After the disastrous termination of the Sonab-company and its manager’s waste of millions of Swedish Kronor, the next series of loudspeaker instead got the name from the designer. The loudspeakers were built by the newly established factory in Skillingaryd, Sweden, and the classic OA for Ortho Acoustic naming remained.
The new OA-50 series consisted of three revolutionary two-way models, where Carlsson OA-50 was the entry-level speaker. However it was far away from a cheap design. The cabinet of OA-50 consis ted of a horizontal rectangular box, where the rear outer corner is raised above the opposite front corner, with the speaker elements mounted on a half pyramid shaped baffle. Acoustic absorbents were placed horizontally in front of the speaker and vertically on the rear part in order to damp the early reflections. The whole top was covered by the largest metallic net in the Carlsson history, as big as the cabinet itself. The cabinet was heavily reinforced inside, with the tweeters standing above the pyramid shaped baffle, mounted only with two screws.
The woofer was an improved version of the 1970’s series famous and loved SC 165, the 6.5 inch 8 ohms Peerless mid-woofer, now in its third generation, with lower distortion and a different membrane material. The tweeter was an omni directional silk dome tweeter, also manufactured by Peerless (115DT26).
The series was built on new and improved measuring principles developed by Stig Carlsson. He stated that his earlier constructions were out of date now and that he finally had built the worlds best loudspeakers for normal living rooms.
The whole series of the 1980’s OA-50/51/52 had in our opinion a not so good textile dome tweeter, the Peerless 115DT26. This element was the reason for giving the OA-50 series more negative reviews than they where worth. This in turn probably sent Stig Carlsson to poorness and a life close to starvation for 20 years. However the tweeter was chosen with utterly care due to its low distortion and because it was the most omni directional tweeter available at the time. It could also handle large very large currents.
The Sonab OA-50 was sold during 1984 – 1989.
1996 the heavily improved follow-up OA-50.2 was presented.
2002 the upgrading option OA-50.3 was introduced with even better tweeters and new filters.
RESTORATION
The OA-50 model is very easy to restore. Most of the originally mounted bass elements today have damaged foam surrounding and are a potential threat both to the amplifiers survival and the element itself. It is absolutely necessary to restore the woofer, alternatively replace it with a new preferably further enhanced series 4-element as used in the OA-50.2 and OA-50.3 models. These have the foam surrounding replaced with age resistant rubber surrounds, the coil have a short circuit ring, decreased distortion, etc.
As mentioned above also the tweeter should be replaced. Earlier an OA-50.2 version existed, with a metal dome from Vifa. However since autumn 2002 a much better alternative exists, the new developed tweeter Carlsson T-11oa. This leads us to:
UPGRADING
From spring 2003 all OA-50-owners are offered the possibility to upgrade their ageing speakers to the best 50-version so far, namely the OA-50.3 with the very latest specially developed silk-dome tweeter Carlsson T-11oa and the rubber surround Peerless bass SC 165 in its fourth and best version including corresponding filter.
The price for this upgrade, recommended by CarlssonPlanet, is:
OA-50.3, price: 3800 SEK
If you already have upgraded to OA-50.2 (with the rubber bass above and the metal dome Vifa tweeter), or already bought a OA-52.2, and want to enhance the quality further, there also exist a low cost solution including the T-11oa tweeter and new filter:
Upgrade OA-50.2 to .3, price: 2400 SEK
Correct upgrade kits are available from Carlssonfabriken in Skillingaryd: Tel +46(0)370-70 900
John Larsen HiFi.
VENEERING THE OA-50 SERIES:
Old tired OA-50 cabinets from the 1980’s often have hard-to-repair scratches in the vinyl veneer and are debated on our Forum. The corners are breaking apart, as well as the thin strips on top of the cabinet sides. As the new upgrading kits for the OA-50 series where finalised, the Carlsson factory decided to, as an extra service, offer the owners the possibility to also re-veneer the old worn cabinets.
This is naturally not for free, for those hesitating to do this can see the fine result on the site. What do you say about getting your old worn pair of OA50 re-veneered in beautiful cherry tree? “Yum-yum”, that’s the editor’s opinion! Check for your self at OA50.3.
VENEERING PRICES:
Re-veneering a pair of OA50, price 2500 SEK. All questions and orders regarding veneering are sent to
Carlssonfabriken in Skill ingaryd: Tel 0370-70 900
John Larsen HiFi.
TECHNICAL DATA Carlsson OA-50
Principle: 2-way omni-directional bass reflex
Positioning: On the floor against a wall with damped floor and reflecting ceiling
Cabinet: 22 mm chipboard, 30 mm baffle of MDF/chipboard
Inner volume: 20 litres
Mid/bass: 1 pc Peerless 6.5 inch 8 ohms SC165
Tweeter: 1 pc Peerless 25 mm textile dome 115DT26 (K10DT according to some articles) provided with auto-fuse
Sensitivity: 89 dB/W/M
Impedance: 8 Ohm
Frequency range: 28-20.000 Hz according to DIN
Frequency range: 30-18.000Hz within 3 dB measured against a wall in a room
Measures W x H x D: 38,8 x 46,6 x 31,6 cm
Weight: 14.4 kg
Finish: Black and white lacquer
Price:
Second hand price: 400-3.000 SEK depending on finish.
Fully restored pair in good condition should cost at least 5.000 SEK
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