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If I change internal dimensions, while keeping internal volume the same...

Discussion in 'Amps and Cabs [BG]' started by LongHairFreak, Oct 5, 2013.


  1. LongHairFreak

    LongHairFreak Insert cool nickname? Nobody's given me one yet. Supporting Member

    Aug 7, 2006
    Twin Cities - MN
    Will output, sound, etc change much?

    My EV 2x15 has become heavier than my bandmates and I wish to lug, so I was thinking of remaking the cab with lightweight build specs (i.e. thinner panels, more bracing). I'm wondering if it'd really be worth doing.
    Since I'll be keeping the same heavy speakers, will I save any significant weight?
    Will the sound I dig so much out of my EV change much?

    My apologies if this is answered elsewhere on TB, but I've not been able to find it. Thanks everyone.
     
  2. will33

    will33

    May 22, 2006
    austin,tx
    If you keep the internal volume and the port the same size, your tone will be maintained. While you'd still have the heavy speakers, you could shave off at least 20lbs. of the original Mesa 215.
     
  3. LongHairFreak

    LongHairFreak Insert cool nickname? Nobody's given me one yet. Supporting Member

    Aug 7, 2006
    Twin Cities - MN
    Saving 20lbs would be cool. That's sort of my cut-off point; that is, if I can save a minimum of 20lbs, then it's likely going to be worth it to me. Any less??? it may not be worth the trouble.

    Some (band mates and non-musicians alike) are throwing that line 'Why mess w/a good thing?' at me; claiming that a change in anything (panel thickness, dimensions, etc.) will certainly alter that wonderful tone. Granted, I'm also tossing around the idea of using a single bottom slot port, rather than the two simple round baffle ports the cab currently has, but I'm hoping that may not change things much either. Although I'm not holding out much on that idea.

    Any other opinions?
     
  4. xk49w

    xk49w

    Apr 13, 2008
    Somewhere I read that the round port design is supposed to be easier to nail the tuning frequency than with a slotted port. Round ports worked out very well in my case. They are easy to install and adjust. Cut em long and trim to tune.

    To duplicate the response I think that is more important to get the tuning right than getting the volume spot on. (Hopeful that others may confirm or refute that.)
     
  5. Mr. Foxen

    Mr. Foxen Commercial User

    Jul 24, 2009
    Bristol, UK
    Amp tinkerer at Ampstack
    You can make round ports telescopic with another tube inside, which is good for adjusting tuning.

    Various stuff has minor effects on tone with the inside, if the mesa cab is not lined, part of the tone will be from internal reflection, and changing the size will change that colour. If its properly lined though, should make no odds as long as new cab is also properly lined.
     
  6. LongHairFreak

    LongHairFreak Insert cool nickname? Nobody's given me one yet. Supporting Member

    Aug 7, 2006
    Twin Cities - MN
    Currently, my EV's ports are simple holes cut into the baffle with no tubes. I'm guessing duplicating this would likely be the easiest way to go. I just thought changing things up a bit might be the way to go instead.
     
  7. will33

    will33

    May 22, 2006
    austin,tx
    Your current port depth will be the thickness of the baffle. If using thinner plywood, you would add a little depth behind the cutout to bring it back to 3/4", or however your current baffle is.

    Should be easy to keep the internal height, width, depth of the box the same.
     
  8. LongHairFreak

    LongHairFreak Insert cool nickname? Nobody's given me one yet. Supporting Member

    Aug 7, 2006
    Twin Cities - MN

    Yeah... Except that I'll be adding additional bracing, but aI'm guessing that'll be easy enough to figure in the HxWxD.
     
  9. Keep in mind, it's not going to be cheap build a good solid cabinet, especially since you want to avoid the heavier (cheaper) materials. Those 20 lbs are going to cost you a fair bit of change.

    You may not need extra bracing if you design the cabinet with better joinery.
     
  10. frankieC

    frankieC A swell guy from Warren Harding High

    Jul 21, 2012
    Sounds like a lot of work for little (if any) gain (weight loss).
    Great fodder for discussion and debate, but, IMO the end doesn't justify the means in this case.

    ...an old trucker once told me that you can't reduce volume (or weight) by rearranging the mass. Good advice. A 20 lb savings doesn't seem to be sufficient gain (loss) for the amount of work and cost involved to do it right.

    I might suggest you simply add more, or better handles, or move the existing handles to better positions, and a good set of removable casters (softer than the usual factory wheels), and come to the reality that improving the method of handling it the cab in transit is probably more cost efficient, and more effective than trying to build a cab of the same volume from lighter materials, for the purpose of shaving off 20 lbs.

    I used to use 4 Sunn 200S (2-15) cabs, They had crumby little casters on the bottom of the cab, and a single handle in the middle of on size, and 4 little plastic/rubber "feet" on the opposite side.
    To ease the handling of these cabs. I added 4 handles to each cab (2 at the top L&R, and 2 at the bottom L&R). I removed the factory casters, and built dollies that had 8" tall pneumatic tires, and mounted to the cabs with 1/4" "T nuts" and hand hand wheels.
    They rolled over just about any surface, including grass, dirt, and gravel with little effort.
    The were also removable. The looked very similar to the dollies that came with the Ampeg Portiflex B15's back in the day, but with better wheels.

    Adding the extra handles made moving the cabs up and down steps very easy for two guys. The Sunn 200S cabs are pretty heavy, too. Making them easier to grab hold of for 2 people was a marked improvement.

    I built all the dollies in a weekend, and adding the handles to all for cabs took about an hour.

    This is Just my 2¢.

    I wish you good luck with your endeavor.
     
  11. PDGood

    PDGood Supporting Member

    Sep 19, 2010
    Nashville, TN
    If you're going to go to all that trouble, why not build a composite version of what you already have?
     
  12. LongHairFreak

    LongHairFreak Insert cool nickname? Nobody's given me one yet. Supporting Member

    Aug 7, 2006
    Twin Cities - MN
    Yeah, as I said, 20lbs weight savings is the minimum I was looking for; but you're right, it'd be a lot of work for even that amount. You bring up some good points--Larger wheels, another handle or two, perhaps a rollbar, maybe even some skid rails would all be helpful. Much of these mods can be done by myself too; which is a plus for the wallet.

    You actually added 8" tall wheels?
    BTW, a 2 cent contribution is exactly what I was looking for.




     
  13. LongHairFreak

    LongHairFreak Insert cool nickname? Nobody's given me one yet. Supporting Member

    Aug 7, 2006
    Twin Cities - MN
    I wanted to stick with wood, mostly because more folk know the use of wood and I cannot do such a build myself (This being 'cause I'm blind).

     
  14. Blues Bass 2

    Blues Bass 2 Supporting Member

    Oct 3, 2001
    Davenport Iowa
    You could really save some weight if you built with 1/2" ply and braced it well . Here's a pic of the bracing I did for a 115 bass cab with an Eminence CB158 speaker . The cab also had a large horn in it and the cab came out very light for a 115 cab even with the large magnet 15 driver .

    Legendcabinet001.

    Here is a pic just before putting all the lining , hardware and speakers in just to give you and Idea .

    Legendcabinet004.
     
  15. JoeWPgh

    JoeWPgh

    Dec 21, 2012
    The estimate for plywood weight is 25 lbs per 1/4 inch of 4x8 material. Going from 3/4 ply to 1/2 will reduce the weight of the wood roughly a third. I would recommend additional bracing for 1/2" ply, so you will lose a little of that weight savings. How much weight you shed depends on the amount of plywood you are replacing. I'm guessing 20~25 lbs. On 2nd thought, I would keep the front at 3/4" for speaker mounting. So maybe 20 lbs, max. Personally, I'd rather lug around 2 cabinets @ 1x15 than 1 @ 2x15
     
  16. will33

    will33

    May 22, 2006
    austin,tx
    The OP is blind.

    The picture of the 115 looks like what amounts to building a ribcage inside the cab. The idea being to use the bracing out in the middle expanse of panel to make it stiff. Don't really need any in the corners as it is already stiff there.

    Another way it to put sticks of crossbracing connecting opposing panels, like building a cage behind the speaker.

    Often some combination of those two methods makes the stiffest box.

    Baltic Birch is some of the stiffest plywood there is, but also some of the heaviest. Other types are lighter weight per sheet. They will cost more.

    Some stuff you'll find at places like Home Depot are very light, but also not as stiff, and their outer veneer is paper thin. That makes weak glue joints.
     
  17. LongHairFreak

    LongHairFreak Insert cool nickname? Nobody's given me one yet. Supporting Member

    Aug 7, 2006
    Twin Cities - MN
    Yep. That's the general formula I used; figuring I wouldn't get much more than 20lbs shaved off.

    Splitting the cab in two is a good idea; I had thought of that. However, the problem is that the horn sits directly btwn the two 15"s (off to one side), so there's a lot more involved than just cutting the cab in half and adding a panel to each half.


     
  18. LongHairFreak

    LongHairFreak Insert cool nickname? Nobody's given me one yet. Supporting Member

    Aug 7, 2006
    Twin Cities - MN
    Thanks Will33.
    Your explainations are vg; now I get it.

    Thanks to everyone else too. It appears that my next step (for definite direction) should be some more detailed math for closer estimates on weights.




     
  19. Arjank

    Arjank

    Oct 9, 2007
    Above Amsterdam
    +1
    Crossbracing works best, if you connect opposing panels their resonance frequency moves up. If you would only add a perpendular brace on a panel it's likely it will only reduce it's amplitude. Just try to add crossbracing where ever you can and as asymmetric as possible.
     
  20. LongHairFreak

    LongHairFreak Insert cool nickname? Nobody's given me one yet. Supporting Member

    Aug 7, 2006
    Twin Cities - MN
    OK. A couple more observations/Qs.

    It turns out that only the floor and baffle is made of ply; whereas the ceiling, back and both sides are of 3/4" mdf/partical. Might this make more of a weight difference/savings than if it were completely of ply?

    Also, say I were to make this into two 1x15s. It was suggested that I make a separate box for the self-enclosed 5.5" mid driver rather than trying to fit it into one of the 1x15 boxes. What do you all think of this idea?

    Thanks
     

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