In 1973 the first true stereo speakers of Stig Carlsson’s design were introduced. Named Sonab OA-12 and Sonab OA-14 and the first Carlsson speakers built as left and right. Both models had the majority of the speaker elements pointed in direction to the listening place resulting in more direct sound than from the earlier omnidirectional models. Sonab OA-12 and OA-14 were before long regarded as budget version of the more exclusive OA-116 and OA-2212 and were sold in large quantities judging by the amount of non restored pairs turning up every year.
OA-12 and OA-14 models are siblings. They both have the same 8 ohms woofer; OA-14 uses four 8 ohms tweeters and OA-12 two 16 ohms tweeters. However the box volume of OA-12 is only the half of OA-14. The bass reproduction therefore is not as deep as for OA-14. In most recordings the difference is nevertheless not easily detected, ie. OA-12 is in proportion to its size extremely bass capable. Both OA-12 and OA-14 are two-way speakers in classical Carlsson-manner to be stood on the floor with its back close to the wall.
The care, ingeniousness and foresight of Stig Carlsson permeate OA-12.
For example, the bass reflex port is conical preventing chuffing noise, something discovered by other speaker designers in the nineties! And the speaker is standing on thick, soft rubber feet, working as kind of oldish SD-feet, still far ahead of his contemporaries. This allows the speakers on the whole to be acoustically disconnected from the room/floor and the neighbours are less intrudes on than with conventional designs.
(SD-feet are a Swedish innovation: a type of gas-free urethane feet that never collapse and disconnect the speaker mechanically from the listening room. The result is that vibrations from the speaker never reaches floor and walls and thereby not fed back into the speaker as distortion. This effect is measurable which neither American expensive hifi-magazines nor English discovers.)
For everything else the design is as thorough worked through as the whole seventies series, left/right speakers, thick baffles made from ABS-plastic, not less than three sturdy, latticed, internal reinforcement sections also made from ABS-plastic, the selected elements, the today classical, 6.5” 8 ohms mid-bass Peerless SC165, tilted towards the listening position and the, for its time, excellent Peerless cone-tweeters MT20HFC. OA-12 also was equipped with high quality crossover (the same as in OD-11 but for two tweeters) with expensive components. The styling was as simple as good-looking, marked Lars Lallerstedt. OA-12 was sold 1973 to 1979.
OA-12 reproduces the classic sensual Carlsson-sound, lively and relaxed, with the same ability to create the illusion of the back wall disappearing as the other Carlsson speakers from the seventies. They are not demanding particularly high currency capability, so they could be used with relatively cheap amplifiers with still very good result. Sound reproduction from well and fully restored and upgraded pairs is strikingly revealing, relaxed and non-straining. In particular OA-12 also was kind of Stig Carlsson’s own favourite among his seventies designs. ”I am still struck by how much excellent bass-reproduction it was possible to achieve from these tiny cabinets”, Stig said in 1996. OA-12 makes quite the same impact as Sonab OD-11: it is easy to forget how small and old these speakers are. Instead you can enjoy the qualities of the music and the sound reproduction. Hour after hour, listening to music instead of speakers.
Correctly upgraded and restored OA-12 matches new speakers priced 10.000 to 15.000 SEK and even more exclusive speakers at least when it comes to the ability to create the illusion of the back wall disappearing from high quality recordings.
This especially when the original tweeters are replaced by the new polypropylene Peerless CT62.
RESTORING AND UPGRADING
OA-12 is comparatively easy to restore. Mostly, just follow instructions given in the Restoring and Upgrading section. Most important, as for all Carlsson speakers manufactured in the seventies, is to replace or to restore the woofers. Either, you replace the foam surrounds and re-center the element or, which is better but more expensive, buy new woofers elements. The tweeters are seldom out of order, but invariably worn and not sounding as good as when they were new. It is highly recommended to replace them with the new Peerless CT62, see Restoring and Upgrading.
The old terminals are today usually gravely oxidised and in bad shape. Therefore they should be replaced by new goldplated binding posts fitted to the bottom of the cabinet. It is not possible though to reach the inside of the speaker at the bottom, as the base of the speaker is an integrated part of the design and thus cannot be removed. And from the upside you cannot reach the bass either, due to the reinforcement sections. Instead you have to take the lead out through the bass-reflex tube to the new binding posts. Done this way the new binding posts are not visible from the front and hence the original design is very little affected.
According to Sonabs handbook and/or ”Hifihandboken”
Box volume: 18 litres
Measures: B x W x D: 20 x 46 x 34 cm
Weight: 7 Kg
Principle: Omnidirectional, bass reflex type. With increased quota between direct and reflected sound. Diagonally facing mid-bass speaker. Two tweeters, one facing listening position and one diffusing / omnidirectional Impedance: 8 Ohms
Frequency range: 35-18.000 Hz
Frequency response: 42-15.000 Hz ± 3dB placed on the floor against the wall.
Crossover frequency: 1800 Hz
Mid-bass: 1pc 6.5 inch 8 Ohms Peerless SC165.
Tweeters: 2 pcs 5 cm 16 Ohms Peerless MT20HFC
Finishes: Rosewood, walnut, teak and black or white lacquer.
1978: 1550 SEK per pair.
Second hand: 100 up to 1300 SEK per pair for perfect and complete pairs.
Restored and upgraded: With new tweeters (Peerless 62CT). Prices ranging up to 5.000 SEK.
They are well worth this.