BK-29725-000 Knowles Acoustics, BK-29725-000 Datasheet - Page 26

• Manufacturer Part Number: BK-29725-000
• Description: SPEAKER Z=640OHMS SS PORT ON END
• Manufacturer: Knowles Acoustics
• Series: BKr
• Type: Magnetic, Balanced Armature, End Portr

Specifications of BK-29725-000

• Frequency Range: 200Hz ~ 4kHz
• Impedance: 640 Ohm
• Size / Dimension: 7.87mm L x 5.59mm W x 4.01mm H
• Sound Pressure Level: 122.5dB
• Termination: Solder Pads
• Shape: Rectangular
• Termination Style: Wire
• Dimensions: 7.87 mm L x 5.59 mm W x 4.01 mm D
• Depth: 4.01 mm
• Length: 7.87 mm
• Width: 5.59 mm
• Transducer Function: Speaker
• External Width: 5.59mm
• Sound Level Spl: 128dB
• Frequency Response Min: 4kHz
• Frequency Response Max: 200Hz
• Device Type: Balanced Armature
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power - Rated: -
• Power - Max: -
• Material - Cone: -
• Material - Magnet: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: 423-1103

26
MICROPHONES
Microphones measure sound pressure. Inside a Knowles microphone is a thin flexible diaphragm, an electrically
charged plate, and an amplifier (Fig. 1). The output voltage is proportional to changes in the small separation
between the diaphragm and the charged plate (Fig. 2).
As sound pressure inside the front cavity increases, the diaphragm is pushed closer to the plate. As the
pressure decreases, it moves further away. The motion of the diaphragm produces a small electrical signal that
is amplified by a miniature circuit inside the microphone.
The sensitivity of a typical Knowles’ microphone is measured in units of dB relative to 1 Volt per 0.1 Pascal.
Fig 1: Cross section of a Knowles EM microphone
FIG. 2: EM diaphragm and electret
MICROPHONE AND SPEAKER BASICS
MICROPHONE AND SPEAKER BASICS
AMPLIFIER
OUTPUT TERMINAL
CHARGE PLATE
CHARGE PLATE
DIAPHRAGM
DIAPHRAGM
www.knowles.com
FRONT CAVITY
AIR GAP SEPARATION
WIRE
SOUND PRESSURE