uFonken speaker cabinet: Design question

[underwurlde]

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

 

[gaust]

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.

 

[ZirconiumZephyr]

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.

 

[underwurlde]

Thanks so far chaps..

Won't adding foam dampen the effect of bracing?

Andy

 

[chrisb]

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.

 

[planet10]

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

 

[Bigun]

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.

 

[underwurlde]

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

 

[Pit Hinder]

Andy - #1, the bracing...other way round. Don´t underestimate the driver´s "recoil"...it´s tiny, but it´s there. (Sir Isaac´s actio=reactio). Coupling the driver to the cabinet´s mass helps a lot to slow it down...remember that cone excursion in the highs is incredibly tiny, so Doppler effect raises it´s ugly head.

#2 - yes, by all means. A driver without a gasket of sorts can produce noises you don´t want, plus the gasket helps decoupling the driver from the front panel.

 

[underwurlde]

^ Ah, gotcha.

 

[Pit Hinder]

I wasn´t sure you´d get it - explaining physics in my mother language is bad enough, but ve donn´t shpeek ze Englishe over here

 

[underwurlde]

heh! If it wasn't for your German flag giving you away, judging my the use of English in your response, I'd think your first language was English! It's a damn sight better than my German!

(BTW, spent some time in Stuttgart & Düsseldorf - EXCELLENT places! ).

Danke schön,

Andy

 

[Pit Hinder]

Your use of German might be better than most Germans´...especially in Düsseldorf. But getting back to your project: I could use it to build some saleable speakers to finance my Sachikos - will we get some hands-on news about how things go?

 

[underwurlde]

^ sure, why not. I'll post some pics up.

 

[Pit Hinder]

Thanks in advance, and greetings to - let me guess...Wales? Anyway, posting where you got your wood might be a big help for other UK dwellers - sourcing material can be a pain in the neck, wherever one lives. TIA, again.

 

[planet10]

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)?

A good seal is very improtant. The foam gasket the FF85 comes with works well -- you just have to make sure it stays in place when you place the driver.

dave

 

[underwurlde]

Crossover network

Oh, another question sprang to mind over the weekend....

Does this speaker design require a filter network?

I see on the Solo 103 design that a 'crossover' network is used for the full range FE103E speaker (that consists of paralleled 0.82mH, 10Ohm & 4.7uF).

Is such a filter needed for this design too?

Andy

 

[planet10]

You are welcome to play... i've never used a filter on them.

dave

 

[underwurlde]

Hah! No intention of playing: If no filter needed, then none it is. I like to keep things SIMPLE.

Andy

 

[underwurlde]

mouting speakers:

I'm gunna have a hard time explaining my question, but let's try all the same:

The speakers are designed to be screwed into a hole. If this is done, the actual metalwork of the speaker will protude 2 or 3mm over the surface of the wood to which it is screwed.

When I look at the designs for the uFonken speaker, am I correct in assuming that the speaker is RECESSED into the wood such that the surface (for want of a better word) of the speaker is now FLUSH to the surface of the wooden cabinate?

If so, how is this recess cut into the wood? The hole (for the magnet) is circular BUT the outer metal frame of the speaker is not because it's outer shape is 4 conjoined arcs.

Does that make ANY sense??

Andy