The front requires a hand router to properly recess the drivers. I like to start by getting out a square and compass and drawing my planned cuts. The front already has rounded edges and, since it is harder to see the edges as clearly, I start by drawing on the backside.
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Forgot to get in a fuller pic before I cut it, but normally you’d see concentric circles showing the outer driver recess and the cutout. Apologize for not using metric measures, but all my tools are in standard! Will supply some drawings for those using metric system. So, next I find the center line on the 8.5“ width. Had to adjust as this one was slightly wider. Placing the square at the top, marked off tweeter center at 2 3/8 inches and 8 3/32 inches from the top. Then used compass to draw driver outlines.
Tweeter cutout is at 2 7/8 inch diameter and outer edge is at 4 1/8 inches. Depth should be .25 inch.
Woofer cutout is 5.75” and outer edge is at 6 15/16 inch diameter. Depth is at 3/16 inch.
Like the above pic the tweeter edge should be about 5/16” from top and a 3/16“ space between the drivers. If all is good, I repeat drawing on front for good measure and then drill centering holes for the router jig. Check back to ensure the center holes are aligned. If not, may want to mount the baffle on scrap backing board for cutouts.
Suggest you start with the more shallow cuts for the woofer recess and then move on to the deeper tweeter one. At this point, it is good to check the recess depths as once the holes are cut through will be more work to deepen them. My router depth gauge is not very precise and had to deepen. Will get to that later. Now I set up to do the cutout passes. I do each about a .5 inch deep and then flip over the baffle to complete. At this point, touch up with bit of filing and/or sanding and clean off any remaining dust.
Time to check the driver fit. The woofer is pretty straightforward, but until the terminal slots are cut, can only check the tweeter face down. If your recesses are cut slightly too deep, some gasketing tape can help. If too shallow, see below for my tip. If all is well. then time to cut the tweeter terminal slots. Centering horizontally on the tweeter midline, the slots need to be about 3/4" tall and 3/8" wide on each side. I use a square to draw them and then a 3/4" chisel to rough cut them. I file them to smooth the edges and then clean before checking the fit. If all is well, should look like this...
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Before you forget, now is good time to mark the driver screw holes and chamfer the woofer cutout. I show this for the woofer below. I chamfered it and left some material for T-nuts. Even you do not use them, leaving the material around the left and right holes will allow more surface for them to secure to the internal brace.
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Next you should prepare to glue the cabinet together. In my case, the woofer recess was too shallow and so here is how I dealt with that....
As I mentioned earlier, you can do this with a chisel, but if you want a smoother result, you need a rabbeting bit for your router. If they had them that were 5/8" wide, it would be the best way to do the driver recesses. The bad news is the widest in 1/2" and so a bit more work is needed. On MDF, this is not too bad. Once you have cut to the new depth with the router. take a small, sharp razor knife and carefully score along the recess outer perimeter. Now, take a chisel and use to lift under the remaining material. You may have to repeat with both tools a bit to clean the recess completely, but should get a good final outcome.
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