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

[Kevin K.]

Not sure if you're kidding around or not. It might actually add a little character to the tops, not that they need it. Another thing to consider is that once they are cut off to match the top, they wont be a circle, they will be elliptical due to the slopes, could look cool.

[KEtheredge87]

Not sure if you're kidding around or not. It might actually add a little character to the tops, not that they need it. Another thing to consider is that once they are cut off to match the top, they wont be a circle, they will be elliptical due to the slopes, could look cool.

Oh, right... Hazards of the Internet and communication! I really like your idea. It's simple and would add a nice touch of class while fixing a goof up. I also had the elliptical look in mind after thinking about it. Going this way will save a boat load of time, money, and rework effort. Thanks for always having a great solution! 👌

[Wolf]

Tip- use a hacksaw blade (sans handle) to cut the dowel excess off, and then sand smooth.

Later,
Wolf

[KEtheredge87]

Tip- use a hacksaw blade (sans handle) to cut the dowel excess off, and then sand smooth.

Later,
Wolf

Thanks Ben, I like your idea for flush cutting dowels. I have a more complicated version already in mind, building a router sled setup to curve the whole top surface. This was in the plan already (I didn't just invent the rube goldberg version of flush cutting a dowel!). If the box were designed to be flat in this spot, your method is spot-on.

[KEtheredge87]

Mid-day update for you all. I've completed the router cutouts on all pieces to give me my mid-way shape. I did end up switching to a straight flush cutter that I had to finish the pieces. Somehow that spiral bit just wasn't performing up to snuff without concerns of burning, so I'll have to send it off for a sharpening. I figure the spiral action ensures the entire cutter surface contacts the plywood glue, where the straight cutter only ends up with some bands of more dull spots.



At any rate, I'll soon need to curve the top piece, but first I needed to go back to my CAD model and re-work a few things. I wanted to better plan which holes to drill in the top 7 layers of each piece to make sure I left a good looking pattern for the walnut dowel idea. Additionally, I remembered my original model was made off idealized assumptions of 3/4" material being exactly 3/4", so I wanted to adjust the material thickness to match the 0.7135" and 0.49" materials I actually had. I knew this was going to mess up the easy dowel pin installation for the structural dowels in the sides of the subwoofers, but I wasn't sure just how much. Judging by the look of things alone, I'll have to glue these up one layer at a time and make sure I custom cut each dowel pin to leave enough of a hole for the next layer to firmly dowel in against. Obviously it won't do me any good to have a dowel pin finish flush with the layer I'm gluing up if I can't continue doweling in the next layer on top!



At this point I am getting very close to the glue up stage. Just a few more evenings paying close attention to what I am doing and we should be there.

[scottvalentin]

Impressive progress and nicely done especially considering the router bit challenges! Keep up the good work!

[KEtheredge87]

Impressive progress and nicely done especially considering the router bit challenges! Keep up the good work!

Thanks Scott! My patience was being tested daily with the whole process of preparing each individual part! Now I can focus on making some baffles and starting the glue-up process.

[KEtheredge87]

Happy Memorial Day Everyone!

I hope you've all had a good time with your friends and families, enjoyed a few cold ones, and got to spend some quality time in the workshop. I am happy to report I've spend plenty of time in the garage this weekend, and have some decent progress to show for it. At last, glue up has begun! I've got the base layers glued together, and two of the wall pieces glued up on one cabinet. I can tell already that I'll be hitting up Harbor Freight for some more 24" clamps. I've only got 3 or 4 in that size, and it turns out I used 10 clamps on just one subwoofer. It's too bad HF only give me 20% off one item instead of my whole order... buying 20 clamps would be expensive, even if they're only $6 each. maybe I just need 20 friends to each buy one clamp with a coupon .



While I sort out my clamp shortage and speed toward MWAF (or decide to be patient while building two subwoofers ), I've started making some 1.25" MDF panel glue-ups from sheets of 3/4" and 1/2" MDF. These will be used to make the front and rear baffles of the subwoofer, which will be veneered with quartersawn walnut on the outside, and okume backer veneer on the inside. I'm told this is a good thing to do for "panel balance", but it does kinda seem like a way for the veneer guys to make an extra $30 off me... oh well... can't put a price on quality sometimes.

My current worry on the baffles is how to actually install them and get them seated right. My templates for the wall pieces have a 1/4" radius curve built into them (unavoidable due to that surface being an inside corner with a 1/2" router bit). I'm not going to kid myself and assume that each part of my walls will stack 100% in line with the previous one, so there's going to be some high spots and low spots along that joint line. I'm really wanting to make sure the baffle seats flush with the outside of the cabinets. Sitting proud of the cabinets won't do (since the front will be veneered prior to install), and sitting recessed in the cabinets won't look right either. I guess the only way to make this work is to sneak up on the flush flt by sanding away a little material from the baffle at a time.

If anyone's got thoughts on how to address the baffle install when it is time, I'm happy to hear them! Thanks for any help!

[tomzarbo]

Keith,
If it were me, I'd consider using PL Premium construction adhesive to bond the baffle to the enclosure. It has gap-filling properties and bonds good. I'd machine the baffle so that it sits flush or just the tiniest smidge inset, then apply a generous amount of the PL adhesive, then push in flush and clamp. It takes a bit longer to cure, but I think it would hold fantastic. I think Bill Fitzmaurice recommends it for his horn subwoofer builds because of the gap filling qualities.
I used it on my Tenacious Bass 6 subwoofer on the top and the vent assembly because I wanted some gap-filling, but no squeeze out. Worked great.

Just a thought.

BTW, looks fantastic!

TomZ

[fpitas]

Another vote for PL Premium. It's kind of thick, so when I've bonded large panels together I've used a spreader intended for floor tile adhesive to get a uniform thickness of PL.

[KEtheredge87]

If it were me, I'd consider using PL Premium construction adhesive...

Another vote for PL Premium...

Thanks Tom and Francis (assuming your name is the signature line ). I've never used PL premium before, but I'm willing to give it a try. I did some quick research online as well as on a few "Pro" and "Anti" PL Premium tech talk threads to get a feel for it. Having Bill Fitzmaurice's stamp of approval was really all anyone would ever need to say the stuff is legit. The flipside there is a thread from Lunchmoney where he had some horrid experience with the stuff never curing up and just being crumbly and flaky that was never really explained.

The Loctite / Henkel bunch dont make a big deal about this stuff having gap filling properties. At least, they don't talk about it expanding like Gorilla Glue polyurethane glue does... I assume the stuff isn't meant to foam up and seal gaps? Maybe it's more that it ends up being applied as a thick bead and will naturally deal with some surface irregularities? Also... how do you not get any squeeze-out with this stuff? I'd think there has to be something there, and everyone says this is a royal pain to deal with from a "gets everywhere and all over everything" perspective. The last thing I'd want is for some of this stuff to squeeze out to the outside of the cabinet and stain the plywood (or equally worse, the walnut veneer that'll be in place). I'm thinking the veneer happens before gluing this panel in place, since I'm not sure how to keep the heat lock veneer glue OFF the plywood part of the cabinet and then trim it nice and flush.

Anyway... I'm starting to ramble. Thanks again for the great ideas and help along the way!

[fpitas]

I'll try to address some of your questions on PL. I've never had the "No cure" experience, although I've used at least 100 tubes of the stuff over the years, even in winter when the humidity was very low indoors. Maybe Lunchmoney had a bad batch?

The gap filling is because the stuff is thick, and it foams a bit, so the strength under those conditions is lower than normal. It's still plenty strong. I've used PL to join MDF boards meeting at crazy angles for trapezoidal cabinets, and it filled in the gaps just fine. I wouldn't count on it filling more than maybe 1/4" of gap though.

I certainly do get squeeze out, although I tend to apply a lot (maybe more than I really need). The stuff has lots of surface tension, so the nature of the squeeze out is it tends to form a bead. If you let the bead dry about halfway (8 hours maybe) you can come back and trim it with a hobby knife etc. without making much of a mess.

As I said, the trick for large panels is to use an adhesive spreader. Just like wood glue, it works best if it's clamped while it dries.

Yes, it can be messy. You'll have to judge your particular job to see whether it may stain the work. If you get it on your skin and it dries, it takes a while to get it off.

Francis

[skatz]

For wood or veneer that you are worried about from the squeeze out perspective, you can put painters tape on the surface first, and it will be protected.

[KEtheredge87]

I'll try to address some of your questions on PL... I wouldn't count on it filling more than maybe 1/4" of gap though.

Thanks Francis, I appreciate the first-hand knowledge! I'm hoping to have a snug fit on my joints here, but I can tell it will require some amount of custom fitting. I'm stacking these wall layers up with 1/4" hardwood dowel pins bridging each layer, and most of them are stacking well... but occasionally one will be 1/16" off axis to the left or right. I'm trying NOT to artificially force them one way or the other while gluing up so that I don't induce the leaning behavior I am trying to avoid in the first place. I guess there's a limit to how exact I can be, even with aluminum templates and a router table. I'll have to sand those differences out, or risk a much more noticeable glue line facing forward on the cabinet! I can try to take a picture of that tonight if it isn't all that clear what I mean. I'm concerned with the transition between the translam walls and the MDF/Veneer baffle, not so concerned for the translam outside wall surface. That'll obviously need to be sanded smooth.

For wood or veneer that you are worried about from the squeeze out perspective, you can put painters tape on the surface first, and it will be protected.

Of course! Thanks for bringing me back to reality, skatz. It is amazing how soon I forget the simple and obvious answer when worrying about something I've worked up to be super complex in my head.

[Kevin K.]

Keith, I used the PL Premium Adhesive on a part of my array build, suggested by members here on the board. Needed some gap filling properties and it worked great! You can control the squeeze out to an extent by where you apply it and how big of a bead you use. Try to favor one edge of the board, the side you aren't worried about squeeze out on. In your case, probably the inside edge so it will squeeze more towards the inside of your enclosure. It takes a little longer to dry but man the stuff is strong! Good luck.