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Old 18th August 2006, 03:18 PM   #1
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Default Petite Onken Quardry

I've been reading the "Onken Enclosures" and was hoping I could pick your collective brains and ask for a little hand-holding specifically regarding the Petite Onken.

I've been wrestling with the notion of building a pair of these cabs for a pair of 414A-16 drivers I acquired some time ago. I have a pair of Oris 200 horns with Bert's (B-D Designs) Compact Reference bass cabs, and I'm thinking I'd like to try the Petite Onkens in their place. They would be bi-amped using a line level filter to cross them around 250Hz, but I'd expect that 250Hz and below they'd provide would be EXTREMELY tuneful!!!! Anyway, I'd love to hear opinions if I'm wasting my time with this application, or if it's a worthwhile undertaking.

Regarding the build, I have some questions (I've indicated in red the attached photo the area in question)...

1) Thereís a note in the plan about adding a "front-to-back brace as in the 15" enclosure." I'm assuming this is nothing more than a 1.5" x 3/4" brace that is centered below the driver. Is this correct?

2) Can the rectangular corner braces be replaced with a brace that has been ripped @ a 45 deg and sits flush in the corner?

3) Regarding stuffing, is there a consensus on what material, or combination of materials (deflex and polyfiber), will work best? And what area should be stuffed (I'm assuming the area behind the driver, leaving the vents unobstructed)?

I realize that my questions may be remedial, but Iím new to this design and was hoping to glean some valuable insight from the experts out there.

MANY thanks!!!!!

Mike
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Old 19th August 2006, 07:35 AM   #2
jamikl is offline jamikl  Australia
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Sorry you haven't had a reply Hadfield and I can't help you either. I have only read about them as have you. I am interested in using one in the way you intend to but there are some other types of enclosures I'm looking into as well.
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Old 19th August 2006, 03:20 PM   #3
kevinkr is offline kevinkr  United States
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I recently built a pair of full size Onkens which are discussed quite heavily in one of the recent Onken threads.

I would suggest proceeding as I did, nothing like the experience of doing to find out whether it works or not. (And it does.. )

The damping/cabinet tuning is an area I am currently investigating. You have probably read the Altec sourced guidelines for damping the cabinet. It is very trial and error.. I currently have lightly damped my boxes and plan to add just a little bit more at a time.

I am pretty happy with the overall performance of the system.

Mine in theory is tuned to ts max flat parameters using the spreadsheet calculator, however due to a miscommunication the ports ended up about an inch too long.. This pushed the low end port tuning down to 30Hz and seems to work just fine.. Just slightly extending the low end response. I will probably fix it though..

One of the really important things is to be able to measure things so that you can fine tune as required - this is probably going to be the key to getting the best possible performance out of the Onken.

You should probably measure the TS parameters of your woofers and design using the measured values, provided they seem reasonable compared to the manufacturer's published values.

Making a rigid box is critical given the large expanses of plywood in these designs. I don't think most classic systems using this approach are adequately braced.

More thoughts later as I have the time to post them.
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Old 19th August 2006, 05:36 PM   #4
kevinkr is offline kevinkr  United States
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IMO in terms of reducing vibration in the baffle board I don't think that brace is going to do a whole lot. The corner braces shown are a good idea, mine don't have them..

Top, bottom, rear panels should be braced. I screwed and glued additional pieces of plywood to them. It helped to deaden the panels a lot. I recommend additional bracing on the inside port dividers (probably a 1 x 2 top to bottom) near the ends. The outside cabinet walls are pretty stiff to the point where the ports end, and may benefit from some additional stiffening/damping towards the rear.

I cut several smaller pieces of plywood and glued and screwed them to the baffle board above and below the woofer.

I think with the petite onken you can probably build it pretty much as is with your drivers and it will work and sound good.

Key point is to make sure all joints are tight and properly sealed to prevent leaks and buzzing at the joints. Butt or rabbitted joints seem to work best. Cleats in corners where front/sides/back meet are de rigeur.

Make cleats from solid wood like 1 x 2 popular, NOT plywood! Vertical braces can also be this material.

Marine plywood has become prohibitively expensive, some cabinetry grades of plywood are almost entirely void free and that is what was used in mine. So far no obvious problems from that decision.

PVA type (expanding) construction super strong adhesives work well, and is much less expensive than gorilla glue which also works extremely well. Any glue that expands to fill the joint as it sets/cures is a good idea.

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Old 19th August 2006, 09:24 PM   #5
Pano is offline Pano  United States
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The Onken enclosures that I heard and liked in the past used wool felt for damping. Not a cheap solution, but a great one. I've used it in TQWT boxes with great results.

Failing the pure wool felt, the fabric (rag) based carpet padding works well. It's becoming hard to find, mostly it's the rubber type you see now.

Maybe wool blankets?

If I had the space for the petit Onken, I'd be right there with you. But I can't fit them in my living room, alas.

I believe the answer to question #1 is "Yes"
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Old 21st August 2006, 06:01 PM   #6
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Thanks for the replies.

Kevin, I've been following your progress extensively - I appreciated you posting the process here for us all to benefit from! I'm planning on using 13-ply Baltic birch and solid wood cleats as you suggested.

I'm sure the voicing will be a long trial and error process, but should be blast! I've heard a pair of dual 15" Onkens with 500Hz horns w/ BMS drivers. It was among the some of the most authoritive bass I've heard - lighting fast and incredibly articulate. Although Iím well aware Iím not going to duplicate the depth of performance from the dual 15 Onkens Ė Iím hoping to achieve the same voice with the Oris/Onken combo.

Iíll have to keep updating my projectís progress.
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Old 24th August 2006, 04:45 PM   #7
GM is offline GM  United States
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Default Re: Petite Onken Quardry

Greets!

Sorry to be so late to the 'party', but 'life' is increasingly keeping me from indulging in my hobbies. Anyway, it looks like between my responses elsewhere and other's here, your Qs have been answered.

FWIW, due to the 'nature of the beast' WRT the Petite Onken's vents boosting/comb filtering with the driver's output combined with the 414's step response, XOing below 800 Hz somewhat defeats the point of using the P.O.. Ditto for the 416/500 Hz version. Factor in that B-D has the experience/means/desire to voice his designs to a 'fare-thee-well' and at a glance I'd be reluctant to mate his horns to other than his bassbins unless he recommends viable alternatives.

That said, padding the horn down and fiddling with the XO point(s)/slope(s) should trim it out, so good luck with it and look forward to periodic updates/final review.

GM
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Old 14th November 2006, 06:41 AM   #8
hum4god is offline hum4god  United States
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Default onken or reference compact bass

hi
i am looking for a bass solution for ob ,and was wondering if you compared the ref. compact to the onken?

to call that beast petite is a joke .

would the measurements for the altec 414 be as posted on your thumbnail?
what driver do you use with your ref. compact?

malcolm
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Old 15th November 2006, 04:46 PM   #9
kevinkr is offline kevinkr  United States
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Sorry I can't answer your question directly. I have heard the Oris horns but not the compact reference unfortunately.

I did build and currently use a much larger version of the Onken than the "petit" which by Onken standards is quite small. LOL

I cross mine to the midrange horns (JBL) at 800Hz. The Onkens were everything I had hoped for, built them on an instinct.. FWIW you might find some more information on here:
Onken Enclosures
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