Joinery and Assembly Patterns

Discussion in 'DIY Speakers and Subwoofers' started by HopefulFred, Jun 21, 2013.

  1. Most of the speakers use those handy CNC flatpacks. The rabbett joint seems to make the whole process pretty well dummy-proof. I'm building my own box from scratch, and have a few questions. (Because I have never built so much as a bird house from scratch)

    I feel comfortable with butt joints because I know how to measure for them. I'm sure that I could work out how to do the rabbett joints, but then I would have to go buy new saw blades, and while assembly would be easier, I don't think it would actually improve my end results.

    I have a brad nailer, but I wasn't planning to use it. I have four long clamps, and plenty of scrap wood and such, but no fancy corner clamps or anything like that. I could use screws, but I don't see the point.

    I've received my baffle for the Cheap Thrill, and it is the full height and width of the cabinet already. Here's my plan for cutting and assembly, which I think is generalizable to any cabinet. I hope someone can tell me if I'm making this harder than it should be or doing it in some way that will likely compromise my results (either aesthetically or functionally).

    I'll cut the back the same size as the baffle. The two side pieces will be equal to the final depth minus the thickness of both the front and the back. I will also cut the sides short (by the thickness of the top and bottom) so that the top and bottom fit between the front and back, but against the ends of the side pieces. That way, I can clamp the top, bottom, and sides together first and then apply the front and back and bracing to that part of the cabinet. Does that make sense? Is there a better or simpler way? Please correct me where I'm wrong here.

  2. You're on the money.

    A tip. Set your table saw fence to the right width for the sides top and bottom and run them all through at once. Resetting the fence is a sure way to end up with slightly uneven cuts. Also, you could make the rear panel an 1/8th of an inch to large all around. Then once its glued up and looks like a box, just run a flush trim bit around it with the router. It'll leave a very smooth edge this way.
  3. Hey Fred, Dave here.

    I also have the Cheap Thrills kit, but I have not yet built my cab. The only thing I own is a jig saw, and after failing to come up with a better idea, I'm going to approach Lowes or Home Depot and see if they will cut the wood to spec.

    Can you detail what you used, type of wood, size, and exact dimensions you came up with? Also, do you have any tips for me? Things to avoid, that sort of thing? Thanks.
  4. Hey Dave,

    Check with Erich and see if he has any of the 2.5 ft^3 flat packs for the Karma 15. Buy the flat pack with a Karma 15 front baffle and you should be good to go. I checked the dimensions for the Karma 15 woofer (a Celestionn TF1525) and it appears to match the buyout Celsestion used in the Cheap Thrills. Buy some Titebond II glue and some masking tape to hold things together while the glue dries and you can have those bad boys assembled in no time! ;)

  5. I've checked with Erich before on this. Believe me, if there were a 2.5 cuft flatpack, I'd jump on that in a minute! I used a 1.0 cuft flatpack for my Fusion 10 Pure and they are fantastic. There is a 2.0 flatpack, but the dimensions are for the 12" sized woofs, I think at 14" wide, and my baffle requires 17" wide.

    I think the reason there is no flatpack for the 15" or so designs is that you can't cut one from a single piece of MDF, which drives the costs way up. The other problem is shipping weight and the size of the package also drove the costs up.

    At the time the Cheap Thrills was available, Erich said he would need something like 40 orders to make it economically feasible, but that never happened and no 2.5 cuft flatpack was ever available.
  6. Ahhh, OK. Never mind. :-[

    I was just going off the "Speaker Notes" section in the Karma 15 listing. I guess Erich should remove the reference to the Karma 15 flat pack....

  7. You know Mike, you're right. That note is definitely referring to a 2.5 flat pack. Maybe he had one once upon a time, but there is not one listed on the DIY SG site for flat pack, and PE does not have one.

    On PE's site I did find a birch 2.5 flat pack for a trapezoid PA enclosure, but it has been out of stock for a month, and when I looked at it closely, it looks like it has about 2 inches of overhang in the front, making that a deal breaker for me, since I have no way to cleanly cut those two inches out.
  8. Rather than cut the overhang off, bring the baffle forward (just run some wood square dowel around inside the front, very easy to do). You end up with a slightly higher volume too.
  9. Hey Dave, I'll add the images here for what I used, but you may not find it super-useful. Since I was building three (is that what you're doing?), I organized my cuts to minimize waste for three, not two. I was able to get everything I needed out of 2 sheets of MDF. The design I started with included curved braces, similar to what Erich sells in the flat packs, but I found they were not easy to cut. So I just made posts that I glued in. The good news is that two sheets MDF will be plenty for up to three cabinets, so your materials cost is fixed there - and you'll have plenty of scrap if you mess one or two panels up. Note, however, that I made no allowance for a double baffle: I assembled mine with the provided baffle and five panels I cut. Also - the baffle I received was not exactly the dimensions advertised - mine were about an extra 1/2" wide, if I remember correctly - so they needed trimming after assembly, since I made my cutsheet and cuts based on the given numbers only.

    My success, such as it is, hinged on having a table saw and an extra set of hands. Even once I had the guy at the big box store cut down the sheets, they were large enough that they wouldn't balance on the table saw without help. Could I have had the guy cut them all to final dimensions? I doubt it. I was trying his patience as it was, and while the saw they use will make great 90 degree cuts, the measurement process is totally inadequate for anything resembling neat edges. It might be possible to get enough pieces all the same width, so that some panels can just hang over and you still get tight seems, but they won't be neat.

    I had them cut each full sheet two or three times, to get me 7 smaller panels that would fit into my VW. (label them for sanity!)


    Panels A B and C are backs (same as baffle)
    Panels D through J are sides
    Panels K through P are tops/bottoms

    If you don't have a table saw, repeatable cuts to make all the panels match is very tough. You'd need a fine toothed blade and a good fence to use with a circular saw, at a minimum in my opinion. The router is a great help, and basically required if you want neat corners - I don't know how you could neaten them without it. The clamps of course are useful, but like Mike said, if the edges are good, a little tape will hold them together.

    I have a few more posts and pictures relevant in my theater build thread, starting here: The active work on them continued through most of July, with a good set of tips and such in this post, as it all came together:
  10. LOL! You don't know the lack of skill with whom you are dealing! Your advice reminds me of when I was racing motocross and the Japanese instruction manual told me I could repair the engine by "removing the engine from the frame and dis-assemble the motor." Great. :'(

    Still, given a choice, I would still prefer a flatpack, and I'm willing to try out that "wood square dowel" thing if I can figure it out. I was assuming that because of the CNC cut, the front panel would have to fit into a pre-cut daedo, and therefore couldn't be moved. Still no hurry on that, as PE continues to list the flat pack on back order. I need to give them a call to see what's up.
  12. Take your time and visualize it all coming together one board at a time. You can do it - but measure twice, cut once. And you'll need to be very careful with setting up fences to run your saw along to ensure you get straight edges.
  13. Fred, your Once and Future thread has the pic I have been looking for.


    Someone named Mr. Tim told you in the next post not to change a thing, then he suggested you change it! I think he wanted you to put the front and back "inside" the frame, rather than cover the exterior. What did you do?

    Your measurements are also strange to me, since the Erich baffle is exactly 17x26, but you made your front/rear panels 17.25. Comment? I think you said your baffle was 17.25, if that's true I am with the program on your specs, so far.

    And lastly, you said in your Once and Future thread that MDF comes in the size of 49x97, but Lowes lists it as 48x96. Comment?

    Finally, my cut sheet. This is why I thought I could have Lowes cut it, because they will only need to do 5 cuts on sheet one, and 5 cuts on Sheet 2. BTW I modified the design to make it 4" taller (from 26 to 30), to get the drivers closer to ear level.
  14. If you're going to try and have someplace like Lowes or Home Depot cut it, then you are going to want to be there while they do it. It's very hit or miss on the accuracy of their cuts depending on who does them. Also, you might call Home Depot and see what they can do just to compare. In my area Lowes can't cut anything more than .5" thick and you have to track down the teenager they've hired to run the saw, but Home Depot will cut pretty much anything they sell and they guy they have doing the cutting is a master carpenter. I tend to stick to Lowes for the military discount, but for obvious reasons I go to Home Depot when I need cut lumber. I've also found that approaching cabinet guys on job sites I pass about maybe doing the occasional side job for me and they've all been very receptive. If you play your cards right, you might be able to find someone with good skills that will work for beer and a few bucks as long as you buy the materials.
  15. Wow Iron Camel, you nailed it! I made a trip to Lowes today. My comments are in blue.

    quote author=IronCamel link=topic=243.msg3131#msg3131 date=1389766429]
    If you're going to try and have someplace like Lowes or Home Depot cut it, then you are going to want to be there while they do it. It's very hit or miss on the accuracy of their cuts depending on who does them.
    I talked to the guy who does the cuts. He promised me accuracy to THREE EIGHTHS of an inch! Man, I can do that with my jig saw! ;D He was actually very helpful, and he went on to explain that their saw has been around for 20 years, and he showed me the tags where the equipment has been repaired twice in the last three weeks.

    Also, you might call Home Depot and see what they can do just to compare.
    The HomeDepot has a reputation for having lower quality MDF (feedback on the web site), and it does not cut well (fuzzy edges). For that reason I ruled out HD. I examined the Lowes MDF and it was marked "Premium Quality", although I realize that may just be marketing. The edges were very sharp and consistent.

    FYI, a sheet of MDF is indeed 49x97 inches, as marked on the material, even though the web site says 48x96.

    In my area Lowes can't cut anything more than .5" thick and you have to track down the teenager they've hired to run the saw,
    In our Lowes, there are very experienced people on the floor who usually give expert level advice on projects and material, and at our Lowes, they cut anything. I live in West Virginia, where getting a job at Lowes is a pretty desirable job! 8)

    but Home Depot will cut pretty much anything they sell and they guy they have doing the cutting is a master carpenter. I tend to stick to Lowes for the military discount, but for obvious reasons I go to Home Depot when I need cut lumber. I've also found that approaching cabinet guys on job sites I pass about maybe doing the occasional side job for me and they've all been very receptive. If you play your cards right, you might be able to find someone with good skills that will work for beer and a few bucks as long as you buy the materials.
    The Lowes guy referred me to a cabinet maker who was a few blocks away from the store. I drove right over there and talked with Rob of Rob's Cabinetry, a one-man shop. We made an appointment for me to bring the MDF to him next Monday, and he would make the cuts for me. :) (Dave does happy dance) Rob said he did not have time to make the speaker cabinets, but he was very nice and willing to help me out with the cuts. His equipment and skills are exactly what I was looking for. He has 30 years of experience.

    The 3/4 MDF from Lowes will be about $34 a sheet x2, and I although we didn't set a price, I'll pay Rob what he asks. He was a very straightforward man and helpful, and that's worth something.
  16. (note: I posted the following on the "Celestion 15" thread as well)

    After my attempts to find someone to cut boards for me for months, things are now going fast and I need some help to finalize my dimensions as the cut will be made tomorrow (Friday). The kit baffle is 26x17. The DIY website Notes says:

    In the beginning of this thread, Bill said he did his original box for this with a "2.0 cuft" enclosure, sealed. On the DIY Sound Group site, 2.5 is the minimum recommended.

    26x17x14 = 6188 inches. The converter I used says that translates into 3.5 cuft.

    Edited: I got my wood cut today, standard size 17x26x14. Thanks for all the help. :)
  17. Sorry I didn't get back to you the other day, but it looks like you're ready to get really moving. Good luck! Take your time and take plenty of pictures. :)

    For what it's worth, I stuck with my original design. I trimmed the baffle down to 17 exactly after I assembled the cabinet. With good straight cuts, I was confident that it didn't need much clamping pressure, so here's how I did it:

    Lay out the back on the work surface (wax papered floor or other surface you can get slue on without gluing your work to it). Arrange the top, bottom, and two sides nearby. Wipe all the edges to be sure the're not caked in dust, then test fit. Male sure you've got some braces handy as well. Go ahead and clamp it up so that you can figure out where the clamps will need to be to hold everything square. I think I used two clamps to squeeze the sides together - but I overlapped the clamp so that it was only squeezing to the same position as the top and back - just bringing everything flush. Then two more clamps to squeeze the top and bottom together around the sides. Position the braces inside to keep everything from falling in - particularly the sides. The first time I did it I needed two sets of hands, but I think the second and third I was able to do by myself. Once you've tried it once or twice, glue it up. I felt like the weight of the sides and top/bottom resting on the back was enough to secure it, but, maybe I went ahead and laid the baffle on it to help press it all together (not sure) - just make sure you don't accidentally glue the baffle on it yet.
  18. I take this back. I remember now that I was working on top of my table saw, and the edges og the cabinet hung over the edges of the table, so I was able to clamp the cabinet front to back as well.

    I don't have any pictures of that, but there's this picture, which shows how I let the clamp help to line up the various panels, to make the seems as smooth as possible.

  19. Your advice is timely! I have dry fitted one cab together, and now I am exactly where you are describing, figuring out how (what sequence) to glue it all together.

    The flat pack kit from Erich was glued two panels together at a time, but it was CNC cut with dado's and channels, so the parts didn't just fit, they matched! It sounds like you are advising I simultaneously glue 1)back 2)sides 3)top and bottom, and then dry fit the front, holding all the items with clamps.

    My cuts look fairly straight, but I won't be able to tell until the final gluing and clamping. It you have further suggestions, please offer. Also, as I look at your cut sheet, you have an awful lot of half circles in there. I can cut with a jig saw, do I need to make mine like that? And what is the purpose of the holes?
  20. The half-circles are actually the bracing. The half-circle part is the part you're going to throw away, the arch surrounding the half-circle is what you'll be using.
  21. That is the sequence I used - you've got it straight, based on what I had success with.

    The circular sections are what I was going to use for bracing. I skipped much of that, and added some scraps as posts. It worked out well for me that way. Here's a picture that shows some of it.

    ^^this one's probably the best (but I have a few other pictures). You can see two braces that connect from side to side, as well as connect the back. Then there's once of a similar shape, connecting top and bottom, also glued to the back. Then there is one post that connects baffle to back, and one from left to right.

    This next one shows the same pieces, but makes clearer that the horizontal pieces don't reach all the way to the baffle. I think there wasn't room for them, plus I used some small strips of scrap to glue into the vertical front corner, where the baffle glues to the sides. Those pieces can'e be seen assembled, but are laying out next to the other pieces in the last picture below. They were not long enough to reach top to bottom.



  22. I've been mulling over your pics, Fred. Mulling is what I do A LOT before I do anything. The one thing that scares me is gluing all the surfaces at the same time. I could glue a couple of sides at a time with the flat pack kit, so I had a lot of time to lines things up.

    Your internal bracing pattern looks a lot more sophisticated than what I will be able to do. Part of that reason is because I don't have the MDF scraps you had. When I had the original pieces cut, the guy cutting my stuff had just enough MDF to make the ONE panel I was lacking, so I didn't need that second sheet of 3/4" MDF. As a result, I have very few, small scraps to make my braces, but at least I only have $34 into the MDF. Without the scraps, that's why the dowel idea looks good to me.

    Here are a couple pics. The first is the box with my DIY baffle on top, the other is with both the front panels removed. I have a few pieces of duct tape holding it together.


  23. Those look pretty good to me. If you've got enough clamps (6 for me, I think), I think you're ready to glue. Of course, don't glue on the baffle(s) until you have the bracing worked out.

    I think if I were using dowels, I'd want two from left to right, one from front to back, and one from top to bottom.
  24. That helps. :)

    • Do I need to install the dowels at the same time I do the initial gluing?
    • Do I want to counter sink the dowels into the MDF maybe a quarter inch with a 1" hole?
    • Do I want the sides to "connect", or do I want some slight pressure?
    • Do I need to connect the dowels to each other, somehow?
    My guess is it would be pretty tough for me to be so precise drilling hold on opposite pieces of unbraced wood and expect everything to line up. I guess I could counter drill one side, then fit the other end somehow, like a clothes rod in a closet would connect ends.

    I am so spoiled with the flat pack kit being so well engineered and cut, and now I have to over think everything! BTW, I have four 24" clamps, and I think I'll need a couple of 36" clamps to do an entire speaker at once.

    Edited: I just picked up my two 36" clamps from Harbor Freight, $20 with a coupon, and they threw in a free multi-meter! :)
  25. I've seen others glue in bracing with sides all at once, but I didn't do that (for the horizontal post style brace - I did for the braces that connect several panels at least on one of the cabinets - I think I changed it up form one to the next). Cutting them close enough so that they barely squeeze in is tough. I spent more than a couple minutes shaving off fine fractions until they would just barely squeeze in. Alternatively, you might glue them with lots of glue and lots of clamping pressure, but then the glue is under tension, trying to hold it together - I wouldn't want to do that.

    The braces I used for my custom sub cabinets were screwed through the sides as well as glued. That was a more fool-proof approach, but required significant filling and finish work to hide. I also had to buy a countersinking drill bit.

    So, to answer your questions (from my perspective, limited as it is)
    1 - no, but you might find it simpler - depending on your patience for fiddling with them later and your number of clamps
    2 - no, either glue or screws would be plenty without a recess
    3 - they should, IMO, fit and stay put without any fastening, but be glued for surety
    4 - it's best if you can connect the braces in the case of high pressure (where there may be more panel flex) applications, like subs. While there may be a benefit for doing it in these, I wouldn't worry about it.

Share This Page