Sennheiser HMEC 25KA active headsets
Sennheiser's line of electronic noise-canceling headsets has, in a sense, come full circle. When the firm began showing prototypes of its ANR headsets in the late 1980s, the active circuitry was not demonstrated with full-enclosure headsets, but on lightweight, open-air units. Sennheiser has always kept a lightweight ANR in the lineup, but recently has dramatically upgraded its offering with the HMEC 25KA.
Using the feathery open-backed headphones and microphone of the HMC 25KA lightweight as a basis, the HMEC 25KA employs the latest of Sennheiser's active electronics for a claimed 30 dB of noise attenuation; half comes from the passive absorption of the leatherlike ear seals and half from the electronics. The active circuitry is tuned to concentrate its efforts between 100 Hz and 2 kHz.
Sennheiser claims that the 25KA weighs just 6 ounces and benefits from an adjustable split headband and thicker ear seals than its other models intended for high-end turbine equipment. In this way, Sennheiser hopes that the 25KA can be used in the quieter piston (and louder turbine) aircraft in which the less generously padded models are unsuitable.
For the most part, Sennheiser hit the target. We tried the 25KA in a variety of airplanes, ranging from simple piston aircraft to a turbocharged and pressurized single. At the high end (meaning the quieter airplanes) the 25KA performed admirably, blocking the low-frequency noise well and providing a comfortable fit for long days in the cockpit. The pilots who used the Sennheisers said that the earpads were sufficiently comfortable and therefore frequent repositioning was unnecessary. The split headpad also won accolades; the two bands looping over the top are pivoted just above each ear cup, offering a variety of positions and fits. Given the light weight of the headsets, the thin headband padding is not a detriment.
For louder airplanes, particularly in the Aerospatiale Trinidad TC used for some of the testing, the HMEC 25KA was simply out of its element. The ear seals could not keep the high-frequency noise at bay, and even the sophisticated electronics were hard pressed to keep the engine rumble down to a dull roar. The additional 10 dB of attenuation brought by the rigid ear cup active models really pays dividends in louder cockpits. Our early headset also had difficulties with high noise levels; it would sound as though the electronics were overloading in the attempt to cut the low-end noise.
Sennheiser reports that a poorly chosen component in the power supply was restricting current flow during high-demand use; the problem has apparently been fixed. A pair of AA batteries are carried in a small plastic case that's attached near the plug end of the hookup cord. Sennheiser says that the batteries should last 30 hours, but we averaged between 15 and 20 in the noisier airplanes before the cells went flat.
As you might expect, Sennheiser's microphone was a solid performer, although it was set up with a bit too much gain for the average intercom or audio panel. Unfortunately, the monaural sample that we tried did not have a volume control, so we had to live with an unusually loud side tone in some of the airplanes. (An optional stereo cord can be fitted at the company's U.S. branch and comes with twin sliding volume controls. All Sennheisers are made in Germany.) In addition, not all testers were enamored of the rigid microphone boom. Although it could eventually be manhandled into place, the stiff arm would be better replaced with a flexible piece.
Sennheiser expects the HMEC 25KA to reside at the top of the lightweight active headset pile, and the company has priced the product accordingly. With a retail price of $949 (and a street price about $150 less), the German product is significantly more expensive than the similar Telex ANR 200. In its favor, the Sennheiser has better audio quality, as well as generally superior fit and finish.
For more information, contact Sennheiser Electronic Corporation, 6 Vista Drive, Old Lyme, Connecticut 06371; telephone 860/434-9190; fax 860/434-1759. — Marc E. Cook
Atlantic Aero engine mounts
Vibration is kind to neither the airplane nor its occupants, so any way of smoothing an engine or propeller is usually appreciated by airplane owners. For those pilots with Cessna 206, 207, or 210 model aircraft, Atlantic Aero has an STCed kit to modify the standard front-bed mount from a single isolator to two. Cessna used this style of mounting on the later turbocharged 200-series airplanes, but the Atlantic Aero mod is available for the nonturbo and turbo airplanes alike.
According to a vibration survey conducted by the company, cabin vibration was reduced up to 70 percent, most noticeably at lower rpm settings. Atlantic Aero claims a decrease in vibration at the seat tracks from about 3.5 inches per second to about 0.6 ips at 2,200 engine rpm. The kit includes all new engine mount isolators, new dual-point front mounts, heat shields, and all necessary hardware and paperwork. Prices range from $2,350 (and about 20 hours of labor) for the normally aspirated models with an additional cost of $1,050 for the turbo airplanes. (The turbo mod requires altering the locations of some of the turbo gear.) Atlantic Aero will install the kits for a flat fee of $900 for the nonturbo airplanes, and $1,500 for the turbo models. If you elect to have Atlantic Aero install one of its IO-550 retrofits, the cost of the six-point mounting scheme drops to $1,850.
For more information, contact Atlantic Aero, Piedmont Triad International Airport, Post Office Box 35408, Greensboro, North Carolina 27425; telephone 800/334-2001 or 910/668-0411; fax 910/668-4434. — MEC
Briefly Noted
John Merry reviewed 1,000 aviation web sites and narrowed the field down to the 100 best of the best to save you search time when browsing for aviation topics. They're all in his new guide, 100 Best Aviation Web Sites. (Yes, AOPA's site [www.aopa.org] made the cut.) It is available for $14.95 plus shipping by calling 916/676-7271 or ordering on line ( www.100bestaviation.com). Write to Merry at Specialized Marketing Agency, 2575 Meadow Lane, Suite 3, Cameron Park, California 95682. — Alton K. Marsh
LoPresti Speed Merchants of Vero Beach, Florida, has completed its Seneca GTO modification package, which employs various aerodynamic devices designed to increase top speed by 11 knots. Among the products are a new cowling design and new wing tips with built-in landing and taxi lights. The cowl modification is available only for Seneca models II, III, and IV. For information, call 800/859-4757. — Peter A. Bedell
In a world of high-tech electronic instruments and sophisticated trend monitoring, it's sometimes the simplest items that are the most amazing. So it is with the Pilot's Gauge Marker. Looking like a standard white grease pencil — though in fact it's not a grease pencil in the conventional sense — the gauge marker is intended to be used to mark the normal needle positions on analog engine gauges. Therefore, if the oil pressure, for instance, declines from its normal value by just a few psi, you'll have a clear visual indication that it has done so. In many instances there are few marks between the ends of the green arcs printed on the gauges. The gauge marker lets you make your own. The Gauge Marker costs $9.50 plus $3.75 for shipping and handling. Order through Gauge Marker, 627 Many Oaks, San Antonio, Texas 78232; telephone 800/561-6864. — MEC
Aviation Media Incorporated has released a new four-volume video series called The Wonderful World of Warbirds. Each videotape in the series is 60 minutes long and is hosted by Jeff Ethell. Among the warbirds featured are the North American P-51 Mustang, Curtiss P-40 Warhawk, and Douglas A-26 Invader. To order, contact Aviation Media, 50 East 42nd Street, New York, New York 10017; telephone 800/772-9963. — PAB
If you want children to be interested in aviation as young adults, the theory goes, you induct them into the lifestyle early. Such is the goal of the ToySmith Walk Abouts. These kid-sized plastic toys come in three forms — a helicopter, a biwing aerobat, and a space shuttle replica — and are intended to be worn by children for the myriad things children do, like play. Some assembly is required, but no batteries are needed; price is $29.95 from ToySmith, 8992 Preston Road, Suite 110, Frisco, Texas 75034; telephone 214/335-3631. — MEC
Unless otherwise stated, products listed herein have not been evaluated by AOPA Pilot editors. AOPA assumes no responsibility for products or services listed or for claims or actions by manufacturers or vendors. However, members unable to get satisfaction regarding products listed should advise AOPA. To submit products for evaluation, contact: New Products Editor, AOPA Pilot, 421 Aviation Way, Frederick, Maryland 21701; telephone 301/695-2350.
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