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Onkens - Benefits? Design Considerations?
Onkens - Benefits? Design Considerations?
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Old 7th December 2017, 06:40 AM   #21
lisoformio is offline lisoformio  Italy
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Quote:
Originally Posted by kevinkr View Post
The Onken design is based on the old Jensen Ultraflex.
I'm not so sure. Ultraflex is some sort of boom-boom box. The "technical bulletin" speaks of how to build them and nothing more, but using Jensen loudspeakers.
The Onken were designed as maximally flat BR and the ports have high surface in order to get high efficiency. They told the story of some researches with some japanese university and some japanese professors...
If you look at impedance measurement as published on the french L'Audiophile, Onkens are BR. Then that french peopled begun the Onken novel with the mini, micro, pico onkens...
The japanese Onken site tell a different story... you have to take care of the loudspeakers and drivers the japanese Onken site describes and from what they are derived.
BTW, the more recent designs are using standard bass-reflex ports.

Last edited by lisoformio; 7th December 2017 at 07:02 AM.
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Old 7th December 2017, 07:57 AM   #22
planet10 is offline planet10  Canada
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Onkens - Benefits? Design Considerations?
Quote:
Originally Posted by planet10 View Post
If i had software to edit text in a pdf (i might be able to import it into something and then re-eport it) i’d have the inclination to go in and clean it up a bit.
I found some. Here is my 2nd pass.

http://www.planet10-hifi.com/downloa...ns-English.pdf

If someone who speaks French could have a look and see how i did i would appreciate it. In particular there are some words in Red and sentence in Blue that i had trouble with.

dave

Edit: updated with the input of soendervig. Thanx
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Old 7th December 2017, 11:27 AM   #23
soendervig is offline soendervig  Switzerland
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Default Translation

Quote:
Originally Posted by planet10 View Post
I found some. Here is my 1st pass.

http://www.planet10-hifi.com/downloa...aga-Onkens.pdf

If someone who speaks French could have a look and see how i did i would appreciate it. In particular there are some words in Red and sentence in Blue that i had trouble with.

dave
Hi Dave ,

give me an hour or so and i'll try to have it sorted out .

Cheers

Kim
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Old 7th December 2017, 12:28 PM   #24
soendervig is offline soendervig  Switzerland
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Default Translation

Hi Dave ,

from the top down the red parts :

...multiple drivers , separate bass-amplification...
...to absorb multiple peaks and resonances...
...tonearm , headshell , turntable-mat...
...hitting this type of plywood with a fingertip one notices...
...can not be done by hand ( use a t-bar driver or a speeder-handle )

The sentence in blue essentially states objective quality being the result of well calculated enclosures . The original french sentence as a whole doesn't make much sense ; i'd call it the rethoric equivalent of tap-dancing.....

Hope this helps,
cheers

Kim
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Old 7th December 2017, 05:13 PM   #25
GM is offline GM  United States
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Quote:
Originally Posted by lisoformio View Post
I have to read it again because I do not remember the french people described that enclosure an aperiodic system. I remember it as a bass-reflex sistem.
Aperiodic 'style' as in somewhat acoustically resistant [semi-aperiodic] is the way the late JMMLC translated it along with all the pertinent Onken articles for me way back when I decided to create an Excel calculator, which they are if a high enough vent aspect is used [> ~9:1], such as Dave p10's designs.

GM
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Old 7th December 2017, 08:23 PM   #26
kevinkr is offline kevinkr  United States
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Onkens - Benefits? Design Considerations?
Quote:
Originally Posted by lisoformio View Post
I'm not so sure. Ultraflex is some sort of boom-boom box. The "technical bulletin" speaks of how to build them and nothing more, but using Jensen loudspeakers.
The Onken were designed as maximally flat BR and the ports have high surface in order to get high efficiency. They told the story of some researches with some japanese university and some japanese professors...
If you look at impedance measurement as published on the french L'Audiophile, Onkens are BR. Then that french peopled begun the Onken novel with the mini, micro, pico onkens...
The japanese Onken site tell a different story... you have to take care of the loudspeakers and drivers the japanese Onken site describes and from what they are derived.
BTW, the more recent designs are using standard bass-reflex ports.

Read some of the history behind the Onken, the people who developed the equations are quite open about where the inspiration came from, and indeed the box design, internal volumes and port lengths of an Ultraflex are all very similar. I have both the original Onken articles in French and the Ultraflex design documentation as well, they are not very different.

The ultraflex is a large vent BR and definitely not a boom, boom box. Just because it was designed in an era before ts parameters does not mean the design isn't competent.

Low port velocities because of large surface area avoid some common BR noise artifacts at the expense of significant comb filtering starting in the low midrange. They also look somewhat imposing.. LOL

There are multiple tunings for the Onken box, one at one extreme is the maximally flat (I used this) and at the other is "Onken concept" which is somewhat higher Q IIRC. It has been quite a while since I built these and there are some things I may have forgotten.

The equations make it possible to use drivers other than those specified by Jensen and achieve generally very similar results. There are not very many suitable drivers for this large vent bass reflex (Altec 515/416 and Iconic 165/GPA515 are suitable, Eminence and some European speaker makers at least at one point made suitbable drivers.)

Because I have the spreadsheet and equations I was able to design an Onken bass bin that suited my particular drivers (Iconic 165-8G) - it turns out that the box I designed is quite similar to the Ultraflex box.

All Onkens and Ultraflex are extremely sensitive to electrical source impedance as it effects driver qts and the box design doesn't tolerate that well.
I designed for a specific (tube friendly) rs of 3 ohms to allow for XO inductors and amplifier source impedance since I use 0fdbk GM70 SE amps (20W) to drive them.
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Old 7th December 2017, 09:47 PM   #27
planet10 is offline planet10  Canada
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Onkens - Benefits? Design Considerations?
Quote:
Originally Posted by soendervig View Post
from the top down the red parts
Kim, i think i have gotten all that integrated. I have updated post #22 with the new document.

At some point i might redraw some of the figures to clean it up and shrink the document size.

dave
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Old 8th December 2017, 02:01 PM   #28
Pano is offline Pano  United States
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Onkens - Benefits? Design Considerations?
My experience with the Onken goes back over 30 years (ouch). I've played with the 360L, the Petit (12" Altec) and the Mini - I think it was called - with the Focal 10", then about eight years ago Dave's Fostex versions. All good, all clean and enjoyable. Also an attractive design, which doesn't hurt.

Kevin is right about the internal stuffing material. In France we used a 100% wool felt about 25mm thick.. Mr Hiraga told me that he found it at a hospital supply store - it was made to cushion bedridden patients. It wasn't cheap, but sure worked well for audio. Hanging a curtain of that felt about midway in the box did a lot to keep the midrange from coming back at you. The Bonded Logic cotton insulation might do almost as well, but I have not directly compared the two.

IMO, a lot of what's good about the Onken is its rigidity. The design itself is well braced, and we used Nantex marine grade plywood which is the densest, hardest damn wood I've ever had to work with. Cutting and drilling it was like working with steel. Alas, Nantex is no longer made and I don't know of anything as dense -maybe bamboo ply. I say that the rigidity of the walls has a lot to do with it, because I used Nantex to rebuild and shore up an A7 bass cabinet (Altec 828) and the results were just as good, maybe better, than the Onken.

The Onken W is another beast, and not at all in the style of the Ultraflex. It's a twin 15" woofer box with two tiny ports. Nantex 25mm again, but this time double wall with sand filling. By far the most natural, clean bass I've ever heard. One of those "I didn't think speakers could do that!" moments.
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Old 8th December 2017, 02:42 PM   #29
EarlK is offline EarlK  Canada
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Pano,

Any idea who introduced the felt partition into the Onken scheme ( & when ) ?

It doesn't seem to be part of the Japanese formula.

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Old 8th December 2017, 02:52 PM   #30
lisoformio is offline lisoformio  Italy
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Quote:
Originally Posted by GM View Post
Aperiodic 'style' as in somewhat acoustically resistant [semi-aperiodic] is the way the late JMMLC translated it along with all the pertinent Onken articles for me way back when I decided to create an Excel calculator, which they are if a high enough vent aspect is used [> ~9:1], such as Dave p10's designs.

GM
Onken-Jensens are not aperiodic, they are bass reflex enclosures. May be "lossy bass reflex" :-)
You have to read these articles: 1) "La petit Onken (Hiraga)" and "La mini Onken" (Mahul)
Simple bass reflexes... tuned "a la Thiele". Nothing more.
Jensen never gave infos on how to calculate the Ultraflex (I'm wrong?). Koizumi invented a "k factor" to get a correct alignment for his enclosures.
To understand Koizumi work you have to take care the loudspeakers he was using and developed. That's the "secret"... not the enclosure.

Onken = mythology... to be polite :-)

Last edited by lisoformio; 8th December 2017 at 02:55 PM.
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