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.
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I found some. Here is my 2nd pass.
http://www.planet10-hifi.com/downloads/Hiraga-Onkens-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
Translation
Hi Dave ,
give me an hour or so and i'll try to have it sorted out .
Cheers
Kim
Hi Dave ,
give me an hour or so and i'll try to have it sorted out .
Cheers
Kim
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
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
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
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.
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
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.
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.
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
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The when would be about 1986. I remember going by the shop and it being a new thing that we all liked. Who came up with the idea, I don't remember. Could have been Jean, William, Philip, Gerard - it sure wasn't me!
Yes. You can tune the Onken the way you want, the way you like. Thiele and Small gave us a methodology to make good vented/ported enclosures.
Everything else is nonsense... to be polite again
Boom boom boxes are all the vented/ported enclosures developed/designed before Thiele/Small works.
Do you have the matematics for the Ultraflex? Really?
I only found a technical bullettin with dimensions and the parts to use. Is there any other documentation?
These days I am not sure what I've got as I built these 11 years ago, and have had a couple of computer crashes.. A cop out I know.
Strange that you make so many negative comments about the Ultraflex which is clearly the progenitor of the Onken, I believe Onken designer admitted as much in at least one article I read, and probably will not be able to locate after this length of time. I can only assume you have not heard one, well implemented it's not particularly different in performance than the Onken and the internal volumes and port lengths are quite close to the results I got using the Cyre Marc Debien, Jacques Mahule spreadsheet calculator for my own pair. I would agree that designing using ts parameters is easier and likely guarantees a better result without a lot of cutting and trying.
Your comment is somewhat puzzling given that almost all the early American stuff from Jensen, JBL, Altec, Western Electric, and countless others is revered in Japan and has been the inspiration for a lot of the activity there. The original Onken certainly is not very original in any sense and is just an improved Ultraflex and I don't really care what you think about that.. (nicely)
Strange that you make so many negative comments about the Ultraflex which is clearly the progenitor of the Onken, I believe Onken designer admitted as much in at least one article I read, and probably will not be able to locate after this length of time. I can only assume you have not heard one, well implemented it's not particularly different in performance than the Onken and the internal volumes and port lengths are quite close to the results I got using the Cyre Marc Debien, Jacques Mahule spreadsheet calculator for my own pair. I would agree that designing using ts parameters is easier and likely guarantees a better result without a lot of cutting and trying.
Your comment is somewhat puzzling given that almost all the early American stuff from Jensen, JBL, Altec, Western Electric, and countless others is revered in Japan and has been the inspiration for a lot of the activity there. The original Onken certainly is not very original in any sense and is just an improved Ultraflex and I don't really care what you think about that.. (nicely)
The when would be about 1986. I remember going by the shop and it being a new thing that we all liked. Who came up with the idea, I don't remember. Could have been Jean, William, Philip, Gerard - it sure wasn't me!
Thanks for that bit of history Pano .
Yes. You can tune the Onken the way you want, the way you like. Thiele and Small gave us a methodology to make good vented/ported enclosures.
Everything else is nonsense... to be polite again
Untrue.
Also untrue.
a/ You are apparently unaware of James Novak, who created a similar filter-derived methodology for ducted vent box design some years before Thiele's (let alone Small's) work, and
b/ Classic bass reflex design was emphatically not all 'boom boom'. A lot were, but they were not properly damped and tuned. There seems to be some peculiar assumption going around that before Small got in on the act, people just built a big box, drilled a hole in it, slapped a driver in and said 'that'll do'. Not so. The theoretical basis involved was far less precise (although with superior acoustic efficiency in the majority of cases) and they therefore required more empirical work in developing and refining the design. The fact that many did not put that work in does not automatically condemn every single bass reflex (as distinct from later T/S vented boxes) enclosure to the dustbin of contempt. Many worked perfectly well when properly implemented, and some of the approaches are still used, very successfully at that.
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I've currently got Novak's 1959 paper (in which he derives electrical equivalent circuits for both drivers and ducted vent enclosures) on my other monitor.
Right. About the only thing the pioneers didn't cover was digital & some later transitor types. They pretty much built & & measured everything to death from the '20s - early '60s, as Olson & Beranek illustrate in their respective works.
Right. About the only thing the pioneers didn't cover was digital & some later transitor types. They pretty much built & & measured everything to death from the '20s - early '60s, as Olson & Beranek illustrate in their respective works.
Thanks, Scott! I've discovered that a lot of the really good stuff they did then still stands up rather well against modern competition. I was taught otherwise by the HIFI press here in the U.S. and perhaps to a lesser extent the U.K. as well so it all came as a bit of a surprise when I started to run into people into unfashionable vintage gear like horns, BR, and SE amps. (More than 20 yrs ago now) The surprise of course being how good it sounded.
DEnse is not really an asset, but it often goes along with high stiffness. There are 3 basic types of bamboo plywood, all differ in the surface layers. A horizontally oriented construction, a vertically oriented one, and one where the bamboo is pulled apart into strands and bonded together into a panel. The latter is by far the stiffest and also heavy and dense. It is a very good speaker building material, but it is also hard to work and requires sharp tools.
I have speculated about a plywood using all stranded plies — abandoning the block cores. I have a friend witha 10-ton press who is, or is planning to makes some — the veneer surface layesr are available separately. I have also heard rumour that some manufacturer has beat him to the punch.
I think a similar very stiff plywood could be made from hemp plant fibres using the same method. I have had the fantasy of driving down the Trans Canada hiway in Saskatchewan with stands of 20 foot high hemp plants on either side
dave
A lossy BR is not aperiodic, but is pushing towards it. That is one of the goals of my alignment.
dave
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