Very lightweight
Two-piece adjustable headband ensures excellent comfort
16 dB of passive noise reduction
Excellent transmission of speech due to noise-compensated condenser microphone
Flexible mic boom, can be worn on either left or right-hand side
Single-sided cable
Very comfortable
Create a custom fit
Less interference due to environmental conditions
Greater intelligibility
Adapt to your preference
Easy to position cable where it is most convenient Q: Which accessories come with my Aviation headset purchase?
A: Windscreen, clip, bag, and manufacturer certificates
Q: Attenuation Passive?
A: The ability of the headset to reduce the ambient noise
level by merely wearing the headset (Measured in db) without
the aid of any electronic assistance (active noise
compensation circuitry).
Q: Attenuation Active?
A: The reduction of noise, particular in the low frequency
range by using active noise compensation electronic
circuitry. (Measured in db)
Q: Caliper Pressure (or contact pressure)?
A: This is the amount of force applied to the sides of the
head while wearing headphones. A tight coupling between the
headphone and the ear is necessary in order to maximize
passive attenuation. However, too much pressure can make the
headphone uncomfortable to wear for long periods of time.
Caliper pressure is measured in Newton’s (N) and could range
from 1.6 N (loose fit) to 10 N (snug fit).
Q: Circumaural?
A: The Circumaural headphone encircles the ear creating a
seal thereby effectively reducing ambient noise from getting
to the ear (this is known as passive noise reduction). This
type of headphone is most effective in a high noise
environment where it's necessary to eliminate as much of the
environmental noise as possible for effective communication.
Q: Condenser (Electret) Microphone?
A: A microphone that is based on an electrically charged
diaphram/backplate assembly, which forms a sound-sensitive
capacitor. Here, sound waves vibrate a very thin metal or
metal coated-plastic diaphragm. The diaphragm is mounted
just in front of a ridged metal or metal-coated-ceramic back
plate. This assembly is known as a capacitor (condenser),
which has the ability to store a charge or voltage. When the
element is charged, an electrical field is created between
the diaphragm and the back plate, proportional to the
spacing between them. It is the vibration of this spacing,
due to the motion of the diaphragm relative to the back
plate that produces the electrical signal corresponding to
the sound picked up by a condenser microphone. The
construction of a condenser microphone must include some
provision for maintaining the electrical charge or
polarizing voltage. An Electret condenser microphone has a
permanent charge, maintained by a special material (Electret)
deposited on the back plate or on the diaphragm.
Q: Dynamic Microphone?
A: They employ a diaphragm/voice coil/magnet assembly, which
forms a miniature sound-driven electrical generator. Sound
waves strike a thin plastic membrane (diaphragm), which
vibrates in response. A small coil of wire (voice coil) is
attached to the rear of the diaphragm and vibrates with it.
The voice coil itself is surrounded by a magnetic field
created by a small permanent magnet. It is the motion of the
voice coil in this magnetic field that generates the
electrical signal corresponding to the sound picked up by a
dynamic microphone. Dynamic microphones have a simple
construction and are economical and rugged. They can provide
excellent sound quality and good specifications in all areas
of microphone performance. They handle extremely high sound
levels: it is almost impossible to overload a dynamic
microphone. They are relatively unaffected by extremes of
temperature humidity.
Q: Diaphragm?
A: The thin membrane in a microphone, which moves in
response to sound waves.
Q: Electret?
A: A material (such as Teflon) that can retain a permanent
electric charge.
Q: Gain?
A: The amount of increase in audio signal strength, often
expressed in dB
Q: Mic Gain Control?
A: A level control on a microphone preamplifier that sets
gain and is used to prevent overload of a preamplifier.
Q: Pre-Amp?
A: A low-noise amplifier designed to take a low-level signal
(such as that from a microphone) and bring it up to normal
line level.
Q: Why is it a good idea to have a mic gain adjustment on
your microphone?
A: This gives the technician the ability to make adjustments
for minor anomalies that may occur during the installation
of the audio system. While the microphone may work fine,
often a small adjustment may make a big difference in the
total performance of the microphone.
Q: Maximum SPL (Sound Pressure Level)?
A: This is the lowest input impedance rating the mic input
of the radio can have. The microphone may not function
properly if the input impedance of the radio is too low.
Q: NRR (Noise Reduction Ratings)?
A: NRR is a rating of the passive reduction and this is by a
set standard (ANSI). However, there are no present standards
for measuring ANR. Each Manufacturer uses their own
standards. Sennheiser uses the standards and results of an
independent laboratory that is accredited by the National
Institute of Standards and Technology. One should be very
careful in assuming that all manufacturers use these results
in a fair and unbiased way.
Q: NoiseGard on/off switch?
A: This is the switch that allows you to turn the active
noise compensation circuitry on or off. It comes with a two
colors LED for-power on and low battery-on headsets using a
battery pack. NOTE: If you should turn off the NoiseGard
system there is no loss of, or reduction of, the received
audio and you still retain the passive capabilities of the
headset. You may have to increase the receiver volume to
compensate for the increase of ambient noise due to the loss
of the NoiseGard feature. The LED is located on the battery
pack of the headsets. The battery pack in included in-line
on the HMEC25/45 series and is an optional accessory on the
HMEC300 series.
Q: Nominal impedance?
A: This is the amount of opposition to alternating current.
The ideal nominal impedance of a headphone would exactly
match the output impedance of the source. Differences
between the output impedance of the source and the impedance
of the headphone could result in louder or softer volume
than expected.
Q: Output voltage?
A: This is similar to sensitivity except it takes into
account additional electronics used to amplify the signal.
This is typically measured over a range of frequencies and
will include the term + or - 3 dB. Rather than using 1
Pascal, this specification may also include the input level
used such as 114 dB at a distance of 6 mm.
Q: Overload?
A: To put too much signal level into thereby causing
distortion
Q: PJ055 Headphone Plug?
A: Standard ¼ in. plug, found on most aircraft headsets.
Q: PJ068 Microphone Plug?
A: Standard 5.25mm plug found on most aircraft headsets. On
some Sennheiser headsets (HMEC25/45 series KAP version only)
the tip of this plug can be used to power (28volt aircraft
only) the NoiseGard power supply.
Q: Sensitivity?
A: This is a measurement of how much voltage is produced by
a microphone for a specific measured input (1 Pascal).
Sensitivity is measured in micro volts (uV) or millivolts
(mV). A typical rating for a dynamic microphone would be 1
mV, for an Electret would be 3.5 to 10 mV, and an Electret
with amplifier would be 170 mV. The higher the number the
stronger the signal produced by the microphone.
Q: Supra-Aural?
A: The Supra-Aural headphone does not encircle the ear but
rests on the ear. Because the ear cup is smaller it is
generally lighter and more comfortable. This type of
headphone is recommended for an environment where ambient
noise is not excessive and where noise reduction can be
effectively reduced for communication clarity using active
(electronic) noise reduction or where noise reduction is not
a factor in choosing a headphone.
Q: TSO?
A: FAA technical standard order. JAA The European Joint
Aviation Authority. HMEC 25 and 45 Series headsets. The
success of Sennheiser to receive these approvals, C57a and
C58a go a long way in providing evidence of the superior
quality and performance of Sennheiser products. That is why
they are used in over a hundred Air Carriers all over the
world both on the flight deck and in the cabin.
Q: Transducer?
A: A device that converts energy from one form to another.
Example: A microphone converts sound waves into electrical
energy. An earphone converts that electrical energy into
sound waves.
Q: XLR-5 Connector?
A: This is a single connector that can be used in place of
the PJ055 headphone and the PJ068 microphone plugs on some
Sennheiser headsets. Pin 5 of this plug can also be used to
provide aircraft power for the NoiseGard power supply on
some Sennheiser headsets.
Q: XLR-3 Connector?
A: This is the connector that is used to power the NoiseGard
power supply. It provides 12-35VDC from the aircraft. It is
used in conjunction with the PJ055 and the PJ068 plugs.
Q: What is the exact meaning of the Sennheiser product
nomenclature?
A:
H = Headphone
D = Dynamic Transducer
M = Microphone
E = Electret
C = Active Noise Cancellation
K = Kit
300 and 100 series = closed cup (Circumaural) Headphone
25 series = Supra-Aural (closed back) headphone
45 series = Open-Aire® Supra-Aural headphone
KA = PJ068 connectors
CA = 5 PIN XLR connector
KAP = PJ type connector, MIC jack powered (28V Aircraft)
CAP = 5 PIN XLR, Pin 5 Powered (28V Aircraft=
KAX = PJ Type connector, XLR-3 Pin Powered (12-35V)
