Sonab OA-5 Type II

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Ceristimo
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Sonab OA-5 Type II

Post by Ceristimo »

I'm the proud owner of a pair of oa-5 type II speakers. Although they've sounded great in earlier days, what they're producing now is far from a natural reproduction of a recording.
The bass is still very strong and low and still sounds good. But it has some problems with high-tones. One of the speakers (which was standing in direct-sunlight) is producing a disturbed sound at certain tones. (strangely, those are mostly voices. Very high tones like drum hihats still sound reasonably). The other speaker which was lucky enough to be standing in the shadow the most of its life is better than the other one, but it's also having problems producing high tones. High tones are just way too loud, hissing and sounding a bit distorted. The nylon net protecting the speakers is also coming off, exposing them to dust and damp.
That really is a shame and it bothers me. I love those speakers and I really don't want to get rid of them. They have been used on a daily base since 1971 and I'm kind of attached to them.
My question is not íf they can get renovated, but if there are company's still doing that, or if I myself can make my speakers sound a bit better again. I've searched the net already to see if someone can get my Sonabs back to the day they were bought, but most of them are asking alot of money for it, and although I love my Sonabs, I wasn't planning on spending a fortune on them.

So, to be short, are there any wayz of improving the sound a bit myself. (you have to know first that I'm not a very handy person.) I heard from a friend of mine that rubbing the edges of the speaker with vaseline can help imroving the sound alot. What would it help if I would replace the nylon nets protecting the tweeters. Is it reasonable to keep using the old tweeters, or would it be better to replace them with other ones. (seeing the fact that they are really old and heavely used).
By the way, I've giving the individual speakers a close visual inspection, and as far as I can see, nothing is cracked or scratched. They're "only" dried out I guess.
So if anyone knows how to make my speakers a bit better, I would really like to know.

P.S. I wanted to search this forum first to see how to improve my speakers a little, but I can't read Swedish.

P.P.S. The Sonabs are still beeing used everyday, together with a pair of other speakers, because they don't sound so bad in combination with other speakers. Should I stop using them for now, or can't it do many harm?
Last edited by Ceristimo on Tue 30 Aug 2005, 15:50, edited 2 times in total.
Martin Dellstig
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Post by Martin Dellstig »

Hi!

As a starter I would recommend you to check the drive-units according to "restoring and upgrading"
http://www.carlssonplanet.com/ShowPage.asp?p=tips

If they are OK change the capacitor in the crossover.

Thats a good starting point that cost little money. After this you can decide what to do next.

Good luck

Martin

PS.
Replacement for the tweeters can be found, there is no woofer in production that fits, you need to fix that.
DS.
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Ceristimo
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Post by Ceristimo »

Thank you very much for your quick reply.
The fact that there is no good replacement for the woofer isn't so bad, I wasn't planning on changing it anyway, due to the fact that they still sound good.
Now, the tweeters. I wasn't aware of the fact that there are some good replacements for them. If I can choose between restoring them, or just getting some new ones, I prefer the last, because I don't think that these tweeters are ever going to sound good again.
Now this'll probably sound stupid, but how do I know which tweeters are installed now? On the website they're talking about a replacement for the "MT20HFC" tweeters. I really don't know what model my tweeters are, and I can't find it anywere.
Also, is it hard replacing the tweeters with new ones? I guess I don't have to take the whole speaker apart (it seems to be glued together anyway, so to get good access I have to use a saw I guess). Keep in mind that I've never restored a speaker before, but I'm willing to try.

(And again I've typed alot more than I was planning to do :oops:)

To be short: How do I know what tweeters I have, how do I take these particular speakers apart, where can I get replacements for the tweeters, and can a noob like me change the tweeters, or should I contact somebody with a bit more experience?

P.S. Replacements for the capicitors can most likely be picked up at my local audio-store, or do they need to be ordered somewere?

P.P.S On the webpage the oa-5 speakers are referred to as the 60's model? But I'm sure mine are from the early seventies? Or are the oa-5's from the 60's and the typeII from the seventies? And are they're any noticable changes between them, accept that my speakers are on top and not sunken into the cabinet?
Martin Dellstig
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Post by Martin Dellstig »

Hi

Tweeters are always MT20HFC if you have the original tweeters.

They can be replaced with Peerless CT62, these are however put out of production this year but you should be able to find them somewhere.

The difference between OA-5 and OA-5 Type II is as you describe it.
If I remeber correctly the OA-5 was replaced by OA-5-II around 1970 and was produced unti OA-14 was introduced in 1973.

Capacitors something like this
http://www.elfa.se/elfa-bin/dyndok.pl?dok=2012665.htm

Best regards

Martin
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Ceristimo
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Post by Ceristimo »

Thank you so very much. This is helping me alot. I'll change the capacitors first, see what that helps. After that I'll try and get some replacement tweeters. I hope I can find them. (I live in the Netherlands, and these Sonab speakers are very rare here, probably one of the reasons I'm so attached to them. Nobody else has speakers like this :wink: ) When I can't find the correct model, should I replace them with any tweeter of the same size, or better not change them at all then?

And also, if anyone has a good idea how to open the cabinet? I can remove the woofer and use that hole to get acces, but I prefer to take the whole speaker apart. I doubt I can reach the capacitors through the wooferhole.
Martin Dellstig
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Post by Martin Dellstig »

Hi!

Regarding the baffle on all my spekers they are screwed sodn with screws all around the baffle, this gives easy acess to the speaker.
Some people say that the baffles are glued which would make it more difficult.

Look at your speakers, if the have a lot of screws going all around they are screwed together which makes it easy.
The woofer is held by for screws.
The damping basket is held by three screws just outside the perimeter of the woofer do NOT touch these.

Best regards

Martin
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Ceristimo
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Post by Ceristimo »

I've cleaned these speakers about half a year ago. They were completely dust free again. I just took a close look, and guess what? There's already a thick layer of dust on them again. After quickly whiping the worst off, I could see the screws holding the baffle on it's placed. I always thought that they were glued, but I'm so happy they aren't. I'll take a look tomorrow to see if it comes off easily.
So if I'm right, I can touch the screws with those rubber damping thingy's on them? These are holding the woofer in it's place. There are (I think three) small screws around the woofer, I can't touch them?
Oh man, I'm getting exited about this. I honestly can't wait to replace those capacitors and see if I can get replacement tweeters. I think the audio-store around the corner here does have the right capacitors, but I wasn't able to find replacement tweeters. I will have to think up something for that :?.

Included are three pictures of my speakers, so now you know what they look like. The first one is a closeup from the woofer, the second one represents the overal condition of the tweeters (they don't look so good, I know) and the third one gives you a good impression about how the cabinet looks. It's scratched a bit, but that's something that can be easily fixed, and I don't really care about that at the moment.
Attachments
One of the woofers. It's a bit dusty, I'm going to clean them, as described on the page, first thing tomorrow.
One of the woofers. It's a bit dusty, I'm going to clean them, as described on the page, first thing tomorrow.
IM000172 (Medium).JPG (84.97 KiB) Viewed 3123 times
This represents the overal condition of the tweeters of both speakers.
This represents the overal condition of the tweeters of both speakers.
IM000173 (Medium).JPG (88.1 KiB) Viewed 3125 times
They still look cool though.
They still look cool though.
IM000174 (Medium).JPG (66.33 KiB) Viewed 3128 times
Martin Dellstig
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Post by Martin Dellstig »

Hi

You´ve got it right about the screws.

Regarding where to buy check first with http://www.audiocomponents.nl

They are listed as distributors.

Failing all else check with http://www.hifikit.se.

Best regards

Martin
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Ceristimo
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Post by Ceristimo »

you're probably getting bored by me already, but I still have one stupid question. The capacitors you showed me have a capacity of around 5%. I can't get those. The closest one available here are 4,7 or 5,6. There is one downside on both of them though, they're both 100V, and not 250, but they're still listed as professional.
Martin Dellstig
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Post by Martin Dellstig »

Hi

Just see to that you get the same value on the capacitor.
I don't remeber exactly if it is 6,8uF or what it eas but that should be no problems just take out the old and read the value.

Otherwise you have to wait until me or someone else checks the correct value.

100 Volts is OK.

Best regards

Martin
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