Ribbon Microphone

Ribbon Microphone

1. Ribbon
Microphone

By Prof. Hitesh Dholakiya

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2. Outlines
“ Basics of Ribbon Microphone
¢ Structure of Ribbon Microphone
« Elements of Ribbon Microphone
« Working of Ribbon Microphone
** Directivity of Ribbon Microphone
“ Characteristics of Ribbon Microphone
« Features of Ribbon Microphone
< Applications of Ribbon Microphone

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3. Basics

« Moving coil Microphone — high frequency response is poor due to
mass of the diaphragm.

< Mechanical mass is equivalent to inductance — attenuates higher
frequency.

« To increase frequency response - light weight aluminum ribbon is
used in place of diaphragm and coil assembly.

«<* Ribbon acts as a conductor (placed in a magnetic field) as well as a

diaphragm.

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4. Structure of Ribbon Microphone

Ribbon foil |
Ribbon

Built-in matching
transformer

Output terminals

Ribbon
Microphone
Wagners
ill,
Permanent magnet with
pole pieces extended

5. Elements

“* Magnet — horse shoe magnet with extended pole pieces —
provides strong magnetic field

« Ribbon - light aluminum foil — corrugated at right angles to its
length to provide greater surface area

“ Main feature — lightness of ribbon — 0.2 mg — a few microns
thick and about 3 mm wide

whole unit is enclosed in a circular or rectangular baffle

6. Working

Sound Pressure — Ribbon (an electric conductor) placed in magnetic
field — is made to move at right angles to magnetic field — change in
magnetic flux through ribbon — emf is induced across ribbon

«<* emf is proportional to the rate of change of flux - i.e. proportional
to sound waves striking the ribbon

« Driving mechanical force is proportional to the difference of the
pressures acting on two sides of ribbon — particle velocity of sound

waves — ‘Pressure Gradient’ or ‘ Velocity’ Microphone

7. Directivity

8. Characteristics

“Frequency Response : mass is very small — low mechanical
inductance — results in good high frequency response up to 12000
Hz | stiffness of the suspension of ribbon is also small — results in
good low frequency response | overall frequency response is 20 to
12000 Hz

* Directivity : force of sound can be applied to the ribbon from the

front as well as from the rear side — bi-directional — Figure of Eight

9. Features

“+ requires careful handling as ribbon is very light

« DC current through ribbon from a battery of meter can strain the ribbon —
resistance or continuity should not be measured with a meter

« should not be blown into — causes strain in ribbon — sensitive to breathing
too — kept at about 50 cm or more away from the source of sound

« slightest wind causes rumble noise in the output

« excellent transient response

does not need external bias

cost is high

10. Applications
O Suitable for dramas — due to figure of eight pattern — side by side

Q Two dead sides — dead area on stage