HiFi Speakers

terry@allans.org

Around 1976 I built a set of KEFKIT 3 speakers. These were based on the highly regarded KEF CONCERTO speakers from the late 60s/early 70s. The Concerto was a vented speaker box of 62 litres (64 pounds weight), fitted with three drive units - the T27 (high frequency), B110A (mid) and B139 (low). I built it according to my own specifications with cladding to match furniture in the room.

The specs of the units are as follows: LF Unit- B139 Type SP1044; MF Unit B110 Type SP1003; HF Unit T27 Type S1032; Dividing Network - DN12 Type SP1004, 400Hz and 3500Hz.

Three years ago I upgraded the tweeters to Scan-Speak D2905-9300; had new cross-overs (tri-wired) built by Wilmslow Audio, internal wiring replaced, external (binding posts) connections changed to accommodate tri-wiring (all from Wilmslow Audio). I then added spikes and sat the spiked speakers on concrete slabs which are surrounded with wood. Felt pieces on the bottom face of the stands protect the wooden floors. The speakers are now incredibly easy to move - they just glide over the floor. Nearly all my floors are 14mm wooden laminated parquet (Kahrs) and I experienced no ill effects (from a listening point of view) over carpeted floors.

A significant sound improvement was noticeable at most stages of development.

Naim amps apparently don't appreciate tri-wiring and so I didn't even try it - but the Naim NACA5speaker cabling which I added made the speakers sing. My tests showed that the Scanspeaks were no better than the T27s, but were just different - perhaps some people would call them dry compared to the T27s - some would call them more neutral. I stuck with the Scanspeaks but may sometime put the T27s back for further tests.

I have been tempted to change the midrange drive unit for an ATC unit - but haven't really investigated the feasibilty of this.

It has all been great fun and continues to be so.

Initially I worried that the highly priced speakers available in hifi specialists may be significantly better but after various listening tests I am convinced that I have a fine pair of high quality speakers.

By chance I came across a short refererence to the Linn Isobarik drive units somewhere on the Internet and I recognised them as the LF and MF drive units which I have in my speakers (Low frequency B139 type SP 1044 and mid range unit B110 type SP 1003). I have the Scan-Speak 2905 HF unit which is different to the Isobarik (actually better I think). The Isobariks do however use drive units similar to mine but just twice the number - 6 drive units per speaker.

I have scanned the the following original documents:

'KEFKIT 3 construction document' supplied with the kit

KEF KEFKITs Leaflet

KEF Units

and they can be viewed online.