Vertical 4x8 build thoughts

Discussion in 'Amps and Cabs [BG]' started by muddycreek, Nov 9, 2017.

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  1. muddycreek

    muddycreek

    Feb 26, 2010
    Because why not.

    My old band will be playing again a few times a year, which has left me needing some sort of rig bigger than the old GK MB200 my daughter has been using. I recently found a Shuttle 6.0 locally for a fantastic deal.

    That got me thinking about cabinets. I'm kind of a DIY fanatic, as well as being fairly, uh, frugal. And unfortunately open to half baked ideas.

    I wanted to put together an inexpensive cabinet with a small footprint, reasonable dispersion, without the need for a crossover. I don't need as much output as others seem to- I borrowed two qsc k10's last week, plugged directly in, and was fine on a fairly large, very loud stage. So the idea of a vertical 4x8 lodged itself in my brain. I'd like to check my thinking a bit before actually sawing anything.

    I've bought four MCM 55-2960 8" drivers. The plan is to put them in a braced half inch cabinet 11" wide, 12" deep, and 42" tall. This gives me an internal volume of just over 2.6'. I'm hoping cabinet stuffing will roughly offset the volume lost to drivers and such. Tuned to about 50 hz, it looks like I will have decent output above about 55 hz or so, which is fine for me with PA subs. And besides, when I had an early red Bag End 410 years ago, it took me freaking forever to notice it's almost total lack of output below about 60... :)

    So that's the plan. Tell me what's wrong with it and I'll probably do it anyway this weekend. But I still appreciate the input in advance!

    I'll post some pics as I go if there's any interest.

    Jon
     
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  2. emjazz

    emjazz Supporting Member

    Feb 23, 2003
    Brooklyn, NY
    Give David at Revsound a call. Great guy to talk to. He makes a 4x8 vertical cab.
     
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  3. Post soundclips when you're done.

    Other than that, it's not that bad of an idea, sounds like you've modeled the idea and have a bit of a clue as to what you're doing. Maybe make two, just because.
     
  4. dawind99

    dawind99 Supporting Member Commercial User

    Mar 30, 2012
    Revsound.net and Revsound on Facebook
    Owner: Revsound
    There's nothing wrong with that at all! Good for you. It should sound just fine. My only suggestion would be to raise the tuning frequency. Vertical alignment is the way to go in my opinion. It can look a little odd, but once you hear one beside and old cube it's a no brainer.
     
  5. muddycreek

    muddycreek

    Feb 26, 2010
    Interesting. When I raise the tuning frequency anywhere above about 50-52, I lose the little bit of extra extension and the bump from that gets lost in the bump between 70ish and 120ish, which I believe is from the smaller than ideal box volume. What would you be going for with the higher frequency?
     
  6. Rick James

    Rick James Inactive

    Feb 24, 2007
    New Jersey
    It's not just the small cab, it's also the high Qts. With a ported cab you want that between 0.3 and 0.4.
     
  7. muddycreek

    muddycreek

    Feb 26, 2010
    Would moving the tuning frequency up do anything sonically other than a little less extension and a little more midbass bump? Or is it more of a keeping the drivers within their optimal range or something?

    Thanks, I really appreciate the input!
     
  8. Rick James

    Rick James Inactive

    Feb 24, 2007
    New Jersey
    What software are you using? I just modeled it in WinISD 0.7, tuned to 50 hz I don't see a hump at 70-125 hz, just a bit of a rise. If you tune it at 68 hz you'll see a real hump centered at 85 hz, typical of vintage cabs. That's technically optimal, you can tell because the upper and lower impedance peaks are the same value, but optimal doesn't mean that's what sounds best. I'd go 55 to 60 hz, that gives the best compromise between response and displacement limited maximum SPL. 60 hz would still have some of that vintage midbass without being outright boomy. Also, don't stuff the cab, you only do that with sealed cabs that have a Qtc of 0.8 or more, just line it to smooth the mids.
     
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  9. muddycreek

    muddycreek

    Feb 26, 2010
    Great, thanks for the information. I'll bump it up to 55-50. I've been using a couple different sites and an Android app that all seem limited, but I can generally get them to agree. The hump I was talking about is probably just the rise you see, it's not excessive. And given an xmax of 4.5, it probably makes sense not to try to squeeze any additional low end extension from tuning lower anyway.

    And yes, line, not stuff. I have some 1 1/2" inch-ish loft poly fill I was going to use on the interior.

    Thank you for checking my numbers!
     
  10. muddycreek

    muddycreek

    Feb 26, 2010
    Halfway. Ish.

    4x8.jpg
     
  11. MarkA

    MarkA In the doghouse. Supporting Member

    Sep 26, 2008
    Interesting -- and a tiny footprint. I do prefer vertically aligned drivers to the traditional 4x setup for the usual reasons given -- better dispersion, easier to hear standing very near the cab. I think that you'd get a little less floor coupling, too, for better or for worse.

    I've no advice to offer on the cab design other than to brace it well and carefully consider your handle placement. That, and I wouldn't put an especially big or heavy amp atop it! Does the box as-is feel fairly stable?

    Interested to hear how it turns out.
     
  12. muddycreek

    muddycreek

    Feb 26, 2010
    Yes, I'm actually surprised with how stable it is, and in that picture it's just held together with corner clamps. It'll be used with a Shuttle 6.0, so not a lot of weight.

    I am considering putting a little cleat on the bottom I can slide a piece of flat wood or metal through for stability if necessary, and just carrying that with me. Right now I'm not thinking that will be necessary.

    I'm mulling over the handle now, both placement and type. Probably on one side right at the finished balance point, the whole box shouldn't be too much to one hand.
     
  13. DukeLeJeune

    DukeLeJeune rational romantic mystic cynical idealist Gold Supporting Member Commercial User

    Nov 24, 2008
    Princeton, Texas
    Owner & designer, AudioKinesis; Auth. mfg, Big E (Home Audio only)
    Very nice work.

    If at all possible, I suggest reinforcing the thin areas in between the front baffle cut-outs. The front baffle is the most critical as far as stiffness, and the least stiff (in this case) because of all the wood that has been removed. Ideally, use a brace that connects the front and rear panels. Imo corresponding side-to-side bracing would also be desirable. The technique I would use is to glue a horizontal "window pane brace" in between the drivers, which accomplishes all of this at once, and would result in a fairly solid cabinet.

    If the cabinet has already been glued up, it might be possible to cut 1x2 white pine boards to fit well enough that they can be glued in place. It's okay to use screws too if the fit isn't perfect.
     
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  14. Interceptor

    Interceptor

    Mar 29, 2005
    Madison, WI
    Nice project!

    Sealed cabinets are surprisingly forgiving of everything except air leaks. Make sure you gasket the drivers. I've had great success with the foam tape sold at automotive parts outlets. Also, gluing up with PL Premium has its advantages in filling any voids the seams.

    I agree with Duke - bracing between the front and rear will be worth the effort. Numerous builders have used dowel stock for that task.
     
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  15. muddycreek

    muddycreek

    Feb 26, 2010
    Yep, I'll be bracing both directions. Probably by epoxying in pieces of used carbon fiber golf club shafts. :) I'll consider horizontal/perpendicular shelf braces in between the speakers, too, reinforcing that thin little area makes sense. It's not glued yet.

    It's actually a ported cab, there's a shelf port on the bottom (not in the picture). I was considering gasketing the speakers anyway, though.
     
  16. ThisBass

    ThisBass

    Aug 29, 2012
    Germany
    I agree with @dawind99 to raise the tuning a little bit.
    Which software did you use for modelling?
    Most of all "generic" software modelling tools can't accurately predict shelf ports.
    If in doubt you may want download BoxSim which is freeware just to predict more "accurately" the shelf ports of your DIY cab
     
    Last edited: Nov 12, 2017
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  17. muddycreek

    muddycreek

    Feb 26, 2010
    I did move the tuning up to 58, assuming small differences would still probably keep it within that 55-60 range. I used a combination of an Android download program called speaker box designer, a website I forgot to bookmark, and did a little of the math by hand to check the website. And Excel to convert round ports to shelf. Because I can't seem to either take the easy way or leave well enough alone...
     
  18. ThisBass

    ThisBass

    Aug 29, 2012
    Germany
    Remodelled for 2.4 cu ft cause four drivers loaded into the empty cab will "eat up" some "air space" of the net volume of 2.6 cu ft.
    58 Hz tuning for this format looks pretty reasonable to me. Some "smallish" bump at the low mids is not so bad. At least on paper F3 predicts to be pretty low with about 53Hz.

    Just to protect your cab from "harming" transient noise you should power the cab with amplifiers that "protect" the woofers from sub Harmonic content with a HPF. You'd hate it notice your cones "jumping" out of the baffle cause a protecting HPF was missing.;)

    edit,
    transient noise does not be mismatched with sub Harmonic content.
    Harmonic content is something that relates to total Harmonic content of a note or the lowest tuning of an instrument.
    Transient noise is something that is "generated" at just the moment when ever plug a string. The generated frequency "spectrum" is hard to "exactly" predict. But its common sense that transient noise can easily underrun even the lowest tuning of the instrument. That's why protect woofers with a HPF is always a good idea independent of the lowest tuning of the instrument.
     
    Last edited: Nov 12, 2017
  19. muddycreek

    muddycreek

    Feb 26, 2010
    Makes sense, a 30ish high pass should probably be standard on most bass amps. That being said, I've got a Shuttle 6.0, not sure how I'd implement a high pass without another piece of gear.
     
  20. emjazz

    emjazz Supporting Member

    Feb 23, 2003
    Brooklyn, NY
    Here you go... :)

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