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Discussion Starter #1
Hi all, I built 6 speakers a while ago and now I'm stuck with the finish.
The speakers are made from BB ply and the finish is supposed to be piano black (like what an actual grand piano would look like).

I've watered and sanded the speakers (down to P320, which seems to be 240 grit US), then applied spray putty, sand, spray, sand, spray, sand, prey, but for the love of god, I can't get the grain out, I'm sure I'm doing something wrong. I've used up 7 cans for a single speaker now and the grain still comes through.

I was looking for a bit of info here and it seems like most use Bondo, but didn't tell which product exactly or how to use it, but I guess they refered to 3m 261c.

I really only want a smooth surface to apply my paint to, but I can't get there. Any pointers?
 

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I always used automotive grade materials as I do bodywork on the side. It is expensive but there are low cost materials available. I like to buy supplies from this vendor Automotive Paint | Buy Custom Car Paint Colors Online from TheCoatingStore as their materials are good quality and are relatively inexpensive. Another option would be go to O'Rieleys parts store or Eastwood.com to buy a few quarts of their lacquer based primers and paints for roughly $20/qt.

Use body filler to fill the voids in the wood, sand the wood and filler to 320 grit then prime and block/wet sand to 1000-1500 grit then paint. If you want a mirror finish, wet sand the top coat with 2000-3000 grit then buff and polish
 

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Discussion Starter #3
I always used automotive grade materials as I do bodywork on the side. It is expensive but there are low cost materials available. I like to buy supplies from this vendor Automotive Paint | Buy Custom Car Paint Colors Online from TheCoatingStore as their materials are good quality and are relatively inexpensive. Another option would be go to O'Rieleys parts store or Eastwood.com to buy a few quarts of their lacquer based primers and paints for roughly $20/qt.

Use body filler to fill the voids in the wood, sand the wood and filler to 320 grit then prime and block/wet sand to 1000-1500 grit then paint. If you want a mirror finish, wet sand the top coat with 2000-3000 grit then buff and polish
Do you sand at all before applying the filler? And do you spray or brush/rub the coat on and do I have to wipe off excess? I'll have to see which products are available here in Germany, because Bondo isn't, for example. I think my best bet is to drive to the closest car repair shop and ask what kind of stuff they use.
 

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I always used automotive grade materials as I do bodywork on the side. It is expensive but there are low cost materials available. I like to buy supplies from this vendor Automotive Paint | Buy Custom Car Paint Colors Online from TheCoatingStore as their materials are good quality and are relatively inexpensive. Another option would be go to O'Rieleys parts store or Eastwood.com to buy a few quarts of their lacquer based primers and paints for roughly $20/qt.

Use body filler to fill the voids in the wood, sand the wood and filler to 320 grit then prime and block/wet sand to 1000-1500 grit then paint. If you want a mirror finish, wet sand the top coat with 2000-3000 grit then buff and polish
Don't you need clearcoat as well?
 

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Do you sand at all before applying the filler? And do you spray or brush/rub the coat on and do I have to wipe off excess? I'll have to see which products are available here in Germany, because Bondo isn't, for example. I think my best bet is to drive to the closest car repair shop and ask what kind of stuff they use.
If your cuts are not super square and you have high spots over a few MM I would sand those down before I use body filler. Generally I use body filler over all the seams where boards meet sand to a smooth flat surface. Fill any divots or imperfections then begin the priming process. If you want to do it the right way, use a sealer primer over the body filler, then spray filler primer to further smooth the surfaces with your fine block sanding. Start with 240 grit work until at least 800 grit. You may have to re apply primer several coats depending on how rough your starting point is. Once nice and straight with no visible sanding scratches you can apply color. Then clear if required or desired.
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For any type of wood, I first use a 50/50 wood glue / water mix and pre paint the hole box, sand, the start the automotive style paint job. And I also use acrylic primer first. I spray 3 coats on before I start any sanding. That’s the yellow looking primer it works wonders on wood.


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Discussion Starter #9
I decided to just sand and stain until I've found a good solution because I want to listen to those damn speakers already lol! I'm running short on time and getting this done at a local shop seems to be ridiculously expensive. Need to get the cabs out of the shop because I need the space.

From the info I gathered this should be a decent approach:

-fill big voids with putty
-water the speaker and let it dry again
-sand (P320)
-apply automotive 2k filler (sprayed, wear a mask and ventilate the space)
-sand again (P320)
-apply primer
-sand again (P800)
-paint
-sand depending on the paint
-apply the clear coat
-polish
-glaze

While cleaning the surface before applying any kind of treatment. Thoughts? Anything I need to pay special attention to?
@notnyt I read your build on the Classix, but you weren't very detailed on how you sanded/applied the filler, I think your finish looks great!
I also really liked @Javs 's system with the matte front, but I think you didn't even use filler because your system is made from MDF?
 

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Discussion Starter #10
@petethekiller That's one nice looking finish, I'd love to see that in person. All speakers are fully CNC machined so my only worry is the grain, which I can't seem to get rid of.
I have a build thread you can check out if you're interested: Jim Holtz's Bordeaux Build (x6)
@hessc50 Sounds interesting, do you do the glue thing to make the surface less absorbent? I hate sanding as much as the next guy, so the more steps I can skip the better.
 

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@petethekiller That's one nice looking finish, I'd love to see that in person. All speakers are fully CNC machined so my only worry is the grain, which I can't seem to get rid of.
I have a build thread you can check out if you're interested: Jim Holtz's Bordeaux Build (x6)
@hessc50 Sounds interesting, do you do the glue thing to make the surface less absorbent? I hate sanding as much as the next guy, so the more steps I can skip the better.
I've built and painted probably 20 speaker enclosures... Some MDF, Some particle board other plywood the finish always turned out the same. I used shellac to seal MDF with good success and never have tried the glue method but always wanted to. I have not had issues with my seams showing but that doesn't mean someone else wont.
 

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I decided to just sand and stain until I've found a good solution because I want to listen to those damn speakers already lol! I'm running short on time and getting this done at a local shop seems to be ridiculously expensive. Need to get the cabs out of the shop because I need the space.

From the info I gathered this should be a decent approach:

-fill big voids with putty
-water the speaker and let it dry again
-sand (P320)
-apply automotive 2k filler (sprayed, wear a mask and ventilate the space)
-sand again (P320)
-apply primer
-sand again (P800)
-paint
-sand depending on the paint
-apply the clear coat
-polish
-glaze

While cleaning the surface before applying any kind of treatment. Thoughts? Anything I need to pay special attention to?
@notnyt I read your build on the Classix, but you weren't very detailed on how you sanded/applied the filler, I think your finish looks great!
I also really liked @Javs 's system with the matte front, but I think you didn't even use filler because your system is made from MDF?
I used two fillers, grain filler and spackle. Since you don't have any wood grain here, I'll assume you're talking about generic void filler. I applied with a plastic spreader and went heavy. I sanded it flush with a sanding sponge.

The filler part is easy, trickier is blocking to get a nice flat surface.
 

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Using the 50/50 glue water does seal the wood. It helps stop the following coats from soaking into the wood.


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I spent about a year experimenting with getting a mirror finish on wood. I have two processes, one for a clear surface over wood grain and the other for a painted surface. I don't use the glue/water mix to seal the woodgrain, instead I spray a polyester primer as my grain sealer. It fills better, is easier to sand, and is a better substrate for spraying epoxy surfacer/sealer prior to base/clear.

1: Sand wood at 220 grit.
2: Spray polyester primer with primer gun, 2.0mm tip, do not thin. Typically 2-3 very thick coats does the trick. Don't worry about runs, they will be sanded out.
3: Guide coat and block sand 120 grit, work up to 360 grit dry. Do not wet sand polyester primer
4: If your panels are perfectly flat and you have not sanded through the primer, you can move to the next step. If not, re-spray with polyester and do more guide coat/block sanding
5: If you are happy with your surface you can move straight to epoxy sealer, if you still have some areas that need filling then you want to spray epoxy surfacer. Spray surfacer with primer gun 1.6mm tip 2-3 wet coats
6: Sand surfacer to 500 grit wet
7: Spray epoxy sealer with primer gun 1.4mm tip. If surfacer was sprayed, consider thinning an extra 10% for improved flow out. Typically 2 wet coats is good. The surface should be perfect at this point. If it isn't then you need to go back and do some more bodywork after the epoxy cures.
8: Do not sand or touch sealer. About 30min after sealer, spray base typically 2-3 coats 1.4mm tip
9: spray clear 2-3 coats 1.3mm tip
10: If you are happy with the texture of finish you are done. If you want a mirror finish, forge ahead
11: Dry sand 800 grit block or DA to remove all orange peel.
12: Spray 1-2 coats of overthinned clear 1.2mm tip
13: Dry sand 1500 grit DA to remove all orange peel
14: Wet sand 3000 grit, then 5000 grit DA
15: Polish with 3 step buffing system

 

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Discussion Starter #16
Hey all, sorry for the period of silence, I was a bit busy with all kinds of stuff.
Thanks all for the help so far! The putty I have doesn‘t work at all and I‘m looking into automotive materials now.
3m/Bondo stuff isn‘t available in Germany, but there are other brands making body filler of course.

Should I use Polyester filler or Epoxy filler? Some of you mentioned epoxy sealer - can I just use the spray primer I‘ve got or is this something different?
 

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I feel like the missing ingredient in here is the sanding block. Other people in this thread have mentioned it, but I'm going to highlight it. If you use sandpaper with your hand or something soft then the sandpaper will hit the high spots and low spots evenly making the topology more or less remain the same. If you first wrap the sandpaper around a block of wood then only the high spots will get cut down until it's perfectly flat. It's similar to how a smoothing plane works.

Take a particularly uneven part and put a pencil mark on it. If you use the sandpaper with your hand then you'll be able to see the pencil marks all go away at the same time. If you do that experiment in a different but similar spot while using the block you'll see the marks on the high spots go away first.
 

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Discussion Starter #18
I feel like the missing ingredient in here is the sanding block. Other people in this thread have mentioned it, but I'm going to highlight it. If you use sandpaper with your hand or something soft then the sandpaper will hit the high spots and low spots evenly making the topology more or less remain the same. If you first wrap the sandpaper around a block of wood then only the high spots will get cut down until it's perfectly flat. It's similar to how a smoothing plane works.

Take a particularly uneven part and put a pencil mark on it. If you use the sandpaper with your hand then you'll be able to see the pencil marks all go away at the same time. If you do that experiment in a different but similar spot while using the block you'll see the marks on the high spots go away first.
Thanks for the heads up, this is certainly important, but wasn't my problem. I have (literally) 4 different power tools for sanding and differently sized sanding blocks and hundreds of sheets of sanding paper. My only problem so far was getting the wood grain out. Most likely this was just a problem of the filler I used, because no matter how much we sprayed and sanded, the grain structure wouldn't disappear, plus the filler would break and rip when machine sanding it. So my question is now if I should go with poly or with epoxy filler and do I need anything else with that or can I apply my primer (doesn't say what kind of primer it is) and paint?
 

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The most aggressive way to fill grain is to first use standard wood filler. By that I mean the material that is sawdust and bonding agent. Let that dry. Mix together wood glue in water and paint that on. It will absorb differently based upon grain patterns or if you're going over rough endgrain so you'll probably want a second coat. Lightly block sand that with 220 and proceed putting your glossy coat on. When I say lightly, I mean about 3 strokes. You're just looking to knock down any rough high spots or stuck on particles that were floating in the air.
 

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Hey all, sorry for the period of silence, I was a bit busy with all kinds of stuff.
Thanks all for the help so far! The putty I have doesn‘t work at all and I‘m looking into automotive materials now.
3m/Bondo stuff isn‘t available in Germany, but there are other brands making body filler of course.

Should I use Polyester filler or Epoxy filler? Some of you mentioned epoxy sealer - can I just use the spray primer I‘ve got or is this something different?
There are many ways to do it. In my method you use both. Polyester primer as grain sealer then epoxy as polyester sealer and surfacer. I have tried to use epoxy as a grain sealer and it just doesn’t work as well. It cures slowly and is expensive, it takes a lot to seal the grain. Polyester does it quickly and is inexpensive.

Using rattle can stuff, I’m sure it can be done but it is difficult to do. You will never get as durable of a finish using uncatalyzed materials.

There is no right way though, everyone comes up with the method that works best for their workflow, budget, experience, and tools.


-Trevor
 
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