Filter
Top Products
Euviroampf Table 2-1
shows
typical
opentino
=ts
and
tbs
ofof
mi= pd.
A
very
quid
openting
mvhmnmt,
such
as
a
television
studio,
may
require
that
Damd
does
not
leak
from
the
headphones,
meanbig
the
badphoaes
should
have
good
'acoustic isolation'.
A very
noisy
or
Loud
mvironmat usually
requirts
headphones
tbat
prevent
outside
muud
from
ledring
in
(again,
gwd
rcwatic
isolation),
headph
that
can
pmQes
a
loud,
dor
d,
lad
noist
ancelliag
mi-
cmph-,
as
well.
U~g~inanoisymvimamant~~
theaormd!iumtheheadphoapisasloudorlouderthmtbe
sound
lding
into
the
headphmes
from
the
noisy
en-
~~geaonl,~-~f~hs;ldphoaedcpcads
upon
its
ability
to
ho&
powar
at
a
givm
voltage
(impdame)
and
the
efficiency
of
its
design.
Practically.
theimpdwxhasalargerefhxtwith~tdaybeulstts.
Lav~oe~uelorder,&g
theluorstltiontodnwmncwrrntfromthepower
supply.
High
hqdmce
hadplmss
am
not
as
lad,
dmuing lcss -t
from
tbs
paves
apply. The
user
stationdssignmgsof~fortheberdphoasprt
of
the
hadsat
is
25
ohms
to
600
ohms.
Head-
~MX)toUXX)ohrmwillopnteatIsduwd
levels.
InadoublemuffhadsetruchastheBcyerDT109
sold by
RTS
Systems,
them
ue 50
ohm
hadphes
eoa-
nected
in
parallel
dting
in
m
impedaaca
of
25
ohms.
Efficiencv
The
user
station
pmd-
the
loud&
sound
in
low
impdwx
headplmw
svch
as
the
DT109.
In
this
headphone,
ons
milliwatt
of
dcchical
power
produce
94
dB SPL
(sound
FlwsIUa
Level).
PracticalLoudllw
TheuserSt.tionuuproduce.aSPLof
111 dB
in
each
or
of
a
DT109
or
DTlO8 headset.
LMV
impdance
htPdstts
such
as
the
DTlO8
and
DT109
heodsets,uusstheuserstationto~morrpaw~from
the
power
supply. With DT109
hdsets,
CM300mM300
peak
cumnt
is
75 milli.mpWe.
The
CM300URM300L
mak
currsnt
is
ismillhoeres.
With
600
ohm
bdpbcmes,
peak
eumnt
d
30milli.mpnss
for
the
CM3001RM300
user
sation.
40
milli~~b
for
the
CM~OOURM~WL
user
mion. (quissc2at cumt
is
23
millipmpms
for
tbe
CM300/RM300, 33 millirmperes
for
tbe
CM300URM300L).
The
ability
of
hadphones
to
shut
out
mwmted
envi-
~talaoigvaiesfromnons(odBisolation)to.bout
1/8th
as
ioud
(30
dB
isolation).
The
degree
of
isolation
depads
both
on
the
design
of
the
bssdset
sad
the
hpacy colltmt
of
the
mhtal noise.
Lightweight,
'opm'
hesdsetg
such
as
the
RTS System
Lt1267 (single
muff)
md
LEI268
(double
muff),
have
plmwt
no (0 dB) isolation.
The
trade-off
is
that
the
LH267/LH268 am very comfortable
and
can
be
worn
for
long
Mods
(8
to
12
hours)
without physical
did&
fromtheeandfsorlwndbd.
TheLH267/LH268are
lowilqdmceandcanbetlnneduploud.
The
DT108lDT109
headmt6
have
m
isolation
mgbg
from
1odEtomdB.
At
last
four
companies, Telex,
Sstcom,
David
Clark,
and
Cuter
Eagbmhg
adl
kadscts
intended
for
heavy
iduskid,
.aosl#rc,
md
militmy
mark&..
Thcsc
hdsets
ern
pVi&
dc
isohtion
figma
of
2odB
to
40dB.
Gdy
slmking,
tlwo
kadscts
us
heavier
and
Less
mmfortablo to
wcu.
Ingsnml,tbsoomfortofberdsetsdepmdsuprm
their
weight,
padding
and
dssign.
In
the
head&
cpnaeetinO
able, ptsvent coupling
be-weu~
the
microphone
and
headphone leads by using
at
I&
a
shielded
wire
for
the
micmphone,
aad
a
seporrte
pair
of
wires
for
the
hcdpkm@).
&ttor
isolation may
be
possible
with
a
twisted,
shielded
pir
for
the
micmpbne
leads.
Do
not
allow
hadphone
ground
to
mutact
micmphw
ground
or
shield. Tie
the
shield
to
microphone
ground
or
miuopboae low.
Do
not
tie the shield
to
the
case
of
the
Mnncetor
or
the
case
of
the
user
station.
In
gcaeral
the
maximum
lmgth
for
the
headset
cable
is
ten
feet
(3.1
meters).
Lar@
over
ten
feet
require
a
special
exteasion able.
Check
with
RTS
Systems
for
help with
longer cables.
Page
8