Powersupply Sennheiser HMEC-25-KAP/KAP-2

[Ziggy]

I want to buy the above mentioned headset but cannot find an answer to my questions.

Some of you might be familiar with the KA version of this headset in which the active noise reduction (ANR) uses power supplied by a small battery box attached to the headset cord. The new KAP version (according to Sennheiser's website) receives power from the aircraft through the microphone connector PJ-068 (the so-called microphone bias) instead of a battery box and requires 28V DC. The KAP-2 is similar but works with anything between 12-35V DC.
Telex sells the Airman 850 ANR which works exactly the same (according to the wording on their website) but on a lower voltage, I believe 8V DC.

I fly the B737-NG and have several colleagues using this Telex headset and it works! Will the Sennheiser work as well?
To be sure I asked both Sennheiser Germany and Sennheiser USA. Where Sennheiser USA didn't even bother replying, Germany said the following:
"You cannot compare the system operation of the Telex Airman 850 and the Sennheiser HMEC25-KAP like this and we cannot confirm that the KAP or KAP-2 will or will not work on your aircraft."

Since I do understand that a big company like Sennheiser apparantly doesn't have time to test their equipment on a rare and impopular airplane like a 737, I see no other option then to put the question to my fellow ppruners.

Does anybody have any experience using the Sennheiser HMEC25/45-KAP or -KAP-2 on a B737-NG or any Boeing aircraft?
Or does any engineer know (or is willing to test) the power supply voltage from the microphone bias on the 737NG.

Thanks very much,

Ziggy

[RadAlt]

i.d.

Here's me hoping somebody can come up with an answer, as I'm trying to find out exactly the same!

[Marvo]

As an ex aircraft engineer I borrowed an HMEC 45 headset from my old employeer and I am successfully using it on the 73NG. I would suggest that you get a headset that has a powerpack. Because they don't draw power from the aircrafts electrical supply they tend to be approved for use by the airlines. I bought some re-chargeable batteries and change them every couple of days to keep the anr functioning.

Headsets with use ships power will work irrespective of the voltage. A regualtor in the headset draws just the correct amount of current but can sometimes have weak anr.

Hope this helps.

Marvo

[dv8]

Also with the power bias version if you turn off the hot mic you lose the 'power supply'. The headset will then revert to a bog standard headset.
I have opted to the battery version

[Ziggy]

Originally Posted by dv8

Also with the power bias version if you turn off the hot mic you lose the 'power supply'. The headset will then revert to a bog standard headset.
I have opted to the battery version

I believe this is not correct, at least not for the Telex Airman 850 according to some of my colleages using it and according to Telex.
Telex emailed me the following: "The Airman ANR 850 requires constant power to the microphone in order for the ANR to work properly. Note that the mic doesn't have to be "hot", just have power supplied to it constantly. If the power to the mic is interupted, the ANR will cycle on and off. We have seen the 850 used in the 737 at Southwest with great success."

Ziggy