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Old 6th October 2010, 07:49 AM   #1
ficus is offline ficus  Germany
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Default Sonab OA-4 crossover and tweeter impedance

I am restoring some 60ies Sonab OA-4 (mkII) speakers, but have encountered a small problem. I am new at this so hopefully this question isn't too dumb


The OA-4 usually has a tweeter configuration of 2x 8 Ohm + 1x 16 Ohm tweeter impediances.

However, mine, for some reason, have a pure 3x 16 Ohm configuration.


Originally, the crossover has 2x air-core 0.5 mH inductors and an 1x 6.8 uF capacitor.

It is obvious that some work has been done on the crossover, and both inductors and capacitor have been changed, but being unable to measure the induction I only know the capacitor value is 4.7 uF. Obviously this changes the crossover frequency.

However, I would like to restore the crossover to original condition, but I was wondering if the fact that I have 3x 16 Ohm means that the original components won't work or what effect it will have on the crossover generally.


Any help would be very welcome, thanks!
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Old 6th October 2010, 11:33 AM   #2
UrSv is offline UrSv  Sweden
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Have you checked for answers at CarlssonPlanet?

CarlssonPlanet.com • Everything about the Carlsson loudspeakers
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Old 6th October 2010, 12:19 PM   #3
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That's a helpful link. Just had a brief look at there are TWO versions of the OA4 so that might explain things.
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Old 6th October 2010, 04:13 PM   #4
ficus is offline ficus  Germany
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I have looked around on that site, but haven't found any info regarding my question. It is obvious that the crossover has been modified by a third party, and I believe the tweeters must have been accidentally changed at the same time. If I were to restore the filter to it's original condition (2x 0.5 mH inductors and 6.8 uF capacitor), would the higher impedance of the tweeters compared to normal theoretically be a problem?
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Old 6th October 2010, 05:47 PM   #5
UrSv is offline UrSv  Sweden
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Quote:
Originally Posted by ficus View Post
I have looked around on that site, but haven't found any info regarding my question. It is obvious that the crossover has been modified by a third party, and I believe the tweeters must have been accidentally changed at the same time. If I were to restore the filter to it's original condition (2x 0.5 mH inductors and 6.8 uF capacitor), would the higher impedance of the tweeters compared to normal theoretically be a problem?
IMHO, it would. I would try to ask the question in the forums on CarlssonPlanet. The guy who has been developing the Carlsson range since the inventor passed away has full track of the speakers and he might be there´. If not then I would register an account on http://www.faktiskt.se/ were he spends time, as IngOehman, and ask a question in the section "Carlsson Illuminati". There's a whole bunch of very Carlsson oriented people there.

On the other hand I would not spend a lot of money or time on the OA-4.
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