Frugel-Horn Mk3 Builds & Build Questions

frugal-phile™
Joined 2001
Paid Member
I can supply DWG/DXF files from the pdf. I cannot tweak them for a particular CNC — kerf zllowed on the drawings is 5mm, a CNC bit is usually wider than that. 15mm is fine, and there are drawings for that, especially with the Pluvias, which can get away without any rebate on the front, and if you do a rebate it is not that large. None of the drawings have the exact cutout for the Pluvia so that would need adjustment.

Here is the standard DWG?DXF/CNC boilerplate:

<boilerplate>
DXF or DWG files are easily exported from the CAD software, native format is Vectorworks. I need to know the page of the PDF you need, and the version of DXF/DWG that can be handled. (i do have a collection of already exported)

It should be noted that a CNC is only really useful for the sides and the driver rebate. Unless the CNC is 5-axis, you will still need to pass all the internal pieces thru a table saw -- it is quicker & easier to just do them all on a table saw. You could rough cut the other pieces but they still need to go thru a table saw to angle the ends.

The drawings all assume a 5 mm kerf, so the CNC operator would need to adjust for the larger kerf needed for CNC work. You/they will need to adjust for actual wood thickness as well.
</boilerplate>

dave
 
Since the Pluvias mounting flange is much thinner than the A7s and most of the CH series, they don't require rebating, and 15mm would be sufficient for the front baffle - but then will definitely need the rear of the driver cut-out to be chamfered.

Also note, as Dave says, that there is only one of the lateral panels - the vertical internal divider - that doesn't require a 5 dg angle on at least one end, and on the Planet10 kits, a scarfe joint is used to add some additional glue surface area at the joint between it and the back panel. I also set the fillet radius on the CNC route for those internal panels to 3/8" and radius the ends at that joint to match. This makes for a very secure joint - the radius is probably not critical acoustically.

see post#2 in the mock assembly thread
Frugel-Horn Mk3 Flat-Pak Mock Assembly Instructions
 
Thanks for the hint Dave and Chris. I will discuss them with the guys at the CNC place.

In the meantime, I just received the Pluvias, yeay.

Noob question - I have an old ipod lying around and wondering if I can just use it to 'break-in' the Pluvias, how do I do it ya? Or shall I just use the audio output from my iMac to do the low volume long hours break-in?
 
Hi, I have the flat pak 15mm MK3's with the fe126en cutout. I've been considering a switch to the Alpair 7.3 sometime soon, and wanted to confirm based on older posts here:

I should glue 9mm (3/8 US) Baltic Birch to the entire length of the front and then rebate for the 7.3 with a router to make the bezel fush? Should I use wood filler to fill the old FE126en rebate to eliminate the gap left behind or is it too small to matter?

I also need to add additional poly-fill for the Alpair too, correct?

Thanks.
Kevin
 
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frugal-phile™
Joined 2001
Paid Member
I have the flat pak 15mm MK3's with the fe126en cutout. I've been considering a switch to the Alpair 7.3 sometime soon, and wanted to confirm based on older posts here:

I should glue 9mm (3/8 US) Baltic Birch to the entire length of the front and then rebate for the 7.3 with a router to make the bezel fush? Should I use wood filler to fill the old FE126en rebate to eliminate the gap left behind or is it too small to matter?

I also need to add additional poly-fill for the Alpair too, correct?

Attached is a comparison of the A7.3 vrs FE126En rebate. The dark blue is the A7.3 with bezel cover, the lighter blue without.

If you have a P10-hifi flat-pak then the baffle is 18mm, and althou tricky, you can just rebate for the A7. If you use the bezel cover (we don’t use it) then no one will know it started out as an FE126 rebate. If you don’t then some fill will be needed to make it pretty.

Alternatively you can ream out a big hole on the baffle and fit a supraBaffle (lots of options wrt shape) and rebate it for A7.3.

Yes, the A7.3 will need a bit more damping. All below the driver. We supply 40g for each speaker, but typically only half of that is needed — room, room placement, taste all play a role. We supply FE126 flat-paks with 40g as optional fill for under the driver (usually not used), so half of that in each speaker will get you into the ballpark.

dave
 

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Attached is a comparison of the A7.3 vrs FE126En rebate. The dark blue is the A7.3 with bezel cover, the lighter blue without.

If you have a P10-hifi flat-pak then the baffle is 18mm, and althou tricky, you can just rebate for the A7. If you use the bezel cover (we don’t use it) then no one will know it started out as an FE126 rebate. If you don’t then some fill will be needed to make it pretty.

Alternatively you can ream out a big hole on the baffle and fit a supraBaffle (lots of options wrt shape) and rebate it for A7.3.

Yes, the A7.3 will need a bit more damping. All below the driver. We supply 40g for each speaker, but typically only half of that is needed — room, room placement, taste all play a role. We supply FE126 flat-paks with 40g as optional fill for under the driver (usually not used), so half of that in each speaker will get you into the ballpark.

dave

Yes, I have the P10 flat pak. Ok, this gives me some options.
Thanks.
 
As Dave notes, we don’t normally use the extra bezel rings on either our personal build or any of the kits, but his would be a case where they’d probably be justified. Although that means a deeper rebate for flush mounting, with less core of the 18mm baffle left for the screws, I think you’d still be fine. The BB ply is very strong, and with right sized pilot holes and pre-tapping with the MA supplied screws, a more than secure mounting will be achieved. The drivers aren’t heavy, and this ain’t the cylinder head of a Cummins Diesel engine.
 
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As Dave notes, we don’t normally use the extra bezel rings on either our personal build or any of the kits, but his would be a case where they’d probably be justified. Although that means a deeper rebate for flush mounting, with less core of the 18mm baffle left for the screws, I think you’d still be fine. The BB ply is very strong, and with right sized pilot holes and pre-tapping with the MA supplied screws, a more than secure mounting will be achieved. The drivers aren’t heavy, and this ain’t the cylinder head of a Cummins Diesel engine.

I think I'm leaning towards a removable supra baffle so that I can try a variety of drivers. I'm building the Amp Camp ACA amp right now and I think I've caught the bug and it won't be my last amp.

I have access to quite a bit of woodworking equipment right now and although my skills are still beginner figured I should take advantage while I can. My listening area right now is small (10x11) so sticking with a modifiable FH3 seems to be the best course rather than building another speaker.
 
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We built a few with removable baffles, and I embedded M4 threaded inserts (not T-Nuts) in the enclosure, and counter sunk holes in the removable panels. We also extended them wider than the full 170mm, and added little return pieces to wrap around the sides.

Attached is PDF of my CAD drawing for the CNC patterns for these, as well as the first photo I could find in my files of an FH3 fitted with the SB - seen with MAOP7, and a prototype build of FHXL . If you're interested, there are a couple of kits of the supra-baffle parts for both FE126 and A7.3 available.
 

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We built a few with removable baffles, and I embedded M4 threaded inserts (not T-Nuts) in the enclosure, and counter sunk holes in the removable panels. We also extended them wider than the full 170mm, and added little return pieces to wrap around the sides.

Attached is PDF of my CAD drawing for the CNC patterns for these, as well as the first photo I could find in my files of an FH3 fitted with the SB - seen with MAOP7, and a prototype build of FHXL . If you're interested, there are a couple of kits of the supra-baffle parts for both FE126 and A7.3 available.

Thanks for the specs. I'm going to try doing them myself since I'm slightly more DIY oriented than I was back when I bought the flat pak 4 years ago. However, if I fail miserably it's nice to know you still have some for sale.

Do the wider baffles with wrap-arounds improve anything? If not, I'd like to keep the silouhette stock if possible and just go edge to edge with bevels on top and bottom.

Also, would it hurt to glue a permanent piece to the front middle/bottom to match up with the baffle (skipping bevels) and make the front completely flush?
 
Thanks for the specs. I'm going to try doing them myself since I'm slightly more DIY oriented than I was back when I bought the flat pak 4 years ago. However, if I fail miserably it's nice to know you still have some for sale.

Do the wider baffles with wrap-arounds improve anything? If not, I'd like to keep the silouhette stock if possible and just go edge to edge with bevels on top and bottom.

All imagineering aside, and absent any scrupulous acoustic measurement "proof" I can't honestly say they do.

Also, would it hurt to glue a permanent piece to the front middle/bottom to match up with the baffle (skipping bevels) and make the front completely flush?
If you mean to hog out the driver opening to something like that shown in my sketch, and add another layer to the front to match the new driver plates, I can't see why not.
For the A7.3s, I'd suggest at least 15mm material (without extra bezel ring) - or 18mm if with.
Just be sure to chamfer the rear side of driver openings.
 
All imagineering aside, and absent any scrupulous acoustic measurement "proof" I can't honestly say they do.

If you mean to hog out the driver opening to something like that shown in my sketch, and add another layer to the front to match the new driver plates, I can't see why not.
For the A7.3s, I'd suggest at least 15mm material (without extra bezel ring) - or 18mm if with.
Just be sure to chamfer the rear side of driver openings.

Great, will do.
I will make the baffles to your spec using 15mm baltic birch (no Alpair bezel) but without the wings so that I can keep the beautiful simplicity of the look.

Then I will basically "veneer" the remaining 70% of the front surface area with 15mm BB (cut from same piece so the grain pattern matches) so that in the end the only difference in appearance is a small seam where the baffle and veneer meet and the recessed 4mm hex screws around the baffle which look kind of cool.
This also allows me to cover the plywood edges originally visible from the front which was the only cosmetic change I wanted to make to this speaker. Now I don't have to use iron-on veneer to cover the edges and can just stain the speakers.
Thanks.
 
why is it recommended to have speaker driver flush mounted? is it to make the driver in level with the front baffle or is to push the driver deeper into the box?
Also different drivers have different (size) depth in the box and same 4 inch driver with bigger/deeper magnet cap, will be more close to the internal "V" piece. For bigger deeper drivers is it better not to flush mount so that they will have better gap from internal "V" piece.
 
why is it recommended to have speaker driver flush mounted? is it to make the driver in level with the front baffle or is to push the driver deeper into the box?
Also different drivers have different (size) depth in the box and same 4 inch driver with bigger/deeper magnet cap, will be more close to the internal "V" piece. For bigger deeper drivers is it better not to flush mount so that they will have better gap from internal "V" piece.

Here's some measurements from Troels on the difference between a flush mounted tweeter and one directly on the baffle.

Loudspeaker Measurements
 
The Stealth was a triangular prism shape, conveniently able to be sized small by using the CSS SDX7 woofer, of which we had a slew on hand and found best results with in small sealed boxes. Nothing really rocket science about the design, but finding an appropriate woofer that could be shoehorned into such an enclosure would take a bit of looking - it's the depth and diameter of magnet that limits the dimensions to which such a triangle can be reduced.

Based on pretty decent results with multiples of little Peerless 4" driver, there's probably no reason that approach wouldn't work.