Sonab OA-12 rebuild project

[Ile]

Got Sonab OA-12 -73 pair from friend and I'm rebuilding these for livingroom speakers.

Original bass drivers was swapped to some universal crap drivers at some point and two tweeters was missing and two was broken. So I ordered B65oa II, Obi T22-oa and crossover parts from Hifi kit.

I also found out that other speaker had bad crossover, bass inductor value was only 0.6 mH, so it have short somewhere in wounds. So I ordered also new parts for bass section of the both crossovers.

Made crossovers ready yesterday. Boards needed few new holes, one extra jump cable and one trace was needed to cut to get new circuit made to old board. I'm going to solder all cables to board, so I also removed cable connectors. All parts are glued to board like originals was. Tweeter inductor are also attached with caple tie and bass with non ferrous A4 screw.



New varnish for cases can wait until I have tested how these sounds.

[jansch]

Nice job!
What kind of varnish?

[Ile]

Nice job!
What kind of varnish?

I like how full matt varnish look like. I guess it will looks lot like original Sonab varnish, but without dents and scratches.

So probably I use same full matt Helo speciallack like in my DIY speakers below, I might actually have it enough for two OA-12 in carage.



Link in my signature have few construction photos of these speakers.

[Ile]

Modified crossover is bit higher than original, so some parts had only few mm gap to reflex port inside opening. Yesterday I lowered top baffle legs for crossover about 15 mm, so now air flow shouldn't be compromised.

[Ile]

I got speakers ready yesterday, sound pretty good. Might bee little too much treble though, tweeter crossover might need bit higher series resistors.

Top grilles doesn't fit very good with new tweeters, some rubber c-strip might help to lift grilles to bit higher so that grilles aren't laying over tweeters. I will listen more and take some measurements after I get grilles installed properly.

I soldered all cables straight to crossover and elements, speaker cables included so there will be no terminals.

[Ile]

Installed rubber c-strip to top grilles and now those fits fine and there is room for tweeters under grille.

Been listening speakers now some time and these sounds just great for livingroom use. Mostly I use these for radio and tv, but also sometimes for movies and music since my theater/music room is still under construction.

Yesterday I measured room response and all was fine. Tweeter level is ok with "standard" Obi crossover and start to roll off at around 15-18 kHz . Bass extension is not that great, but considering speaker size it's ok.