Onken, anyone?

kelticwizard said:

By the way, Roscoe Primrose, who made such a beautiful set of Onkens, is now a member here. Email him if you wish, or ask the mods to pass a message if his Email is not enabled.

I didn't build them, I bought them. Nothing I build ever looks that good :bawling:

However, they're just your basic Onken cabs, no mods to the original design. Sound is quite good with 515Bs or 604s. I think the sound was actually a bit better on the homebuilt Onken style cabs I built.

Peace
 
analyzing onken as a reflex box

The family of Onken cabinets depicted at the http://www.studiomaudio.com/onken.html site are described as sharing these characteristics:

Box volume of 13,300 cubic inches
Total duct area of 134 square inches
Duct length of 8 inches

Analyzing this as a reflex enclosure, I come up with a box tuning frequency of about 50 Hz.

Does this sound right?

It seems to me the elegance of the Onken configuration lies in the killing of two birds with one stone: The large vertical slots combine large-area ports with excellent mechanical stiffening of the enclosure walls.
 
It is the theory behind these calc's I am looking for. From what I have been able to find sofar, the Onken is supposed to give very fast and clean bass transients,- with an F3 a lot lower than a closed box.
I read somewhere that the Onken aproach is to be treated like a reflex enclosure with a system Q of appx. 0.5. My current system is a reflex enclosure tuned in accordance with an SC4 alignment, about .65, and this gives a conciderably tighter bass than the usual QB3 "boomers".
The calculator uses variables like "Onken factor" and "Koizumi factor". The numbers for "Onken factor" looks like 10*Q, but otherwise I don't have the foggiest idea..???
 
Re: analyzing onken as a reflex box

Alidore said:
It seems to me the elegance of the Onken configuration lies in the killing of two birds with one stone: The large vertical slots combine large-area ports with excellent mechanical stiffening of the enclosure walls.

And it makes them look so cool.

dave
 
Just came back from a visit to Adire Audio. They have a bunch of stuff sitting around including a Onken style Shiva sonosub. It has a smaller tube inside the larger one. The spacers between the tubes also serve as the legs for this downfiring design. I didn't get the tube lengths. I could ask and let you know.
 

fdegrove

diyAudio Senior Member
2002-08-21 1:20 am
Belgium
Hi,

If these are still the same bass-reflex enclosures as 15 years ago
then I should have all possible details at the office.

Most of the time the woofer used was either an old Altec or a Focal Audiom Alnico.

I had the chance to listen to them on several occasions and one thing really stood out; you never had the impression of listening to a woofer that's boxed in, if you know what I mean.

Very fast and clean bass although not the deepest I ever heard, whatever came out was impressively fast in starting and stopping with the music. Absolutely no overhang whatsoever.

In case I can help with a scan of an article I'd happy to oblige.
Be warned though, everything I have regarding the Onkens is written in French...
If it's just figures you need that wouldn't be a big deal anyway.

Cheers,;)
 
Onken Enclosure

Agree with previous posters about about superior side wall construction of Onken. Back in "the day" everyone was using 5/8" or 3/4" plywood without much bracing, so it must have been an improvement.

Assume most of you have seen copies of the original designs in "Le Audiophile", a French pub that detailed the Japanese concept after the author's trip to the Orient.
The original design was for the Altec 416 I believe and clocked in around 12 ft^3, if IRC. Another smaller design was offered for the 414 woofer at half that size.

Pure speculation on my part, but if these boxes are considered "fast" (much controvery) it is due to the high tuning, stiff enclosure, and very low vent noise due to the large vent size, all of which can be accomplished with a normal reflex box so long as resonance and distortion are kept low.

Here is one I built from double thickness of 19 mm baltic birch plywood and 416Z woofers. Altec MR902 drivers/511 Horns on top. Tuning around 40 Hz in a ~7 ft^3 box.

Tim
 

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kelticwizard

diyAudio Moderator Emeritus
2001-09-18 2:33 am
Connecticut, The Nutmeg State
Ding's link doesn't work for some reason.

If you want the route to the Onken enclosure calculaton program, you go:

http://melhuish.org/
Single Driver Website
Other Stuff
Software Tools For Speaker And Audio
Onken Box Calculator (Cyr-Marc Debien)

You'll have to look around each successive page to find those choices, but that is how you get there.
 
Hi Frank,
Do you still have the articles on the Onken enclosure designs, french language is fine. I would like design a speaker system around my D130's and 075 probably based on the Onken enclosure design. May add as yet undecided JBL midrange horn to the system.

Actually I am open to suggestions about this and any other similar type of enclosure for high efficiency bass reproduction.

Also it does not have to be small, they won't be going anywhere. Something up to 360L - 400L should be acceptable for the space.

Umm, I should also admit to not knowing a whole heck of a lot about speaker design, and as this is more or less a one shot deal I want to get as right as possible.
 
Thanks,
I downloaded both articles and while it will take me a while to read them there does seem to be a lot of useful information to get me started.

I know there used to be an onken spreadsheet in excel based on thiele small parameters that I am trying to track down.. Now just to find someone who has measured them on the D130...

Just found the provided link in this thread which did not seem to work earlier is now working and downloaded the spreadsheet.

I might deviate slightly from the original onken tuning where the spread sheet indicates that a slightly different tuning would be better.

Kevin

edit: add comment
 
D130

kevinkr,

The JBL D130 is a good sounding midbass driver, particularly for a midbass horn, but it is not well suited for low bass. It has very little excursion (.76 mm), Fs of 40 Hz. The tuning frequency for a flat alignment is much higher than one would desire for low bass duties. If you intended to use it with a sub, it would be fine in that application, but as the only bass driver, you would be better off looking at other woofers such as the Altec 416 used in the original onken.


Tim
 
Interesting, I was wondering about the suitability of this driver for that application. I have the drivers and the original C37 cabinets so I am pretty much stuck with the D130, (I won't be buying something else) I will have to look at some other cabinet options. Bass extension in the stock reflex cabinet is quite good and I don't need or use a subwoofer. It's just that this "low boy" cabinet is both very unattractive to look at, and the construction quality is not commensurate with good current practice. (It's not very dead)

I do wonder though whether the current D130 is all that similar to the vintage ones I am using. JBL did not use TS parameters obviously at the time these drivers were made, as the research had not yet been performed. The contemporaneous claims made for this driver are quite different from the currently published specs from JBL Pro. Mine are at least 40 yrs old, based on where I got them from.
One of the claims JBL made was of a considerably lower FS although I am having a problem finding this information.

The spread sheet designer indicated that I should be able to get down to the low 40 Hz range, box volume around 288 liters, with the source impedance of the amplifier I am using. SPL level with the current C37 cabinets achieves nearly 110dBspl with the 10W amplifier I typically use.

I have noted that the Onken with this driver has a strong sensitivity to source impedance. (Amplifier and x-over resistances.)