Philips FB 825

The digital series 800 is a computer model developed by philips in the laboratory Eindhoven the Netherlands, and used to determine the optimum ratios between cabinet thickness, cabinet construction, loudspeaker type, filters and damping material. a unique, rubber finish between speakers and cabinet prevents unwanted vibrations.

The Speakers were manufactured in Dendermonde Belgium, the immense site of 81,216 square meters with 23,500 square meters of buildings that was located in the industrial park Hoogveld.

Philips FB 825

The twin drive scheme which is parallel and drives two 20cm cone type Woofers is adopted as low-pass. Moreover, the 13cm cone type squawker is carried in the midrange.

The FB 825 ISOPHASE tweeter by Philips specific technology is carried in the high region.
What printed the ribbon of unguided nature on the polyimide thin film dumped of the micra glass fiber is adopted as a diaphragm. This has gained the linear phase response and the outstanding transient response.

Double-density H2 chipboard of 19mm thickness is adopted as an enclosure, and MDF with the chipboard 3 times the density of usual is used for a baffle board. 

Gross price per piece 1150 guilders in the year 1990


Front panel: Removable

Dimensions: (HxWxD) 110x29x40 cm

Contents Internal / Ex: 93/128 Litre

Material sounding board: 30mm MDF

Case material: 19 mm H2 with 2 reinforcement ridges, insulation 5 cm wool

Colour: Black or Dark, walnuts motif

Weight 28.5 Kg


Continuous power: 250 Watts (RMS)

Music power: 350 Watts

System impedance: 8 Ohm

Sensitivity: 88 db/1W/1M

Crossover: 350/5000 Hz

Frequency response: 32-20.000 Hz

Maximum sound pressure 103 db

Speakers / Connection

Tweeter: Isophase type

Midrange: 13 cm double coating

Woofers: 2 x 20 cm double coating

Gold-plated terminals, Banana male plugs 4mm


  • Tweeter protection and Service
  • Phases-linear, Frequency response 32 to 20,000 Hz , Nominal Impedance 8 ohms, Sensitivity 88dB / 1W / 1 meter
  • Crossover points: 400 and 4500 Hz, High from 4500 to 21,000 Hz, Mids from 400 to 4500 Hz


AD 21601/ RT8

Dimensions: 120x135x38 mm
Back Cover dimensions: 30 mm 94x86
Material: Plastic + Aluminum grille
Weight: 700 Grams


AD 51654/SQ 8DC 

Dimensions: 130x130x64 mm
Magnet dimensions: 90x90x21 mm
Speaker frame: Aluminum
Weight: 900 Grams


AD 80669/ W15DC 

Dimensions: 200x200 x 92 mm
Magnet dimensions: 90x90x21 mm
Speaker frame: Aluminum
Weight: 1.1 Kg

Repair of decayed foam surrounds is often expensive, if you are a little handy you can do this by yourself. 

Complete Repair

Foam surrounds (€ 34.98)
4x 8 inch foam surrounds + 2x 5 inch
3x Glue and 3x brushes

Separate Foam

Foam ring Midrange (€ 5.48)
Foam ring Woofer (€ 6.98)
Foam ring 4x Woofers (€ 22.98)

Crossover & Protection tweeter

What parts do you need !



R1 = 8,2 Ohm 30 Watt, R2 = 8,2 Ohm 30 Watt, R3 = PTC 50 Volt Weerstand, R4 = 2,7 Ohm 20 Watt, R5 = 2,7 Ohm 20 Watt

To rinse

L1 = 3 micro Henry (uH), L2 = 3 uH, L3 = 1 uH, L4 = 0.33 uH


C1 = 68 micro Farad (uF) 35 Volt Bipolair, C2 = 22 uF 35 Volt Bipolair, C3 = 8,2 uF 35 Volt Bipolair, C4 = 3,3 uF 35 Volt Bipolair


D1 = dubbele diode type 1N626CA



2001= 680UF/50V PM, 2002= 470UF/16V PM


5001= VD 18STBU/18VDC NIH


3003= 22R/5W 4%


6001= BAV20 DO35 4E, 6002= BAV20 DO35 4E, 6003= BZX79 B3V0, 6004= BAV20 DO35 4E


7001= BSS38

Edges Refoaming

This (Clamp) method is based on 'fixing' the new foam edge to the frame in such a way that the coil can move freely in the air gap of the magnet. We assume that the new foam surround has been glued to the membrane.

Step 1

Center on the 'horizontal axis

Place a clamp on the right side of the woofer. Outer edge of the frame.

Step 2

Center on the 'horizontal axis

Place a clamp on the left side of the woofer

Step 3

Center on the 'horizontal axis

Press the woofer on the left, feel...... and listen.....

Step 4

Center on the 'horizontal axis

Press the woofer on the right, feel...... and listen.....

If the voice coil of the woofer starts earlier on one side than on the other, then the coil is slightly skewed! Then pull the woofer on the edge slightly to the left/right (away from the side that approaches!) and secure the edge again with the clamps. Press the woofer again on both sides, and move if necessary. Repeat this until the woofer 'runs free' on both the left and the right side.

The woofer is now centered on the horizontal axis. Make sure these clamps stay in place from now on!

Step 5

Center on the 'vertical axis

Place a clamp on the top of the woofer

Step 6

Center on the 'vertical axis

Place a clamp on the underside of the woofer

Step 7

Center on the 'vertical axis

Press the woofer at the top, feel.....

Step 8

Center on the 'vertical axis

Press the woofer at the bottom, feel.....

Proceed as with the previous centering: if the woofer is at the top rather than at the bottom: pull the woofer at the edge slightly downwards (away from the leading edge!) and clamp the edge again! Press the woofer again on both sides. Repeat this until the woofer 'runs free' at both the top and bottom. The woofer is now also centered on the vertical axis.

Make sure that these clamps also stay in place from now on.

Glue the edge to the frame (last step)

Leave the clamps in place and glue the edge between the clamps to the frame. Let the glue dry. If necessary, also clamp the glued parts with clamps. After drying, remove the clamps and glue the edge to the frame where the original four clamps were.

It is about improvement

To prevent the tweater from getting defective a protection unit has been developed.  This unit is available under service codenumber 4822 214 51842.  It is advisable to mount this unit in every set which in brought in for repair. 

To connect the unit see the download below.