I am a DIY newbie... I am finding building subs completely frustratingly fun... Here are some issues I have run into... Maybe it will help you in the future...
- Make sure you have the proper tools. Circular saw with guide, router, jigsaws at minimum; a table saw would be really nice. Real nice.
- If you use a circular saw, verify that the saw blade is set at 90 degrees by cutting test pieces. Stand the piece on edge and see if it perpendicular. If it is not, the glue won't have much to hold on too. You don't want to see the sub split along the seams under pressure. It is not nice.
- Don't let the stores cut the wood for you... Their saws are never accurate. You will cry when you find one piece is 19" on one edge and the other end is 18-7/8" and nothing lines up.
- This is really important. the largest pieces of the build should be slightly oversized. Maybe 1/4".. It is a LOT eaiser to trim oversized pieces with a router than to build up a piece that is too short.
- Measure twice, cut once... Repeat. Repeat again.
- If you use T-Nuts or Hurricane nuts, use Gorilla glue to hold it in place. Otherwise you will need a real gorilla to tear the box apart to remove a driver that is stuck because you have a nut that is free-spinning behind the driver.
- Don't just arbitrarily drill holes in the cabinet until you know what size bolts the speaker will take. Just because one speaker uses 10/32 bolts does not mean another driver the same size will accept it. I found out Polks will only take 8/32 bolts unlike DA's 10/32.
- When cutting out driver holes, make it a tad bigger than recommended. After applying paint, you may be surprised the perfect cut is no longer perfect. My DA RSS390HO-4 is now a permanent fixture in my cabinet.
- When you primer MDF, use a sealing primer, such as Zinnser BIN Shellac primer. Do NOT user odor-free (water-based) primer, painting solvent paints over it will cause really bad wrinkles. You will see your finish age before your eyes. The canned version of the primer is a lot easier than using aerosols. Take my word for it. You apply it with a small 6" roller. It dries after an hour, reapply. After a few coats, sand it down with 220 grit paper using a random orbital sander. The finish is real smooth, plus it is not as messy as sprays. , the box looked better with the primer sanded down than the finished results.
- Painting is harder than veneering. It leaves a big mess with overspray. Removing overspray from a car is NOT my idea of fun.
- Finishing to a mirror smooth finish is very time consuming. You have to apply a primer, sand smooth, repeat until no unpainted surfaces appear. After applying a few coats of gloss paint, I chose to sand it down smooth and then polishing it with rubbing compound, polishing compound and then car polish. This will be a looong process.
- Do not use steel wool if you will be using any water based product to finish the box. Any steel fibers in the finish will start to rust. What may look nice now, will be ugly as the finish starts to look like it's getting chicken pox.
- If you use lacquer based paint, do not even think of finishing it for a month. Lacquers take a looooonnng time to cure, months even. If you sand too early, the paint will come of in chunks and adhere to the sandpaper, gouging the finish. When you sand lacquer, it should be removing like dust. If not, it ain't ready for sanding
- If you veneer chamfered boxes, veneer the chamfers first. Then trim with a router with a laminate trimmer. Then cover the flat surfaces with veneer cut to size. It will be difficult to trim otherwise.
- Do not use PSA (Peel and Stick Adhesive) veneers if possible. I find the quality inconsistent. Sometimes the PSA itself separates from the veneer side because of the way it is rolled up. If this happens, it is almost impossble to avoid getting a bubble. Also, PSA veneer does not allow you to adjust placement or dry fit.
- Avoid cherry veneers that are sold in a roll. Cherry wood darkens in light. You will find the exposed part of the roll is a LOT darker than the hidden rolled part.
- If you stain veneer, make sure you test the stain on a scrap that is exactly finished as the final piece. If the final box is sanded, sand the scrap. Otherwise the color will be different.
- Sand veneers before staining to raise the grain.
- If you stain with wood stain, always use wood conditioner before staining, otherwise the finish will likely be blotchy and uneven.
- make a list of what steps need to be done. If will be surprised how often you end up skipping a step (like using wood conditioner) with a lapse in memory, ruining all your careful work.
- Figured out how to easily veneer chamfered cabinets. Or at least I think it will work as i have not tried it yet. Veneer the entire box BEFORE chamfering. When I chamfer a box, it removes about 7/8" of material from the edge of the box. When veneering, you just need to cover to about 3/4" or closer to the edge since the rest of the material closer to the edge of the box will be removed anyway. You must make sure that the veneer is bonded along the edge of the veneer really well to prevent fraying or chipping while chamfering.
Once the veneer is bonded to the surface, you can use a chamfer bit and route the edges (remember, when chamfering a box, you must chamfer all the vertical edges first, then the horizontal edges, otherwise the corners will be at different angles, I learned this the hard way).. If all goes well, the router will trim the veneer edges flush as you chamfer the box. This should be easier as you no longer need to trim the flat panels exactly to size. Now you just have to apply the veneer to the chamfered edges. You can overlap the edges a bit as well but not too much as the router will lift a bit on the overlapped edges. Then use a sufficiently long laminate trim bit (in this case, 1" since 7/8" was trimmed) to trim the chamfered veneer. Again, this should give you a clean cut. All you have to do from there is to apply veneer to the corners.
I do not recommed that you use PSA veneer for chamfered boxes. The PSA is very thick and will leave a noticeable band between the veneer edges. Also, PSA tends to gum up the trim bits on the router because the glue is thick and does not really seem to dry (it actually looks like globs of thick rubber cement). If you stain light colored woods with a darker stain, the edges will become very dark and look like pinstripes on the finish. Its because the paper backing on the veneer absorbs the stain more than the veneer itself, becoming darker. Also, since you trim the veneer at 45 degrees, the area of the backing exposed is larger than veneer trimmed at 90 degrees.