Waterproofing MDF Subwoofer (endtable)

Put a piece of glass on top of it

Do you plan to use primer on the MDF or will you keep it bare? Some primer and paint should do the trick.

If you use a water/woodglue mix to seal up the exterior of the box (sand smooth), then prime and paint with an outdoor type paint, it should hold up well to various abuse.

Paint, then epoxy. They use that stuff on bartops, non reactive to water in the least.

That's what I used in my build, and I use one of my dual opposed boxes as an endtable.

The finish has held up greatly, I get complimented all the time when people see them in person.

I don't have any experience really at all but just wanted to add my 2 cents of knowledge in wooden tables. From everything i've heard, the rings you get under a wet or hot glass when not using a coaster is not actually from an unfinished top of the wood. It's from not sealing the wood underneath the tabletop.
A beverage whether hot or cold causes the condensation of air to come up from the bottom and seep through the wood and get stuck in the top where you have finished it.

Best bet if you're not adding a glass top is to make sure you do some finishing on the inside layer to keep the moisture out. (I think)

Pretty much any paint will do. Especially on mdf which is super smooth to begin with.

I used walmart brand cheap paint on my faces of my sub build.

Check out my build link for detailed instructions, but here is a pic.

Prime, paint, no sanding, epoxy equals..

This thread pains my eyes to read!

Coatings are not remotely considered equal, and shouldn't be suggested as such. For a group of people so meticulous about ensuring a flat frequency response, I find it ironic how often a build is finished with such inadequate coatings.

I am going to try to simplify sub boxes as basically furniture for the sake of this conversation. The #1 recommended finish if I were to sell to a furniture manufacturer would be a conversion varnish. They exhibit great moisture resistance, short recoat time, stain/chemical resistant, gloss retention. Downfall is they can be temperamental to environmental conditions when applying, thin dry film thickness (not good for filling voids), and smell like the devil. My choice Sherwin Williams Sherwood Conversion Varnish

My next vote would be a precatalyzed lacquer. These are typically approved for KCMA specs for moisture resistance, stain resistance, chemical resistance. Short recoat time, fair gloss and color retention, easily sandable, and imo user friendly. I say they are user friendly because any mistakes you make can be sanded away in seconds (think sanding drywall mud). Downfall is they require spraying, smell like hell (however not as bad as conversion varnish), thin dry film thickness (not good for filling voids). My choice is Gemini Precat Lacquers

In this case I may suggest an epoxy as well. And when I say epoxy I don't mean that Nancy boy waterborne epoxy. Sure it has it's place in the coatings industry, but furniture typically isn't one of them. If you're going with an epoxy I want a two part solvent borne epoxy that shows excellent moisture resistance. Call a local paint store for their specific branded recommendation if you want to go this route (and no Lowe's and HD don't count as paint stores) Positives:great moisture resistance, chemical resistance, mar resistance. Downfalls: two components mean more $, not as easily sandable, dry time mediocre typically, ideally needs sprayed, and also smells like death. My choice for pigmented epoxies PPG Amercoat, Sherwin Williams Macropoxy 646, or save your money! There are 2 part "bar top pourable" epoxies as audiophile mentioned which could also be an option depending on your set up.

My next vote good old polyurethane. I don't love it, I don't hate it. Does it work, yes. Does it work perfectly, no. Is it incredibly versatile absolutely. Positives:brush, roll, spray application. Good abrasion resistance, fair moisture and chemical resistance, priced just right. Negatives: Slow dry time, slow recoat time, mediocre sanding, propensity to yellow, mediocre gloss retention. My choice:Minwax Fast Drying Polyurethane.

If you can spray use the Gemini system. If not hit with an alkyd based primer or paint, and top coat with polyurethane.

Notice I recommended no waterborne finishes. Let your wife use those. They have their place and are incredibly revolutionary in the industry, but not for furniture!

^ Well aren't you just the elite wood worker!

I think Audiophile34's build/finish on that sub is outstanding. And I also think that for the average DIY'er, 99% of the finishes you see here will suffice very well! Even for the not so average DIY'er really. I also imagine that few worry so much as you do if their finish will meet KCMA specs or not.

For the record I don't do woodworking. I don't have the patience or the skill. I do coatings tech and application of coatings for a living.
The question isn't whether the finish on audiophile's sub is nice or not. The point is the recommendation opens the door to problems. Some solvents in pourable epoxies can cause wrinkling, lifting, or delamination of waterborne coatings. Will it always happen? Clearly not. Can it happen? Absolutely. You're pouring a hard high build coating over the top of a soft base coat as well. In the real world this can also cause issues. No one wants to work hard on a finish only to have to strip it off because of a compatibility problem that can be prevented.

Since few care about finish quality I'll ignore the questions in my PM box, and we'll pretend that everyone doesn't follow PI threads for his insane finish abilities.

I never said people didn't care about finish quality. I also never put people down about their DIY project or decision how they finish their project. Hope your eyes are feeling better!

For the record I used an enamel based primer, and paint. Then the (pourable) two part bar top epoxy, that you can get from Home Depot, or Lowes.

Pour the epoxy on one side at a time, spread it around, (I used a cheapo foam brush)

One kit of the epoxy was around 25 bucks. 99 cents for primer, another 99 cents for paint..

cheap, durable, and IMO looks good.

but I wasted my time cause it doesn't meet KCMA standards. lol..

My point is and will forever be factual that solvent lifting, wrinkling, and rewetting can ruin a project. I realize it did not effect your finish, but that does not mean someone else will not have it happen. Various solvents can be used over the top of other solvent borne coatings and some can not. The xylene, tolulene, acetone, etc in your spray primer could be rewet with what's likely xylene, mek, tolulene in the pourable epoxy.

Just as we do not recommend people to use ported subs without high pass filters, I do not recommend people to use coatings systems that run the same risk of failure. I won't comment anymore on this issue as apparently the only thing worth being OCD about is frequency response not the entire finished project.

Since I have used the product in the manner of the original posting, ie waterproofing a mdf box, I CAN recommend the product.

This is the product I used.

http://www.rustoleum.com/CBGProduct.asp?pid=448


if you don't want to follow the link, then I copied a overview of the product below.

Super Glaze Pour-On Finish and Preservative is an ultra-thick, high gloss, crystal clear epoxy that provides maximum durability. It is ideal as a water proof finish for table and bar tops. Also it is great for crafts and refinishing furniture and can be used over almost any interior surface; from rough and unfinished to stained, painted, or smooth surfaces.
It can finish bar tops, table tops, game boards, clocks, plaques, and ceramics.

I have personally seen people use this to coat pictures, sea shells, coins, all sorts of stuff with zero negative reactions with whatever product they were covering.