uFonken speaker cabinet: Design question - diyAudio
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Old 29th September 2009, 10:50 AM   #1
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Question uFonken speaker cabinet: Design question

Hello, hopefully someone knows the answer to this question.

I am 1/2 way through building a pair of small desktop speakers using the uFonken design.

Part of the internal design of the cabinate uses a flat piece of wood, 2 corners chopped off with 3x 1 inch holes. This piece of wood appears to be positioned inside the cabinate such that it's nose end is placed directly behind the speaker magnet.

Question: Should this piece of wood actully touch the back of the speaker magnet or should there be a small gap???

Cheers,

Andy
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Old 29th September 2009, 12:14 PM   #2
gaust is offline gaust  United Kingdom
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Hello,
Although I'm no expert and I am sure Dave (Planet10) or someone else involved with the fonken designs will be along soon - I understood that the brace made contact with the back of the speaker magnet.
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Old 29th September 2009, 12:44 PM   #3
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It should fit tightly with the back of the speaker as it is there to brace it. I believe it is advisable to cut it to size last of all when you can test fit it with the speaker. You don't want it so tight that it deforms the speaker surround but not too loose either, I believe sometimes a bit of foam helps to pad the gap.
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Old 29th September 2009, 12:46 PM   #4
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Thanks so far chaps..

Won't adding foam dampen the effect of bracing?

Andy
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Old 29th September 2009, 03:06 PM   #5
chrisb is offline chrisb  Canada
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Quote:
Originally Posted by underwurlde View Post
Thanks so far chaps..

Won't adding foam dampen the effect of bracing?

Andy

Dave tends to incorporate similar bracing when ever possible, in practice it should contact the magnet as tightly as possible without stressing the flange when driver's mounting screws are tightened. If they're slightly loose, a small piece of closed cell foam tape or, blu-tak/duct seal etc on works well to couple the surfaces. Even better would be a piece of real veneer edge-banding tape.

I assemble and glue up the first 5 sides of the box before iterating a few cut and dry fits of the brace. Since I'm able to get the driver baffle routed on CNC (including rebate for flush mounting), and tend to cheat on smaller boxes with an air powered brad nail gun, it frequently takes longer to get the driver braces right that cut and assemble the box up to that point, particularly on the smaller designs.
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Old 29th September 2009, 03:59 PM   #6
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In some cases a piece of paper (or 2) is all that is needed to fill any gap.

The brace helps spread the driver's motional energy to more wall panels, spreading the energy & reducing the chance of exciting a resonance (instead of putting all the energy into the baffle)

dave
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Old 29th September 2009, 04:54 PM   #7
Bigun is offline Bigun  Canada
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I have used a felt pad to close the gap, the stuff that they sell for putting on the legs of furniture when you have a hardwood floor. It's good because it doesn't compress very easily and you can get different size/thicknesses.
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Old 30th September 2009, 08:06 AM   #8
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Thanks for the replies guys!

Am I right in thinking that this bracing of the back of the speaker akin to using a tuning fork.... Stike the tuning fork (silent), put base of tuning fork on a stiff surface and you then hear it's resonant tune: i.e. stiff surface becomes the soundboard for the tuning fork...??

Another question:

Should the outside of the speaker driver be sealed to the hole in the speaker cabinate (e.g. using a thin strip of sticky closed-cell foam)? I'm guessing 'yes' to best induce sound pressure differentials inside the speaker cabinate....

Andy
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Old 30th September 2009, 08:22 AM   #9
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Andy - #1, the bracing...other way round. Donīt underestimate the driverīs "recoil"...itīs tiny, but itīs there. (Sir Isaacīs actio=reactio). Coupling the driver to the cabinetīs mass helps a lot to slow it down...remember that cone excursion in the highs is incredibly tiny, so Doppler effect raises itīs ugly head.

#2 - yes, by all means. A driver without a gasket of sorts can produce noises you donīt want, plus the gasket helps decoupling the driver from the front panel.
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Old 30th September 2009, 08:24 AM   #10
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^ Ah, gotcha.
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