In the fifties, sixties and seventies building your own Hifi components was a popular hobby. Many production models were also available as kits.
They could be either sold as a complete kit identical to the original unit like the Dynaco/Dynakit amplifiers requiring only assembly.
They could be sold as “half kits” providing the necessary parts but leaving things like the cabinets to the builder.
There were also of course a large number of copied products on the market riding on the popularity of successful designs.
Carlsson loudspeakers were heavily copied by different companies selling kits to the market.
Sonab saw the need for a DIY kit and therefore introduced the OA-5K on the market.
The Sonab OA-5K is similar to the OA-5 typ 1 (Mk I). It was equipped with the same units as the factory made OA-5. The only visible difference is how the filter capacitor for the tweeters is placed, between the front tweeters above the baffle. The inductors are placed under the baffle and all wiring is made point to point without a printed circuit board.
The important part with the 1960’s models V1, OA-4 and OA-5 of both Type I and Type II is not to touch the screws holding the damping basket behind the full-range speaker.
The full-range speaker should however be removed and managed. The speaker may otherwise be restored according to the RESTORATION AND UPGRADING.
Restoring this speaker is like restoring a standard OA-5 but usually without the problem of the baffles being glued.
Consider starting with only upgrading the filter capacitor and check up on the woofers.
TECHNICAL DATA Sonab OA-5K
According to Sonabs handbook and/or ”Hifihandboken”
(NOTE! All data below refer to OA-5 Type II, which may have had a slightly larger volume, due to its raised baffle)
Box volume: 47 litres
Measures: B x W x D: 24 x 61 x 43 cm
Weight: 10 Kg
Principle: Omni-directional, bass reflex type.
It is not a traditional bass reflex box due to the fact that there are no port tubes, just two tuned ports in the bottom of the cabinet similar to Dynaudios “Variovent”.
Impedance: Approx 7 Ohms
Frequency range: (DIN 45500): 37-18.000 Hz
Frequency response: 42-15.000 Hz ± 4dB on the floor against the wall
Crossover frequency: 2700 Hz
Mid-bass: 1pc 22 cm 8 Ohms Philips 9710 full-range speaker
Tweeters: 4 pcs 5 cm 8 Ohms Peerless MT20HFC
Finishes: Rosewood, walnut, teak, oak, natural pine and white lacquer.
Also available in red, blue or green stain.
Prices: 1973: 745 SEK per pair (Type II).
Second hand: 100 up to 1.200 SEK.
Restored: If well restored up to 2.500 SEK. They can well be worth this if one is not too critical regarding the musicians’ lateral placement in the sound image. If the baffle is raised and new polypropylene tweeters (Peerless 62CT13 or the coming Carlsson papercones) are mounted, new filter cabling, etc. and the speakers otherwise in excellent condition, the prices may even reach up to 4.500 SEK.