OA-51 UE

Carlsson OA-51 UE - The project from start to finish


Carlsson speakers has been a part of my HiFi history since the day the Carlsson OA-51 came into our living room many years ago, even before I was born. The speaker performed well in its original version, but was never an outstanding speaker. It got pretty good reviews back in the late 80´ and compared to similar priced speakers in those days, I guess it did well.

The design was new, the ideas well thought off and yet kept in a smal speaker box..


Here shown are some of the speakers Stig Carlsson designed for Sonab. The Sonab V-1, Sonab OA-5, Sonab OA-4 and Sonab OA-6.



The design required a special tweeter. It was a challenge to find a tweeter that would perform well under the approx. 30 deg angle. The one selected was a textile dome tweeter .


I think some of the problems with the original speaker from the 80's was the quality of the drivers as well as the filter component available in those days.


The Midwoofer was at that time the newly released Scan-Speak 18W8532. A driver that performs well in small box volumes. The driver has a paper membrane and a soft foam band, giving it a soft edge and a smooth sound. The foam band does have a time limitation. It will eventually crack. I guess many has either changed the driver or replaced the foam band.


The distortion in the tweeter was another problem Stig Carlsson had to accept. For sure the tweeter had some advantages, but also some set backs, which he needed to accept.


The sound was in my opinion a bit “wooley”. Never really accurate, though very plessent. It was the first real great speaker my father bought and he claim he had great times with the speaker.


Above the original tweeter from the 80’s compared to the new Scanspeak ringradiator tweeter. The original is still in perfect condition.


Tthe speaker was stored in our basement for years, till I by coincidence decided to bring them back to life again.


The woofer was gone. The foam band was corroded and needed a repair or an exchange. The box did not look good either, and I needed to have them refreshed.

I bought a pair of second hand ScanSpeak 18W8444-9 to replace the old 18W8542. I did not change anything in the filter, but the result was not bad.


Through the CarlssonPlanet website, I got in contact with John Larsen, from whom I bought the LE, or Larsen Edition, upgrade to my Carlsson OA-51.

The LE was supposed to be better than the original OA-51.3. The difference should only be in the crossover. As I never played the 51.3 version, I can’t speak from my own experience on the differences between the 51.3 and the LE versions.


I played the LE for a year before upgrading it to the LE2 version. No need to spend a lot of time on those two versions, the LE2 was better, which is a result of a better sounding ScanSpeak D2608 tweeter compared to the Vifa made T-11oa used in the LE version. The LE version, which was adopted for the OA-51, was never available for the OA-52. Therefore the OA-51 LE2 upgrade is similar to the upgrade OA-52 LE available today.


I had the OA-51 painted in a silk mat dark grey color and the result is very nice. The OA-51 LE, upgraded two years ago, is not a bad upgrade at all, but it does not bring the speaker up to the level of performance of the best 2-way constructions on the market today.


The sound is great and the width of the soundstage is good, but the dept of the sound stage could be better.


Selecting the new drivers for our upgrade was perhaps the most critical part. The ScanSpeak 2608 and 18W8545, used in the John Larsen upgrades, are very good drivers, and both works well in the OA-51 LE2 version, but many new drivers have been developed since those two were introduced.

Just because new drivers are introduced, does not make these two old constructions any worse, just many later developed drivers are simply better!


On the picture the OA-51 LE2 shown with M.I.T. CVT 1 speaker cables.


Our OA-51 LE2 is here placed on 350 mm high stands and is resting up against the wall. One of our listening room is approx. 20m2 and we are listening in a distance of 3,5m.


I have also tried to use 55 cm high stands and it is a matter of taste, and roomsize which one is the best.


The OA-51 LE2 has been used as one of my reference speakers for the development of the Carlsson OA-52 UE kit.









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