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Old 23rd December 2012, 04:52 AM   #11
chrisb is online now chrisb  Canada
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Quote:
Originally Posted by arnoldx3 View Post
thanks guys for the help i know i am probably asking stupid question but i just want to get it right so what you are saying is that the first chamber behind the driver i should extend everything by the thickness of the baffle?
I'll stand to be corrected, but yes, pretty much


Quote:

by the way how do you calculate the size of baffle i was thinking either round or elliptical
Well I've long been a fan of the "Golden Ratio / Phi" thing, which when rounded off the the first 3 decimal places is roughly 1.618, and I'm also drawn to the aesthetics of elliptical shape that is a bit harder to draw and cut by hand than with a CNC - trust me, I probably couldn't do the former to save my life, but it's 5 minutes of programming and machining for my friendly machine operator. (worth every penny of the bribes and "petty cash disbursements")


Anyway, to calculate the dimensions of the SB, just take the width of enclosure ( in the case of the Kongo, =130mm + 2*material thickness) , multiply x 1.618 for the width (or minor axis of ellipse), then repeat for the length (major axis of ellipse)

deliver the six pack of cold-ones to the machine operator and wait 5-10 minutes


so if this seems a rambling and grammatically disjointed post (where's Bill Bryson when you need him?) , at least I trust there's no major typos

good night mrs callabash
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Old 23rd December 2012, 01:31 PM   #12
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well thanks for the help everybody bare with me i still have a few more questions

what is meant by add irregular contours to chamber behind driver

and also i have seen people support the back of the driver is this a good idea?
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Old 23rd December 2012, 01:45 PM   #13
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also just wanted to ask how would i calculate the baffle if i went for a round one thanks
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Old 23rd December 2012, 02:09 PM   #14
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It doesn't require one.
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Old 23rd December 2012, 07:15 PM   #15
chrisb is online now chrisb  Canada
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Originally Posted by arnoldx3 View Post
well thanks for the help everybody bare with me i still have a few more questions

what is meant by add irregular contours to chamber behind driver
Dave could post some pictures or a link to projects demonstrating this - definitely a case were a picture is worth a thousand words

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and also i have seen people support the back of the driver is this a good idea?
I suspect Dave will argue the point, but the manifold cabinets are inherently quite well braced laterally, and the FE126 is simply not that substantial a driver that bracing it to the enclosure structure would likely make little discernible difference. I'd opine that over damping of the line path or poor joinery /assembly of the enclosures would have far more deleterious effects.

Of course this is coming from a guy than generally includes such a brace, even in boxes as small as the uFonken with FF85WK or equivalent sized Mark Audio or Fountek.


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Originally Posted by arnoldx3 View Post
also just wanted to ask how would i calculate the baffle if i went for a round one thanks
Circles are certainly easier to cut by hand than a pair of ellipses - just pick a number that "looks right" - in proportion to the enclosure itself. Model a few in cardboard.

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Originally Posted by Scottmoose View Post
It doesn't require one.
Brace, SB or both?

FWIW, it's interesting to note that the FH3 which sounds quite decent with a wide range of drivers does not include such bracing, nor generally a SB - except for a truncated version for use with removable baffles for driver swapping.
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Old 23rd December 2012, 09:57 PM   #16
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SB. It's not really needed, but people can if they feel so inclined, in which case, anything goes. Whether it'll mess things up is another matter entirely. FWIW, if I were doing one, I'd probably come over all Terry Cain & go with an oblate spheriod, 14in diameter. Since you know what the acoustic XO frequency is, you can probably figure why I suggest that particular size.

Last edited by Scottmoose; 23rd December 2012 at 10:02 PM.
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Old 21st February 2013, 02:45 PM   #17
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A local cabinet maker is constructing a Kongo cabinet for a FE126 driver. He's using 18mm Russian birch ply. After cutting all the pieces and laying them out using the plans the central channel is 1/2-3/4" wider than spec'ed in the drawings. How critical is this measurement to the sound?

Is it better to make measurements from the center and then just trim the excess material at the outer edges? I'm wondering if the construction method he's using (locking miter joints) for the sides and back are leading to this error.
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Old 21st February 2013, 02:57 PM   #18
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Originally Posted by CorradoBrit View Post
A local cabinet maker is constructing a Kongo cabinet for a FE126 driver. He's using 18mm Russian birch ply. After cutting all the pieces and laying them out using the plans the central channel is 1/2-3/4" wider than spec'ed in the drawings. How critical is this measurement to the sound?

Is it better to make measurements from the center and then just trim the excess material at the outer edges? I'm wondering if the construction method he's using (locking miter joints) for the sides and back are leading to this error.
if i was you i would build it the same as the drawing what are you doing with them painting or veneering because if you are veneering them i would do the internal parts too remember veneer is 0.6mm so roughly it will give you the correct size hope that helps

Last edited by arnoldx3; 21st February 2013 at 03:19 PM.
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Old 21st February 2013, 03:04 PM   #19
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Originally Posted by CorradoBrit View Post
A local cabinet maker is constructing a Kongo cabinet for a FE126 driver. He's using 18mm Russian birch ply. After cutting all the pieces and laying them out using the plans the central channel is 1/2-3/4" wider than spec'ed in the drawings. How critical is this measurement to the sound?

Is it better to make measurements from the center and then just trim the excess material at the outer edges? I'm wondering if the construction method he's using (locking miter joints) for the sides and back are leading to this error.
sorry forgot to add no the use of biscuits wont have anything to do with it

Last edited by arnoldx3; 21st February 2013 at 03:18 PM.
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Old 21st February 2013, 04:01 PM   #20
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Start from the centre & work outward.

No, the construction method is not leading to that. 3/4in = 19.1mm. It adds up with the multiple panels involved.
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