Translam Subwoofers with 18" Passive Radiators - The Jedi Mind Tricks

[KEtheredge87]

Hey Everyone,

Tonight I got some good work done! The second cabinet has completed final rough assembly by gluing the top and bottom together, and epoxying the vertical dowel rods in place. The first cabinet was the guinea pig for my router cuts to true up the outside edges that accept the front and rear baffles. I made a simple slot jig for my plunge base and cut a 1/4" slot. From there I used a drywall square to reference off the bottom of the cabinet and draw a line across the layers that would straighten up that edge while removing the minimum amount of material. All I had to do was line the cutting slot up with the pencil mark and clamp it down. A few quick router passes was all that was needed to fix that issue. I did leave some material in the corners so I could clean that up with a chisel. All in all, very easy to do!

The plan for tomorrow is to true up the edges of cabinet #2 and get ready for epoxy. I'm trying to plan a few steps ahead, and this is where I think I'm at:
01) Coat the interior of both cabinets with epoxy
02) Rough sand the outsides of each cabinet to 80 then 120 grit with my sanding blocks
03) Lightly sand with random orbital sander to 180 grit
04) Trim MDF baffles to fit in openings
05) Veneer back of baffles with Okume backer
06) Machine baffles for drivers and paint recess surfaces black.
07) Veneer front of baffles with quartersawn walnut
08) Apply stains / dye finish schedule to walnut veneer before glue-up (risky, but easier to handle stain and dyes away from the birch plywood.
09) Glue baffles into place with PL Premium (Bias squeeze-out toward the inside of the cabinets)
10) Apply General Finishes High Performance Water Based Polyurethane

Holy crap that's a lot of work to get these off to MWAF... and that doesn't even include time to fiddle or tune the PRs. We'll see how it turns out! In the meantime, enjoy the photos of the project, and the Shop Mascot, Toby!

[KEtheredge87]

Hi Guys,

More progress tonight, as I routed the edges of the second cabinet to true up those edges, then worked on shaping the raw baffle stock to fit the openings. I'll need to add a rabbet around the back edges of these baffles so they fit flush with the exterior surfaces, but I won't do that until I'm satisfied with the sanding of the cabinets. I'd hate to get things decently flush, then sand the cabinet and mess all the leveling work up!

You might notice I jumped ahead to #4 of my list from yesterday... I'm nervous about the epoxy for no obvious reason. Just don't want to screw anything up, and the baffles were more of a known quantity to deal with tonight. I'll bolster the courage and get to the epoxy soon!

[jhollander]

FYI, I like to glue and screw the braces where they cross. That may not be possible with what you have.

[tomzarbo]

That first pic really shows off all your hard work with the layers. It's a very interesting effect! How do the cabinets feel when you rap on them or pound them with your fist? I'd imagine they're pretty solid?

TomZ

[KEtheredge87]

FYI, I like to glue and screw the braces where they cross. That may not be possible with what you have.

Hey John, that's a great idea! I could probably do something creative with dowels scraps and some 1" forstner bit holes. Makes me think of my days on the solar car team where we made a roll cage from round aluminum tubing and had to cut circular holes and cutouts to mate the round pipes at odd angles. I've attached my layout PDF that shows where these dowels are located. This idea could be done, but I'm not sure if it's needed.

That first pic really shows off all your hard work with the layers. It's a very interesting effect! How do the cabinets feel when you rap on them or pound them with your fist? I'd imagine they're pretty solid?

Thanks Tom! Yeah... they feel very solid! I gave them a knuckle rap last night while the baffle bits were just bumped into place, and I didn't get anything that sounded super hollow or resonant. The sound was a bit higher pitched than I expected...hard to describe, but not a bad sound. I expect things will improve and be even less resonant once the baffles are actually glued in, the epoxy coat is reinforcing the walls, and the drivers are gasketed in.

[jhollander]

The idea of securing the braces it to keep them from vibrating like a guitar string. I'm a fan of rectangular braces placed close so they can be screwed and glued together.

[KEtheredge87]

The idea of securing the braces it to keep them from vibrating like a guitar string. I'm a fan of rectangular braces placed close so they can be screwed and glued together.

Ohh... That actually makes a lot of sense Maybe I'll rig something up after all! Thanks for politely reinforcing the point.

[KEtheredge87]

OK folks... I am reconsidering my sanding approach. Not because the giant sanding block approach isn't working, but because I'm not sure how long it's going to take to actually get things moving along! I spent an hour and a half going at one side of one cabinet with my homemade 80 grit sanding board before my arms gave out. Leading an upper body resistance training class at the gym prior to garage time didn't help that cause!

I like John's idea of a stanley #80 scraper plane, but I don't have one of those without going ebay'ing or buying a modern clone at a decently up-there price. Same thing goes for any kind of cabinet scrapers since I would also need to buy the sharpening materials to maintain them.

That brings me to the tool I do have... a dewalt random orbit sander. The biggest concern I have here is that I'll sand things unevenly. I still have that possibility with my giant sanding block, since I'm only making two points of contact across the whole cabinet. Eventually one side will wear down, and it may end up deeper than I need to be. I tried concentrating on the highest high spot first, but I wasn't sure if I was doing things the hard way when I really don't need to.

I know folks weighed in on this debate earlier, but If anyone's had more current thoughts, or think I'm not likely to ruin things with the DeWalt random orbit, I think that could be a better solution. Am I on the right path, or should I consider a change in strategy? (Thanks in advance!)

On the pictures, you can see the before (mostly Titebond II yellow colored) and the after pictures where I managed to knock down two large high areas, but got both tired and chicken that I was going to overdo one of the high spots since the top layers of the cabinet were about 1/16" or so above the rest. See the big obvious line in the left hand side of the "after" pictures? That's the edge that's bothering me.

Before:


After / In-Progress:

[Kevin K.]

Sorry man, every time you turn around you're having to spend more money, welcome to DIY! IMO, the orbital sander has to small a footprint for what you are trying to do, it will probably do more damage then good.

I warned you, end grain on plywood is tough to sand especially on a translam. The scraper John suggested would work but I suspect you will spend as much time sharpening it as you will using it on this project. Time to go get that belt sander! When a belt wears out, it's a quick change to a new one and your back up and running. Good luck!

[marvin]

In my experience a belt sander is harder to control than a random orbit sander.

[KEtheredge87]

...I warned you, end grain on plywood is tough to sand especially on a translam. The scraper John suggested would work but I suspect you will spend as much time sharpening it as you will using it on this project. Time to go get that belt sander! When a belt wears out, it's a quick change to a new one and your back up and running. Good luck!

Hey Kevin, Yes... you did warn me I have a few lowes gift cards that are hanging around in the wallet, so best to use them and get out of a tough situation instead of spending them on piddly little odds and ends. I'm thinking this Hitachi model that's on sale. The reason I'm going there instead of the Black and Decker or Skil models is the variable speed. My thought is to use a higher grit belt like 120 with the lowest speed possible to maintain the best control over the rate of material removal.This approach should help me with the larger curved surfaces.

In my experience a belt sander is harder to control than a random orbit sander.

Thanks Marvin! I agree there's a definite difference in control, hence my hesitancy to use a belt sander until I've found myself backed into the proverbial corner. I also have a 3M foam backer pad coming from Amazon for my DeWalt random orbit sander. I think I'll use this gently on the corners of the cabinet where there are radiuses around 5/8" or so. Maneuvering a belt sander around those corners sounds like a very high risk operation for sure.

Thanks again for all the feedback and suggestions. I'll report back later today/tomorrow with some in process results!

[Kevin K.]

In my experience a belt sander is harder to control than a random orbit sander.

Agreed. Keith strikes me as one that could pick up on using the belt sander rapidly. No matter which piece of equipment he chooses, he just needs to knock down some of the high stuff so he can get back to the sanding block for the finish cutting. The sanding block John suggested earlier in the thread would be a good choice for this job. And a more progressive cut, start with 40 grit and then progress to finer grits. I'm speaking from experience on my "Archers" from last year, there was a ton of block sanding required to get the translam end grain smooth. Like Keith, I started with 80 grit and wore myself out pretty fast.

Keith, do you have a local automotive paint supply store anywhere near? They would probably carry the 2-3/4" sandpaper in a variety of grits and the block sander. Most body shops use this for cutting bondo on car repairs. If not, Amazon is always an option if you are in a hurry.

[KEtheredge87]

Hey Kevin, I think there is an automotive paint shop nearby. No website though... Sounds like you're suggesting I belt sand to knock down the high spots then switch back to the block sanding approach? If I took this multiple tool approach, I would probably change my belt sander approach from the Hitachi to the Black and Decker and sacrifice the variable speed option. That would let me distribute the budget a bit more and get some of the other block sanding tools.

If I didn't go with the block sander, my plan was to belt sand with lowest variable speed and 120 grit until things are evened out, then switch to the random orbit sander with that backer pad and go up to 180 or 220.

So many ways to get the job done!

[Kevin K.]

The Black and Decker should work fine Keith. Variable speed would be nice but it's not a must have for this job. Run the sander at a 30 or 45 degree angle to the translams, this will help prevent gouging. And yes, it's back to the good ole block sander for most of the finish cutting. You're just trying to get everything leveled back out, once you have done that with the belt sander and blocks, you could switch over to the random orbit sander to remove some of the coarser grain cuts and get it baby's butt smooth.

[KEtheredge87]

Thanks Kevin! I'm assuming your 30 - 45 degree comment means to angle the sander in relation to the grain layers, not to hold it "nose down" so that the sanding is happening on the front roller instead of the base plate. I'll go pick up the B&D model during lunch and grab some coarser grit belts. If I can drop in on the automotive paint shop, I'll look for a flexible sanding bar so I can follow the radius of the cabinets instead of dealing with a small contact patch when a rigid sanding block moves over a curved surface.

Also, I see the forum software finally got with the times and realized that butt isn't a "bad word". Hooray for no more b*u*t*t* spellings!