Finishing plywood speaker cabs - black, matte, utilitarian finish? - diyAudio
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Old 13th June 2014, 07:37 PM   #1
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Default Finishing plywood speaker cabs - black, matte, utilitarian finish?

I recently built a set of speakers with birch plywood. (Specifically, the dMar-Ken7.3 from a flat pack supplied by Planet10 HiFi. If Dave or Chris sees this thread, he might offer some more detail about the wood.)

I'm happily enjoying the speakers in unfinished form, but will have some time in a few weeks to hopefully make them slightly more presentable.

I read a handful of threads about finishing plywood, but there are infinite options. I'm hoping that if I post some specifics about what I'm looking for, I might get some more targeted suggestions.

So, in order of decreasing importance, I'd like the finish to be:
  1. Relatively easy. By that, I mean no esoteric tools or skills-that-need-to-be-practiced. Something that can be done successfully with basic tools (rags, paint brushes, sponges, etc) and by somebody with very little wood-finishing experience in a few days' time (or less).
  2. Inexpensive. Doesn't require unobtanium or purchasing from obscure/boutique/specialty shops.
  3. Durable, low-maintenance, easy to clean. One face of one of these speakers will likely spend part of every day in sunlight. I don't expect them to be moved around too much though.

Notice that "aesthetics" didn't make that list. Obviously I care a little about how they look, or I wouldn't bother finishing them at all... but I tend to like very plain or utilitarian stuff (I think "understated" is the fancy word for this). So I'm really just looking for a rugged, matte black finish that's fairly easy to apply.

The only area where I would like to tidy up a bit is some of the joints I didn't glue perfectly square... some edges might have a 1/16" or so lip from sliding that occurred from my sometimes impatient clamping. Is sanding down these edges with coarse sandpaper the best bet? Or is there a point at which you forgo sanding and use something like wood filler?

I'm guessing paint is probably my best bet? But what kind? Should I use a primer coat? And what about varnish or lacquer? Maybe a marine-grade product for durability?

Thanks!
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Old 13th June 2014, 08:29 PM   #2
zobsky is online now zobsky  India
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Use a router with a flush trim bit to clean up the lip. I still think pre-stain and a lightly tinted danish oil such as watco is the easiest finish for birch which tends to splotch otherwise.
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Old 13th June 2014, 09:10 PM   #3
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Speaker Cabinet Coatings | Texture Coating for Speakers | Road Cases Protective Coating
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Old 13th June 2014, 09:32 PM   #4
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I've recently built some workbench cabinets from baltic birch plywood, and used a wiping varnish for the final finish. I used Minwax 'clear satin' and it's virtually fool-proof in its application. I first sanded the wood to 220-grit, and using a rag, applied a coat of the varnish. After it was completely dry, I very lightly sanded the surface with 330-grit. I repeated the process at least 3 times, and as many as 6 times for top horizontal surfaces that will be subject to more abuse.

This method is a little slower than some, but it avoids problems with drips and sags common to other methods. It yields a nice final finish.

The Minwax wiping varnish is a little pricey (about $11 USD per quart), but you can also make your own wiping varnish by mixing regular polyurethane varnish with thinner. I think the ratio is 1:1 but don't quote me on that.

If your wood is not as attractive as baltic birch, then painting may be a better option.
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Old 14th June 2014, 10:07 PM   #5
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Quote:
Originally Posted by zobsky View Post
Use a router with a flush trim bit to clean up the lip.
Yeah, that sounds like the best approach, unfortunately, I don't have a router... that's why I commissioned Planet10 to make me the flat pack.

That's interesting... maybe a bit more rugged than I really need, although it's tempting. I couldn't find too many pictures of finished products to get a better feel for what the finished product looks like (the "textures" tab gives a few small pics). You'd think a site like that would have lots of pictures of what the product looks like (either that or I'm overlooking all them).

Quote:
Originally Posted by zobsky View Post
I still think pre-stain and a lightly tinted danish oil such as watco is the easiest finish for birch which tends to splotch otherwise.
Quote:
Originally Posted by AcoustatAnswerMan View Post
I've recently built some workbench cabinets from baltic birch plywood, and used a wiping varnish for the final finish. I used Minwax 'clear satin' and it's virtually fool-proof in its application. I first sanded the wood to 220-grit, and using a rag, applied a coat of the varnish. After it was completely dry, I very lightly sanded the surface with 330-grit. I repeated the process at least 3 times, and as many as 6 times for top horizontal surfaces that will be subject to more abuse.
Thanks guys, I'll look into those.
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Old 14th June 2014, 11:21 PM   #6
zobsky is online now zobsky  India
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Unfortunately, the router is the only reasonable way to trim off the lip . You could try a sander but it might turn out as well.

Perhaps find a friend who has one, or buy a basic plunge router. Harbor freight has cheapies but the bare minimum would be a craftsman like this Sears.com

I'd suggest a dewalt ideally but I get the feeling that you're on a budget or space limited or maybe don't intend to use it frequently
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Old 15th June 2014, 12:41 AM   #7
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I checked the second pair we made... they are Murphy Ply which has maple face-veneeres, and is generally higher quality than BB.

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Old 15th June 2014, 12:49 AM   #8
sippy is offline sippy  United Kingdom
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Trimming a 'lip'...... try a good old fashioned block plane, Stanley 220.
Cheap (second hand from a market stall = 5 / $8), QUIET and less chance of doing damaging everything.
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Old 15th June 2014, 03:34 PM   #9
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Careful use of a belt sander will remove excess....
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Old 15th June 2014, 07:39 PM   #10
chrisb is offline chrisb  Canada
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Or just some elbow grease and stroke sanding in the direction of grain with block of scrap plywood or MDF and PSA backed sandpaper - starting with 80G and progressing down to at least 220. Fit a cardboard "mask" cut to the same diameter as driver to prevent dust and finishing products from contaminating the enclosure interior. A lot easier to control that a belt sander or electric random orbit. Although the air powered ROs are much lighter and easier to manipulate, and can remove fairly aggressively, they do require more CFPM than most small compressors can muster.

As for finishing products, I generally use professional grade NC lacquer and HVLP spray equipment, but have recent found a very nice hybrid water/oil varnish that brushes quite nicely with foam brushes - of course it does take much longer to dry between coats than would a solvent based spray, but once cured, is quite durable (it's engineered as a flooring finish)
- Products - [SamaN Canada]

I tried one of their water based stains and quite hated it - I much prefer the ML Campbell Woodsong solvent based stains.
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Last edited by chrisb; 15th June 2014 at 07:49 PM. Reason: Grammy & spellink
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