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Sonab OA-2212


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HISTORY
OA-2212 is the masterpiece in the 1970’s series. A design absolutely without any compromise with double 6.5 inch bass elements, double 6.5 mid range elements and no less than 12 cone tweeters. This means that you are listening to 32 (thirty-two) speaker elements, and in the first series all speakers were equipped with low distorting AlNiCo magnets. A high, wide, deep and powerful sound is spread around in the room. It is possible to play almost at unlimited levels with OA-2212. No wonder that people at the time were impressed and worshiped the master.

The expensive and powerful design was aimed as a professional studio monitor, and was used in double pairs at the “Fylkingen” scene during the performance of large electro acoustic music events. However as a studio monitor it made no real success in spite of its enormous capacity, its professional connectors (XLR) etc. The OA-2212 was considered in the selection, when Sveriges Radio (Swedish National Radio) was going to buy some hundreds of monitor speakers during the 1970’s. However OA-2212 was not chosen as it was designed to stand on the floor and disappeared behind the high mixer tables.

OA-2212 was the wet dream for stereo enthusiasts during the 1970 and as quickly the favourite among the wealthy audiophiles. For years the Ljudtekniska Sällskapet (Sound technical association) considered the OA-2212 as the world’s best speaker. Even today many musicians, sound technicians, and professionals are using the OA-2212 as their home speakers. OA-2212 was sold during the years 1977-79.

LISTENING IMPRESSIONS
Connecting a pair of OA-2212 in an ordinary living room is a overwhelming experience. It is so much coming on to you, that you don’t know where to turn. You find yourself enchanted, loosing all time awareness. You play disk after disk – food? Sleep - what is that?
The editor of CarlssonPlanet (Per Gulbrandsen) has owned three pairs of OA-2212 and restored around ten pairs and each time it has been equally difficult to be separated from the speakers. There is powerfulness in the sound, an undetermined feeling that they can handle anything. As a listener you feel like you can enter the stage and walk around the musicians. All music is reproduced with a natural power and authority. There are hard rock musicians that would rather burn in hell than be separated from their newly restored OA-2212. A music expert almost only listening to sonatas and classical songs is doing this through two pairs of OA-2212 – concurrently! However OA-2212 has, as all speakers, its negative sides too. The bass is moving so much air so it tends to be too voluminous in smaller rooms. Measurements show some disturbance in the frequency response and significant phase distortion. Additionally the stereo picture can be a bit strange: If for instance a listener is moving to the right in the couch, the sound level in the left speaker increases, and on the contrary if you move to the left. This is strange but is probably an effect due to the fan shaped assembly of the tweeters and the two mid range speakers.

One of the largest hifi experiences to CarlssonPlanet chief editor Per Gulbrandsen was in September 2001 in Peter Steindl’s (former Bremen) home with a pair of super restored OA-2212. All 24 tweeters were replaced with the new polypropylene based CT62 from Peerless. The mid range speakers were replaced with four newly developed Ino elements (developed and produced for Ljudtekniska Sällskapets technical oracle Ingvar Öhman and his company Ino Audio) and the bass baffle was completely redesigned by Ingvar Öhman with new double 8 inch aluminium bass elements (also from Ino), new double and larger bass reflex tunnels etc. All filters were of course new. The CarlssonPlanet editor reported that it sounded superb! The sound was performed with no effort, a presence and a deep musicality. The treble was one of the best ever heard. A few shortcomings existed (read more in the CarlssonPlanet Newsletter 3), however they should be fairly easy to overcome. These OA-2212 speakers are the most expensive Carlsson speakers in the history – they were sold the same day for 55.000SEK. 

RESTORATION
Restoring the OA-2212 speakers requires a considerable amount of time. You should carefully consider the job whether you can manage it before you start. It is necessary with a large working space and good tools. Just to dismount the bottom part without damaging the veneer can be a nightmare. In addition to this, the large bass filter and all internal cabling are attached to the bottom plate, making it necessary to unscrew both the double upper baffles and the bottom plate before you can start. The glass fibre is flying everywhere (keep your dust cleaner and washing gloves prepared!) and the risk to damage the veneer is high.
A pair of the upper baffles screws is difficult to find at first. They are mounted below the small rubber plate under the tweeter corner which can be lifted to reach the screws. These screws are shorter that the rest, so keep them well organised! A wise tip is to make a diagram showing the cables before they are disconnected and replaced. There are many screws! Another tip is to clothe the separate mid range chambers internally with a thin vibration absorbent asphalt carpet. Some restorers find the sound more clean in the mid range registers.
Another tip is to replace the original XLR connectors’ with their small contact surface with modern gold plated terminals providing larger contact surface and no oxidation and they are not visible under the speaker.
Those who want and understand the filter principle may rebuild the speakers for bi-amplifying. This was something Stig Carlsson approved regarding the OA-52.2. However the technical editor of the “Ljudtekniska Sällskapet” advises against this bi- and tri-amplifying regarding three way speakers due to the risk of phase errors. The bottom XLR-connectors should however not be removed in order to keep the cabinet tight and of respect for the original design.

SPEAKER ELEMENTS
As with all speakers from the 1970 the most important action to take is to replace or restore the bass- and mid range elements. To play with trashed or dry foam edge surround may cause the speaker elements to burn by sudden spikes or transients, it is also a damage risk to the amplifier.
Those who can afford should absolutely invest in the new Peeless polypropylen tweeters. In spite of the low price per speaker, it is rather expensive to do on the OA-2212, with its totally 24 tweeters, in total 4.400 SEK. But this places the treble sound in the absolute high-end sphere and there is a risk that you will do nothing else in the rest of your life than listening to music! I.e. it is worth the price to replace the tweeters – period. For further information regarding replacing the speaker elements – click on RESTORATION & UPGRADING.

THE FILTERS
OA-2212 has the most advanced filters ever mounted in a pair of Carlsson speakers. There are also many components to solder and replace. The speakers therefore provide the complex load for an amplifier, among the speakers Stig Carlsson designed. The filters should be restored according to RESTORATION & UPGRADING.
Per Gulbrandsen means based on a long period of monitoring and comparing, that the filters should be upgraded according to the original modification instructions that Stig Carlsson produced 1979, giving a cleaner bass and mid range. Only two companies were authorised to do the modifications at that time. However today, the documents describing this are available through “The Stig Carlsson Trust” (Stiftelsen Stig Carlsson, see below). According to engineer Ingvar Öhman, at ”Ljudtekniska Sällskapet”, the modification was introduced in the last series of OA-2212 production, manufactured in 1978.
The modification of existing speakers is a complex work and was not always done with the highest quality during the 1970’s. Different types of capacitor were mixed both in the filters and between right and left speakers, inductors spooled in various manners and even bass inductors replaced by so huge inductors that the cabinet volume was negatively affected. Stig Carlsson would probably have gone crazy if he had known what was going on in his name during the 1970’s. Now he is probably crying in his heaven if he can read CarlssonPlanet there! For those who want to do a serious filter upgrade should order the instructions here.

COSTS
The cost for restoring Carlsson speakers is fairly moderate. But with the OA-2212 you should know that it will cost an additional amount of money due to the number of elements. It is eight 6,5 inch elements that must be replaced or restored, and 24 tweeter elements that should be replaced, a number of capacitors and cabling, a considerable amount of work to be done and this causes the restoration to be rather expensive.
The element cost is around 10.000 SEK. If you are satisfied with restored bass and midrange elements the cost is decreased to around 3.000 SEK. In addition to this – if you want to do a complete restoration – additional costs for capacitors and cabling, not to mention all the work a restoration includes. Expect a final cost close to or even exceeding the new price for a pair of new OA-52.3 (18.000 SEK), which is more than double the cost compared to the new price during the 1970’s.

But you should anyway consider a full restoration, it is worth every cost if you can afford. A tip to cope with the cost is to start with the life saving actions: new bass and mid range elements. Next you replace the tweeters and additionally the filters and the cabling. When all is done, the OA-2212 plays easily in the same division as today’s 20-25.000 SEK speakers and will still manage the music as no other speaker will do. It is however assumed that the speakers are powered by a high current amplifier. The speakers are compared to many of today’s speakers much cooler and more beautiful, and they are loaded with Hi-Fi history and magic.

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TECHNICAL DATA Sonab OA-2212

According to the Sonabs instructions manual and/or HiFi-Handboken 19788

Princip: Omni directional, bass reflex type. With 2-4 times increased quota between direct and reflected sound.
Left/right versions.
Volume: 75 litres
Measures: 30 x 75 x 53,5
Weight: 32,5 Kg
Frequency range: 26-18.000 Hz
Frequency response: from 30 to 15.000Hz within +/-3 dB measured against a wall in a room
Impedance: 8 ohm
Crossover frequency/Hz: 450, 2000
Woofer LP filter: 6 dB air-cored inductor
Mid range filter: 12 dB air-cored inductors, age resistant plastic film capacitors
Tweeter filter: 24 dB as above
Finish: Rosewood, walnut, teak and black or white lacquer
Bass: 2 pcs 6.5 inch 5,3 ohms Peerless bass SC 165
Mid range: 2 pcs 6.5 inch 8 ohms Peerless mid range SC 165
Tweeter: 12 pcs 8 ohms Peerless tweeters MT 24 HFC
The cabinet is internally reinforced in three levels, using fibre board with large holes.
Price 1978: 8200:-/pair
Second hand price from 3500:- up to 7000:-
Seriously fully restored pairs may cost over 22.000:-. They are worth it according to Per Gulbrandsen.



Bo Sehlberg - Translator
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This page was last edited 2006-07-23 14:07:22 by Jonathan
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