[TenTec] Field Day Drill
Richards
jruing at ameritech.net
Sat Jun 30 13:36:06 PDT 2012
> On 6/29/2012 9:30 PM, Kim Elmore wrote: .
>>
>> You mention head sets. I've been told that the noise cancelling
>> headsets are the cat's meow (because the cat can't be heard). Do you
>> have any good recommendations for something that won;t break the
>> bank?
I have David Clark (or is that Clamp?) >> aviation head sets
that are very quiet, but they are not stereo and so I can't
put the main rx in one ear and the sub rx in the other using them.
>> Happy Fourth!
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Great questions. Unfortunately, no. I have heretofore generally
eschewed "active noise canceling" headsets for a couple of reasons.
Initial Observation:
(You might be able re-wire the David-Clamp
set to provide stereo / diversity sound -
probably not too difficult to accomplish, as
high quality replacement headset cables are
readily available.)
Note - David-Clamp -- GREAT PUN AND ACCURATE.
My Take on Active Noise Cancelling Headphones:
Active noise cancelling phones are designed to reduce broadly
heterogeneous or random (white?) noise, and allow other signals to pass,
BUT... and herein lies the rub... they often introduce digital
artifact and white noise of their own which covers the intended audio
signal. Therefore, many sets, SONY in particular, seem to supplant one
type of noise with another. And I believe the added digital noise is
worse than the original noise it supplants. (I acknowledge not
everybody will agree with me on this... so it is an open question for
sure.)
Of course, much depends on the type of noise you are trying to reduce,
and what your expectations are concerning acceptable digital artifact.
For example, you might willingly accept a little light hissss-ing over
the music or intended audio signal, if the active noise cancellation
circuit sufficiently reduces the dull roar of a jet engine and the
ubiquitous whooshing sound you encounter in a passenger jet. Similarly,
you might eagerly trade some digital artifact for the roar of a sports
car or truck under way. I believe (just MY take, anyway) the "analog"
white noise from my linear amp cooling fan is easier to overlook than
the digital artifact caused by the noise reduction circuit. Others,
of course, may reasonably reach the opposite conclusion.
Presumptively, hams desire a significant reduction in power supply and
amplifier cooling fan noise. But I figure trading that sort of
hisss-ing noise for digital artifact (generally ALSO a high, hissing
type noise) is a poor exchange. Moreover, the times the noise I most
want to reduce during a contest is the sound of 6 guys in one room, all
all calling CQ or complete a contest exchange at once - and noise
canceling headphones do not perform well at reducing this type of noise.
I have, therefore, avoided the so-called "active" noise cancelling
headphones because they 1) add digital artifact that does not improve
speech intelligibility, and 2) do not reduce the types of noise I
really find most distracting when operating, and 3) I believe a good,
closed cup earphone receiver can reduce enough ambient noise (OF ANY
TYPE) by as much as 20 to 30 dB, so I save the cost of the active
cancellation circuit and put that money to better use - perhaps into a
better headset with better earphone receivers and better microphone
element. A well made broadcast headset is designed to reduce ambient
noise without introducing deleterious digital artifact.
I think it is no coincidence that I cannot recall seeing any serious
headset designed for the broadcast or recording industry that uses
active noise cancellation. I believe they all employ passive noise
suppression - there may be an exception out there, but I cannot recall
it now.
The KOSS Model QZ5 is an inexpensive headphone that provides
significant PASSIVE noise reduction, initially designed for racing
scanner and metal detector users. These provide decent sound
reproduction, substantial reduction of ambient noise, but do not add any
digital artifact.
Most better quality closed cup headphones provide substantial passive
reduction of ambient noise - enough to save me from having to buy
headphones with active noise cancellation. This is major feature I look
for when selecting a headphone or headset for the station. Again, I
would rather put the extra money into better earphone receivers and
better mic elements, than the cost of active noise reduction circuitry.
My take on Headsets over headphones and a separate mic:
Mostly, I prefer a HEADSET which includes a microphone mounted on a
short boom that presents the mic element at the corner of my mouth - not
in front of it as you often see in ham operator and marketing photos -
so that I cannot breathe on the mic element. Pet Peeve No. 8276 =
working a guy who huffs and puffs into the microphone while he talks -
very distracting and annoying. Many hams would benefit from a short
presentation on good microphone technique.
This raises the separate matter of so called "noise canceling
microphones" which are usually what I call merely
noise-"rejecting"-close-talking microphones.
A few headsets, the minority, employ an "active" noise cancellation
system, which typically deploy two mic elements in opposing directions,
such that sounds reaching them end up producing signals which are
opposite in phase. Ambient room noise will generally hit both elements
roughly equally, while your voice will reach the mic element facing your
mouth much louder than the opposing mic element facing away from your
mouth. The difference in resulting electrical phase causes the signals
to cancel - ambient noise cancels more completely as it is approximately
equal in each mic element, whereas you voice, which is be louder to one
mic element than the other, suffers less reduction, and the voice signal
on to the rig. (Please forgive me... I find this hard to describe in
words, while I can diagram it easily...) ;-)
Headsets like this were initially designed for the military and Air
Force - notably by companies like AndreaElectronics, which markets this
technology today as computer headsets, aimed primarily users of speech
recognition software. Personally, I don't much like them.
More common is the so-called "passive" noise "cancelling" microphone,
which I (personally, again, just MY take, as some in the industry may
differ with me on this) consider "noise rejecting" more than
"cancelling." In this application, the mic element is placed close to
the mouth, such that the voice is relatively loud compared to ambient
noise coming from farther away in the room. This means you can set the
input volume much lower, such that the rig hears your voice at a normal
input signal strength, while ambient noise fades away, and may become
hardly noticeable. We do a similar process when we reduce RF Gain so
hear the intended DX signal, while reducing band noise - at some point,
the signal seems much louder relative to the volume of noise and the
noise sort of "disappears" (not really, but that is kinda how it seems,
anyway.)
Sidebar on Studio Quality Microphones:
Many hams use large diaphragm studio condenser microphones, because they
provide clear, precise sound reproduction - but they are typically so
sensitive they can pick up the sound of a gnat's sneeze across the room
- and the sound of cooling fans in the shack - which means they are not
very noise cancelling! These are favored by the Hi-Fi crowd, but I
think they work against the goal of providing clearly intelligible
speech on the air. My conversations with Bob Heil indicate he agrees,
and that is why he generally promotes dynamic performance type
microphones for this application.
Many microphone marketers refer to close-talking microphones as noise
cancelling, where as I think that is stretching the term a bit too far.
Nevertheless, the Marketing Departments of many vendors have clearly
prevailed. In any case, the reason I use a HEADSET and not headphones
with a desk-mounted microphone, is that a close-talking microphone will
generally provide the most noise rejection, with clear, CONSISTENT voice
pickup - AND HEREIN LIES THE RUB - the headset keeps the microphone
capsule or cartridge in pretty much the same place at all times,
notwithstanding the fact I will occasionally turn my head, lift my head,
or even sit back from the microphone while talking, which causes a HUGE
variation in voice signal strength over time. This, alone, contributes
to a loss of speech intelligibility, as well as a substantial loss of
speech energy - reducing signal strength on the antenna. We all know
shouting is not going to give us greater energy output - and may just
degrade the signal by over-modulating the microphone element, etc., but
talking quietly CAN reduce speech energy into and out of the rig, with
resulting loss of signal strength and degradation of speech
intelligibility. MANY TIMES SELECTIVE FADING FROM ODD PROPAGATION IS
LESS WORRISOME THAN UNINTENTIONAL FADING OF THE MIC INPUT SIGNAL.
Either way, you fade away. Remember, Buddy Holly sang, "Not Fade
Away." ;-)
What makes a good headset for ham use?
* Clear sound reproduction
* Bass is natural, but NOT enhanced - after all, we are only listening
to a mere 3000 MHz audio bandwidth (+/-) - adding extra bass just makes
it difficult to hear - and the speech intelligibility data is mostly in
the mid-range, anyway. Even MFJ knows this, and there is a good
explanation of this in the product description to their MFJ-616 speech
intelligibility enhancer: http://tinyurl.com/5r4ean8
* Closed earphone receiver cups generally provide significant passive
sound reduction - at least on the better quality headphone/headset models
* The microphone boom must place the mic element at the corner, but not
in front of the mouth - the microphone boom arm on some headsets are too
long and either overshoot the mouth or encourage placement in front of
the mouth where you can breath on it. This is dumb.
* The microphone is clear and provides a modest to strong signal, so
you can adjust input volume to pick up speech, but reject ambient noise
* The mic element is NOT TOO HOT... so it works in the middle of the
mic input volume range - you don't want to crowd your ALC circuit, it
needs some dynamic range to work its magic without being on or off all
the time
NOTE: Many computer headsets work great with our transceivers, but
require a 10 dB attenuator to place the open signal voltage (i.e.,
signal strength of the mic audio electric signal) within the middle
range of the transceiver - so it appears more like the open signal
voltage of a dynamic type microphone. This is a simple circuit that can
be purchased in the form of an adapter or be home brewed as a voltage
divider from a pair of resistors. AndreaElectronics sells such an
adapter for $5: http://tinyurl.com/76s6n3y
So, what HEADSETS do I use and recommend ?
1) AudioTechnica BPHS-1 - best earphone receivers, excellent microphone
cartridge - very durable and comfortable - look really good, too - at
$200 street price. My favorite headset of all time.
2) Shure SM-2 - Best microphone performance, and good earphone
receivers which are limited to the speech audio range - roughly 100 -
8000 Hz to reduce unwanted noise outside the speech audio spectrum -
costing about $225 street price.
3) Sennheiser HMD-45-6 (open air receivers) - very expensive at $300 -
excellent audio in and out - open air receivers are VERY comfortable for
use when there is little or no ambient noise - such as when I operate
barefoot and no power supply or amp blowers are running. These are used
most often in airport control towers where high quality sound and
long-use comfort is essential.
4) Superlux HMD-660 - The Bargain of the Century - Solid performance at
a very low cost around $80 street price, super quiet noise-suppressing
receiver cups, good microphone, fabulous earphone speaker elements, and
excellent noise dampening (but only if you do the receiver damping mod
which is easy to do and costs just pennies.)
5) TEN-TEC Model 777 Headset - Here is a real sleeper - well built and
durable, with the heaviest duty, strongest goose neck type microphone
boom arm I have ever seen - only the stainless steel tube boom arm of
the Shure SM-2 is stronger but it is not a goose neck type. Earphone
receiver pads are comfortable, durable and noise reducing. Earphone
speaker elements sound good. The microphone is full range, but clear.
This is a good product for the price. (Compare it to the HEIL PRO SET
ELITE - parts is parts, ya know, but TEN-TEC specified a different
microphone element.) I had one of these headsets and it was excellent.
I only sold it because I preferred the Audio-Technica BPHS-1 overall and
already had a number of other headsets - but if I did not have the Shure
SM-2, I would have kept the TEN-TEC Model 777 as my backup set.
6) Yamaha CM-500 - A real bargain at around $55 street price
7) KOSS SB-45 and SB-49 - GOOD VALUE - EQual to the CM-500 in
performance and quality, and at a lower $30-40 street price - we use
these AND the Yamaha CM-500 at the contest station and no one prefers
one over the other - and no has complained about either - and nobody has
tried to use another set, instead. No one utters the "H" word in any
case.
8) Some of the BeyerDynamic headsets look good, and work well, but look
for one that has lower earphone impedance lest you need a headphone amp
- but these are costly, and cables cost extra, so I have eschewed all
but their computer headsets, like the DT 234-pro which has smallish ear
cups and are uncomfortable to some users with large ears.
9) MANY COMPUTER GAMING HEADSETS work well with ham transceivers.
HOWEVER BUYER BEWARE! Many of them are cheaply made and will not be
sufficiently durable for the long haul, and may not take the stress of a
contest or portable application, so be careful not to pay too much for
too little. This is a rapidly expanding market right now, and many
companies make low quality, but charge high prices for glitzy, fancy
looking sets that are poorly made. Sennheiser makes great computer
gaming headsets. BeyerDynamic makes a good, well built set. The
Sennheiser PC-350 is a very comfortable, great sounding choice, but
costs a pretty $170 street price. Worth it to me, but not going to fit
everyone's budget. Many hams are pleased with the Creative, Logitech,
SteelSeries, ASUS, and other branded gaming headsets. I am not
impressed with Turtle Beach and many other brands.
Note - ASUS makes a popular wireless headset
which incorporates active noise cancellation
and this is a popular product. It might
incorporate everything one is looking for in
a lightweight wireless, noise cancelling,
headset - and costs around $120 street price.
I have not tried one yet, but it is on my
list of future sets to try. I have not
proceeded further because I am very happy
with my Audio-Technica BPHS-1, Shure SM-2,
and modded Superlux HMD-660s which are
very quiet and have good microphones. I
have found no need for active noise cancellation
but the ASUS set may be a giant killer after
all the dust settles.
Note: I recommend avoiding ON-EAR earphone
receivers as these may cause discomfort pinching
or pressing the ears against the head - eyeglass
wearers should avoid this type of earphone
receiver in most cases. Some of this type
work OK, but you want to be sure before you buy.
Note: There are LOADS of cheap Chinese made
computer gaming headsets that have decent
sound quality and these can be purchased for
as little as $5 on up. The microphones are
usually good quality, and it is the earphone
speakers that may lack - but THE IMPORTANT
POINT is that the earphone receiver cups
often lack any substantial sound reduction
capability and are, therefore, ill suited
for use in the typical ham shack, and
are definitely not suited for use in a
noisy contest environment (except, perhaps
in a quiet CW contest shack where there is
little talking going on.)
I purchased and tested 20 cheap Chinese made
headsets for potential use at a multi
operator contest station I sometimes play at,
and while most were good enough for daily use
in a single-op home ham shack, only a few were
well suited for use in the contest environment.
It was not so much sound quality, but the
noise suppression that was lacking.
YOU CAN MODIFY MOST HEADPHONE AND HEADSET RECEIVER CUPS TO FURTHER
REDUCE NOISE. One way I do this is to affix self-sticking rubber pads
to the inside of the (usually) plastic cup shells, and then I pack the
inside of the shell with wool-like batting (like the stuff gals use in
quilting) to further insulate the receivers from ambient noise, and to
deaden unwanted reverberation from the earphone cup, itself, while
talking.
The Superlux HMD-660 suffers from earphone cup reverberation when you
talk into the microphone - the vibrations from you voice echo in the cup
and then back down the mic boom and you can hear it in the mic output.
Dampening the earphone receiver cup resolves this admirably. Many
headphones would provide substantially greater passive noise reduction
with a similar modification - and it is easy and cheap to perform as
most higher quality headphones and headsets are built with screws, and
not glued shut, to enable one to replace broken parts, such as broken
cables or blown speaker elements, etc.
I BELIEVE MOST HEADPHONES AND HEADSETS CAN BE MADE SUFFICIENTLY MORE
NOISE CANCELING (suppressing, really) BY DAMPENING AMBIENT NOISE TO MAKE
ACTIVE NOISE CANCELLATION UNNECESSARY. There are multiple benefits from
this: a) lower cost, b) no digital artifact, and c) wider selection
and more models available for the application.
>
> Kim N5OP
>
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