The project - How it all started

Carlsson OA-52 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. 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 prices speakers in those days, I guess it did well.

The design was new, the ideas well thought off and yet kept in smaller speaker boxes.


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 disign required a special tweeter. It was a challenge to find a tweeter that would perform well under the approx. 30 deg angle. The choise 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 a 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 great advantages, but also some set backs, one needed to accept.


The sound was in my opinion a bit “wooley”. Never really accurate, though very plessent. Though I must admit I had great time 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.


After some years I had moved on, and the speaker was parked in the basement for some years, till I by coincidence decided to have them brought back to life again.


The woofer was gone, the foam band was corroded and needed a repair or an exchange. The box dis not look good either and I needid 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 but as I never played the 51.3, I can’t speak from my own experience on the differences between the 51.3 and the LE versions.


I played the LE for one year before upgrading to the LE2 version. No need to spend a lot of time on those two versions, the LE2 is far 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 LE2, 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 sound 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, but many new drivers have been developed since those two were introduced.


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





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






We have also tried 55 cm high stands and it is a matter of taste and the room which one is the best.


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


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


The OA-52 boxes were bought in 2011. They looked realy bad and needed a big helping hand to shine again. As I already had the OA-51, I decided to make an even better version as I believed the latest driver technology and new membrane technology could bring even more out of these unique boxes.



With the Carlsson OA-52 UE kit, I wanted to create something superior, something unique, something which shows what this constructions can do, if drivers, crossover and all other parts are selected for their superior performance only and where cost is no object.



The list of opportunities for selecting the drivers are long, and I will spare you all our thoughts and the discussions I have had with all the persons who have helped me in this project. I would rather state, that we believe we have found the best combination for this project.


The boxes were well made, very solid also taking the old age into account. The above picture shows how the boxes looks before we start upgrading them.


Even the speaker had some scratch marks; it is in a remarkable good condition.


The drivers are described in the "Parts used" page. Click here to enter that page or see the menu on the left side.





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