Sennheiser HMEC25KA

I have been using this headset in B737-300/400 aircraft for almost a year. I find the comfort level of the earcups and the adjusting head piece to be very good. I can hear almost all of my F\O's with the exception of a very few who speak quietly in a low voice. This situation only occures at slow speeds. Once the ambient noise of the cockpit increases with speed even these F\O's raise their voice and are easily heard. The cups have a joint that rotates 90 degrees so I find on the ground and in low speed flight I just rotate the right earpiece off my ear until the noise level increases. This way I miss no communication. ATC reception is so good I have the A\C volume control almost off. Battery life seems to last for about 5-6 days of flying. I am currently trying the rayovac rechargable batteries. They seem to last less time but I feel they will reduce the cost of operation. The headset folds up in the pouch provided and fits in the top of my flight bag. I would recomend this unit since it gives both active and passive noise reduction.

Steven Flom

I recently settled on a pair of Sennheiser HMEC25's the noise cancelling closed earcup model. Sennheiser was superb to work with. They are very knowledgeable and give US Airway's (and I'm guessing other airline pilots) a substantial discount (around 25% of retail). But I found the headset lacking in comfort. The clamping pressure was high to me and the earcup is round and does not totally enclose the ear. To me, that created pressure points on the outer ear. The boom mic was flawed at the earcup pivot and it kept coming loose. I'm sure Sennheiser would have fixed that immediately for as I said, they were excellent to deal with. I didn't get to see how long the battery life was. But if it's anything like Sennheiser says, it is quite adequate.

So I'm back using the Telex supplied by the company. The mic on the Telex is very good but I find the earpieces suck. They have poor tonal range and are uncomfortable. I am in the process of building my own pair of noise cancelling headsets. For the record, I have checked and only the mic needs to be TSO'd. The impedance of the F100 radios is 600 ohms and keep that in mind when and if you bring your own in. If you have any doubts, go to the hangar and talk to one of the avionics guys and have him test them. Remember, the mic has to be TSO'd according to the FAA (something to do with the cockpit voice recorder) and if you bring in a set (mic) that is not, your technically in violation. Don't take the chance...

Jorge de Cubas

I had the opportunity to use the HMEC25KA for 14 hours as part of an ALPA evaluation. The combination of ANR and PNR produces a claimed reduction of 31dB. This really does make the 737-300 into a "whisperjet." I had some difficulty hearing cockpit conversation with the headset in place, particularly at low speed when cockpit ambient noise is lowest. Earpieces rotate on a pivot at the base of the headband, so it was a simple matter to move the inside cup away from my ear so I could hear the other pilot. This action eliminates any noise reduction to the effected ear.

The microphone is mounted on a rigid tube that pivots at the earpiece and at the mic. The instructions with the headset suggest that the tube can be bent for mic placement, but then say that excessive adjustment can lead to breakage. I had no trouble with the tube, but I wondered about the long term durability of the tube as it is bashed around in the top of a flight bag, and dropped on the cockpit floor. A better solution would be the flex boom found on the new model 45. The mic has a tiny set screw for gain adjustment. My demo headset had the gain set too low, but I didn't have a small enough screw driver to change it.

The battery box holds two AAs. A green "operating" light on the box turns red when the batteries get low, a nice touch. Batteries needed replacement after 32 hours of operation.

A ground test in a Fokker F100 during a "productivity break" highlighted a weakness of ANR headsets not equipped with a volume control. The Fokker plays alert sounds through the headset. There is no pilot operated volume control for these sounds in the aircraft, and the model 25 has no headset mounted volume control. This had the effect of increasing the relative loudness of alert sounds compared with normal ATC communications. The same problem surfaced in 737s equipped with the "paddle switch" jack box. At the low volume levels used with ANR headsets, tiny adjustments of the paddle switch changes the radio volume from "too loud" to "off." I believe pilots flying aircraft which play alert sounds through the headset, or those equipped with "paddle switch" jack boxes may need to purchase an inline volume control in order to use an ANR headset.

Richard Nelson

I use this headset in the King Air series, and find it to be amazingly comfortable. The low frequency attenuation is very evident, and high frequency attenutation is excellent. Extremely comfortable on long duration flights. In my opinion, it is much better than both of the Telex models. It also works very well in the Falcon 10, but I find that our HMEC-45 is better suited.

David Callaway

We have used four HMEC-25KA headsets in a Beech Bonanza B36TC for almost one year. The high frequency noise canceling works very well. It improves our ability to hear ATC communications clearly and reduces fatigue on long flights. The batteries only last for about 10 to 14 hours on our environment.

[These numbers for battery life seemed low, so I asked Jim for clarification. (RM Nelson)]

I always use new alkalines. I don't know if the life is affected by the noise of the cockpit or not. I think Sennheiser was having trouble with the battery life of these early on. Maybe mine have some problem.

Jim Frost

In reference to battery life on the HMEC25 series, typical use is 15 to 20 hours however the greater the noise the more ANC is needed and more current is used. For private aircraft there is a battery eliminator available through the Sennheiser Dealer network. This product is not made by Sennheiser but we know it works well. For further information please contact me at and reference the DCDC3 Battery Eliminator.

Michael Feldbauer

I have used the HMEC-25 for two weeks now in a 727. While it does an excellent job of what it is designed to do, it does nothing for the upper frequencies which now seem more pronounced. I still end up wearing earplugs at anything above 250K. I wish Sennheiser would apply their technology to the whole spectrum. Also, there is not enough sidetone. Mainly for the first reason, I could not recommend someone spend the large sum of money for these until the upper frequencies are covered as well.

A subsequent pirep from Dave:

Some additional comments on the HMEC25KA headset. I have used it for about six months now, and much of my previous comments on the headset came from flights in a 727-100. The earplugs are not needed in a 200 series, and quite a bit of difference is noted with the headset on and off. I still wish the frequency spectrum was larger.

Dave Thiel 727 FO Fedex

I have been using my Sennheiser HMEC-25KAS since the beginning of 2001. I like its noise cancelling properties both with and without the ANC unit on. Yes, I have caught myself leaving the unit on after use and finding dead batteries the next morning and I use it anyway. I use the headset with both cups on my ears and find intra-cockpit conversation acceptable. When on long range flights I have a personal 280 kt. IAS limitation, below which I remove the headset and turn it off. Although it is very comfortable I guess I get claustrophobic after a while.

I am 49 years old and was a bag smasher for Allegheny around CV-580's, a Cessna single engine flight instructor, a BE-99 commuter pilot, and have done many walk-arounds during my airline career with only my fingers in my ears. Even after all that abuse I am bothering to try to save what hearing I have left and will continue to do so.

With regard to batteries-the airline I work for will supply me with AA's for my headset just for the asking.

Doug Stansbury-Airbus A320

Coming from several years in turboprops and regional jets using the Bose X headset, I settled on the Sennheiser HMEC-25KAS for use in the Airbus 318/319. I "test drove" the HMEC-45, but decided that the 25 would work better for me. We always turn the intercom on after the push, and then take the headsets off above 18K. Headsets usually come back on around TOD and stay on until we reach the gate. I figure if I'm going to have a headset on during the busy times anyway, it might as well be a good, quiet one. I know, I could have kept the Bose, but it is a bit much for the Airbus.

If I had to wear a headset for the whole flight, I could not tolerate the "clamping" of the 25. It's fine for a half hour or so, but for me, the pressure would be too great for much longer. As an aside, the 45 is very comfortable for longer periods (just not as quiet).

The closed ear cup of the 25 does not pose any "hearing the other guy" issues for me, as we use intercom (I'm assuming those complaints come from crews that leave the intercom off?). During the push, when the intercom is not on (so the tug driver doesn't have to listen to us), I just rotate the earcup of the 25 back (it's designed to do so).

I've found that ANR headsets very effectively reduce low frequency noise (ie engine drone) with active attenuation-- both the 25 and the 45 do this well. But, the high frequency noise (ie wind noise) is best blocked passively, which the 25 does, but not the 45 (the 25 reduces noise passively due to its closed ear cup). In all, the 25 claims around 30 db of protection (half active, half passive)- ear plugs are in the neighborhood of 28 to 32 db.

Also, the foam windscreen on the 25 is obnoxiously large, and can easliy be swapped (for about $6) with the windscreen that is designed to fit the Telex 750. It doesn't look like it'll stretch over the 25's larger mic, but it will (careful not to rip it).

I got the "S" (in HMEC-25KAS) which means "stereo," and I highly recommend it. I like to keep company barely audible on #2, and without the stereo version, even the lowest setting on your audio panel will probably be too loud. So, I don't independently adjust L and R volumes (which is the intent of the stereo version), but what I do is drive both volumes way down, put #2 at the lowest setting on the audio panel, and adjust ATC up to where they belong. Follow?


As for power, I got the version with the external battery pack for 2 reasons. First, our a/c won't power the headset. And secondly, having the portable power makes the headset more versatile. To see if your a/c wiill power it, check with your avionics guys (the Airbus requires power to the 5th pin of the XLR plug-- if that pin's not powered, you'll need the battery pack.)

All in all, a great value for the money. I bought mine refurbished (directly from Sennheiser) and saved some cash, and I would suggest doing the same.

Brad Blythe

Frontier F/O

If you use this headset, please send your .