Another ONKEN finished

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Hi, i just want to share some pictures about the finished Mini Onken. Thanks to GM who convinced me to look for Altec 414 drivers.
They sound great in the cabinet.
I started with Altec 806A on 811 Horns. They sound great for the money. Very smooth, but lacking some detail and HF extension.
I ended up now with TAD 2002 and a simple 6dB crossover at about 900Hz with Autoformer -12dB. This driver is simply amazing with a very simple crossover.


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I built something similar some years ago for the big brother 416 woofer and 511 horn. Tons of fun, and a big wall of sound. While the bass was slightly better with the larger woofer, the 414 has an addictive midrange when paired up well with a horn.

Feel free to experiment, as that's part of the fun. I used both the TAD 2001 and the Altec 901 drivers crossed at around 900 Hz. Not a big difference, really, on that horn. The 414 will easily go higher, and may even match up better in directivity at 1200 Hz or so. Your call.
I did use 2nd order on the crossover, and added a small cap/resistor to the HF circuit to raise the response a bit at higher frequencies. Not a massive change, either.

What size is the Onken enclosure?

It's hard to imagine using a "bookshelf" speaker after something like this, eh?

Nice work.

Dimensions and more

i have attached the drawing i used for the for the bass cabinet.
I'm still fiddeling around with the crossover. First i just compared the Altec's with the TAD's using the same simple 6dB crossover.

1.5H on the woofer and 12uF for the TAD or 22uF on the 16Ohm Altec. Simple L-Pad to adjust the levels.

The whole setup is fired through a 300B direct reactance AMP and a DIY CD-Player with PCM1704 NOS Dac usind a Pass D1 output stage. Just to give you an idea what overall sound i like.

I did not want to use a very low crossover point because i like the mid's of the 414 very much. So around 900 - 1000Hz will be the final XO point.

In comparison the TAD's are not lightyears ahead of the Altecs. The overall character of both drivers is pretty close. The TAD's sound super fast and super revealing but still smooth. Never harsh, like some people claim here in the forum. This is exactly what i was looking for.The Altec's keep a more romatic sound and i'm missing some details. It is like comparing vinyl with a CD sound. With the Altec's i would for sure add a supertweeter.
I also tried BMS 4590 drivers and listened to the Orphean horns. That is what i do not like ! You need a hell of a crossover to get this drivers sound nice and smooth. If you have a huge listening room there are advantages to use a very low crossover point around 300Hz with a huge horn and you can do that with the BMS They only integrate well if you sit at least 5 - 10 meters away. I do not have that distance.

So far i owned the following compression drivers i can compare the TAD's with :

- JBL 2420 drivers as midrange with a Klipschorn
- BMS 4590 with a Klipschorn
- B&C DE25 as tweeter (very very nice sounding mylar driver) would be my first choice as tweeter driver

I now moved to a 12dB crossover with 1.5H, 10uF as lowpass and 12uF,3H as Highpass. I compared resistors against my auto transformer, both set at -12dB. What is strange is, that the resistors simple kill the sound of the Horn. It sounds like **** compared to the auto trafo ....

I'm not sure wether i should test also a 18db Le'Cleac type crossover or not ? Usually the more complex the crossover gets the sound gets worse ...

One question would also be if the Altec 811 is working weel with the TAD, maybe at some point in time i will also test a tractrix horn ....

Currently i'm happy with 12dB crossover and the 811 ...


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I like the autotransformer idea. Something I intend to try...

As far as differences in the 1" drivers, I had the same experience. I believe the horn dominates the sound to the extent that it masks the qualities of each driver, to some extent.

I tried other 90 degree dispersion horns, both wood and a fiberglass DDS horn, and the sound changed dramatically. I think you would be pleased with a tractrix or similar flare. Vuci fiberglassed up his own pair of round horns.

Anyway, your right about the Altec being softer on top, which effects the overall tonal qualities - a warmer, less detailed sound . The TAD 2001 I used rolled off about 16K Hz with a slightly ragged break-up on the larger Altec horn, but could load down to 500 Hz. I actually liked it crossed higher.

Glad that your enjoying this older design. It may not be cutting edge, but it IS fun.

And thanks for the information on the various drivers you've tried.
Much as I thought, but it is nice to have it confirmed.

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Thanks for the good info, DUC.

Le Petit Onken, bien sur! I should have known. Nice box. I remember when the plans came out, oh so many years ago.

And thanks for your comparisons of the different drivers. I have a set of 811/806a myself and ended up with very much the same crossover values that you did. From what you and others say about the autotransformer, I'm keen to try them What type do you use?

You might also want to have a look at my old thread Horn Honk and Towels for some easy to do ideas. Cheap and easy to try. You may find that you like it. I find that it also works on the edge of open baffle speakers.

at the end it is all a compromize and personal preference with all speaker designs. But you are right they are FUN.

Well got my autoformers from Al Klappenberg. I used his crossover design for the Klipschorns. This is years ago, but i think you can still get them cheap. Just google his name and Klipschorn. They are not state of the art, but i think in this application you do not need anything special.
If you want something special and want to spend some bucks, there is a ebay seller "mast mutter" selling nice looking ones. I do not know how they sound.
love to come here...

nice work DUC,

I was thinking of building a pair myself...
already have the B&C DE25 (in a ME45 horn for the moment)

Some Stereo Lab tractrix horns (400Hz?) are coming in one of these days... (are they any good?)

next step was some petite onken and looking for the perfect driver...Altec or alternative...

does anyone have a suggestion?



the DE25 works very nice on the Stereo Labs horn. A friend of mine is running them also.

If you want to go for a Onken design is think there are not a lot of driver choices. Initially i also wanted to go for other drivers because the 414 is very are hard to find. But there is no today driver which has similar specs and some of the new drivers are also expensive. So you can burn a lot of money and it does not work later.

My recommendation is , if you go for the Petit Onken find a 414. If you have space you can find more easy a used 416 or you can even by new drivers 416 / 515 clones from Great Plains Audio for the "real" Onken.
Hi DUC985,
Very nice looking speaker you have build. This is the 1st time I come across Onken design. What is the sound difference between this and say closed or ported box? How do you calculate the box size? Do you use the same size box as ported and add the extra Onken outlet?

Crossover Parts value


Very interesting post. I have a question. I too own a pair of 414 16 ohms. And I am trying to cross them at 1000hz. I too love the MID sound of the 414s and am trying maximize the MID. Did I read it right that you used 1.5mh and 10uf combo?

If anyone has recommendation please feel free to do so.

By the way. I am using 614 3.5cft plan.

Thank you.


To my ears, the 16 ohm 414 woofer may require a much higher value coil than 1.5mH for a ~1K Hz 12 dB crossover. I would start with around 3.5mH coil in series, and perhaps 5uF on the capacitor in parallel for a 12dB second order slope on the woofer, and be prepared to add or subtract as needed. That is, make up a string of (3) 1.0mH coils, and add a .50mH, all in series, then listen for several hours/days, and change if needed. Be sure to separate and rotate the axis of the coils from each other, or inductance will fluctuate and values change.

You will need an equal amount of components for the high pass network on the horn, so buy accordingly.


Of course, measurements would really help to get a handle on the impedance, phase, radiation pattern, and overall response, among other things. Try Speaker Workshop.

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