Birch plywood vs regular plywood for cabinets

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers T' started by Scabiosa, Oct 3, 2012.

  1. Scabiosa

    Scabiosa Member

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    Hi folks!!

    Wonna make myself a nice cabinet!!

    Now I have some nice piece of 18mm plywood (no idea what kind of wood) that I can use...
    But I see that all quality cabinets are made of birch plywood.

    What is the reason, will it make a huge difference in sound or is it maybe because it is lighter?

    I want to make a GOOD sounding cabinet, so I wonder if I better buy some birch plywood or can I just the plywood I have at home? :crazyguy

    Thanks!
     
  2. Jef Bardsley

    Jef Bardsley Member

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    When people say "birch", they mean a marine grade Baltic birch plywood. It's prized for having many laminations (13) and no voids. If the "nice" plywood meets those criteria it should be fine. It's really about structural considerations more than tone, but the two are related. Lots of laminations means lots of glue for stiffness, and no voids means no holes with wood chips rattling around inside.
     
  3. Keyser Soze

    Keyser Soze Member

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    Everything Jef said. Also the laminations on the Baltic ply are all quite similar, resulting in a very stiff, and sturdy final product that responds well to machine tools (like router bits for the round overs) and overall behaves like the very uniform material that it is.

    Many other plywoods - even ones with high quality exterior veneers - will have a center sandwich of soft, low quality material. You don't want that, no matter how good/sturdy it looks from the outside.
     
  4. SatelliteAmps

    SatelliteAmps Member

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  5. Jesseehhh

    Jesseehhh Member

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    All of that is true, but to keep things in perspective, many of the hands-down greatest amps ever made were constructed using cheapish plywood.
     
  6. SatelliteAmps

    SatelliteAmps Member

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    I can't actually think of one company that used poplar core, birch veneer plywood. Which greatest amps are you thinking of? I can think of plenty that used voidless birch ply (Marshall, Orange, Hiwatt, sound City, Selmer), or others that used cabinet grade ply that was a consistant wood (Fender and Vox when they used ply).
     
  7. audiozone

    audiozone Member

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  8. jamme61

    jamme61 Supporting Member

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    why not use pine, like the old fender cabs?
     
  9. sharpshooter

    sharpshooter Member

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    Their are some other choices besides birch, that are very high quality, and can result in more of a "furniture" appearance.
    Not inexpensive, but not that much more than birch.

    http://www.marine-plywood.us/index.htm
     
  10. '58Bassman

    '58Bassman Member

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    If someone wants to make a cabinet that will be finished with some kind of clear coat to look like the modern furniture (Scandinavian, etc), use cabinet-grade birch plywood. It should have no voids, thinner layers and better quality outer veneers- both sides will be more similar than standard plywood, which is often graded B/C (B is a better grade than C). A/C is OK but cabinet grade is what drawers for kitchens and offices are made of. It comes in various thicknesses but will probably be sized in Metric, not inches. 3/4" would be 19mm and it requires metric cutters if dado joints will be made. Using a standard router bit or setting a dado saw to 3/4" will be slightly loose.
     
  11. '58Bassman

    '58Bassman Member

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    And what Fender used was nothing special- the knots were pretty big and it had pitch pockets that could bleed into the tweed or loosen the Tolex. Still, it resonates differently from plywood.
     
  12. trancedental

    trancedental Member

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    3/4" / 19mm Pine sold in England is usually just laminated 1 1/2" strips glued together unless it's under 200mm / 8" wide. It might well be the same in Europe.

    You can sometimes get 20mm Parana or Redwood Pine 10 1/2" width locally if you get lucky. It's a bit heavier / dense than American pine.

    I don't know how much of of a difference that actually makes in reality? I've actually used this Pine in a 2x10" combo for my 6G16 Vibroverb build.

    Are the new Fender "65 reissues made with plywood cabs instead of Pine? I was told this a while back?
     
  13. Peteyvee

    Peteyvee Premium Platinum Member Silver Supporting Member

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  14. sunburst79

    sunburst79 Member

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    Anyone know if the older Fender Tonemaster cabs like the 4-12 were Baltic or regular plywood?
     
  15. blueswah

    blueswah Silver Supporting Member

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    What I call "The Baltic Birch craze" is IMHO a function of the advances in machinery and production methods
    and has little to do with getting a 'superior tone' or some other BS being spewed by amp and cabinet making companies.

    All Plywood at one time was of concern for speaker cabs due the issue of sympathetic frequencies.
    Plywood can resonate or "buzz" at sympathetic frequencies.
    MDF board was used in lieu of plywood especially for baflles. But I digress....

    For years and years; many, many, hundreds of thousands of speaker cabs for musical instruments are made with all sorts of species of plywood.
    Also many levels of quality were used from shop grade plywood to various levels of cabinet grade plywood.
    And many, many of these cabs are still in use today.

    So what's the deal with "Baltic Birch"?

    Many if not all of todays manufacturers cut the parts for speaker cabs etc on CNC machines.
    Visualize a huge pool table with a moving overhead router that makes cuts based on electronic drawings.
    The thickness of the plywood being used is critical toward making sure the cabinet parts cut on the CNC machine fit properly.

    3/4" plywood (of any grade) is not exactly 3/4" thick. In fact they vary quite a bit form say 0.70 to 0.76 inches thick.
    May not sound like a lot but a 0.05 difference in thickness will be the difference of part fitting or not when cut on a CNC machine.

    This may not sound like much but 0.05 is getting close to 1/16" of an inch (0.06125")
    The only way to address this issue is to measure and enter the thickness of each sheet being cut into the CNC machine.
    And even then different locations on a sheet may be thicker or thinner than other locations!

    Variations in thickness will create a lot of problems when using a CNC machine to cut the parts if this is not done.

    Here is where Baltic Birch comes into play.
    The manufacturing process they use to make Baltic Birch plywood creates a very consistent thickness for each sheet. 18mm or about .070"
    This in turn makes it the perfect plywood to cut using a CNC machine.
    When making hundreds of cabs, manufacturers need things to fit properly, with no issues so the assembly process doesn't get slowed down or stop.

    IMHO and experience all the above is why Baltic Birch used so often.

    So unless you are cutting cabs on a CNC machine use whatever plywood you want.
    Use a decent grade but you don't have to use Baltic Birch!
     
  16. teleman1

    teleman1 Supporting Member

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    What determines that Baltic Birch is the material to use. Its better than Mahogany, Maple,Poplar? What about wood harvested from 50's and 60's organs?????
     
  17. Jef Bardsley

    Jef Bardsley Member

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    Baltic birch offers consistency and stiffness, two attributes that increase the chances the cab will work in a satisfactory fashion. Solid wood will resonate a lot more than an equal thickness of plywood. The trick is keeping the resonances above the fundamental range of the guitar, so the cabinet produces overtones, and not ghost notes.

    The other consideration is energy storage and release. This is what makes hollow things ring. A steel drum rings a lot, a cardboard box, not so much. A brace connecting two side walls can increase the stiffness of the structure, raising the frequency of the resonance, but also increase the ringing. Look inside an acoustic guitar. A whole lot of work as gone into the size, shape, and placement of the braces to ensure that the top rings equally at all frequencies.

    "Better" is one of those things... Les Paul or Strat? Fender or Marshall? What makes a blues or funk player smile may not meet the needs of a shredder. You have to consider the size of the cabinet and the volume level - the small walls of a 1x12 combo won't resonate as much as the back panel of a 4x12.

    In short, solid woods can make a very musical cabinet, but plywoods are a safer bet.
     
  18. Rambergwest

    Rambergwest Member

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    One of the overall best posts I have read, nice job!
     
  19. Tonefree

    Tonefree Silver Supporting Member

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    I am currently building cabinets and have been using a cabinet grade poplar. It works great but I will switching to birch because as mentioned, it machines much better. Less finish time prior to tolexing. I will be posting some pictures of my cabinets within the next week or two...:aok
     
  20. Ken Zuercher

    Ken Zuercher Member

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    Been building cabinets for 1X12 combos for a few years now. I am choosey about the wood at the lumberyard but have noticed two things about solid pine versus any type of plywood. First, if you have many boards to choose from, get the lightest ones in the bunch. Then get the fewest and smallest knots. My finished amps weigh 7 to 8 pounds less than a similar class Fender amp. (40 watts, 1X12) I don't build clones of anything so it's not an apples to apples comparison. The cabinets do seem to have a musical ring about them. I like working with pine and find the plywood amps are somewhat louder than the same amp in solid pine. I would bet the stiffness and the amount of glue in the wood would account for the different output levels. As Jeff Bardsley said. whatever floats your boat.
     

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