I owned a pair of Opus 3 Chorus in the 1987 good back then . Solid performance but power handling was not thier thing designers simply assumed acoustic music . Box tuning was very low considering the drivers and first order filters with no electrolytes and air core coils .
I thought they where much better than heybrook HB something or JPW P1 at the time .
The had already got the new kind enclosure by then ? So the speakers OP where looking at are very old .
It could have been the transmission line totl model I vaguely remember ? There were three Opus 3 models ? One with 6,5” bass and one with 8” bass and this big one who could have been a TL .
Don’t remember the actual history it’s complicated as they say . One speaker company becomes two different companies Opus 3 and Rauna .
Who is now again are one new company making the Opus 3 speakers again with updated drivers etc , called Rauna ? The og Rauna models did not survive.
There is a larger one with coaxial mid/treble and an 8” woofer in the new line up that’s looks interesting in today’s world.
Remember that the original concrete mixture was some special dolomite/crushed marble blend with a binder the cabs did not ring at all and there where no parellell surfaces inside, hence the hexagonal shape with slanted baffle ( also for time alignment ) .
Drivers were not sinus back then ?
There was a record player in the same material a solid block of this concrete
a friend had one off these .
I also remember that I saw traditional wooden versions of these speakers in old magazines from the 70’s . With the same names but a normal monkey coffin.
If you think the name “Opus 3” sounds familiar like the name of a record company that still exists today. You absolutely right.
Early on Bo Hansson was part owner off this record company. He and the others parted ways for reasons unknown to me ?
But he got the rights to also use the name so for while there where also two record companies. I think mr Hansson eventually just focused on the hifi bussiness.
Then I just remembered I’ve heard the speakers in the OP and some Snell EII demoed with R2R master tapes from Opus 3 ! In circa 1987 at “Hifi Huset” in Örebro
I can obviously don’t remember the details.
, that if he doesn't like working with concrete. Sinus replacement drivers that are impossible to get.
. Btw all the pics seems to have died in the link ? But i remember the discussion now . I have a dormant account on that forum but that was mostly before i regained sanity and revoked my audiophile card 
dont look at those posts....
