CT 230 Spezial   Shelf speaker as in K+T 3/2017

Technical data
  • impedance: 6 Ohm
  • sensivity (2,83V/1m): 91 dB
  • size (HxWxD): 586 x 356 x 330 mm
  • frequency range (-8dB): 33 - 21000 Hz
  • crossover frequency(s): 3500 Hz
  • speaker type: bass reflex

CT 230 Spezial is a 2 way compact speaker with drivers from Visaton.

The kit is delivered with the woofer Visaton BG 20 8 Ohm and the tweeter Visaton TW 6 NG 8 Ohm.

CT 230 Spezial is developed by Christian Gather and Holger Barske.

The crossover consists of a 2nd order low-pass filter (12 dB per octave slope) for the woofer. The tweeter is connected to a 3rd order high-pass filter (18 dB per octave slope).

The frequency response of this speaker is nearly linear on axis below 10 kHz. The decay spectrum is without faults except a resonance at 1000 Hz. At low volume, i.e. 85 dB at 1 m, the nonlinear distortions are below 0.5 % above 300 Hz and stays mostly below 1 % at 95 dB at 1 m .

Our kit consists of

  • Visaton BG 20, 8 Ohm
  • Visaton TW 6 NG, 8 Ohm
  • Bass reflex tube BR70, 70x185 mm, black
  • 0,5x PE sealing tape, 5x2 mm, 7.5 m
  • 2x Damping Sonofil 100 x 35 cm for 20 litres
  • Binding Post PK31, gold plated (one pair, red and black)
  • 2m Speaker cable 2x1.5 mm2, transparent
  • Pan screws 3.5x17 black, cross recess, 8 pieces
  • Plan for DIY kit

the crossover components (right),
to be mounted on a small wooden board.

  • Audaphon MKP CAP Superior 3.9 uF / 400 Vdc
  • Audaphon MKP CAP Superior 4.7 uF / 400 Vdc
  • Mundorf, electrolytic capacitor, unetched, 4.7 uF / 70 Vdc
  • Mundorf, electrolytic capacitor, unetched, 8.2 uF / 70 Vdc
  • Mundorf, electrolytic capacitor, unetched, 15uF / 70 Vdc
  • 1.0 mm air core coil, 1.0 mH/0.49 Ohm
  • 0.7 mm air core coil, 0.27 mH/0.44 Ohm
  • Mundorf ferrite core coil F71. 2.2 mH/0.91 Ohm
  • MOX10-resistor 6.8 Ohm/10 Watt (blue-grey-gold)
  • MOX10-resistor 12 Ohm/10 Watt (brown-red-black)

Kit without cabinet, price per speaker   EUR 99,00 excl. VAT: € 83.19 / $ 95.67

Kit with high-end crossover

The high-end kit is delivered with backlack coils for minimizing microphonic effects. - The current flow through the coil creates a magnetic field which sets the reel of wire in motion. This motion induces a voltage in the coil which adds itself to the signal. The stiffer the reel of wire is, the less the signal will be altered. All capacitors are of type MKT or MKP.

Kit with high-end-crossover without cabinet, price per speaker   EUR 119,00 excl. VAT: € 100.00 / $ 115.00

Impedance correction

If you want to use a valve amplifier with this speaker an impedance correction should be employed. In this case the component quality is less important; therefore, we offer only one kit (upon request higher quality components are available).


Price per impedance correction for one speaker, to be mounted on a small wooden board.     EUR 7,90 excl. VAT: € 6.64 / $ 7.63

universal PCBs

If you prefer to mount the crossover components on a universal PCB instead on wood
PCB 220x155 mm, order no. I-8805002, price per unit:   EUR 11,70 excl. VAT: € 9.83 / $ 11.31
We recommend one board per kit (two boards for a speaker pair)


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