• Disclaimer: This Vendor's Forum is a paid-for commercial area. Unlike the rest of diyAudio, the Vendor has complete control of what may or may not be posted in this forum. If you wish to discuss technical matters outside the bounds of what is permitted by the Vendor, please use the non-commercial areas of diyAudio to do so.

mFonken103SolT Build

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
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.

Amazon.com: Pellon W-72 Twin Size Wool Batting, 72" by 96", White: Arts, Crafts & Sewing

Any recommendations? What works for you?
 

Attachments

  • IMG_3142.jpg
    IMG_3142.jpg
    331.9 KB · Views: 387
  • IMG_3124.jpg
    IMG_3124.jpg
    287.8 KB · Views: 378
  • IMG_3127.jpg
    IMG_3127.jpg
    252.8 KB · Views: 371
Last edited:
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.
 

Attachments

  • image2.jpeg
    image2.jpeg
    500.2 KB · Views: 109
  • image4.jpeg
    image4.jpeg
    817.5 KB · Views: 100
  • image1.jpeg
    image1.jpeg
    820.6 KB · Views: 95
  • image5.jpeg
    image5.jpeg
    569 KB · Views: 98
  • image6.jpeg
    image6.jpeg
    630.2 KB · Views: 305
  • image3.jpeg
    image3.jpeg
    591.3 KB · Views: 317
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.
 

Attachments

  • IMG_4044.jpg
    IMG_4044.jpg
    674.7 KB · Views: 103
  • IMG_4040.jpg
    IMG_4040.jpg
    650.7 KB · Views: 134
  • IMG_4036.jpg
    IMG_4036.jpg
    774.9 KB · Views: 110
  • IMG_4035.jpg
    IMG_4035.jpg
    632.2 KB · Views: 117
Last edited:
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.
 

Attachments

  • IMG_4214.jpg
    IMG_4214.jpg
    462.6 KB · Views: 115
  • IMG_4213.jpg
    IMG_4213.jpg
    794.4 KB · Views: 102
  • image1-1.jpeg
    image1-1.jpeg
    566.2 KB · Views: 116
  • image3-1.jpeg
    image3-1.jpeg
    442.4 KB · Views: 118
  • IMG_4195.jpg
    IMG_4195.jpg
    633.2 KB · Views: 101
  • IMG_4206.jpg
    IMG_4206.jpg
    429.3 KB · Views: 94
  • IMG_4191.jpg
    IMG_4191.jpg
    593.8 KB · Views: 106
  • image2-1.jpeg
    image2-1.jpeg
    493.1 KB · Views: 102
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.


I definitely like depth. Do you recommend any particular kind of veneer for that effect? I've never used it before, so I'd be starting from scratch here.
 
Lots of choices there, but I was always partial to sprayed post catalyzed nitrocellulose lacquers or conversion varnishes - such as ML Campbell Krystal. Of course that's a result of working in a commercial cabinet shop for 25yrs, and proper application requires a "few dollars" invested in spraying equipment. Oils such as Watco are easier to apply, but I didn't find yielded the same depth or life on highly figured grains such as Quilted or Bird's Eye Maple, Cherry, Walnut or Ribbon Grain Sapele.

I was never a fan of the one step gel stain/polyurethane finishes - they just never looked organic.
 
Interesting. Thanks for the insight re: spray lacquers. Never even heard of conversion varnishes before!

Today I cut the driver recess in the braces and glued the skeletons. Figured it would be best to start with the front baffle, brace, and bottom, since everything else gets attached to those.

Then I did a dry fit to make sure everything lines up. There's about three inches of minor damage on the top rear edge of one of the side wall sandwiches, the side that glues to the back panel. The interior meets the back panel fine, but I could use advice on a product and best practices to fill what will likely be a ~1mm gap at that spot.

Curiosity got the better of me and I grabbed a piece of scrap and tried staining it with coffee. I like the results. It seems there are two ways that people tend to make coffee stain: (1) brew a strong batch of coffee (or instant coffee) and simply apply that to sanded wood, or (2) mix about 1/4 cup of used coffee grounds with 1-2 cups of vinegar, toss in some steel wool, and let it all brew overnight before applying. The first method tends to result in a light thin stain, while the latter flows on darker and more concentrated. In my mind's eye I saw this as light and thin, so what you see in the pics is the result of five coats of normal strength Trader Joe's French Roast.

The left side is treated with pre-stain (I know, don't mix oil and water), while the other was untreated (the sides are reversed in the pic with the driver). There's little perceptible difference except that the treated side shows the stress lines more and exhibits slightly more contrast over the coverage area. I like the even tone of the untreated side. It doesn't have depth like an oil finish, but I like the modern look and it goes well with the copper bezel and creamy cone of the FE103Sol.

The test piece currently has two coats of polyurethane that's curing in the garage. That turned it a slightly darker amber, and I don't think I'll like it. My instinct is to try the coffee stain with an eggshell or even matte clear coat that won't affect the color. Any products to recommend for that?
 

Attachments

  • IMG_4268.jpg
    IMG_4268.jpg
    428.5 KB · Views: 88
  • IMG_4271.jpg
    IMG_4271.jpg
    279.5 KB · Views: 84
  • IMG_4270.jpg
    IMG_4270.jpg
    355.8 KB · Views: 103
  • IMG_4276.jpg
    IMG_4276.jpg
    247.6 KB · Views: 182
  • IMG_4279.jpg
    IMG_4279.jpg
    210.5 KB · Views: 200
  • IMG_4237.jpg
    IMG_4237.jpg
    412.1 KB · Views: 188
  • IMG_4255.jpg
    IMG_4255.jpg
    355 KB · Views: 184
  • IMG_4250.jpg
    IMG_4250.jpg
    336.6 KB · Views: 185
Last edited:
There's about three inches of minor damage on the top rear edge of one of the side wall sandwiches, the side that glues to the back panel. The interior meets the back panel fine, but I could use advice on a product and best practices to fill what will likely be a ~1mm gap at that spot.

I can't quite visualize where this is, maybe snap a pic of it.

Depending on where it is, and how wide/long, You might try Bondo or similar. It's very hard and adheres well to wood.
 
Mohawk makes a pretty nice line of finishing products, including aerosol sealers, toners and pre-cat NC lacquers . I’ve used the M102-0412 several times on small projects - one or two spray bombs might be all ya need.
Mohawk | Pre Catalyzed Clears M102-0410

Yes, bondo is a perfectly fine approach to repair defects, but doesn’t lend itself to natural or even stained finish. I used more than a few gallons of in my time, but only when covered with veneer or plastic laminate. Could certainly be painted over as well, but a really decent paint job can take much longer and cost more than veneer - OK, let’s be honest, I just got lazy / comfortable with the latter.

As for conversion varnishes- the ones that I used were industrial grade, high solids post catalyzed (two part) product, not generally available to the “retail” public. They’re not inexpensive, require careful mixing, and have relatively short pot-life - but when properly applied, make for a very durable finish.
 
Last edited:
OK, thanks for the info and the link, Chris. That Mohawk product looks like a cost-effective option.

I just checked the test piece from yesterday. It looks better than I thought. Again, this is five coats of regular strength French roast coffee applied with a foam brush, with two coats of Minwax satin polyurethane. Doesn't have the depth or pearlescence of oil, wax, etc, but I like the color. I'd like to look for an eggshell or matte clear coat to try with this.

If I go with the coffee stain, I'd still probably need to veneer it with birch, as the vision in my imagination does not incorporate all the end grain at the chamfer. I'd have to cut hardwood faces for the vent spacers and sand flush with the veneer, if I want to go for that look. Seems like a lot of fuss to veneer something with the same construction material, just to make it look a little different.
 

Attachments

  • IMG_4292.jpg
    IMG_4292.jpg
    657.1 KB · Views: 90
  • IMG_4295.jpg
    IMG_4295.jpg
    821.7 KB · Views: 74
  • IMG_4298.jpg
    IMG_4298.jpg
    413 KB · Views: 72
  • IMG_4303.jpg
    IMG_4303.jpg
    829.7 KB · Views: 91
A quartet of FE 127E mFonken
Cherry with dark port stain
Book matched flat sliced walnut -natural
same walnut with dark brown stain
Cherry - natural

In all cases the clear top coat would be at least 3 coats of satin sheen (40 dg) NC lacquer, and the second from left and far right are as close to natural color of the Fostex cones as you’ll get with over 10yrs difference.

quartet-mFonken.jpg
 

Attachments

  • 199DA3DC-B849-47ED-A61E-03DC955E7D67.jpeg
    199DA3DC-B849-47ED-A61E-03DC955E7D67.jpeg
    17.3 KB · Views: 75
Last edited:
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.