Telefunken OB's finished

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Hi all,

it's been quite some time since I posted the last time....
Well, my new open baffles are finally finished, the carpenter really took his time...%&"!!

This is my interpretation of the theme "transparent baffle", sort of juggling with baffle area and esthetic "impact". They are now 120 cm high and around 60 cm wide, including the wings. The wings are made from 10mm plexi (isn't that lexan over in the US?) and attached with small dowels (?), the baffle itself is 19mm pearwood.

To have the possibility to try different drivers and to NOT have holes in the front I came up with a mounting device made from 5mm aluminium that also allows different clamping forces of the driver from zero to destruction ;) .

Drivers are the venerable Telefunken 8"ers from 1953 with the big magnet and Saba tweeters. The lower Qt of the Telefunken makes for a slight rollof to the lower regions, but with my closed subwoofer for the bottom bass quality is outstanding...very fast and no booming whatsoever!
Sound quality overall truly is the best I ever had....very easy and reveilling, you are sort of looking into the music!!



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You, good sir, have yourself a fine project there. But you didn't need me to tell you that, did you? I keep wanting to try a proper OB project, but the present room is too small to pull them much more than a foot from the room boundaries. Pity -I love the freedom from all boxiness you get with the dipolar (and bipolar, come to that) sound.

I love your woodwork and the mounting device. I realy would like to hear those beauties.

I have also a pair of Open Baffles which are still under development.

I use Richard Allan CG8t (1973) or Philips 9710m (1971) drivers.

The baffle size is 120cm x 40cm, but I also want to add some wings to the back of the baffle.

I have two BR subs which are integrated in the lower part of the Open Baffle and a digital crossover to experiment with the frequencies. Each sub uses two 6.5" drivers. These are just temporary drivers.

At what frequency do you cross with the sub and what kind of sub do you use?

Low Budget Pat


Hi Patrick,

I only have one sub that I built 4 years ago. It is a closed cabinet of 39 litres using an Alumapro Alchemy 12" as driver. This is an awesome driver with perfect TSP for a closed cabinet. Power comes from a Hypex HS 200 (which is manufactured in your homecountry...).
Xover frequency is at around 65Hz, and extends down to 28Hz or so....


PS Nice headamp you got there....I am currently building the Morgan Jones!

Andreas, Ropie,

the tube on the back acts as vacuum cap, I think its an ECF 80 from Telefunken. To try that was suggested to me by Holger Stein from steinmusic.
Although the cap has only a few pF between the plates (?), it audibly improves transient response and resolution of microdetail.
Now those vintage Saba tweets have amazing resolution and natural timbre (how I love all those important words...;) ), short... it sounds bloody good!

best regards,
Very nice looking speakers. I still have those Saba 8" that you recomended I use OB, but I don't have tweeters yet. (A friend bought the radio they came in a yard sale and he'd like to hear it play at least once so we're working on that for now. Later I think I'll build him some OB speaks with them)

the capacitor value in front of the tweeter is just 2.2uF, and it consists out of a bundle of different capacitor types. According to Holger Stein each one adds a bit of quality to the highs, and after listening I can second that.
I started with the ubiquitous Solen cap which sounded ok, and then added a very small KP-Type. The result was added resolution and less sharpness of the treble.
The final step was to put in the vacuum cap (they are all connected parallel), which I got prepared (couldn't do that myself... you have to connect the leads to the correct pins of the vacuum cap!) and ready to hook up.
Now those 50 year old paper tweeters really started to sing (so to speak) and have amazing resolution and imaging!

Maybe try for youself....
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