Cumulus Bookshelf 2023   Shelf speaker as in Hobby Hifi 4-5/2023

Technical data
  • impedance: 4 Ohm
  • sensivity (2,83V/1m): 87 dB
  • size (HxWxD): 410 x 250 x 300 mm
  • frequency range (-8dB): 45 - 25000 Hz
  • crossover frequency(s): 250, 3000 Hz
  • speaker type: bass reflex

Cumulus Bookshelf 2023 is a three way compact speaker.

Cumulus Bookshelf 2023 is a bass-reflex cabinet loudspeaker with drivers of Omnes Audio and Redcatt.

The kit is delivered with the following drivers:
- a Omnes Audio CX 3.3 coaxial driver
- a Omnes Audio CX 3.3 coaxial driver
- a Redcatt Exclusive 8 woofer

The loudspeaker has been developed by Bernd Timmermanns.

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

The frequency response of this speaker is nearly linear.

The decay spectrum is perfect.

At medium volume, i.e. 90 dB at 1 m, the nonlinear distortions are below 1,5% above 100 Hz.

An excerpt from the Hobby HiFi review

Conclusion of the magazine Hobby HiFi:

Our kit consists of

  • Redcatt Exclusive 8
  • Omnes Audio, coax driver CX 3.3
  • 0,5x Damping fleece MT Bondum 800 (30 x 50 x 2 cm)
  • 0,5x PE sealing tape, 5x2 mm, 7.5 m
  • 0,5x Audaphon Damping 10, 970 x 470 mm, adhesive
  • Binding Post PK31, gold plated (one pair, red and black)
  • 2m Speaker cable 2x1.5 mm2, transparent
  • 0,5x Pan screws 3.5x17 black, torx, 8 pieces
  • Pan screws 4x20 black, torx, 8 pieces
  • Plan for DIY kit

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

  • Audaphon MKP CAP Superior 2.7 μF / 400 Vdc
  • Audaphon MKP CAP Superior 4.7 μF / 400 Vdc
  • Audaphon MKT CAP 2.2 μF / 160 Vdc
  • Audaphon MKT CAP 3.3 μF / 160 Vdc
  • Audaphon MKT CAP 22 μF / 160 Vdc
  • Mundorf, electrolytic capacitor, etched, 10 μF/100 Vdc
  • Mundorf, electrolytic capacitor, etched, 100 μF/100 Vdc
  • Mundorf, electrolytic capacitor, etched, 180 μF/63 Vdc
  • Mundorf, electrolytic capacitor, etched, 220 μF/63 Vdc
  • 1.0 mm air core coil, 0.22 mH/0.21 Ohm
  • 1.0 mm air core coil, 0.82 mH/0.44 Ohm
  • 0.7 mm air core coil, 0.27 mH/0.44 Ohm
  • Mundorf ferrite core coil P50 2.7 mH/1.48Ohm
  • Mundorf ferrite core coil P50 3.3 mH/1.71Ohm
  • Mundorf ferrite core coil P50 15 mH/4,79 Ohm
  • Mundorf H core coil H100, 1.5 mH/0.17 0hm
  • Mundorf H core coil H100, 5.6 mH/0.39 0hm
  • Metal-oxide resistor, 5W 2.2 Ohm (red-red-gold)
  • Metal-oxide resistor, 5W 2.7 Ohm (red-purple-gold)
  • Metal-oxide resistor, 5W 22 Ohm (red-red-black)

Kit without cabinet, price per speaker   EUR 316,00 excl. VAT: € 265.55 / $ 284.13

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 Omnes Audio CX 3.3 are of type polypropylen (MKP) Mundorf MCAP EVO Öl 450 V.

  • Mundorf MCAP EVO Oil 2.7 μF / 450 V
  • Mundorf MCAP EVO Oil 4.7 μF / 450 V
  • Audaphon MKP CAP Superior 2.2 μF / 400 Vdc
  • Audaphon MKP CAP Superior 3.3 μF / 400 Vdc
  • Audaphon MKP CAP Superior 4.7 μF / 400 Vdc
  • Audaphon MKP CAP Superior 5.6 μF / 400 Vdc
  • Audaphon MKP CAP Superior 22 μF / 400 Vdc
  • Mundorf, electrolytic capacitor, etched, 10 μF/100 Vdc
  • Mundorf, electrolytic capacitor, etched, 100 μF/100 Vdc
  • Mundorf, electrolytic capacitor, etched, 180 μF/63 Vdc
  • Mundorf, electrolytic capacitor, etched, 220 μF/63 Vdc
  • Mundorf Hepta Coil II45, 0.22 mH/0.18 Ohm
  • Mundorf Hepta Coil II45, 0.27 mH/0.20 Ohm
  • Mundorf Hepta Coil II45, 0.82 mH/0.38 Ohm
  • Mundorf ferrite core coil P50 2.7 mH/1.48Ohm
  • Mundorf ferrite core coil P50 3.3 mH/1.71Ohm
  • Mundorf ferrite core coil P50 15 mH/4,79 Ohm
  • Mundorf ferrite core coil P50 18 mH/5.77Ohm
  • Mundorf H core Hepta Coil LH45, 1,5 mH/0.16 Ohm
  • Mundorf H core Hepta Coil LH45, 5,6 mH/0.40 Ohm
  • Metal-oxide resistor, 5W 2.2 Ohm (red-red-gold)
  • Metal-oxide resistor, 5W 2.7 Ohm (red-purple-gold)
  • Metal-oxide resistor, 5W 22 Ohm (red-red-black)

Kit with high-end-crossover without cabinet, price per speaker   EUR 491,00 excl. VAT: € 412.61 / $ 441.49

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, 33μF / 100 Vdc
  • 0.7 mm air core coil, 0.068 mH
  • ceramic resistor 5.6 Ohm/20 Watt

Price per impedance correction for one speaker, to be mounted on a small wooden board.     EUR 9,70 excl. VAT: € 8.15 / $ 8.72

universal PCB

If you prefer to mount the crossover components on a 240 x 165 mm universal PCB instead on wood:
Universal PCB RA240, order no.. str-RA240, price per unit:   EUR 8,60 excl. VAT: € 7.23 / $ 7.73
We recommend one board per kit (two boards for a speaker pair)


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