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SKU: Crossover F5c

KEF Concerto Upgrade Crossover B139B B110A T27A network, with higher power handling. High Power LF Inductor. See also No. 6, 33 and 53.

All networks are made to order.  Price is for one crossover/network.

Availability: In stock

Excl. Vat: £32.55 Incl. Vat: £39.06

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Excl. Vat: £32.55 Incl. Vat: £39.06
Product Description


    KEF Concerto Crossover Upgraded B139B B110A T27A network, Falcon Acoustics Recommended Upgrade, High Power Low Loss Network version. Similar to Crossover No. 6 but without the Coles 4001G Super Tweeter section.

    Networks can be supplied as kits or pre-assembled unless shown supplied as kits only. Please allow an extra 7 days for delivery if buying pre-assembled. Price is for one crossover/network.


    The No.5 network only will fit in the existing network cut-out. All other types are too deep and in the case of the modified ones too wide. The network edge connector is poor and relies on two tin plated surfaces making good contact. It is best to put the network inside the cabinet on the bottom at the back or on the back at the bottom and rewire with a decent cable. We recommend 76/0.2 mm.

    If you want to keep an authentic look keep the original SP1004 network and wires as they are, but not connected inside. Just leave the existing bits as they are, but disconnect all the wires inside the cabinet (to units and input) and rewire the new network with good wire to the input and units. Unless you want rear panel authenticity, fit a new input panel or terminals. It will sound better without the connector and with thicker wire.

    The No.6 network was originally designed (in a slightly different version) for a prototype Ferrograph system. The network was subsequently offered to Cambridge Audio where Bert Webb was designing the R50 transmission system. Bert made a few simplifications and added a super tweeter.

    The No.33 and 33C networks are a higher power handling version. The design never went into KEF production as the Concerto was coming to the end of production. The sound was flatter and smoother than the DN12 SP1004. Note there are 2 versions of the DN12 SP1004. The first had a 60 μF and a 2mH inductor in the MF low frequency roll-off, whilst the later had a 30 μF and a 4mH. This gave a higher impedance at the LF/MF crossover. This became important when transistor amplifiers standardised on 8 Ohm output.



Additional Information

    Additional Information

    System KEF Concerto 5c based on 6 Network without 4001G section
    Author/Publication Falcon Acoustics Recommended Upgrade
    PCB No. 3
Product Reviews
    1. Review of the Kef Concerto Crossover 5c by Dusan Sudarski

      As I promised to Jerry, here is my review:

      This is a GREAT crossover, a well worth upgrade to the original crossover, I did internal rewiering with Van Den Hul CS12 cable and put crossover inside of the cabinet.

      Sound is more defined, bass is tight and accurate, hights are clear and bright but not harsh and the middles are back to focus.

      Many thanks to Jerry for his time, advices and patient. Keep up with good work!

      (Posted on 25/01/2015)

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