I've been dreading the speaker panel since I started this build. It's by far the most complicated piece, with a mitred top and then the evil speaker grillle. I've read all the various posts on the best way to do it, so I've only got to where I have thanks to the work of those who have come before. So a big "thanks" to them. I spent a stack of time on the planning for this, and then a bunch more time setting things up. If I've one piece of advice to give for this bit of the build it's DON'T RUSH, a mantra that I had to keep repeating to myself. Ready to commence cutting, I started with this:
On top of my workbench I've a piece of chipboard (A), which is clamped along with the speaker panel (F) to the workbench below. The clamps are out of shot at the top of the picture. I've got scraps of MDF (same depth as the speaker panel) to the left and right of the panel (B), which allow the router to move across the speaker panel to make the cuts without dropping off the edges. The slight gap between the speaker panel and the scrap on the left is because of the mitre on the top of the speaker panel. Those MDF scraps are screwed into the chipboard to stop them from moving.
To each side of the speaker panel are some thin MDF scraps (C) that act as the stop pieces for when moving the router left to right. I've cut some rough slots in these and have bolts running through these slots, allowing me to move the pieces of wood in and out as appropriate for the various sized slots in the speaker panel. So with each slot I loosen the nuts, measure and move the new position, the tighten the nuts again. There's a piece of MDF (D) that acts as a fixed position to measure against when positioning piece (E). (E) is used as the piece along which the flat edge of the router runs, so it gets repositioned for each of the 7 cuts. Other people have achieved the same by starting with one piece in the correct position and then adding more pieces to move down the 16mm each time between each cut. I considered this, but the closest I had was 15mm, which would have pushed my cuts off by around 7mm by the time I got to the bottom. I also wasn't sure how I'd stick those pieces together effectively, so decided that moving (E) each time and just adding 16mm to the distance between (D) and (E) was a reasonable alternative.
Hopefully that's vaguely clear. You can see the first (D) to (E) measurement here.
In this position the router will cut the first of the seven slots in the grille. Each subsequent positioning of (E) needs to be 16mm further away.
Below you can see the left sliding piece (C) in its position where it's correctly limited the left-most extent of that first slot. I always did a very shallow cut into the panel at the start of each slot in order to check positions. Small imperfections are easier to patch up.
And here's the full setup for that first slot cut with the router in position.
I took the depth stop on the router down about 3mm at a time so that I was never cutting too much out at once. This is about half way down on the first slot.
And this is once I've hit chipboard at the bottom, which gives a nice visual point to aim for (rather than having another sheet of MDF, and not being able to clearly see when you've cut right through).
My "second" cut was the 7th slot. This is easy because I'm just working in multiples of 16 for my block placement (hardest bit is positioning the block accurately). I cut slots in pairs so that I don't have to move the side stops. Get them correct for slot 1 (and square) and slot 7 will also be correct. Same for 2 and 6, 3 and 5.
You might notice that there's some white electrical tape attached to piece E. I used this to correct if my placement of E was slightly off. Adding a few layers allowed me to move downwards, so generally I placed E a little bit "up" if I had any doubts. This second slot is still slightly too high, but I'd committed too much cut before I realised.
And with four cuts done, and lots of time elapsed!
And six. You may notice the brad nails dotted around. I was using these to attach piece E each time it moved. I'd originally planned screws, but found that attaching the screws often pulled the wood slightly off-target.
Seven done!
It's safe to say that the pressure mounts with each slot cut, because of the impact of any mistake. You can see a couple of places where the router has come a little bit too far down, usually at the point of entry on the left. They're small imperfections, but I've got to consider how best to deal with them. It's possible that a layer of paint will hide most of them. A bit of filler would also do the trick, but I worry that filler will likely result in a different finish to all of the rest of the slot. It's also going to be really fiddly to get filler into the slot and to work on it. There's another similar "notch" at the far-right of the last (middle) slot. That one was really frustrating because it was literally done at the last minute as I pulled the router out of the slot for the last time. Probabaly just a bit of haste at that critical final moment.
You can also see some slight burning on the left at the entry points. I'm not sure if that was me plunging too deep or my cheapo bit blunting.
This is the back of the panel. The chipboard underneath has prevented any blow-out nicely.
Same piece after 10 seconds of sanding to clean off the edges.
And, finally, from the front after a very quick removal of the marking lines.
Pretty pleased with this. It took ages but it's easily the most intricate thing I've ever had to cut and it's turned out better than I could have hoped. Just those little imperfections to figure out now.