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Cabinet construction

Discussion in 'Shock Brother's DIY Amps' started by ReverendRevolver, Feb 26, 2021.

  1. ReverendRevolver

    ReverendRevolver Tele-Afflicted

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    I haven't looked into building a speaker cabinet for several years, then started again recently.
    The information available now seems scattered and less focused that back then (odd given how much bigger the internet has gotten)
    But I can't find as consistent of answers regarding materials, wiring, and general construction. Really confusing.

    I plan on building a cab to pair with the Frenzel 525deluxe plus I'll be receiving next month. Its wired with a fenderish channel that's allegedly akin to a a bigger deluxe with a 5f6a tonestack, and a marshallish channel that's supposed to be plexi-adjascent. This will be my "Marshall equivalent " and I ordered the jcm800 preamp to replace the "bright" mode on that channel so I have gainier options. Also el34s. I have a big tweed, I need more Marshall type sounds here.

    I do not have a cab for it, and plan on building one. I do have 2 Bell&Howell 12" cabinets with ancient and semi valuable Jensen's, so I might buy a 12 and a wiring harness as a temporary solution.

    But I wanted information on cab construction. I was considering a 2×10 with one of the various greenback equivalent 10s that are out there.

    I have 0 closed back cabs anymore, so I was considering leaning that direction.
    I dont honestly know if I should wire parallel or series, and cant find a consistent answer on which is better or even differences in sound.
    I like working with pine more than ply, but again have no idea what differences it makes. Lastly, I'm okish with woodworking. I can make a finger jointed square out of pine common board. I certainly am not able to dovetail or be fancy like that. But I've got no idea how to cut, or attach the baffle in the most ideal way, what sonic differences it makes, or even what to use for the baffle or back.

    I recall all these things mattering 10+ years ago when I was half planning a smaller cab for my SF bassman.
    I have feet, handle, grill cloth already, so my main cost will be speakers. Woods not too pricey (and I have some pine and junk ply around) I'll need glue, tolex and corner covers. This puts total project in the price range of a junk used 4×12 with questionable speakers, with about a days work, not counting drying times. (Which is why I'm building a more optimal cab instead of rolling the dice on a $150ish 4×12 when I'm under $200 with better speakers).

    So, can someone school me on materials, wiring, and construction and how it impacts sound?
     
  2. goldguitarguy

    goldguitarguy Tele-Meister

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    I build all my cabs from marine grade birch plywood. I use 3/4” for the box, 1/2” for the baffle and 1/8” or 3/16” for back panels. It’s void free, more stable, machines very well and as a plus has zero knots to stabilize unlike pine. If you purchase the wood and then shelf the project for a season or two pine can warp and twist if not stored correctly. Plywood will not, it also won’t crack or get checking in the ends. Only down side is it’s harder on tooling and creates more dust.

    Finger joint, dovetail and dowels/biscuits are preferred methods for joining. Most builders staple their low end cabs nowadays and use press board material to lower costs. Anything is an improvement over that...

    I would base your wiring off of what impedance your amp requires and what impedance of speakers you have. Not sound. The difference would be negligible if in fact there is any. I would recommend a wiring harness that allows and impedance selection by switch from series to parallel to make it more versatile.

    As for construction details I would pick what type of cab you want to make then search for plans. If you can’t find exactly what you are looking for, just modify the dimensions of one you like. Again, like the wiring, the baffle attachment difference will be negligible as long as there is sufficient contact between the baffle and cabinet. I would be more concerned about the speaker if it’s front loading or rear loading and then would base my design from that.
     
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  3. Paul-T

    Paul-T Tele-Holic

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    I'll start off with: wiring makes no difference. Simply wire for the impedance you want.

    Depending on what you have, I'm sure 3/4 pine for the cabinet and 1/2 or 5/8 ply for the baffle would be great. FInger joints are perfect. Ply box is more British and more weight.
     
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  4. goldguitarguy

    goldguitarguy Tele-Meister

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    I use a dowel joint for all my personal cabs and heads. If a customer wants finger joint I’ll do it but I’ve never heard any difference between any joint method and dowel is the simplest. Two cabs and a head I built. One Bassman, a 4x10 for a hot rod Deville, and a big box marshall... C933F1DE-9559-45D1-B510-5E0F95CF2FC1.png 17D09B28-F2B3-405A-845D-FC9776F67649.png 70C73CE6-9FDD-43C8-AE35-33D6E6A47323.png CB8913DD-FB06-44B1-BEA3-22A9AFCDF150.png
     
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  5. schmee

    schmee Doctor of Teleocity

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    My two cents:
    -Pine is great because it's light weight. (northern pine)
    -You can just glue and screw the corners if you want. I have used serrated nails (meant for nailing wood panels on walls, they come in colors. Thin long and dont loosen.) I pre drill each hole smaller than the nail.
    -Fingerjoints or other interlocking are stronger and will allow you to drop it off the back of your pickup truck. But you may not need it.
    -Stick with 1/2 or 5/8 speaker baffle. I prefer dense particle board like Home Depot sells.
    -Closed back cab will give you a more compressed sound. Not my thing that much but with an EL34 amp it may be a good thing.
    -Ply for the back is fine, not too thin or it may vibrate too much. I'd use void free 1/2". But 3/8 could work.
    -Attach the speaker baffle to 3/4 x 3/4 Pine cleats.
    -Parallel wiring allows you to not damage your amp if one speaker blows.

    If not dovetailing or etc then I do this:
    [​IMG]
     
  6. sds1

    sds1 Tele-Afflicted

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    All I wanted to add is that Lowes sells Select Pine from New Zealand and it is 99.9% knot-free and no cupping/twisting and this is a big damn deal IMO, there is nothing worse than a box than wobbles when it's done, or that you can't square all 4 corners on glue-up because the board isn't straight.

    Also never cool when a knot falls out lol.

    I hate common pine for all the same reasons a @goldguitarguy , I just get around the problem by buying higher quality pine boards. ;)

    PS They are about 2X the cost of a regular pine board.
     
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  7. schmee

    schmee Doctor of Teleocity

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    It's all a lot of work by the time you are done and covered with Tolex etc. You can probably buy a very nice one from JD Newell for $250 ready to use.
    He did a great Tremolux blonde 2x10 cab for me once.
     
  8. ReverendRevolver

    ReverendRevolver Tele-Afflicted

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    Thanks for the input.

    I'll be sketching up plans while I shop around looking at used stuff.
    I do have an empty cab for a 15 (used to be either a bass amp or a PA, has tweeter in it) and the aforementioned B&H boxes, so I definitely can have a functioning cabinet for the cost of a speaker. It's just a temporary solution for sure, but it gives me time to plan.
     
  9. Lowerleftcoast

    Lowerleftcoast Friend of Leo's

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    Since you have the ability to do a finger joint, do it. You will know the box is strong.
    If you have the materials just use what you have. The sound difference will be negligible. Keep in mind, plywood can have voids which can buzz.

    For a closed back design, the back should be 3/4 inch. A well braced thinner material can be used. The baffle should be at least 1/2 inch. 3/4 inch is preferred. The front and/or back panels can be glued in depending on how the grill and speakers are attached. Or, both can be screwed on. It is your choice. (Open back designs can use thinner baffle and back.)

    A 2x10 cab should have a brace from the front baffle to the to the back panel. It can be a 1x2 or even 1x1 fairly close to the center to stabilize the large panels. If weight is not a factor the 10 inch discs cut from the baffle can be glued to the inside back panel to make it more substantial.

    Cheap and easy, glue and screw some 1x as a cleat for mounting the baffle and back. A fancier front edge, like Marshall and Orange do on their cabs, can be fabricated if you want to go through the hassle.

    Considerations... you need to decide whether the grill cloth will be attached to the baffle or a separate board.

    This is my open back 2x10. You can see the cleats to attach front and back panels. This one happens to have a floating baffle design like the tweed era fender cabinets.

    IMG_20191126_112644x2.jpg IMG_20191203_160747x2.jpg
     
  10. Mark the Moose

    Mark the Moose Tele-Afflicted

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    You seem to have texturized the inside of the box with some kind of scalloping, can you talk bit bit the hows and whys?
     
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  11. Lowerleftcoast

    Lowerleftcoast Friend of Leo's

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    The how: rounded router bit on a hand guided router.

    The whys are two fold.
    One: I wanted to lighten the cabinet 'cause I don't like to carry anything anymore and I don't have a roadie.

    And B: I play African drums that have a similar carved interior to "diffuse the high frequencies". It seems to work in the drums. I was hoping to diffuse the highs reflected in the back of the cabinet. I am not going to bother to compare a copy cabinet without the carving so it will forever be a mystery as to if the carving is a auditory success.

    The cabinet is light and sounds good. It looks good too. So all is good. FYI the interior of the back panels are also routed.

    IMG_20191207_090444x2.jpg
     
  12. RollingBender

    RollingBender Tele-Afflicted

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    @Lowerleftcoast ...How much would you guess was removed? Maybe 10-20%??? I’ve thought about doing something similar solely as a weight reduction measure.
     
  13. Lowerleftcoast

    Lowerleftcoast Friend of Leo's

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    As a guess maybe 10%. I left the bottom smooth so it could be dusted easier. I could have taken more material off but I was getting impatient with how long it was taking.

    When I installed the tolex, I realized the tolex weighed more than what was removed.

    The baffles and back panels are 5/16 inch Baltic Birch. The total weight with 2 x 2.5 lbs speakers, 8 metal corners, 2 thumb screws (for mounting a piggyback head), sphinx glide (feet), and Fender strap handle is about 22 lbs.
    Dimensions: 26.25 x 16 x 10.5 inches.
     
    Last edited: Feb 26, 2021
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  14. CapnCrunch

    CapnCrunch Friend of Leo's

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    Butt joints with screws are all that is needed, especially if you are going to cover the box with some type of covering. No need for fingerjoints. Pine or good quality plywood make good cabs. for a rear mounted speaker, I never use anything smaller than 3/4" plywood baffle. 1/2" plywood can flex, and 3/4" is wide enough to de-couple sound waves from the speaker from those on the face of the baffle. Wiring of a 2 or more speaker cabinet is an interesting topic. In general, speaker experts claim that series wiring sounds different and more complex than parallel wiring. I've tried both, and to be honest I don't think I could hear a difference. Just remember if you have two 8 ohm speakers you'll end up with a 16 ohm cab wired in series and a 4 ohm cab with them wired in parallel. Wire according to the impedance of your speakers and what your amp needs to see.
     
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  15. Nickfl

    Nickfl Friend of Leo's

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    Be aware that you generally can't find really good, void free plywood at the big box stores. When people talk about baltic birch plywood it is not the same as the imported birch plywood at home depot. Real BB ply is all veneer and has many thin layers, the other stuff has veneer on the outsides and a layer or two of chip material as filler in the middle. True baltic birch plywood is much heavier, stiffer and stronger than the other kind.

    Unfortunately there is apparently a shortage of BB plywood right now, last time I went to my local plywood supplier, they had very little in stock and they said their wholesale supplier was out of stock nationwide and didn't even have any on the way from Europe yet, so it would potentially be months before they get restocked.
     
  16. ReverendRevolver

    ReverendRevolver Tele-Afflicted

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    I suppose I'll start poking around for wood next week. I have 1 local lumber place that isn't lowes or home depot, and its feast or famine with them having good pine. Never bought ply from them, so might investigate that.

    Depending on how this build goes, I might contemplate a 4×12 later in life. I have 2 ancient peavey PA speakers that have low handling, comparable to the 4×10 columns of about the same age I use with my powered mixer. They have those tank-esque "pocket handles" along with less exciting parts I could use (corners, jack plate). I'd need to purchase saw horses and make a bench for one of my saws to sit on if I killed one or both of them, since that's what I use them for.

    Thanks for the suggestions so far.
    @Lowerleftcoast , that cab looks fantastic. For the brace from back to baffle, do you mean a full height piece, or would pieces the same size as the cleats (top and bottom) work? I was planning on stretching the grill over a detachable panel that butts up to the baffle/front cleats.
     
  17. sds1

    sds1 Tele-Afflicted

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    Do you feel like this matters sonically? I hate the big box voided birch (voids suck, boards tend to be warped) but I never thought I might be cutting a corner on performance. They have other ply -- maple, etc. Wonder if any of these boards would be better choices?
     
  18. Nickfl

    Nickfl Friend of Leo's

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    I'm sure it makes some difference because veneer core plywood is much stiffer and denser than the Big box store stuff. Whether it's better for sound quality is hard to say. Three quarter inch Baltic Birch is stiff enough to make HiFi speakers, at least in smaller sizes, and keep in mind that the preferred material for stereo speakers is usually MDF because of its Sonic deadness. Whether you want a guitar amp cabinet to be totally sonically neutral is open to debate but I think the general consensus is that you don't want to be totally dead in the way that you want a HiFi speaker to be.

    My feeling is that Baltic Birch is an ideal material for baffles because of strength and lack of voids, but you should probably step down a size compared to cheaper plywood to get the same sonic performance, especially in floating baffle designs which in my experience can sound kind of hollow and woody if the baffle is too thick and stiff.

    As for using it for the rest of the cabinet, I think it makes sense for large closed back Marshall style cabinets that you want to be relatively stiff but it may not be ideal for open back cabinets that you want to have some resonance such as Tweed designs where you're probably better off using a lightweight solid wood like pine.

    The above opinions are based off of my instinct and having just enough knowledge to be dangerous, I have never done a one-to-one comparison of the same cabinet made out of different materials. I suspect there very few people who have compared different grades of plywood to see if they sound significantly different or not, so take all of this was a grain of salt. The only bit I've done direct substitution comparisons on would be baffle thickness where I have replaced a three-quarter inch Baltic Birch baffle with a 3/8 BB baffle in the same cabinet and I felt that the thinner baffle sounded better.
     
  19. PhredE

    PhredE Tele-Afflicted

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    Yup. And glue is stronger than the wood. So, if it is glued properly, strength is hardly a concern (I sit on several of mine fairly often (I weight about 160) with no concern whatsoever (they are made primarily of 3/4" pine). None of mine are fingerjointed -- just butt joints, furring that is screwed and glued. They are plenty strong.

    I don't cover mine for the simple reason that it is more work and just adds weight. I figure I can always sand the exterior and re-finish when the dings get too nasty.
     
  20. Lowerleftcoast

    Lowerleftcoast Friend of Leo's

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    Something like this, linking the front baffle and the rear panel, between the two 10 inch speakers near the middle of the cabinet. It can be a 1x1 or a dowel. (With speaker cabinets, I never position most of the parts exactly in the center, or equidistant from anything else.)

    pvbrace.jpg
     
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