Surprise   Shelf speaker as in Hobby Hifi 2/2021

Technical data
  • impedance: 4 Ohm
  • sensivity (2,83V/1m): 86 dB
  • size (HxWxD): 340 x 188 x 258 mm
  • frequency range (-8dB): 48 - 40000 Hz
  • crossover frequency(s): Hz
  • speaker type: bass reflex

Surprise is a compact loudspeaker with a full range driver, that includes a second speaker on the back for room acoustics.

Surprise is a bass-reflex cabinet loudspeaker with drivers of Omnes Audio and Omnes Audio.

The kit is delivered with the following drivers:
- a Omnes Audio BB4 black full range driver
- a Omnes Audio BB3.AL full range driver (on the back)

The loudspeaker has been developed by Bernd Timmermanns.

The crossover consists of:
- a blocking circuit in series with the full range driver.
- a 2nd order high-pass filter (12 dB per octave slope) for the full range driver on the back.

The frequency response of this speaker is mostly linear.

The decay spectrum (waterfall spectrum) shows a decelerated swing-out behaviour in the mid-range.

At medium volume, i.e. 90 dB at 1 m, the nonlinear distortions are below 3% above 100 Hz.

Our kit consists of

  • Omnes Audio, full range BB3 AL
  • Omnes Audio, full range BB4 black
  • 0,5x PE sealing tape, 5x2 mm, 7.5 m
  • 0,5x 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 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 2.2 μF / 160 Vdc
  • Mundorf, electrolytic capacitor, unetched, 4.7 μF / 70 Vdc
  • Mundorf, electrolytic capacitor, unetched, 6.8 μF / 70 Vdc
  • JB, electrolytic capacitor, bipolar advanced, 33μF / 50 Vdc
  • 1.0 mm air core coil, 0.47 mH/0.32 Ohm
  • 0.7 mm air core coil, 1.0 mH/0.88 Ohm
  • Metal-oxide resistor, 10W 4.7 Ohm (yellow-violet-gold)
  • Metal-oxide resistor, 5W 10 Ohm (brown-black-black)

Kit without cabinet, price per speaker   - not available

Kit with high-end crossover

The high-end kit is delivered with baked varnish air core 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. The capacitors for the Omnes Audio BB4 black are of type polypropylen (MKP) Mundorf MCAP EVO Oil.

  • Mundorf MCAP EVO Oil 2.2 μF / 450 V
  • Audaphon MKP CAP Superior 4.7 μF / 400 Vdc
  • Mundorf, electrolytic capacitor, unetched, 6.8 μF / 70 Vdc
  • Mundorf, electrolytic capacitor, unetched, 33μF / 70 Vdc
  • Mundorf baked varnish air core coil BL71, 1.0 mH/1.02 Ohm
  • Mundorf baked varnish air core coil BL100, 0.47 mH/0.32 Ohm
  • Metal-oxide resistor, 10W 4.7 Ohm (yellow-violet-gold)
  • Metal-oxide resistor, 5W 10 Ohm (brown-black-black)

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

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).

  • JB, electrolytic capacitor, bipolar advanced, 22μF / 100 Vdc
  • 0.7 mm air core coil, 1.0 mH/0.88 Ohm
  • Ceramic resistor 8.2 Ohm/20 Watt

Price per impedance correction for one speaker, to be mounted on a small wooden board.     EUR 14,20 excl. VAT: € 11.93 / $ 12.29

universal PCB

If you prefer to mount the crossover components on a 140 x 102 mm universal PCB instead on wood:
Universal PCB RA140, order no.. str-RA140, price per unit:   EUR 4,20 excl. VAT: € 3.53 / $ 3.64
We recommend one board per kit (two boards for a speaker pair)


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