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jdrouin 18th December 2018 03:52 AM

mFonken103SolT Build
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I've begun to build a pair of mFonken103SolT -- the trapezoidal fonken enclosure for FF105WK but for the FE103Sol, using the alternate vent spacing included at the end of the FF105WK fonken planset. I might ask for some pointers on construction, but at the very least I figured this thread might be useful for other relatively novice builders who want to try one of the trapezoidal designs.

There is enough material left over to make a pair of Classic Golden Ratio enclosures, which I'll be doing at the same time (will post in the pic thread when done). These will be my third and fourth speaker builds, following a pair of Woden Shrike and Falcon, which are really good.

Material is 15mm Baltic birch, along with three 9mm boards of red oak and Brazilian cherry for the vent spacers. The different colors will make for an interesting pattern on the baffle, though I might end up veneering these. We'll see.

All panels were cut to rectangles today, with the width slightly wider to allow for margin of error when making the bevel cuts (will figure out how to do it on scrap first). The cut list in the plans made this really easy!

The plans call for 1/2" UltraTouch denim insulation, which doesn't seem to be available anymore, so I could use suggestions on good alternatives.

There's the 1/2" acoustic damping foam at Parts-Express:

Sonic Barrier 1/2" Acoustic Sound Damping Foam with PSA 18" x 24"

As well is this wool batting with a 1/4" loft. Perhaps it would work by doubling it up. Pellon W-72 Twin Size Wool Batting, 72" by 96", White: Arts, Crafts & Sewing

Any recommendations? What works for you?

pcgab 18th December 2018 05:48 AM Buying Choices: 16 in. x 48 in. Denim Insulation Multi-Purpose Roll (6-Pack)

I order it from amazon. Nice stuff, seems to work very well.

jdrouin 23rd March 2019 10:39 PM

6 Attachment(s)
Thanks for that, pcgab, and sorry for the late response. I recently completed a pair of CGRs and ended up using wool batting with a 1/4" loft, and then doubling it up. It works very well.

It's strange to be taking up a loudspeaker project right after finishing the CGRs (which are superb, btw), but they've made me want to hear the trapezoidal mFonkens.

I started with the exterior side panels and vent spacers, cutting them to lengths that will turn out correct when I cut the big 45* chamfer later.

The spacers are 9mm (3/8" oak and Brazilian cherry from Woodcraft. Some of the oak is a hair thicker than the other material, so I might need to sand or plane it, or else insert paper shims where it seems there might be an unclosable gap with the interior wall.

Also, I had to make some spacers from two cuts of hardwood in order not to have to buy more material

Next I'll make the front baffle, rear baffle, and braces. I cut the brace panels 1/2" larger for inserting into dados for maximum strength and rigidity.

pcgab 25th March 2019 10:37 PM

Funny, I built a pair of CGRs for a friend recently. He's using alpair 10p, iirc.

They do sound great, he's enjoying them quite a bit.

Excited to see you build the trapezoidal cabinets, should be fun!

jdrouin 26th March 2019 02:11 AM

Yes, you and I had a lengthy conversation about sanding and oiling in that thread. ;-)

pcgab 26th March 2019 12:59 PM


Originally Posted by jdrouin (
Yes, you and I had a lengthy conversation about sanding and oiling in that thread. ;-)

Ha, yeah we did!

jdrouin 29th March 2019 03:28 AM

4 Attachment(s)
Sandwich press.

In post #3 there's a picture of the beveled edge of the glued outer side panel and spacers. To do that, I glued the spacers on and then did the bevel cut by using the miter head (not the rip fence), incrementally moving the workpiece closer to the blade with each pass until the entire edge was beveled. The goal was to stop as soon as the bevel met the top edge, so as not to shorten the width of the workpiece too much. All dimensions measure *exactly* what's in the plans, leaving no wiggle room.

After gluing together the outer side walls and spacers, I prepped the interior wall panels. For all panels requiring bevel edges, I cut their "blank" panels about 1/2" wide in order to leave room for mistakes during beveling. The interior side walls only have one beveled edge, so I cut that edge first on all four panels as in post #3, put the saw blade back to 0*, set the rip fence for the width of the longest edge, and then made those cuts. Very easy.

During dry fit, some of the cherry vent spacers did not meet flush with the interior wall because one of the oak boards was a tad thicker than the other ones. On spacers that came from that board, I used a hand plane and then orbital sander to reduce the thickness so that al the vent spacers met flush with that interior wall. It wasn't hard to do (the sander was faster and generally better), but it took a little time.

Now I'm gluing the interior walls to make all the 3-layer sandwiches.

pcgab 29th March 2019 01:10 PM

Looking good!

jdrouin 9th April 2019 04:04 AM

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Thanks! Today I tried a dry fit of the sandwiched side walls, front & back, etc., and then cut all the circles. I also started cutting the dadoes that the brace will fit into.

In the side wall pieces, the vent spacers hang over the front baffle a little, to help with alignment when gluing. I didn't cut the front bevel on the spacers or exterior wall, leaving that for the big chamfer to be done on the table saw after assembly is complete.

Starting to think a little bit about finish. Cherry veneer, sun darkened and then rubbed with natural Danish oil and a satin polyurethane clear coat has been stuck in my mind. However, I really like the pattern of the different colored vent spacers, which remind me of coffee. So maybe I'll lightly stain them with coffee (perhaps Trader Joe's French Roast?) and a clear coat.

Dunno; normally I don't mind displaying plywood end grain, but there will be A LOT with these cabinets.

pcgab 9th April 2019 01:37 PM

Cheery veneer could look really nice. I'm a big fan of danish oil, well applied and rubbed between coats it can look fantastic. I like to finish with a little Howards orange oil and beeswax finish, satin with a bit of depth.

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