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Composite speaker cab build No2 - 2x12

Discussion in 'Amps and Cabs [BG]' started by Petebass, Oct 27, 2011.


  1. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    The first composite cab I built is 1 year old now and still looking and sounding fantastic. It was a 1x12 cab which weighs a mere 19.5lbs (8.87kg)... click here for that thread.
    http://www.talkbass.com/forum/f15/another-composite-cab-build-inspired-zac-663169/

    Armed with this knowledge, my good friend Evan has been inspired to ask me to make one for him. He approached me with the following challenge…...

    Evan’s existing rig is rather impressive:-

    - Epifani UL902 head, through,
    - Epifani UL 212 speaker cab (4 Ohm), and
    - Epifani UL 210 speaker cab (8ohm).

    He’s very happy with the rig, and who wouldn’t be. But he quite often does gigs in venues which have tiny stages and/or terrible load in conditions. He’s planning to assemble a compact bass rig based on a lunchbox style D-Class head (possibly the Aguilar Tone Hammer 500), and one portable standalone bass cab.

    He’s been tempted to just use the UL210 for the compact rig, but has found it can’t quite keep up at the required SPL levels required. It’s also 8 ohms and he is concerned by it pulling the maximum watts out of whatever compact head he ends up getting.

    The UL212 on its own can produce the SPL levels required, and he considers the 4 ohm load is perfect. But this cab is not quite as portable as Evan would like for this mini-rig and it’s footprint on small stages is just that little bit too large.

    So Evan has made a request to me to make him a stand-alone cab that is as close as a 212 cab with a horn can possibly be in size to his UL210, it must be more portable than his UL212, and as lightweight as possible. The dimensions would also governed by Evan’s requirement that this cab must fit into the boot of his Honda Jazz.

    We’ve swapped many emails and texts during the design phase of this cab, and I’ve basically allowed Evan to customize the cab to his hearts desire, within reason of course. Evan has had input in pretty much everything, not unlike ordering a custom bass I guess.

    I’m not going to divulge the technical aspects of this cab because there’s some pretty cool technical stuff that went into this design, too cool to just give the info away…. I will say that’s it’s not just a doubled up version of my previous composite 1x12. That would have been about the same size as the UL212 and even though it would have weighed a lot less, it wouldn’t have met the criteria for compact size. So this cab has been designed from the ground up specifically for Evan. I can divulge the following basic specs:-

    Materials Used:- Composite Sandwich construction as per my previous composite 1x12 cab build, but with some refinements.

    Estimated Weight at start of the build:- 40 pounds (18kg) is the target.

    Size:- COMPACT!! Smaller than the UL212, only slightly bigger than the UL210, lighter than both of them.

    So after spending considerable time and effort designing a cab to meet this criteria, here's how the build unfolded:-

    The front baffle is easily the most difficult and time consuming part of these builds:-
    Baffle01.jpg

    Baffle02.jpg

    Baffle05.jpg

    e9ce405d.jpg

    A Monocouque outer shell - Jointless and super strong!
    18Monocoque.jpg

    Recessing the Horn attenuator (and handles as specified by Evan
    23HornAttenuator03.jpg

    Pic with my Stingray 5, for size reference. A very compact cab!
    27SizeofCabVsBass01.jpg

    Carpet goes on:-
    36Carpet.jpg

    And the finished product:-
    37FinishedCab01.jpg

    38FinishedCab02.jpg

    The final weight was 37.9 pounds (17.2kg), less than his UL210 but will easily outperform it as a standalone bass cabinet.

    Evan and I are both VERY happy with the final result. :hyper:

    I'm so in love with this composite cab idea, I honestly don't think I could ever build another cab from Plywood.
     
  2. ::::BASSIST::::

    ::::BASSIST:::: Progress Not Perfection.

    Sep 2, 2004
    Vancouver, BC Canada
    First of all fantastic job! That looks very pro.

    You may be interested to know that a TBer built a fEARful 15/6 with a final weight of 36LBS. He used italian poplar eurolite. My fibreglass fEARful 15/6 built by AoN has a weight of 39LBS. Knowing this now, I would have gone for the poplar version because I think wood is better in terms of durability and ease of build. Check out the current fEARful thread for more info... near the end.

    Just some food for thought.
     
  3. CDweller

    CDweller

    Oct 24, 2009
    Clearwater, FL
    Like your previous build, this is a beauty. Have to agree with the 2x12; 2x10 is just not enough to do the job. What speakers did you use?
     
  4. 1n3

    1n3

    Sep 13, 2007
    USA
    Nice job again, Pete. Good to see you back in the game. Those are some long ports. Are you able to disclose the drivers?
     
  5. mikell128

    mikell128

    Feb 2, 2010
    NY, NY
    I'm glad to see your back at it! Looks awesome and professional, I'm sure your friend is very happy with this lightweight beast
     
  6. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    Good info, thanks. But to put it into perspective, i used two large drivers. The weight difference between most neo 12's and their 15" counterpart is negligible. If I only had to use one large driver as per the 15/6, I would have been disappointed by 36lbs. Like I said, my previous 1x12 build was under 20lbs.

    Having said that, I've been toying with the idea of making the next one with a lightweight plywood front baffle, and the rest of the cab from composites. This could knock as much as 1/3 off the build time with "hopefully" only a very slight weight increase.... but that's an experiment for another day ;)

    Sorry guys, no technical info on this design. I put too much into it.
     
  7. rpsands

    rpsands

    Jul 6, 2007
    Phoenix, AZ
    You are forgetting the weight of the mid chamber and the crossover. The eighteen sound plus the 3015lf weigh right about what two 3012ho weigh and then the crossover and mid chamber are more than equal.
     
  8. 1n3

    1n3

    Sep 13, 2007
    USA
    That was notable, but... That was a pretty spartan build; the aesthetics won't be for everyone. And with wood that light, I have to wonder about durability and stiffness. After all, we could build cabs out of balsa, but we don't (usually). I'm not saying it's a problem, only that it's something to be aware of.

    I think Robby will continue to make refinements and achieve some weight reductions. I also think there may be potential in other construction techniques. And I think the main tradeoffs will continue to be weight vs durability and cost.
     
  9. ::::BASSIST::::

    ::::BASSIST:::: Progress Not Perfection.

    Sep 2, 2004
    Vancouver, BC Canada
    Wouldn't the stiffness issue be solved with a few well-placed braces?
     
  10. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    What's your point? This cab has a weighty crossover and a weighty horn. The 12" drivers I used are a very similar weight to a 3015LF, and I used 2 of them. The plywood used on the ports and handle mounts more than account for the weight of a mid chamber.......

    You really can't generalise, each design is specific. I didn't build a 3015Lf loaded cab so comparisons to it are heresy at best.

    Like I said, I put a LOT of work into this design, and that includes weight minimisation. If you think you can make a 2 driver cab that weighs less, then go for it.
     
  11. rpsands

    rpsands

    Jul 6, 2007
    Phoenix, AZ
    I already made a 20lb 1x12 out of 3/8 ply without using light stuff. Doing a 35lb 212 would be a breeze. Okoume in 3/8, lighter bracing than last run, done.

    You've done a nice job here. Minimizing Robby's effort with his 15/6 is not necessary.
     
  12. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    Those are great numbers! I'll add Okoume and Italian poplar eurolite to the list of plywoods to look into some more. I suspect they will not be as readily available in Australia as in the USA, but I'll deal with that as it arises.
     
  13. 1n3

    1n3

    Sep 13, 2007
    USA
    (assuming this is addressed to me) I'm not saying there is a stiffness issue; only that with lighter material, it's something to keep an eye on. If stiffness is too low, bracing is an answer, but obviously, braces add weight.
     
  14. ::::BASSIST::::

    ::::BASSIST:::: Progress Not Perfection.

    Sep 2, 2004
    Vancouver, BC Canada
    Yup. Trade-offs for sure.
     
  15. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    You'll notice I only added one one extra brace to this cab i.e the front and back panel. I used Foam wrapped in fiberglass, so it weighs nothing. The side panels are braced by the structure of the ports, some deliberate pre-planning on my part. Bracing need not always add weight.......
     
  16. ive got a challenge for you mate. big cabs weigh ALOT more that tiny ones like that. i wonder how light you could make somthing like a 2x15
     
  17. rpsands

    rpsands

    Jul 6, 2007
    Phoenix, AZ
    Probably right around in the neighborhood of 50lbs if it's 6 cubic feet and using Neo drivers.

    Look at the weights of Barefaced's cabs, and that's right around what you can expect from high end composites.
     
  18. dog1

    dog1

    Dec 30, 2008
    Indiana
    I commend you on a nice looking build. What's the tweeter for?
     
  19. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    Well the person for whom the cab was made specified 2x12's with horn and no mid. If that's what he wants, thats what he gets. It was my job then to come up with a design that would not have a gaping hole in the freq response between where the woofers trail off and the horn kicks in.

    I'm at a gig now, trialing the cab before the handover in 2 days. I'm going to be sad to let it go..... But I can always build another one :)
     
  20. murphy

    murphy

    May 5, 2004
    Canada
    Wow!!! If only you were in canada!!!!:)
     

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