B139B B110A T27A network, KEF Concerto, KEF T27 upgraded MF and HF aB section. Falcon Acoustics Recommended Upgrade, High Power Low Loss Network version. Similar to fully upgraded 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. Price is for one crossover/network.
This network improves the performance of the original B139/B110/T27 units fitted to the KEF Concerto by (A) increasing the roll off of the B110A (SP1003) at high frequencies from 12 to 18db per octave and (B) incorporating a simplified version of the acoustic Butterworth section for the T27. With a little bit of work and squeezing of the components, it is possible to incorporate these improvements on the existing PCB3. Full Instructions supplied.
UPGRADING THE KEF CONCERTO 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.
|System||KEF Concerto with Falcon MH and HF upgrade, 6 Network without 4001G section, KEF T27 aB section|
|Author/Publication||Falcon Acoustics Recommended Upgrade|
|Kit, Assembled, Bi-Wire (if avail.)||Pre-Assembled|