October 2, 2000 LightSPEED's 21st-Century Passive: The QFR "Solo"

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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 review of LightSPEED's top-of-the-line 25XL headset.

LightSPEED just introduced a what?

Did you say a passive headset?

In the year 2000? Are they nuts?

Well, yes, LightSPEED's latest headset is indeed passive. And no, they're not nuts. In fact, after having just flown my Cessna T310R across the country while wearing the new LightSPEED QFR "Solo" passive headset, I think this may be the smartest thing they could have done. Read on and I'll tell you why.

Hard Act to Follow

I remember when I first discovered the LightSPEED 20K ANR headset. It was June, 1997, and nobody in aviation had ever heard of this little company in Oregon. But the moment I put the 20K on my head, I knew they'd hit a home run. Here was an ANR headset that cost less than half the price of the industry-standard Bose Series II, yet was every bit as quiet as the Bose, and every bit as comfortable. (In fact, I found it more comfortable than the Bose, although comfort is extremely subjective.)

Granted the microphone didn't sound quite as good as a Bose or David Clark, and it chirped a bit near ATC radar antenna sites, and it needed a new set of AA batteries with some regularity. But all in all it was a lovely headset, and nothing else even remotely in the same price range could touch it. I wrote a glowing review of the 20K, as did Aviation Consumer, and the 20K went on to become a smash success.

In 1999, after several other firms introduced under-$500 ANR headsets to compete with the 20K, LightSPEED introduced the 20XL and 25XL. These were evolutionary, not revolutionary. The 20XL was basically a 20K with much-improved battery life and a clever automatic shutoff feature that neatly solved the problem of forgetting to turn off the ANR after landing, and then finding the batteries dead at the beginning of the next flight. Both were nice enhancements, and the 20XL is a terrific headset.

How Much ANR Is Too Much?

In its top-of-the-line 25XL (priced at just under $600), LightSPEED's objective was to create the quietest ANR headset in history. They did, but after flying with it for several months in the fall of 1999, I concluded that I wasn't quite as happy with the 25XL as I was the 20K and 20XL. The 25XL headset was slightly better than the 20XL in attenuating low-frequency noise, but it also struck me as being a bit unstable at times. I found that actions such as moving my head or jaws or adjusting my sunglasses would sometimes trigger funny growling or groaning sounds from the headset. Once, I even found a female controller whose voice seemed to drive the thing crazy. In adding sophisticated circuitry to crank up the 25XL's ANR gain to the highest stable value possible, it seemed to me that the headset was operating so close to the edge of the stability envelope that it occasionally crossed the line into instability..

As LightSPEED's own excellent series of technical articles (ANR 101 — A Tutorial on Active Noise Reduction) points out quite clearly, the amount of active noise reduction that one can achieve is limited by the fact that the more ANR you try to achieve, the more acoustic instability you create. Turning up the ANR gain too much can result in oscillation, and it struck me that the 25XL was right on the hairy edge of instability. After a few months of flying with the 25XL, I decided this was just too much of a good thing, and returned to using the 20XL for my day-to-day flying.

(Again, this stuff can be very subjective, and there are lots of pilots who just love the 25XL. LightSPEED's Allan Schrader tells me that the company made some tweaks to the 25XL ANR cancellation profile in recent months to improve stability, and suggested that I give the 25XL another try. I'll probably do exactly that.)

In its XL-series, LightSPEED appears to have taken active noise reduction to its practical limit (and perhaps briefly beyond). But this technology is capable of addressing only low-frequency noise. No matter how superbly ANR is engineered, it can't do much about noise in the middle- and high-frequency spectrum. To deal with noise above about 250 Hz, one must turn to some other technology than ANR. And that's precisely the direction LightSPEED seems to be moving in launching their new QFR product line.

Back to Basics

I flew with the new LightSPEED QFR Solo on a 20-hour cross-country trip from California to Alabama and back, with a bunch of stops. The QFR is a significant achievement. The Solo is a purely passive headset, but it's the quietest, lightest, most comfortable passive I've ever worn. And I've worn a bunch.

For a decade, I flew with David Clark's top-of-the-line H10-80 headset, which was the quietest headset of its day. It cost $300 (in 1987!), weighed something like 24 ounces, and had a noise reduction rating (NRR) of 24 decibels. The "green monster" was uncomfortable as hell — after a couple of hours, it felt like a cross between a bench vise and a blacksmith's anvil — but it did block most of the noise.

When David Clark came out with its lightweight H10-13.4 headset — so named because it weighed only 13.4 ounces, only slightly more than half as much as my H10-80 — I snapped one up immediately (for about $200). The H10-13.4 claimed a NRR of 21, just 3 db less than the H10-80, and I figured that was a reasonable tradeoff for the lighter weight. Boy, was I ever wrong! The first time I applied takeoff power while wearing the H10-13.4, I almost aborted the takeoff because the noise level was so high that I figured I must have left the cabin door open! After a few more flights, I demoted the H10-13.4 to passenger headset status and never wore it again. A lot of folks must have reacted the same way, because David Clark subsequently changed from foam to gel-filled earseals on the H10-13.4, raising its NRR to 23 and its weight to 15 ounces (although the "13.4" model number remained).

LightSPEED's new QFR Solo is significantly lighter (11.8 ounces) and much quieter. Its NRR is a truly astonishing 28.7, far better than any other passive headset on the market. Its NRR is nearly 3 db better than the closest NRR-rated competitor, Peltor's 7005/7006; nearly 5 db better than my old green monster David Clark H10-80 (which weighed more than twice as much); and 6 to 8 db better than the DC's "lightweight" H10-13.4 (depending on whether it has foam or gel-filled earseals).

Incidentally, be very careful in comparing the noise-reduction claims of various headset manufacturers. NRR provides a specific method for testing a headset's noise attenuation over a wide frequency spectrum, weighting the various frequencies, and arriving at an overall rating in decibels. For manufacturers who publish NRR ratings for their headsets (such as David Clark, LightSPEED, Peltor, Sennheiser, and Telex), those ratings can be compared meaningfully (and LightSPEED's QFR Solo is clearly at the top of the heap at the moment). However, some manufacturers do not publish NRR ratings, notably Flightcom, Pilot Avionics, and lots of "private label" headsets (most of which are actually manufactured by Pilot Avionics but sold under other brand names). Sometimes, the marketing claims for these headsets often cite noise reduction figures (generally obtained at one specific optimum audio frequency) that are greatly in excess of what the NRR would have been for that headset. (Some claim 24 to 26 db attenuation, but if their NRR was published, it would probably be around 20.) So never try to compare noise reduction figures unless they're specifically given as "NRR."

In-flight impressions

Earcup.

Earseal.

Headband

Microphone and boom.

My subjective reaction while flying with the QFR Solo bears out these numbers. I found it much, much quieter than the H10-13.4, and also more comfortable to wear. In fact, during cruise flight, I found the QFR Solo to be very nearly as quiet (subjectively) as my LightSPEED 20XL ANR headset. The only time I really noticed the difference in noise reduction (and wished I could switch on some ANR) was during takeoff, and to a lesser extent during climb, when ANR's superior attenuation of high-intensity, low-frequency engine and prop noise is most apparent. But as I leveled off and came back to cruise power, the low-frequency engine and prop noise became less and the high-frequency wind noise became greater, and that's where a good passive headset really shines ... and the QFR Solo certainly did.

During cruise, I tried repeatedly swapping headsets with my co-pilot — changing from the QFR Solo to the 20XL ANR and back — and there really wasn't a clear winner. The 20XL reduces engine noise a bit better, but the QFR Solo reduces wind noise better. The 20XL's deep, ultra-soft thermosensitive foam earseals are a bit more comfortable, but the QFR Solo weighs less and has a better microphone and mic boom (more on this shortly). The bottom line is that while I clearly prefer an ANR headset for takeoff and climb, at cruise (which represents the vast majority of noise exposure time) I found the new QFR Solo passive to be very nearly as good, and in some ways better.

Comfort is even more subjective than quiet. I found the QFR Solo to be very nearly as comfortable as the 20XL. My co-pilot did not. Upon further probing, my co-pilot's problem turned out to be an uncomfortable "pressure point" where the earpieces of his sunglasses passed beneath the earseals of the headset. I was also wearing sunglasses of similar design (wire frames with plastic-tipped earpieces), but I felt no such discomfort. Obviously, either our glasses were slightly different, our head shapes and skull structures were slightly different, or both. Whatever the exact difference, this underscores my often-repeated advice that no matter how many specs and review articles you read, there's no substitute for actually evaluating a headset in the aircraft. Most reputable dealers offer a 30-day return privilege, giving you an opportunity to try the thing in flight, and I suggest not purchasing from any dealer who doesn't.

Look and Feel

The QFR Solo bears very little physical resemblance to previous offerings from LightSPEED. The distinctive triangular earcups that have become the signature of LightSPEED's ANR headsets are gone, replaced by big rectangular earcups that look a lot heavier than they actually are. No volume-control knobs protrude from the earcups — to save on-the-head weight, LightSPEED has placed the volume controls and stereo/mono switch in a small remotely-mounted control box near the plug end of the cord. The earseals are soft foam, quite comfortable but not nearly as deep as the pillowy soft ones LightSPEED uses on its K- and XL-series.

The headband is very thin compared to previous LightSPEEDs. It does have padding, but not a lot. Nevertheless, I found it quite comfortable, as did my co-pilot. When a headset is this light, a thickly-padded headband is apparently not necessary. A bonus is that the thin headband provides much-improved cabin headroom.

The headband is attached to the earcups via adjustable piano-wire yokes very reminiscent of the Peltor 7000-series. These yokes look less substantial than the plastic ones used on previous LightSPEEDs, but the system has proven quite rugged in Peltors and I see no reason why it shouldn't do as well here.

Don't Forget the Mic

I've always considered the weakest feature of the K- and XL-series headsets to be their microphones. I've found LightSPEED's gooseneck mic boom to be too thin and flexible, making it easy for the mic to creep or be bumped out of proper position. I also didn't particularly care for the frequency response of the LightSPEED microphones, feeling that they were weak at low frequencies and too sensitive at high frequencies, resulting in somewhat tinny-sounding speech and too much wind noise in the background. Also, the microphone output level was lower than other headsets, sometimes causing undermodulation and weak-sounding transmissions.

I was therefore delighted to see that LightSPEED addressed all these issues in the new QFR. The mic boom is still the gooseneck type, but it's shorter, thicker and noticeably stiffer, and once adjusted stays firmly in position. The mic itself has a much better tonal quality, with better bass response and less wind-noise pickup. It even has little pointy "muff grabbers" to ensure that the foam mic muff cannot slip off accidentally. Finally, the new mic has a microphone level adjustment so that it can be tweaked for best compatibility with the aircraft radios and intercom. (In my case, however, the output level seemed just fine right out of the box, so I didn't mess with the level adjustment.)

I'm told that LightSPEED is considering this new microphone and mic boom for its higher-priced XL-series, too. I'd certainly encourage them to do this, and would consider it a very welcome improvement.

LightSPEED's Next Headset: QFR+ANR

In a month or two, LightSPEED has scheduled the introduction of an ANR version of this headset, dubbed the QFR "CrossCountry." Their idea is to take what is already an absolutely superb passive headset and add some "mild" active noise reduction to improve noise attenuation in the critical low-frequency spectrum below 250 Hz where all passive headsets are at their weakest. This ANR version should weigh less than 14 ounces.

The QFR "CrossCountry" is expected to sell for under $280 — half the price LightSPEED's top-of-the-line 25XL. Look at it this way: For the price of one Bose Headset X, you'll be able to buy CrossCountry ANR headsets for both pilot and co-pilot plus Solo passive headsets for two passengers, and have more than $100 left over! That's pretty compelling.

I can't wait to get my hands on this headset. Based on what I've seen so far with the QFR Solo, I expect the QFR CrossCountry to be impressive.

Who Should Buy the QFR Solo?

There are a number of reasons why you might want to consider this headset:

1. You're a price-conscious buyer looking for the "best anti-bang for the buck." At under $150, the QFR Solo is around one-third the cost of a good ANR headset like the LightSPEED 20XL or similar headsets from Denali, Peltor, Sennheiser, Telex, etc. Yet the comfort and performance are quite adequate, especially in cruise.
    
2. You're flying an aircraft with less low-frequency noise and more mid-range noise than average. Examples include the Rotax-powered Katanas, some helicopters, and lots of experimentals ... not to mention turbine aircraft. At noise frequencies above 250 Hz, you just can't beat a good passive headset.
    
3. You prefer a headset with less weight and less bulk. My wife, for example, simply refuses to wear "one of those big and clumsy things" (as she calls my LightSPEED XL20s) and opts instead for foam earplugs, cutting her off from the aircraft intercom. The QFR is a more attractive option for such users.

To be sure, the new QFR-series is meant to provide a lower-cost alternative to the XL-series, not replace it. The high-end ANR design of the XL-series still offers some distinct benefits: deeper, softer "confor-foam" earseals, improved speech intelligibility, extended battery life and automatic shutoff, just to name a few. So I don't expect to be giving up my 20XL headset anytime soon.

But with the introduction of the under-$150 QFR Solo and the soon-to-come under-$280 QFR CrossCountry ANR, LightSPEED has once again redefined the price-performance targets for low-price aviation headsets. As occurred in 1997, other manufacturers will undoubtedly follow LightSPEED's lead and introduce competitive headsets. This can only be good news for pilots and their passengers.

Nice work, LightSPEED!

Where to Buy

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.

LightSPEED headsets are also available from various authorized dealers (including several who are AVweb sponsors). Some of these dealers offer the headsets at small discounts from list. There's not a lot of dealer margin on these units, however, so don't expect big discounts.