Sennheiser SER 1-3 User Manual download pdf (Page 5)

the directivity

index

of the MD

441

130°

and

1000 Hz

is 20 dB, this means that a sound

level

from

this

angle at this

frequency generates at the

microphone a

voltage which

is 20

dB smaller

than

if it

were to

irradiated from

0 °.

iiiiiiii íiwñiiiil.iÌr

npYO!I

il.MI\

iiiüiï iiiii11110 iiiii

ï_

ionniMdmn=

onrMr

iiiiiiiiii °Oii

Miiiiiii

Dynamic

Headphone

All Sennheiser

headphones

with the prefix HD

are of the dynamic type operating on the

moving

coil principle. An alternating current fed through

the coil,

which is located in

an annular

gap in

permanent magnet, generates movements

both

the coil and the diaphragm which it

carries

which

h are equivalent to the alternating current at audio

frequency.

Dynamic Microphone

All Sennheiser

microphones

with the prefix MD are

dynamic

microphones. This type of

microphone

incorporates

a diaphragm

within an annular

magnetic

field

generated

by a permanent

magnet.

As the sound

waves strike the diaphragm

they

set both

it and the

interconnected

moving

coil

into

motion. Following

the

induction principle, electrical

voltages are

induced in

the

coil

equivalent

to the

incident sound

waves.

Electret Condenser Microphone

By contrast

with

other

low frequency microphones,

with

the electret condenser

microphone it is not

necessary

to apply any

polarisation voltage

to the

capsule. The

name

" electret"

analogous to

magnet. Similarly to the

manner

in which

magnetism remains

permanently

intact in

hard

magnetic material, it is

possible

with

certain

electrical materials to achieve a permanent

electrical charge through a special

polarisation

process

the

materials.

Electrical Impedance

(also

known

as source

impedance)

This is important for

correct amplifier matching.

The terminal

impedance, i.

e. the

input

resistance

impedance

of the

connected amplifier, should

always be

considerably

higher

than the source

impedance

(voltage

matching).

For this type of

matching it is

sufficient to specify

rated

electrical

impedance.

The true

impedance,

which is more

less frequency-

dependent,

can

vary

somewhat

from

this

rated impedance.

Electroacoustic

Transducer

Principles

With

microphones,

several different

electrical

principles

are used for

transforming

acoustical

energy into

electrical

energy:

1. Piezo- resistive

(carbon

microphones)

2. Piezo

-electric

(ceramic and

crystal

microphones,

Piezopolymer microphones)

3. Electromagnetic

(magnetic microphones

for

deaf aids)

Electrodynamic

(dynamic microphones, ribbon

microphones,

planardynamic

microphones)

5. Electrostatic

(capacitor microphones,

electret microphones)

All

transducer principles

have

their

own

range

application in general.

For example,

the relatively

simple

carbon microphone is

still used today in

telephones.

By contrast

condenser microphones

are employed where

maximum

possible

audio

fidelity is

required.

Sennheiser

concentrates

particularly

on the

production

of dynamic

and

electrostatic

microphones.

Electrostatic Headphones

Electrostatic

headphones

operate on the principle

of attracting electrical charges.

The

extremely

lightweight

diaphragm

permits maximum

audio

fidelity. The highly transformed

audio

frequency

voltage

used to drive the diaphragms.

Sennheiser electrostatic

headphones need no

external dc voltage

source

as they incorporate

electret diaphragms.

Equivalent Noise

you

bring

microphone

into

a totally

quiet

room

and also connect it

up to an extremely high -quality

amplifier, you will

still

notice

a noise

originating

from the microphone itself.

This

can be due to a

variety of

causes. For example

the air

molecules

carried by thermal currents

and colliding with

the

microphone

diaphragm will

cause

noise.

With

dynamic

microphones

the noise

caused by thermal

movements

the

electrons predominates in

the

resistance

of the

moving

coil. The

equivalent noise

has

been calculated

by the German Broadcasting

Authorities from

the

measured

noise voltage

and

the

sensitivity of the

microphone.

According to

standard specifications

the term "volume"

may

no longer

be used

for

this value,

as it differs

widely

also from

the subjectively

experienced

volume.

Consequently

the term

"equivalent

noise"

should

be substituted by "signal

noise ratio"

"S /N

ratio

Free

Field No -load Transmission

Factor

The field

no -load transmission factor

the quotient

of the effective

output

voltage

of the microphone

and the effective

sound pressure

and has

hitherto

been expressed in mV

/µbar.

the

latest inter-

national measurement

system the small par

unit

has

been replaced

by the Pascal.

1 Pa

N/m2 =

Oar.

Thus 1 mV /µbar is 10

/Pa.

The term "free field no

-load

transmission

factor"

indicates

the fact

that this factor has

been

measured

in a free

sound

field

with

the

micro-

phone in

no -load state, i.

e. being subjected

to a

terminal loading.

The free field

no -load

transmission

factor is naturally

dependent

frequency,

as is indicated in

the frequency

response

curve. Additionally

the

figure is

usually

specified with

tolerances

1,000

Hz. A logarith-

mic

chart is usually helpful

for plotting

the

frequency response

curve and this is

then referred

to as the

"free

field no

-load

transmission level ".

Free Field Transmission Level

Coupling

Transmission Level

The frequency response of a

headphone

cannot

be determined as easily as,

for

example, the

frequency response

of a

microphone

loud-

speaker. To date there

is no

coupling device or

"artifical

ear" capable of

producing

a result

sufficiently equivalent to the subjectively ex-

perienced audio-

impression

obtained

from

the

headphone.

Consequently

coupling

devices

can

be used only

for

comparative

measurement

purposes.

The free field

transmission level

determined by

dynamic

comparison

with

a progressive

level

soundwave

(DIN

45619). In

this procedure a

comparison

is made

of the dynamic or sound

levels

generated alternately by a progressive level

soundwave coming from the front

at a constant

sound pressure and

the headphone.

Whereas

determination

of the

free field response level is

also subject to certain

inaccuracies,

it is never-

theless possible to measure headphones

of all

types by

this

means.

Frequency

Range

The frequency

range

audible to the human

ear

between 16

and

16,000

Hz.

Oscillations below

Hz are

described as infrasonic

and

oscillations

above

16,000

Hz as ultrasonic. I o ensure tnat a

sound is recorded with maximum possible fidelity

the transformation

of sound oscillations of

varying

frequencies into

electrical oscillations should

totally uniform.

Frequency Response

Curve

Every Sennheiser studio microphone, whether

the

dynamic or capacitor type,

accompanied by

the original test certificate

the

form

of a

frequency

response

curve. As well

as specifying the

free

field no

-load transmission factor,

which

is also

plotted in

these test

certificates, the

frequency

response

curve

reflects

the criterion

which is

significant

importance

interpreting

the quality of

microphone.

It depicts

the transmission

path

a microphone relative

frequency, which is

often also described

as the

frequency response.

The

picture shows the customary test

layout

used

for plotting

the microphone frequency

curves.

Normally frequency

curves are

recorded

with the

level

soundwave

falling

vertically

on the diaphragm

from

the

front. This

procedure

also often

described

irradiating

the

microphone

acoustically

from

a reference direction

of 0 °.

assess the directional

relationship

of the

frequency

response

curves, particularly

the case of

directional microphones,

additional

frequency

response

curves are also

recorded

for

other

sound

irradiation

directions,

for

example 90° and

180

°. By uniform division

the dB

scale

also

possible to

make

a direct comparison between

frequency

response

curves plotted at different

levels, i.

e. which

come

to rest

above or below

the reference line

on the

frequency

plotting

chart.

direct comparison would

not

be possible with

linear

scale.

Leave

space

for insertion

response

curve chart.

Reference or standard

measuring

microphone

Test microphone

Sóúñdwave

AGC

(automatic gain control)

amplifier

Audio requency

generator

Graphic

chart

from

20 Hz to 20 kHz

recorder

The

generator

frequency

feed

and paper feed

of the chart

recorder

are coupled

mechanically.

1 2 3 4 5 6 7 8 9 10 ... 147 148

Comments to this Manuals

No comments

Sennheiser SER 1-3 User Manual Page 5

Comments to this Manuals

Related products and manuals for Supplementary music equipment Sennheiser SER 1-3