Hi this is my first speaker build and i have decided on the kongo but i have a few questions i am thinking of making a sandwich of ply mdf and chipboard for the contraction and possibly having a thin layer of lead in there i think its 1.3mm thick would it be worth doing?
secondly would it be worth making the sides top and botton 25mm instead of 19mm
and thirdly here is a picture i would like to sort of copy
my question is how can i add a baffle like that does it matter if the driver is another 20mm out?
anyway i would appreciate any help
secondly would it be worth making the sides top and botton 25mm instead of 19mm
and thirdly here is a picture i would like to sort of copy
my question is how can i add a baffle like that does it matter if the driver is another 20mm out?
anyway i would appreciate any help
if you don't mind me asking how would be the best way to do that would i make the baffle an extra 19mm thick so it would be 46mm or wold i have it just 19mm but the driver stands out
am i right in saying that all people do is add say 19 to the front attach the speaker to that then add side peices to ake it look like it say 60mm thick if so will any internals have to be changed thanks
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AFAIC, for drivers of this size class and physical mass the thickness of extra layer of baffle does not provide any sonic advantages, and indeed adds extra complication to the fabrication to avoid creating a very narrow "tunnel" immediately adjacent to the rear side of cone.
I've built several different designs with supra-baffles, and would not consider them and afterthought, but should be accommodated in the build of main enclosure by cutting a much larger hole in the front panel than required by the driver. Actually what I usually do is to cut the front panel as 2 shorter pieces and overlap with the suprabaffle. You can either screw them on and seal with closed cell weatherstrip tape, or something like 3M high strength double edge tape.
Whether or not you decide for a SB- don't forget to chamfer the rear side of driver cut-out, which is much easier to do with a 45dg bevel bit before assembly.
And to echo Dave's earlier comment, I don't think there's anything to be gained from material thicker than 18-19mm, or the heroic efforts to laminate materials and include panel damping for these enclosures. They're well braced by design, and even with the low frequency gain provided by the BLH/manifold, the FE126E is not likely to cause any objectionable cabinet resonances. If concerned about that, I'd be inclined in add a narrow brace between the side panels in the mouths, oriented to approximately bisect the angle between deflectors and horizontal panel that forms last leg of the manifold.
thanks for all of your help i guess i am only doing it for looks but do you think it would be bad idea to add a superbaffle?
if i add a superbaffle to the outside of the speaker and cut the hole out for the driver and then chamfer how big does the hole in the front of the speaker need to be would it work being 20mm bigger i hope this makes sense
if i add a superbaffle to the outside of the speaker and cut the hole out for the driver and then chamfer how big does the hole in the front of the speaker need to be would it work being 20mm bigger i hope this makes sense
Looking at the Kongo plans, the internal width is 130mm, and the driver through hole required for FE126 is 102. I build this type of enclosure with the sides overlaying the internal panels, which in this case would leave 15mm margin either side of the front side of driver through hole.
Some quick doodling arrives at the following figures - surface mounting the FE126 on 19mm suprabaffle, and using a 10mm deep chamfer on back side, the driver cut-out would flare out to approx 122mm. Even without continuing the flare, that would make the front panel a bit delicate to move around, which is why I'd suggest cutting it in 2 pieces, to be overlapped by the supra baffle panel, and sealed with gasket / tape
As to shapes & dimensions for the SB, I happen to be partial to elliptical, but have the advantage of access to a CNC machine, which makes those very simple. Try to avoid square or rectangles that are even multiples of height to width. Ratios such as 1.414, or 1.618 are my favorites for both the width of SB relative to enclosure width, and the H/W of the SB. Once again using 19mm material, that would make the SB either 238x336 ( @ 1.414 * 168mm) , or 272x440 @ * 1.618.
Of course those numbers would change with different material thickness. I happen to use 15mm "baltic" birch type multiple for builds with smaller drivers such as these. While I also like to rebate all drivers for flush mounting, the Fostex FE series drivers have thin enough metal frames that they can be surface mounted with no discernible ill effects (at least to my ears), and don't really need any thicker material than that for baffles. The same cannot be said of Mark Audio drivers, or for that matter Fostex such as FX120 or F120A
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As well as it is done well, a supraBaffle can bring aesthetic and sonic benefits.
One will need to adjust the panel that controls air cavity volume, but if one wants to go to town a sculptured back air cavity panel is a good idea.
dave
I think Dave means to add pieces of material to the back panel of the driver chamber equal in volume to the amount of material displaced by the SB - which isn't really a whole helluva lot, and as he notes would provide an opportunity to add irregular contours to the rear surface of the chamber. Several builders of similar designs have gone to town on that.
Dave - get that keyboard fixes, or start watchinf what yoi typw
I think Dave means to add pieces of material to the back panel of the driver chamber equal in volume to the amount of material displaced by the SB - which isn't really a whole helluva lot, and as he notes would provide an opportunity to add irregular contours to the rear surface of the chamber. Several builders of similar designs have gone to town on that.
Dave - get that keyboard fixes, or start watchinf what yoi typw
geeze Dave, it kinda deflates the message when you post-edit your typos
thanks guys for the help i know i am probably asking stupid question but i jyst 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?
by the way how do you calculate the size of baffle i was thinking either round or elliptical
by the way how do you calculate the size of baffle i was thinking either round or elliptical
I'll stand to be corrected, but yes, pretty much
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
Dave could post some pictures or a link to projects demonstrating this - definitely a case were a picture is worth a thousand words
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.
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.
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.
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.
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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.
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
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sorry forgot to add no the use of biscuits wont have anything to do with it
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