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Old 24th March 2011, 09:59 PM   #1
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Default noob building the fonkens

hi, I just bough some Fostex fe127en and was planning to build the fonkens.

I have plenty of birch plywood to build the speakers.

I have 15 mm birch ply, will it be fine for my baffle?
?6
And can I use the rest of my 15mm ply to make the ports? or the ply I have is too thick? so I need to get different wood for the ports and spacers?

the spacers: what kind of wood and at what thickness.



I have a couple of questions:

1-What type of glue you guys are using?

2- what sort of joints are you doing?

3-what stuffing to use to isolate inside of the fonkens/and how do you make it stick to the interior? By glue?

4-What sort of nail?

Yeah, stupid questions, but can't seem to see a definite answer
Thank you very much
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Old 25th March 2011, 01:11 AM   #2
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Jason,

I'll answer the questions relating to design choices. I've pinged the expert on building these to answer your other questions,

15 mm birch ply will be fine for the baffle even with a rebate which is optional with the FE127.

The Vent spacers need to be 9.5 mm (3/8") thick. Thi was originally choosen because ideally the vent spacers are a different material (MDF or solid wood) and 3/8" MDF scrap can usually be found for free,

The best stuffing is 1/2" wool or cotton felt. This is outlined in the plans (i think)

dave
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Old 25th March 2011, 01:32 AM   #3
doorman is offline doorman  Canada
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A simple butt joint, used with a good quality wood-glue, (Wellbond &c. &c) will achieve all the strength necessary, IMHO. I've built Fonkens using straight butt joints, and also with biscuits.
Dave's covered the rest. (Chris!?)
Good Luck!
Don
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Old 25th March 2011, 06:55 PM   #4
chrisb is online now chrisb  Canada
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After building a few pairs of this particular design topology, I've arrived at the following routine:

Use 3/8" MDF for the port spacers -actually this is one of several aspects of Dave's designs that are adapted as much as possible to dimensions of standard materials.

As Don noted, ordinary butt joints are more than adequate - there are 3 layers of material in the side panel assemblies, providing over 1 1/2" ( i.e. 39mm) of glue surface area for the top and bottom.

Inset the back panel and extend the port spacer blocks to contact same for additional glue surface area and bracing.

There is more than enough surface area on all glue joints to allow for complete assembly without any mechanical fasteners (nails/screws), except obviously for those mounting drivers and input terminals. I've built at least a few that way myself, such as those in bamboo plywood. It does however require a lot more time for glue to cure at each step, so depending on the exterior finishing, there's no reason not to use nails or screws. I use an air powered nailer and #18 finishing brads on all cabinets that will be post veneered or painted.

Just be careful to carefully measure extent of chamfer, and locate any such fasteners to not be in the tool path it's cut after assembly. I prefer this method as it's very quick and I have access to large enough tools for the task. Clamp a sacrificial scrap to trailing edge the enclosure to prevent chipping at tail end of cut.

Standard yellow PVA carpenters glue (Dural / Titebond, etc.) are more than adequate for assembly, and have much quicker tack / cure times than moisture cured polyurethanes such as Gorilla. PURs are great, but they have several disadvantages: - slow cure (overnight is best); swelling that can be used to advantage for filling small gaps, but requires very firm clamping during cure period to avoid part creep; and penetrating stains.

After playing with several materials for internal damping, we've found the 1/2" bonded Ultratouch insulation available from Bob at CSS to be ideal. It's a dream to work with in terms of cutting, and easily glued with white PVA (Weldbond or "melamine" glue).

Creative Sound - Product Details


Build the 3 layered side panels as sub assemblies, using bench clamped jigs and spacers to ensure uniformity of alignment, and glue the damping pads to the inside surface before attaching the tops and bottoms.

The vertical brace that connects 4 panels of this cabinet should not be considered "optional", but it certainly does complicate assembly and particularly the installation of damping material, as the working space gets pretty tight inside the box once it's in place.

Carefully measure and fit the brace with the driver mounted to front baffle, and the completed side panels & top/bottom clamped together. Including the cutting of holes and fitting of magnet contact surface and this other dry-fitting, this is easily the most complicated part of the assembly, but IMHO is key to the integrity and resonance characteristics of the design.
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Last edited by chrisb; 25th March 2011 at 06:58 PM.
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Old 25th March 2011, 08:18 PM   #5
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what are the dimensions of those spacers?? Is it refering to the cutting plan, name as inner side?
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Old 25th March 2011, 10:21 PM   #6
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thanks guys. I hope that you guys will be able to follow my work and prevents errors!

I just got the wood!

My wood experience limits me to ikea build, so any help will be great.
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Old 27th March 2011, 09:45 PM   #7
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is it normal that the back panel is too small wide-wise for the bottom wide panel? IT isnt like wide enough, so the back is not covering both side???

This is weird, or normal?
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Old 27th March 2011, 10:03 PM   #8
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There should be no gaps, everrthing should be tight... pictures?

dave
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Old 27th March 2011, 10:34 PM   #9
doorman is offline doorman  Canada
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Quote:
Originally Posted by murphythecat8 View Post
is it normal that the back panel is too small wide-wise for the bottom wide panel? IT isnt like wide enough, so the back is not covering both side???

This is weird, or normal?
Like Dave says. Have you followed the dimensions on the plans?
Don
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Old 27th March 2011, 11:26 PM   #10
chrisb is online now chrisb  Canada
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Quote:
Originally Posted by murphythecat8 View Post
is it normal that the back panel is too small wide-wise for the bottom wide panel? IT isnt like wide enough, so the back is not covering both side???

This is weird, or normal?
A few words from the Fonken-ator:


I've built dozens of pairs of this design over the past 5 yrs or so, and for various reasons ( experimenting with material thickness, driver models, and refining of port & internal bracing details ), several of them have finished at slightly different dimensions than the stock drawings that I assume you're working from.


I don't have a set of said drawings in front of me, but do have about 4 pairs of the Fostex & Mark Audio versions of this design in my room, as well as a tape measure.

Let's assume for convenience sake that you're using 15mm plywood for panels and 3/8" (9.5mm) MDF for the spacers between inner and outer side walls - which are the materials used for the pair of FE127E Fonkens I have in at my desk, and from which the following measurements are taken. (We'll ignore allowance for .5mm thick veneer on all sides)

The finished outside dimensions are 227mmW x 354mmH x 302mmD (9"x 13 15/16" x 11 7/8") . These are constructed using butt joints, with the top and bottoms overlaying all panels, and assembled with the front panel full width - the chamfers are cut after all except the back panel are assembled.



Top / bottom = 227mmW X 302mmD
Outside wall panels = 324mmH x 287mm W
Inner wall panels = 324mmH x 242mmW
Brace = 324mmH x 272mmW
Front panel = 324mmH 227mmW
Back panel= 324mmH x 197mmW

Width of Port spacers can adjusted for aesthetic variation of location of port slots, but using 9.5mm thick material the 3 slots per side need to be 75mmH. There will be 4 spacers per side - 2 between the slots, and one at each end. Cut these parts to 272mm long to provide additional glue surface area and bracing for the fully inset back panel.

If you're overlaying the back panel, the width of outside panels will need to be reduced to 272mm and the back panel increased to 227mm wide. This might be make assembly a little bit easier, but if all parts are precisely cut, insetting the back is not the most complicated part of the fabrication, and provides a more well braced joint.
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Last edited by chrisb; 27th March 2011 at 11:33 PM.
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