of decibels of active noise reduction as the Bose Series
II...about 20dB maximum. The LightSPEED's achieves maximum reduction at about
110 Hz while the Bose's notch is centered at about 180 Hz. Is the difference
significant? Let's see.
Suppose you fly a propeller-driven airplane with a constant-speed prop, and
suppose your normal cruise is at 2400 RPM. Divide by 60 and you get 40
revolutions-per-second. Now, the biggest low-frequency noise source in your
cockpit is power pulses from the propeller. If you have a two-bladed prop,
your noise peak will occur at about twice engine RPM or 80 Hz; if your prop
is three-bladed, it's three times engine RPM or 120 Hz. Either way, the
LightSPEED's 110 Hz notch frequency is pretty close to optimum.
Another major noise source is exhaust noise. If you have a four-cylinder
engine, your exhaust noise occurs at twice engine RPM (because each cylinder
fires once per two crankshaft revolutions) or about 80 Hz. With a six-cylinder
powerplant, it's more like 120 Hz. So theoretically, the LightSPEED's 110
Hz notch might be a tad better at eliminating exhaust noise than the Bose's
180 Hz notch.
But subjectively, to be perfectly
honest, it's hard to tell the difference. Both headsets do a first-class
job of cancelling low-frequency noise characteristic of piston-powered
propeller-driven aircraft. As far as I can see, the primary difference is
that the Bose costs more than twice as much.
If you're into such stuff, check out the noise graph at right. It shows a
spectrum analysis inside the cockpit of a Cessna 172 with a four-cylinder
engine and two-bladed prop. You can clearly see the prop- and exhaust-noise
peak around 80 Hz, as theory predicts. And you can see that the "20K" knocks
it down by 20 dB (from slightly over 100 dB to slightly over 80 dB), just
as advertised. But you can also see that there's plenty of low-frequency
noise throughout the 50-200 Hz spectrum where ANR circuitry does most of
its magic.
Audio quality
The speakers in the LightSPEED "20K" earcups offer excellent comm
intelligibility, but if you're heavily into listening to CDs in-flight (instead
of Rush Limbaugh or ballgames or news), the fidelity of the Bose transducers
is somewhat better. However, the LightSPEED is certainly acceptable for music
and offers stereo as well as monaural modes (manually switched, not automatic
as in the Bose Series II).
Microphone audio quality and noise cancellation is excellent, as you might
expect from a company that built its reputation manufacturing high-quality
wireless microphones before getting into the aviation headset business.
Hookup
All active headets are at a disadvantage to passives when it comes time to
hook them up, because of the need for a power module for the ANR circuitry.
Bose offers its Series II headset in two different models: a
permanently-installed model in which the power module is mounted behind the
instrument panel, and a portable model with an external power module that
contains a battery pack.
The LightSPEED comes in only one flavor: battery-powered. The
headset is connected to a small power module via a four-and-a-half foot cord.
The power module contains two AA-size alkaline batteries (which are good for
at least 20 hours of use), two slider-type
volume controls, a stero/mono switch, an on/off switch, a battery-check
switch, and three battery-level LEDs. The power module is also connected to a pair of standard mic and
phone plugs via foot-long pigtails.
The question is: what to do with the power module in-flight?
In my airplane, the headset jacks are located at the extreme lower outside
corners of the instrument panel, so the LightSPEED power module simply hangs
down by the lower cockpit sidewall out of harm's way. On the other hand,
if your jacks are located high on the instrument panel or, worse yet, on
the cockpit ceiling, the dangling power module could definitely get in the
way...in which case, you might have to relocate your jacks, use an extension
cord, or secure the power module with Velcro.
Another related hassle is that the on/off switch on the LightSPEED power
module is unguarded. This isn't a problem if you normally leave the headset
in the airplane as I do...you simply have to remember to turn the thing off
when you power down the airplane. But if you carry the headset around with
you, it's awfully easy to bump the button accidentally and turn the thing
on...resulting in dead batteries next time you try to use the headset. I'd
like to see LightSPEED change the switch design to one that's harder to actuate
inadvertantly. Meantime, either be careful or pop out the batteries before
you store the headset.
The lower-priced spread
As mentioned earlier, LightSPEED also offers an even-lower-priced
ANR headset: the "15K". Physically, it's virtually identical to the "20K"
except that it uses earseals that aren't quite as deep and contain two layers
of thermal foam padding (instead of three).
The big difference is that the "15K" uses older and less-effective ANR circuitry,
and offers about 5 dB less low-frequency noise reduction. The decibel scale
is logarithmic, and 5 dB is a lot! So the "15K" is simply not as quiet as
the "20K", but it's equally comfortable and sells for $150 less. The "15K"
also comes with a two-year warranty, compared with three years for the "20K".
The "15K" doesn't offer Bose-quality noise reduction, but it's on a par with
other ANR sets (like the DC and Telex), and it's more comfortable and a whole
lot cheaper. It's also a significant improvement in both quiet and comfort
compared to passive headsets at a price ($299) that's not much higher.
We'd definitely opt for the "20K" for crewmembers of a piston-powered
aircraft...its superior noise cancellation is worth the extra $150. But for
passengers, or for quieter aircraft (jets, turboprops, and airplanes with
geared engines like the Cessna 421), the "15K" would do just
fine.
Where to get them
Avionics West
has th LightSPEED "20K" on-sale at just $425 each, $20 below list. This is
a remarkable bargain when you consider that the Bose Series II battery-powered
model costs $1,075 and that most "low cost" ANRs are priced in the $600-$700
range! Avionics West also carries LightSPEED's "15K"
ANR model priced at $295.
You can order
both models on-line and help support continued free access to
AVweb and AVflash in the process.
LightSPEED is presently building its dealer network, although they tell us
that most of their present dealers are concentrated on the east coast for
some strange reason. LightSPEED will also be at Oshkosh '97, but we wouldn't
advise waiting until then because we expect their supply to sell-out almost
immediately, just as happened with Garmin's GPSMAP-195 last year, and a lot
of folks will wind up going home empty-handed.
Once the word gets out (and I suppose the fact you're reading this means
it already has), I predict that LightSPEED will have a difficult time keeping
up with demand for these headsets. I wouldn't be surprised to see a substantial
backorder situation to develop over the next month or two while LightSPEED
ramps up to meet the demand for these headsets.
I'm not worried one bit. I've already ordered mine!
Read what one AVweb member had to say about
his LightSPEED "20K".
QUESTIONS? Contact Avionics West, Inc., by e-mail at
avionics@avweb.com, by FAX at
1-805-928-3603, or by telephone at 1-805-928-3601.
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