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

[Kevin K.]

Yes, you're assuming right. 30-45 degrees in relation to the grain but still keeping the base of the sander flat.

Hopefully you'll be able to acquire the flexible sanding block. Also, for the block sanding, an X-hatch pattern works well when sanding a large contoured surface like this. Same principle, sand at an angle in one direction and then sand again 180 degrees to that previous angle. You'll officially be ready to take care of your own fender bender's after these subwoofers are completed.

[Wolf]

Don't you mean 90 degrees sanding, not 180 degrees?
Later,
Wolf

[Kevin K.]

Don't you mean 90 degrees sanding, not 180 degrees?
Later,
Wolf

Yea, my bad. Sorry for any confusion there Keith.

[KEtheredge87]

Ohhh-Kaay. B&D "Dragster" belt sander acquired. Belts in 60, 80, and 120 grit acquired. Unfortunately my local auto shop didn't carry any block sanders longer than ~8-10 inches, so I wend to Eastwood.com and ordered their 17" contour flexible sanding board and 6 pieces of PSA sandpaper in 80, 120, 180, and 220 grit.

I think I've done enough spending for today! Thanks everyone for all the helpful suggestions!

Oh, and Kevin... I knew what you meant. Funny how the human mind works. I read 180 degrees, but knew you meant 90. Good to clarify for anyone else following along though!

[marvin]

A word of caution: When you see a great deal on sanding belts, don't buy more than you will use in couple of years. I once stocked up on belts that performed well, but after storing for several years, the belt glue seam fell apart after very little use. Fortunately, I only wasted a few old belts by then.

[KEtheredge87]

A word of caution: When you see a great deal on sanding belts, don't buy more than you will use in couple of years. I once stocked up on belts that performed well, but after storing for several years, the belt glue seam fell apart after very little use. Fortunately, I only wasted a few old belts by then.

Thanks Marvin. I only bought one ceramic belt in 60, 80, and 120 grit. At this point I'm only using the 120 grit belt as a slight control on the speed of material removal. If things continue to go well, I'll probably return the other two and keep the crappy 60 grit belt that came with the sander!

[KEtheredge87]

OK guys,

So far the belt sander has been working pretty well! I made sure to practice my technique on some scrap el cheapo plywood I had laying around to learn how it was going to behave. I successfully sanded the sides and top of the first cabinet to 120 grit with the belt sander! I forgot how smooth 120 grit really is... not too shabby. I didn't see any gouges, and I managed to erase the router plunge marks that I had made in the top of that cabinet too! I used the random orbit sander with a foam backer pad to sand the curves in the corners. I got as much glue out of there as I could without feeling like I was going to start getting things too terribly uneven. I expect a little bit of uneven-ness since my layers weren't stacked with the utmost precision, but you won't see it or feel it unless you're really looking for it. If there's any glue left, I'll get it by hand with some small sandpaper bits as I work up to 180 or 220 grit.

Tomorrow I will set the second cabinet up and start sanding it smooth. I'll also start filling holes with timbermate so they will be smoothed out when I do my finish sanding. I need to get all this done before I cut my baffles to fit. Can't have any of those pieces sticking out or sunken in! The pictures below show my short table setup so I can use the belt sander and a good height for control. The middle picture is with all the pencil marks to show high and low spots, and the right picture is the best "post-sanding" picture I took. No more wood glue yellow everywhere!



Oh, I also made a John Hollander inspired small connector between my braces as a trial run. I think I like it! The picture shows one bit of dowel rod cut to fit between the other dowels. This piece is so tight I had to tap it into place with a lightweight hammer. I don't really want it that tight, since I don't want to put my braces into unnecessary tension before vibration loading gets added to the mix. I'll adjust that one and make the others slightly shorter as I go on.

[marvin]

Those are looking mighty fine!

[Kevin K.]

It's amazing how much better the translams look once sanded nice and clean, huh. Wait until you hit em with the finish.

Glad the belt sander is working out for you, I was confident you would pick up on it pretty quick and from the looks of that last picture, you're a natural with it. I like how you used the pencil marks to check your work, we used to do that when building patterns by hand for the thermoforming. From the looks of it, all you are really going to need the sanding block for is to smooth out the grit marks. Keep up the great work Keith!

[tomzarbo]

Yikes! The rough sanding came out nice! I like it a lot. You're going to force me to try a translam something or other very soon!
Nice work with the dowel connector thing too.
Please, get these done in time for MWAF!

TomZ

[KEtheredge87]

Thanks Marvin, Kevin, and Tom!

I had some more adventures with the belt sander today. I went after the second cabinet to clean it up and quickly realized I was going to need my 80 grit belt. Guess I wasn't as careful wiping up glue squeeze out on this one! I got it all cleaned up with the 80 grit belt, then smoothed it a bit further with the 120 grit belt. Along the way I let the inner engineer get the better of me and I decided to field strip the belt sander because I wasn't convinced it was collecting dust anymore! That took longer than I thought since I actually pulled the motor shaft forward and slipped the brushes off the commutator (oops)!

I also went ahead and added a full compliment of John Hollander style brace...well...uhh...braces These are glued and screwed with #6 1-5/8" screws and titebond II. I'll go back soon and make sure this extra volume gets accounted for in the bassbox calculations, but I doubt I'll see a major impact.

Tom, I really hope I can finish these in time for MWAF. I'm feeling good about it so far, just need some more concerted time to get work done. My finish sanding stuff from Eastwood should arrive by Wednesday, then I'll feel comfortable fitting the baffles in and getting them flush fit before final gluing. That leaves me some time to do the interior epoxy coating and put my veneer on the baffles.

On the topic of MWAF... do people usually show up and enter subwoofers only into the contests? I'm sure the open unlimited class would be a decent place for these, but who listens to just subwoofers on their own?

[Kevin K.]

I'll go back soon and make sure this extra volume gets accounted for in the bassbox calculations, but I doubt I'll see a major impact.

You're not going to need to worry about the additional braces and how they would impact the tuning of the PR's if that is what you are referring to. These boxes should be almost indestructible now with the additional dowels. Knuckle raps could leave bruises.

On the topic of MWAF... do people usually show up and enter subwoofers only into the contests? I'm sure the open unlimited class would be a decent place for these, but who listens to just subwoofers on their own?

You really need everything required for full range, not sure how the judges could judge just subs. You can still bring em, there's a good chance we'll have a little time to play around after the contest with the number of entries we have so far. I would love to hear them with the arrays and I could have a different DSP setting already programmed for the arrays to let your subs do all the heavy lifting.

[KEtheredge87]

Alright guys, tonight my inner five year old came out and did some finger painting on the cabinets. I'm using Maple / Beech / Pine colored Timbermate wood filler to fill any and all voids uncovered in the building process. I really hated to do that after all the belt sanding work, but I knew it was one of those "gets worse before it gets better" deals. I may take some fine grit sandpaper and knock most of the high stuff down by hand before my flexible sanding block shows up on Wednesday, then I can start getting the rest of this stuff off the cabinets and get back to clean!

Also tonight, I cut my veneer pieces into appropriately sized sheets and set them in the garage to acclimate. I have okume veneer as backer, and quartersawn walnut veneer for the snazzy outward facing sides. I'm planning to run the quartersawn pattern horizontally to mesh well with the plywood layers. Some dark stain on the walnut pieces should really make this pop!

Getting closer and closer to primetime!

[Wolf]

I think I woulda just Poly'd the tar out of them and not worried about veneer. Why cover up those beautiful layers?

Later,
Wolf

[AlexRivera]

I think I woulda just Poly'd the tar out of them and not worried about veneer. Why cover up those beautiful layers?

Later,
Wolf

Agreed, it'd be like making kitchen cabinets in walnut or mahogany wood and paint them in solid white....