Double Four   Shelf speaker as in K+T 2/2017

Technical data
  • impedance: 3 Ohm
  • sensivity (2,83V/1m): 85 dB
  • size (HxWxD): 292 x 200 x 256 mm
  • frequency range (-8dB): 40 - 25000 Hz
  • crossover frequency(s): 400 Hz
  • speaker type: bass reflex

Double Four is an 2 way compact FAST (Fullrange and Subwoofer Technology) speaker with Tang Band drivers.

The kit is delivered with Tang Band fullrange driver W4-1320 SIF and a Tang Band woofer W4-1720 for the bass range.

The shelf speaker employs bass reflex technology.

Double Four has been developed by Thomas Schmidt.

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

The frequency response of this speaker is nearly linear below 7 kHz. Above 7 kHz the non-linear frequency response is typical for full range loudspeakers. The decay spectrum is nearly perfect. At low volume, i.e. 85 dB at 1 m, the nonlinear distortions are lower than 0.5% above 300 Hz and doesn't exceed 0.7% at 95 dB at 1 m between 300 and 15000 Hz.

Our kit consists of

  • Tang Band W4-1320 SIF, 12 cm full range
  • Mids-woofer Tang Band W4-1720
  • Bass reflex tube HP35, 35x125 mm, black
  • 0,5x PE sealing tape, 5x2 mm, 7.5 m
  • Damping Sonofil 100 x 35 cm for 20 litres
  • Binding Post PK31, gold plated (one pair, red and black)
  • 1,5m Speaker cable 2x1.5 mm2, transparent
  • Pan screws 4x20 black, cross recess, 8 pieces
  • Plan for DIY kit

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

  • Audaphon MKT CAP 68 μF / 160 Vdc
  • electrolytic capacitor, unetched, 82uF / 50 Vdc
  • Mundorf H core coil H71, 2.7 mH/0.42 0hm
  • Mundorf H core coil H100, 2.7 mH/0.24 0hm
  • Metal-oxide resistor, 10W 4.7 Ohm (yellow-violet-gold)

Kit without cabinet, price per speaker   - not available

Kit with high-end crossover

The high-end kit is delivered with a baked varnish coil in series to the woofer 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. The capacitor for the fullrange driver is of type polypropylen (MKP) Clarity-Cap PX 250 and for the woofer a Clarity Cap PWA 160.

Kit with high-end-crossover without cabinet, price per speaker   - not available

universal PCBs

If you prefer to mount the crossover components on a universal PCB instead on wood
PCB 150x115 mm, tin plated, price per unit:   EUR 4,70 excl. VAT: € 3.95 / $ 4.23
We recommend two boards per kit (4 boards per speaker pair)

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