DIY 2x12 Cab Building Advisory

Discussion in 'The Squawk Box' started by hepsen, May 6, 2017.

  1. hepsen

    hepsen Member

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    Hello everyone!

    I'm thinking about building a closed back 2x12" cab with an angled baffle / front grille on my own.
    The inspiring models are the Bogner 212C or the Friedman 212Ext for sure (probably worth their price but to much for me at this moment).

    Some specs are already clear: outer dimensions, 18-20mm birch plywood for top/buttom/sides, 12-15mm birch plywood for the back, 15mm birch plywood for the front, i do have speakers, i do have cables, i do have a jack, tolex/grille cloth/piping/filling to avoid standing waves/handles/feets is all no problem to purchase/order.

    My questions are more related to the construction itself:
    1. What is the better connection of the tops and sides? Using finger joints vs. screw plain top to sides?
    2. What is the best way to construct the angled front?
    I'm looking forward to your ideas and experiences!
     
  2. The_Nuge

    The_Nuge Senior Member

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    Hi!
    If you've got the tools to do finger joints, that's probably the best!
    I don't, so I glue and dowel mine like so:
    [​IMG]
    I actually glue the panels up first, using screws to clamp the joint. When the glue is set, I remove the screws, drill out the holes and dowel them!
    Works very well!
    For the front baffle, I'd probably build a "frame" on the inside of the cab, and bolt the baffle to that!
     
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  3. bilbarstow

    bilbarstow Premium Member

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    [​IMG] [​IMG]

    I can give you a little advice based on what I built, but I was completely winging it / self-designed based upon my own woodworking experience. (i.e., I didn't use any known audio parameters - it was an experiment). I would definitely advise finger-joints for strength, particularly if it will be moved a lot / gigging. I made mine out of yellow pine, but I have no intention of using it anywhere but at home - no handles or anything, as it stays put.

    Mine is actually a hybrid - a 10" speaker in a fully closed upper section and a 12" in a partially open back lower section. So I placed a horizontal baffle even with the slant. The slant and vertical baffles for the speakers were mounted to internal frames. I used t-nuts anchored into the baffles for the speaker mounting. But you can do the same thing with an open or fully closed cab, you don't need the horizontal baffle like I had, but should probably have some kind of structural connector between the front baffle and the rear panel (a post like seen in 4x12 cabs would be a good idea).

    [​IMG] [​IMG]

    What you are probably most interested in is how to "bend" the Grill cloth frame to define the slant front. You can use this same technique for your speaker baffle (using 1/2" ply ?), if you want it to be one piece. I used 1/4" ply (for the grill), and cut a V shaped groove in the back of the panel - wide and shallow, maybe a little more than 1/2 way through the panel. I then was able to bend it right at the groove to match the profile of the front of the cab. This gave me a very rigid frame that I was able to stretch the grill cloth over. Attached on the back with staples. Sprayed speaker baffles and the grill frame flat black. Attached the grill frame with heavy duty velcro.

    Mine is pretty heavy, because of the Pine and the extra internal bracing, but it is perfect for my uses. And the experiment was a total success, as it sounds great to my ears. The slanted 10" in the upper closed cab gives me a very punchy, tight sound aimed right at my ears, while the open back 12" helps to fill the room and provide a warmer balance.

    Building the slant was the biggest challenge, but it actually turned out to be fairly easy after a bit of thinking. Good luck with your build !
     
  4. hepsen

    hepsen Member

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    Thank you for charing your thoughts!

    Very nice work and interesting concept bilbarstow!

    I do not have the tools to do fingerjoints on my own. But here in the german black forest region are many carpentries located. Maybe one carpenter will do that job for me.

    I was thinking about using birch ply as it is not a heavy as pine, I guess. Here in Germany you usually get standard sizes in hardware stores: 6.5mm/.16", 9mm/.22", 12mm/.30", 15mm/.38", 18mm/.45", 21mm/.53".

    I opened my Marshall head to see what they use. For the sides they use 18mm(.45") + a frame of 21mm(.53") on the front to let it look like 40mm(1.01"). I guess Bogner, Friedman, Orange etc. use the same concept and sizes? What would you use for the baffle and back? Is .38" strong enough to stand speaker vibrations well?

    To realize the angled front I'm thinking about cutting the sides of the inner frame slightly angled and glue it to the side panels (measuring the whole lenght from top to buttom) with the angle facing backwards. But as far as I can imagine this will lead to several gaps in the consequence (see picture):
    • the top and buttom frames aren't angled as the sides so they will leave a gap that might be visible from the front and there will be no connection to the baffle
    • the baffle sides are not angled so they will leave a gap to the top and buttom panels
    IMG_20170507_113151.jpg

    How would you solve this? How do manufacturers solve this? Do they use an angled saw to match the frames and the baffle to the angle?
     
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  5. wizard1183

    wizard1183 Premium Member

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    Finger Joint is quite strong. Glue and nail it/screw it and you have something indestructible. It'll break everywhere and anywhere OTHER than at the joint. Want a stronger joint? Dove Tail. Want an even stronger joint? I'm sure someone has some potent reefer:laugh2::laugh2::laugh2:
     
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  6. The_Nuge

    The_Nuge Senior Member

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    You could route a channel into the housing and slide in the baffle before attaching the last side or top!
     
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  7. Soul Tramp

    Soul Tramp Speaker Snob MLP Vendor V.I.P. Member

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    An alternative way of joining would be to use dado joints. They are easy to cut and very strong if you add dowel pins.

    To eliminate the gap on the top & bottom baffle braces, simply cut the brace with the appropriate angle, and do the same with the top/bottom cuts on the baffle board.
     
  8. bilbarstow

    bilbarstow Premium Member

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    Hepsen,

    You actually COULD do finger joints (or dovetails, for that matter) with simple tools. Those joint techniques are many hundreds of years old, and can be cut with hand saws and chisels. All you really need is to mark them well and cut accurately. That being said, if you have access to a table saw, that is the easiest way. If you like, I can explain it to you in more detail or send pictures.

    For the speaker baffle, 15 mm may be strong enough for your application. Some cabinets have used lightweight baffles for good effect, as the baffle actually becomes part of the sound transmission (particularly older Fender amps). If you are going to make it a fully closed back cab, you might want to step up to 18 mm or 21 mm so that it is more rigid, as the internal sound pressure may make it oscillate too much.

    As far as your "gap" issue, I solved it by cutting my baffle edges at a complimentary angle, so that they fit flush to the top and bottom. Unlike your drawing, my bracing / framing was on the internal side of the cabinet, so that made measuring / cutting the angle a little easier. But you could do yours exactly as you have drawn it, and that gap won't really make much difference as long as you have them firmly fastened and there is a good "seal" formed by the connection of the baffle to the frame. You could additionally trim the edge of your frame to the complimentary angle so that the baffle is at least flush to the frame. This wouldn't be that difficult to to achieve, all you need is an angle protractor to copy the angle and transfer it to your table saw.

    I do a lot of amateur woodworking, and have a lot of books about cabinet making. Tools make things easier, but some of the coolest things have been made with simple hand tools. It's mostly about planning everything out first in detail, measuring well, and cutting accurately. I can give you advice if you'd like.
     
  9. hbucker

    hbucker Senior Member

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    Here is a photo of the back of my 212 cab with an angled front as you describe. It shows how they handled it, anyway.

    fwiw

    good luck

    [​IMG]
     
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  10. Mouse

    Mouse Senior Member

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    [​IMG]

    finger joined old pine with baltic birch baffle board. Imo this makes better sounding cab to my ears and far less heavier than completely built out of baltic birch plywood. i'm building this one these days and enjoying the project. Oh i almost forgot to order the piping :run:

    :cheers2:

    [​IMG]
     
  11. wizard1183

    wizard1183 Premium Member

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    Very nice! Never thought to use pine. I built my 4x12 with all Baltic birch. It's quite heavy lol though I don't move it around even though it's on casters.
     
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  12. Mouse

    Mouse Senior Member

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    Thanks!
    it's all about tone chasing, apparently the speaker alone without any box sounds umm haha a little bit odd. so any box will change the sound of the speaker. the thing with those companies in the 40-60's they used whatever the wood dealer had and it was cheap and strong enough. in my experience pine/spruce/fir (all sold as pine) will have this crisp but warm sound. birch is more like maple, accented open high midd, so in certain box it will sound very good and that's for me a high litre 4x12 box with G12M celestions which have not strong highs and have tremendous decibel fall beyond 5 kHz. with G12H30 or much of the alnico's is a bit on the edge for my ears, in that case i'll rather go with spruce and birch baffle. there is not magic about birch either, it's just in most cases makes a void free plywood, baltic birch is just like maple -cleaner wood to make void free plywood. i've built with mahogany, okume and maple plywood baffle with very nice results. i do like warmer sound of pine wood family and don't have roadies to move my cabinets. now and then i do play 4x12 and that's when i play venues with their backline, ''no problem i will bring my jtm45 head'' thing . Mine spine gets older and if you have problems with spine use spruce, fir and pine Haha :D


     
    Last edited: May 9, 2017
  13. LPV

    LPV Senior Member

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    Here's a 212 I built a while back out of some scraps. Sounds great. My son has it now.
    [​IMG]
     
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  14. hepsen

    hepsen Member

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    Wow, very nice work by everyone here!

    The calculated angle will be around 3 degrees. This will be difficult to cut very precisely to avoid the gaps. Most saws i've seen do have measures in 5 degree steps.

    Have you done a similar angle for the baffle as well? On top I'd set it back 5cm (appr. 2in) to the front and at the buttom 2cm (appr. 0.8in).

    Yesterday I spent some time in the depot store and let some birch ply slides cut. I bought different thicknesses for the different positions of some slides.
    When I came home I've contacted a friend who built some cabs by his own and also did lots of PA cabs as well. I told him what I've bought and he said immediately: wrong choice, it will sound thin and sterile.

    So I went back to the net and searched for the answer why I've chosen wrong thicknesses. The answer is: I miscalculated the transfer from Inch to Centimeters here... So 21mm thickness is not 1/2in. 21mm is instead appr. 0.82in. The conclusion is:
    I do now have 0.82in thick birch ply for the sides and top/buttom, I do have 0.59in thick birch ply for the back and 0.71in thick birch ply for the baffle, and 0.35in for the grill...

    What would you do now? Do you also think that thicker ply is going to make the cab less alive and let it sound thin and sterile?
     
    Last edited: May 13, 2017
  15. Mouse

    Mouse Senior Member

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    Marshall used approx. 12 mm (1/2'') birch plywood in their combos, heads and 2x12'' cabinets. 10 mm for baffle board 2x12''.
    21mm will make very heavy cab.
     
    Last edited: May 14, 2017
  16. Mouse

    Mouse Senior Member

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    Don't be bothered with gaps, use tolex or cloth to it's advantage. anyways many combos have free upper side of baffle. some have just partial frame on the down side to accomodate speakers to sit as low as possible, so your bet is - side frames.
    It can be done with router or industrial table saw but i wouldn't bother at all or waste any time on it because grill cloth and tolex are enough to fill any gap at those angles. Marshall and other have gaps, not to mention frame piping, it's not only visual thing for good look but also to fill the gaps, nothings there dead on line nor it could be once the grill cloth is introduced, nor is acoustically recommended to build solid dead joint of baffle board with music production device () use your time/concentration or pro job to make dovetail or finger joint, this makes good stability of cab and decades of enjoyment once its done good. plenty of videos on yt how to do it with various hand and tool techniques. if it stays only home it doesn't matter, glue it and screw.
     
    Last edited: May 14, 2017
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  17. hepsen

    hepsen Member

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    Thank you for your ideas, Mouse.
    I do have a free day and already began watching videos on making finger joints with a hand router on yt :)

    On some pictures of the inside of the Bogner (and other) cabs I've seen wooden staffs in the edges of the side panels. Do they use them to stabalize the finger joint construction even more? (I do not mean the frame where the back panel is screwed to) Are they neccessary?
     
  18. Alligatorbling

    Alligatorbling ★AstroCat★ Premium Member MLP Vendor V.I.P. Member

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    heres my vertical 2x12 i built with my dad some years ago

    [​IMG]

    [​IMG]
     
  19. wizard1183

    wizard1183 Premium Member

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    You forgot the tolex:laugh2:
     
  20. JCM900MkIII

    JCM900MkIII Senior Member

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    Simple T Bevel and plane job.
    Be carefull with the "end wood". It's easy to chip the corners.

    You need a very sharp plane. And always work towards the middle of the board.
     

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