WaveCenter SOTA-free   Shelf speaker as in Hobby Hifi 4-5/2025

Technical data
  • impedance: 4 Ohm
  • sensivity (2,83V/1m): 90 dB
  • size (HxWxD): 480 x 580 x 200 mm
  • frequency range (-8dB): 45 - 31000 Hz
  • crossover frequency(s): 400, 3000 Hz
  • speaker type: closed box

WaveCenter SOTA-free is a three way compact speaker.

WaveCenter SOTA-free is a closed-cabinet loudspeaker with drivers of Audaphon and Wavecor.

The kit is delivered with the following drivers:
- a Audaphon AMT-1i air motion transformer (ribbon-tweeter)
- two Wavecor MR120BD02 mids drivers
- two Wavecor WF182BD14 woofers

The loudspeaker has been developed by Bernd Timmermanns.

The crossover consists of:
- a 3rd order high-pass filter (18 dB per octave slope) for the tweeter.
- a band pass consisting of a 2nd order high pass filter (12 dB per octave slope) and a 3rd order low-pass filter (18 dB per octave slope) for the mids-woofer.
- a 2nd order low-pass filter (12 dB per octave slope) for the woofer.

The frequency response of this speaker is perfectly linear.

The decay spectrum as shown in the waterfall diagram is exemplary, free of any disturbing resonance.

At medium volume, i.e. 90 dB at 1 m, the nonlinear distortions are below 0,2% above 200 Hz.

An excerpt from the Hobby HiFi review

Conclusion of the magazine Hobby HiFi:

Our kit consists of

  • 2x Wavecor Mid/Woofer MR120BD02, 8 Ohm, die cast, kevlar/carbon cone
  • 2x Wavecor Mid/Woofer WF182BD14 kevlar / carbon, die cast, 8 Ohm
  • Audaphon AMT-1i
  • 3x Damping fleece MT Bondum 800 (30 x 50 x 2 cm)
  • Binding Post PK31, gold plated (one pair, red and black)
  • 3m Speaker cable 2x2.5 mm2, transparent
  • 0,5x Visaton Countersunk screws 3.5x25, 8 pcs
  • 2,5x Allen wood screws, black, 4x25 mm, 8 pieces
  • Plan for DIY kit

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

  • 2x Mundorf MKP capacitor 3.3 μF / 400 V
  • Mundorf MKP capacitor 8.2 μF / 400 V
  • 2x Audaphon MKT CAP 1.5 μF / 160 Vdc
  • Audaphon MKT CAP 3.3 μF / 160 Vdc
  • Audaphon MKT CAP 15 μF / 160 Vdc
  • Audaphon MKT CAP 47 μF / 160 Vdc
  • Mundorf, electrolytic capacitor, etched, 150 μF/63 Vdc
  • Mundorf, electrolytic capacitor, etched, 560 μF/63 Vdc
  • 0.7 mm air core coil, 0.15 mH/0.28 Ohm
  • 0.7 mm air core coil, 0.33 mH/0.48 Ohm
  • 0.7 mm air core coil, 0.68 mH/0.70 Ohm
  • Mundorf vs100 core coil 3.9 mH/0.4Ohm
  • Mundorf ferrite core coil P50 6.8 mH/2.75Ohm
  • Mundorf H core coil H71, 2.7 mH/0.42 0hm
  • Mundorf H core coil H100, 1.8 mH/0.19 0hm
  • 2x Metal-oxide resistor, 10W 0.47 Ohm 5% (yellow-purple-silver)
  • Metal-oxide resistor, 10W 1.5 Ohm (brown-green-gold)
  • Metal-oxide resistor, 10W 5.6 Ohm (green-blue-gold)
  • Metal-oxide resistor, 10W 10 Ohm (brown-black-black)
  • Metal-oxide resistor, 10W 12 Ohm (brown-red-black)

Kit without cabinet, price per speaker   EUR 1619,00 excl. VAT: € 1360.50 / $ 1578.18

Kit with high-end crossover

The high-end kit is delivered with baked varnish air core coils on important parts of the crossover 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 Audaphon AMT-1i are of type polypropylen (MKP) Mundorf MCAP EVO Öl 450 V.

  • 2x Mundorf MCAP EVO Oil 3.3 μF / 450 V
  • Mundorf MCAP EVO Oil 8.2 μF / 450 V
  • Mundorf MCAP EVO Oil 47 μF / 350 V
  • 2x Mundorf MKP capacitor 1.5 μF / 400 V
  • Mundorf MKP capacitor 3.3 μF / 400 V
  • Mundorf MKP capacitor 15 μF / 400 V
  • Mundorf, electrolytic capacitor, etched, 150 μF/63 Vdc
  • Mundorf, electrolytic capacitor, etched, 560 μF/63 Vdc
  • Mundorf baked varnish air core coil BL71, 0.15 mH/0.28 Ohm
  • Mundorf baked varnish air core coil BL71, 0.33 mH/0.48 Ohm
  • Mundorf baked varnish air core coil BL71, 0.68 mH/0.71 Ohm
  • Mundorf baked varnish air core coil BL71, 2.7 mH/1.53 Ohm
  • Mundorf baked varnish air core coil BL71, 6.8 mH/2.68 Ohm
  • Mundorf baked varnish air core coil BL140, 1.8 mH/0.43 Ohm
  • Mundorf vs140 core coil 3.9 mH/0.21Ohm
  • Mresist Classic 10 Ohm / 10 Watt
  • Mresist ultra 5,6 Ohm, 3/30Watt
  • Mresist Ultra cooling rod 6,5K/W + Accessories (Set 1)
  • 2x Metal-oxide resistor, 10W 0.47 Ohm 5% (yellow-purple-silver)
  • Metal-oxide resistor, 10W 1.5 Ohm (brown-green-gold)
  • Metal-oxide resistor, 10W 10 Ohm (brown-black-black)

Kit with high-end-crossover without cabinet, price per speaker   EUR 1826,00 excl. VAT: € 1534.45 / $ 1779.97

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).

  • Audaphon MKT CAP 68 μF / 160 Vdc
  • 0.7 mm air core coil, 0.10 mH/0.27 Ohm
  • ceramic resistor 6.8 Ohm/20 Watt

Price per impedance correction for one speaker, to be mounted on a small wooden board.     EUR 24,72 excl. VAT: € 20.77 / $ 24.10

universal PCB

For one speaker you need 1 pc. of RA140 and 2 pcs. of RA160 pcb.

If you prefer to mount the crossover components on a 159 x 127 mm universal PCB instead on wood:
Universal PCB RA160, order no.. str-RA160, price per unit:   EUR 5,90 excl. VAT: € 4.96 / $ 5.75
Universal PCB RA140, order no.. str-RA140, price per unit:   EUR 4,20 excl. VAT: € 3.53 / $ 4.09


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