May 28, 2002 LightSPEED's Hybrid Headset: The QFR Cross Country

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by	Mike Busch
	AVweb Editor-in-Chief

About the Author ... Mike Busch is editor-in-chief of AVweb, a member of the technical staff at Cessna Pilots Association, and in a prior lifetime was a contributing editor for The Aviation Consumer and IFR Magazine. A 6,000-hour commercial pilot and CFI with airplane, instrument and multiengine ratings, Mike has been flying for 36 years and an aircraft owner for 33. For the past 14 of those years, he's owned and flown a Cessna T310R turbocharged twin, which he maintains himself. In his never-ending quest to become a true renaissance man of aviation, Mike's on the verge of earning his A&P mechanic certificate. Mike and his wife Jan reside on the central coast of California in a semi-rural area where he can't get DSL or cable TV. MBusch@AVweb.com

Also see Mike Busch's previous reviews of LightSPEED's QFR Solo passive headset and LightSPEED's top-of-the-line 25XL headset.

When I reviewed LightSPEED's new $150 QFR Solo passive headset in October 2000, I mentioned how much I was looking forward to trying out the soon-to-be-released ANR-enhanced version, the QFR Cross Country, the first under-$300 aviation headset to offer active cancellation. LightSPEED started shipping the QFR Cross Country in January 2001, and I originally planned to complete my review in February. As things turned out, however, it was six months later before this review was ready to publish. I hope it was worth the wait.

I tried to get my hands on this headset when it first started shipping last January, but LightSPEED had so many backorders for the QFR Cross Country that I didn't get mine until mid-February. That put me in a time bind, since my airplane was going down for annual in early March. I did manage to get one or two short test flights with the headset before then, but ran into a couple of minor glitches with the headset and returned it to LightSPEED to be exchanged for another.

By the time the replacement arrived, my airplane was in pieces. This year's annual inspection turned out to be "the annual from hell" — both tailpipes and turbochargers needed to be replaced, the landing gear retraction linkage removed and re-bushed, wheel bearings replaced, and on and on. It wasn't until mid-April that I was back in the air and ready to give the hybrid LightSPEED a decent workout.

They Don't Call It "Cross Country" for Nothing

But what a workout it finally got! In late April, I made a 6,000-nm trip in my Cessna T310R that took me from my home base in California to Colorado, Ohio, Connecticut, Massachusetts, upstate New York, Maryland, Louisiana, Texas, Arizona, and home again to California. A good friend who is an excellent pilot accompanied me on the trip, and we alternated legs as "pilot flying" and "pilot talking." We also alternated headsets, with one of us wearing the QFR Cross Country and the other my friend's LightSPEED 20XL on each leg. By the end of our three-week round-the-nation junket, both of us had an excellent opportunity to use the QFR Cross Country and to make A/B comparisons it with LightSPEED's pricier XL-series ANR headset.

I hoped to write this review article not long after I returned from that trip in early May. Unfortunately, I was overtaken by events and didn't get it done before launching off on another long trip in early June. This time, it was my annual pilgrimage to the Cayman Islands, where I'd been invited to be a featured seminar speaker for the fourth consecutive year. I flew the plane solo from California to Key West, where AVweb's executive editor Jeb Burnside and two other journalists joined me for the Cayman Caravan flight over Cuba to Grand Cayman. A week late, Jeb flew back to Key West with me, and then I returned to California solo. On this trip, I alternated between using the QFR Cross Country and my four-year-old LightSPEED 20K ANR, until I managed to break the headband on the 20K early into the return trip and wound up using the QFR Cross Country for the remainder of the trip, which totaled about 4,000 nm.

I'll cut to the chase: After four months and 10,000 nm with the QFR Cross Country, I really like this headset. Frankly, I'm surprised how much I like it. That's because I just love the LightSPEED 20K headsets that I've been flying with for the past four years (now superseded by the much-improved 20XL). And despite coming from the same manufacturer, the QFR Cross Country is about as different from LightSPEED's K- and XL-series as it could possibly be.

LightSPEED's XL-series LightSPEED's QFR-series

Active vs. Passive ...

The hallmarks of LightSPEED's K and XL ANR headsets are the unique triangular low-volume earcups, the deep and cushy earseals, the thickly padded headband, and very aggressive active (electronic) reduction of low-frequency noise. Interestingly enough, the QFR Cross Country shares absolutely none of these attributes. It's a complete clean-sheet design.

To create the QFR Cross Country, LightSPEED started with its QFR Solo passive headset, which is without question the quietest and most comfortable non-ANR headset I've ever flown with. The QFR Solo achieves its excellent comfort through ultra-light weight (less than 12 ounces) rather than through thick padding, and it achieves its outstanding noise reduction through purely passive (non-electronic) means. The QFR Solo has a noise reduction rating (NRR) of 28.7, about 6 dB better than most other passive lightweights. For example, David Clark's most popular headset — the H10-13.4 — weighs 1.5 ounces more but has an NRR of only 23. It's also substantially more expensive than the QFR Solo. (I happen to own an H10-13.4 that I purchased in a previous lifetime and carry in the airplane as a backup headset. I don't care for it one bit so it mostly collects dust on the aircraft hat shelf. If I were smart, I'd auction the darn thing off on eBay and be rid of it. To me, the difference between the H10-13.4 and the QFR Solo is like the difference between night and day.)

An inherent property of passive attenuation is that it is most effective at reducing high-frequency noise, and less effective at low frequencies. For example, the QFR Solo offers mean attenuation of 40 dB or better at audio frequencies of 3,000 Hz and up, but just 36 dB at 500 Hz, 24 dB at 250 Hz, and 19 dB at 125 Hz. So a good passive headset does a terrific job of reducing wind noise, air leaks, and other high-frequency sounds. If you're flying a Learjet or a King Air, a passive headset can provide all the noise reduction you need.

Unfortunately, most piston-powered propeller-driven airplane cockpits have a lot of low-frequency noise below 200 Hz, mostly from engine exhaust and prop tip pulses. For most GA airplanes, this noise is concentrated in the 70-140 Hz range. For example, if the engine is turning at 2,400 RPM (40 revolutions per second) and is driving a three-bladed propeller, the peak prop noise frequency is 120 Hz — or for a two-bladed prop, 80 Hz. Similarly, since each cylinder of a four-stroke engine fires once every two crankshaft revolutions, exhaust noise at 2400 RPM peaks at 80 Hz for a four-cylinder engine, or120 Hz for a six-cylinder engine. This noise occurs right in the part of the frequency spectrum where passive attenuation is least effective.

... vs. Hybrid

What LightSPEED has done with its QFR Cross Country hybrid headset is to start with the QFR Solo — a superb passive headset — and add "mild" active (electronic) noise reduction of 10 to 12 dB in the 200-Hz-and-below part of the spectrum where passive attenuation alone is not quite enough. LightSPEED engineers managed to add this much ANR without messing up the passive characteristics of the headset very much, and adding about two ounces to its weight. Increasing active attenuation beyond this level would have required smaller earcup cavities, and that would have seriously degraded passive attenuation performance.

NOTE: LightSPEED recently posted a new "ANR 201" tutorial to their Web site that offers an excellent explanation of why increasing active noise reduction necessarily degrades passive noise reduction, and vice versa. Both this and the earlier "ANR 101" tutorial on ANR basics are highly recommended reading for anyone faced with a headset purchase.

The net result is that the QFR Cross Country reduces low-frequency engine noise substantially better than any purely passive headset and almost as well (but not quite) as LightSPEED's ANR-optimized 20XL headset (with its much more aggressive ANR but less passive attenuation), while at the same time providing superior attenuation of mid- and high-frequency noise. All in all, the QFR Cross Country is a very quiet headset.

After 10,000 nm of flying with it, I can tell you with confidence that it's also a very comfortable headset. You probably wouldn't think so just by looking at it. It doesn't have the deep-cushioned earseals or thickly padded headband that make LightSPEED's XL-series headsets so luxuriously comfy. But what the QFR Cross Country lacks in padding, it makes up for in lack of mass and clamping force. Even at the end of a four-hour leg, I had none of that I'll-sure-be-glad-to-get-this-thing-off-my-head feeling that I've often experienced when wearing other passive headsets.

LightSPEED also offers a a pair of optional "comfort seals" for the QFR headsets, made of the same sort of thermosensitive foam material that LightSPEED uses in the XL-series headsets (but not nearly as thick). They cost around $30/pair extra and make the already-comfortable QFRs even more so, especially if you wear thick-templed eyeglasses when flying. (My co-pilot and I both wear "aviator style" metal-frame sunglasses, and we both concluded that the standard QFR seals worked just fine. I tried the optional comfort seals, and they are a nice improvement.)

Pros and Cons

Compared to LightSPEED's most popular model — the 20XL — the new QFR Cross Country has certain advantages and certain disadvantages. Of course, the most obvious advantage is the new headset's low price, which must be giving LightSPEED's competitors plenty of heartburn: The 20XL lists for $449 and the QFR Cross Country lists for $279 — a whopping $170 less. (If you shop around, you can find these models at "street prices" of about $400 and $250, respectively.) By any measure, the QFR Cross County is a remarkable value.

Other QFR Cross Country advantages include better attenuation of mid- and high-frequency noise, a bit lighter weight and less bulk, and a much thinner headband. If you're flying an aircraft with lots of wind noise or with scant headroom, this might just be the perfect headset. I've also noticed that women often prefer lightweight headsets like the QFRs, especially if they wear their hair in a curly or bouffant style. (Jeb and I offered the QFR XCs to the two young lady journalists who flew with me as back-seaters from Key West to Grand Cayman, and they just loved 'em.)

On the minus side, the QFR Cross County provides a bit less attenuation of piston engine exhaust and propeller noise in the frequency spectrum below 200 Hz, and therefore slightly lower intelligibility in cockpits with high levels of engine noise. It's battery life isn't quite as good — about 25-30 hours for a pair of AA alkaline batteries, compared with over 60 hours for the 20XL. It also lacks the automatic shutoff feature of the LightSPEED XL headsets — if you forget to turn the ANR off at the end of a flight, the batteries will be dead next time you put the headset on. (Hint: I've added "ANR off" to my shutdown checklist.)

Which is more comfortable? That's a toughie, because comfort has no objective measure. In side-by-side tests at aviation shows like Sun 'n Fun and AirVenture, most pilots seem to prefer the heavily cushioned XLs over the lighter-but-less-cushy QFRs. But a quick try-on at a tradeshow is not quite the same as wearing a headset for a couple of four-hour flight legs in one day, as I have done quite a few times now. As far as I'm concerned, this is the acid test of headset comfort ... and all I can say is that both LightSPEED headset series (XL and QFR) pass the test with flying colors. While the 20XL and QFR Cross Country have totally different "looks and feels" and some people might have a strong preference for one or the other, both my co-pilot and I found them both to be very comfortable even after a long day in the cockpit.

Which Model to Buy?

LightSPEED's aviation headset product line now encompasses five different models, making it increasingly challenging to decide which to buy. If you fly a piston-powered propeller-driven aircraft — particularly a single or centerline-thrust twin — the LightSPEED 20XL ($449 list, around $400 street) and 25XL ($599 list, around $525 street) still offer the best engine and prop noise attenuation, the longest battery life, and automatic shutoff. But from a cost/performance standpoint, the new QFR Cross Country offers attenuation and comfort that is almost as good (although different in look, feel, and noise-reduction profile) at an astoundingly low price ($279 list, around $250 street).

If you fly an aircraft where the noise spectrum is concentrated in the mid- and high-frequency range, the passive QFR Solo or hybrid QFR Cross Country might actually be quieter than the ANR-optimized XLs. This includes open-cockpit aircraft, Rotax-powered experimentals, helicopters, turbine-powered aircraft (especially jets), gliders, and so forth. In cockpits with minimal headroom, the low-profile headband of the QFRs may also prove advantageous.

For passenger headsets, it's hard to imagine a more cost-effective choice than the passive QFR Solo ($150 list). It's light, comfortable, non-intimidating, and hassle-free (no switches, no batteries). The QFR Solo is also a fine primary headset for jets and other aircraft without much noise below 200 Hz.

The 1979 Cessna T310R that I fly has a lot of low-frequency noise. I've got three-bladed props and six-cylinder engines. My engines turn 2,700 RPM at takeoff, 2,350 RPM during climb, and generally cruise between 2,100 and 2,200 RPM in cruise. Therefore, my peak noise problem lies in the 105-135 Hz range, and ANR is an absolute must. I plan to trade in my two old well-worn 20K headsets for the newer 20XLs, and to buy a couple of QFR Cross Country headsets for the back-seat pax (and to serve as backup in case one of the XLs breaks).

LightSPEED has a web site where you can review the features and specifications of LightSPEED XL and QFR models, read answers to frequently-asked questions, learn a great deal about the theory and design of ANR headsets in general (and LightSPEED's in particular), and order the headsets online if you wish (at list price, of course). You'll also find those excellent ANR 101 and 201 technical tutorials that I mentioned earlier.

LightSPEED headsets are also available from various authorized dealers (including several who are AVweb sponsors). Most of these dealers offer the headsets at discounts from list. I've found a surprising spread of selling prices among various dealers, and they tend to be a moving target depending on what each dealer happens to have "on special" at the moment, so you can generally save a few bucks by shopping around.

Please keep in mind that choosing a headset is a very subjective matter, especially when it comes to comfort. Just because I like a particular headset model is no guarantee that you'll like it. Therefore, I always recommend that you purchase any aviation headset from a dealer that offers a 30-day no-questions-asked return privilege. That gives you the opportunity to try the headset on your own head under actual in-flight conditions in your own cockpit ... and if it's not all that you expected, you can send it back for a refund. (I learned this lesson the hard way when I purchased that David Clark H10-13.4 and discovered I didn't care for it.)