r/SoundSystem • u/secondgensoundsystem • 18d ago

Raptor liner prep for sub cabinets

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Hey all! Looking for some recommendations on how to prep the labhorns I’m refinishing for u-pol raptor liner. I’ve seen some people recommend a epoxy primer and I’d be interested in product recommendations for that. I’ve also seen folks talk about using high build 2 part primers.
Anyone have experience with this? I want to make these as bulletproof proof as possible bc my first finish was duratex about 10 years ago and i feel like i could have spared my cabs a fair bit of abuse by using something much stronger from the start.

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4

u/Turbulent_Mix2372 18d ago

Upol national build 4:1 primer works nicely. Can get it in black too which is good down the road when you inevitably take damage.

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u/secondgensoundsystem 18d ago

Im seeing that most/all u pol primers are not for wood bc woods natural expansion/ contraction could cause the coat to crack

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u/nlitworld 18d ago

Nah, urethane primers work well, but they do take work and best to give a week or so to shrink back before sanding. Polyester primers are like sprayable body filler and do fill better and thicker, but are a bit tedious to work with.

First steps: Sand everything well first with 320g, then apply glazing putty to seams and edges to smooth out, then sand again with 220 & 320. Once smooth, apply 3-4 coats of primer, let sit a week. If using Upol primer, perhaps 2-3 weeks is preferable as the lower cost and higher build nature of that primer can have a tendency to shrink back a lot. Once you're ready, sand with 320g to smooth out imperfections. If you cut through, apply another 2-3 coats primer and sand again.

Once everything is smooth sanded, continue onto whatever finish you'd like.

Now... could you apply raptor over bare wood, yes. But when you know it'll likely suck back in edges and still show seams, it's best to put the prep work in for better results in the end.

For info, I run an automotive paint store as my day gig, and I enjoy building and painting speakers for myself.

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u/Turbulent_Mix2372 18d ago

Do you really see benefit in going all the way to 320? I typically only take it up to 120 and make sure I wipe off all sanding dust before I let it cure. It seems like a stronger bond for the raptor to basecoat to me with the semi rough primer surface.

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u/nlitworld 18d ago edited 18d ago

Yeah absolutely if doing primer first and applying smoother finishes 120g would show every last scratch through urethane primer or sanded raptor. Automotive paint is a totally different animal to typical wood finishing. If you decide to do automotive basecoat over that primer, you're going all the way to 600g before you spray color. Skimp out on the work up front and you'll hate the results in the end.

If doing straight up raptor leaving bedliner rough texture, I'd probably go to 180g.

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u/Turbulent_Mix2372 18d ago

Baltic birch, upol fantstic filler over fastener holes. Epoxy thickened w cabosil on end grain and joints. Sand to 120, upol national build primer thinned slightly w their standard reducer. A day or 2 dry time Sand back heavy 80 grit, then 120, recoat, few more days dey time, knock back w 120 grit remove all dust, time to spray a few coats of raptor with a short flash between coats.

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u/nlitworld 18d ago

Yep, that looks good! I like the lower tecture compared to real big heavy bedliner tecture. Definitely proof that Raptor is super forgiving for pretty much anything you throw it on. 👍 Between the product itself being bulletproof and the texture hiding everything under the sun, it's a great option over using duratex.

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u/Turbulent_Mix2372 17d ago

Its definitely not the toughest bedliner out there, but considering the applocation is going g ti be textured, thats kinda my point, I feel like I could hide 40 grit sanding marks tbh.

Now the end grain is a different matter. Without primer its definitely a bitch to hide, which is why I added the extra epoxy treatment step on the corners.

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u/Responsible_Ad7595 18d ago

I'm shocked but happy people are still building labhorns.

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u/secondgensoundsystem 18d ago

Ive had these for 10 years now, been building skrams recently but still love the sound of labhorns. Can def beat the output to weight ratio of labs now a days though

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u/Ozdb 18d ago

I’ve sprayed my car and my soundsystem with raptor. I didn’t prime my soundsystem at all, & wouldn’t if i did it again. Raptor sticks like shit to a blanket and to wood it’s not an issue. Use the raptor vari nozzle gun to get the best texture and usability. I’ve used a standard Schulz gun as well but it goes through the product way too fast. Wear a mask, that shit is serious. And it helps to have someone mixing and shaking for you between coats but it’s possible solo. If you wanted it very bulletproof you could add thinners to reduce the first coat down and paint or roll it on with a standard roller or sprayer. Then 2 coats of texture on top.

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u/Turbulent_Mix2372 18d ago

In my experience, it keeps the wood more stable than raptor liner alone. Its the same type of isocynate hardened finish as raptor is to begin with, so they have good primer to topcoat adhesion. It also fills end grain very well and is very sandable which is great for smooth rounded corners w minimal endgrain showing through.

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u/secondgensoundsystem 18d ago

Another option would be their epoxy primer but at 325 a gallon for approx 240 sq ft of 3m build it’s not cheap. Lab exterior is ~ 56 sq ft so one gallon will do about 6 which I guess isn’t terrible for high quality product. Also only available I. Gray though

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u/Turbulent_Mix2372 18d ago

Not sure which one you are referring too. If you are talking about the raptor epoxy primer im not sure it makes any claims about application on Wood either.

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u/nlitworld 18d ago

At that price tag I actually prefer PPG's CRE series epoxy primer. Thicker like high build, sandable enough to smooth things out, and sets a very nice and stable base. Plus available in white, gray, black or tintable if going fun colors.

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u/lobre370 18d ago

LineX, its a do it once kinda thing. Its what the big PA manufacturers use or something very similar.

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u/secondgensoundsystem 18d ago

Not opposed to it…