Brolin's Sub Woofer Page

Background  Solution  The result  Technical data for the sub  Pictures  Technical data for the woofers used  Loudspeaker links and email


Background To top of page

I have a pair of speakers called F3-Lyd Trapez-X, a 3-way Danish speaker design from 1987 with an excellent sound reproduction. The Trapez speakers are driven by two power amplifiers each 250W r.m.s.  

The frequency response of the Trapez-X is around -3dB down at 50 Hz and below at 30 Hz the speaker is -10dB down. A 10" woofer from Focal is used and the woofer has a free air resonance Fs=24 Hz. I like very low and powerfull bass reproduction so assistance in the lower end was needed.

F3 Trapez-X, an oldtimer still going strong !!!

Solution To top of page

I surfed round the Internet and after a few hours i found the The Subwoofer DIY Page, a serious loudspeaker page with lot of formulas and design hints. I bought two woofers equal to the ones in my Trapez-X speakers and designed (all the formulas was put into an Excel worksheet) a ported speaker with the two woofers mounted in an isobaric configuration to reduce cabinet volume to the half . A separate power amplifier is used to power the two woofers and an active crossover is used at the power amplifier input. The woofers used have a low equivalent volume resulting in a small box with a very good bass reproduction. Woofers with a higher equivalent  volume (such woofers are often less expensive) can also be used, but the goal was a relative small box. 

The result To top of page

The reproduction of the music has got i new dimension in the lower end. Now i can feel the music even at lower volumes. The difference between CD's with sub bass or not can now be heard. Just to mention a few of my CD's, where the sub really makes a difference :

Technical data for the sub To top of page

Pictures To top of page

The Sub woofer without front protection. Only one of the woofers are visible the other one is hidden in the cabinet. The Sub woofer with front protection. In this position (corner placement on the floor with the front backwards with 3-4 inch. to the walls) the bass coupling to the room is maximum. 

Technical data for the woofer units used To top of page

The woofer units used are equivalent to Focal 10 C 5411 DB but only with one voice coil.

 

SPECIFICATIONS (From Focal homepage)

Nominal power handling

 

 

 

 

100

 

 

 

 

W

Program power handling

150

W

Sensitivity

92.1 (89dB with one voice coil)

dB (2.8V/1m)

Cone

Coated Paper

-

Surround

Rubber

-

Nominal impedance

2 x 8

Ohms

DC resistance

2 x 5.5

Ohms

VC diameter

40

mm

VC height

13

mm

Former

Kapton™

-

Layers

4

-

Wire

Copper

-

Inductance

0.66

mH

Xmax

3.5

mm

Magnet diameter x height

121 x 30

mm x mm

Magnet weight

876

g

Flux density

1.1

T

Gap height

6

mm

Net weight

3

Kg

PARAMETERS    

Fs

23.9

Hz

Vas

148.4

I

Qts

0.26

-

Qes

0.27

-

Qms

12.66

-

Re

2.6

Ohms

Sd

346.4

cm2

Cas

106E-8

m5/N

Mas

496.9

Kg/m4

Ras

41.8

Ohms.ac

Cms

881E-6

m/N

Mms

50.2

g

Rms

596

g/s

Ces

685.1

F

Les

64.5

mH

Res

122.8

Ohms

BI

8.6

N/A

SPL

90.6

dB/W/m

 

Loudspeaker links and email To top of page

The Subwoofer DIY Page

Speaker online - Germany

Jamo - a Danish manufacturer of loudspeaker boxes

Vifa / Scan Speak - a Danish manufacturer of loudspeaker units

Focal - a French manufacturer of loudspeaker units

Visaton - a German manufacturer of loudspeaker units


Last revised: 25122003