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".5 Aligned" 4x10 cabs

Discussion in 'Amps and Cabs [BG]' started by groovaholic, Dec 1, 2014.


  1. groovaholic

    groovaholic The louder the better. Supporting Member

    Sep 19, 2004
    Grand Rapids, MI
    I've read a couple threads about .5 alignment of speakers using multiple woofers, and also several threads describing the square 2x2 arrangement of the common 410 bass cab and 412 guitar cab as basically the worst designs possible (from an acoustical perspective, at least).

    I didn't want to "put lipstick on a pig" but I've had a pair of 410 cabs since 1999 and they have always gotten the job done for me, but I've definitely noticed big changes in tone depending on where I stand in relation to my stack.

    So, I did a bit of reading, and the .5 alignment could be accomplished by adding an inductor in series with the + lead on the woofer(s) in question -- which prompted me to order a pair of solid-core inductors to set an LPF point of approximately 450 Hz.

    After I had "converted" the first cab; I did a side-by-side comparison with the other 410 and heard a lot more clarity and detail -- it cleaned things up a lot.

    So I proceeded to mod the second cab and the effect is even more pronounced when they are stacked.

    I felt like I was hearing the winding on my strings.

    For $30 in parts and a couple hours of my time, it seems like a great bargain, and it's completely reversible if the result doesn't turn out to be helpful at gigs.
     
  2. Not only is it reversible, you could wire that inductor to a switch. Jump between the two voicings.
     
    bassmeknik and BurningSkies like this.
  3. kringle77

    kringle77 Supporting Member

    Jul 30, 2004
    Massena NY
    Ive done this with 4x10 cabs and it works great, especially if the cab doesnt have a scooped midrange.
     
  4. agedhorse

    agedhorse SUSPENDED Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    If using a ferrite or iron core inductor, be sure that you choose an inductor that has adequate core headroom to prevent saturation. Air core is probably a better choice IMO.

    Incidently, choosing an inadequate ferrite/iron core series inductor in a 2nd or greater order LP crossover filter is potentially one cause for failure of (some) class D amps. When the core saturates, what's left is the more purely capacitive load of the shunt capacitor. The DCR of the inductor may not be enough to isolate the amp from the capacitive load. The same possibility occurs with a conventional amplifier, except the failure mechanism can be that it bursts into oscillation and cross-conducts resulting in damaged output devices.

    There's more to designing a (plays well with others) crossover than meets the eye.
     
    xelaalex and DukeLeJeune like this.
  5. silky smoove

    silky smoove Supporting Member

    May 19, 2004
    Seattle, WA
    Refresh my memory: In this case, a .5 alignment is basically high passing one of the vertical pairs in each of the cabs. Correct?
     
  6. groovaholic

    groovaholic The louder the better. Supporting Member

    Sep 19, 2004
    Grand Rapids, MI
    Nope, low passing actually.

    In response to the concerns raised by @agedhorse, I used 16 ga bar-core inductors from Erse:
    5.60mH 16ga ESQ - Super Q Coil.
    .261Ω - 500w


    Since only half of the wattage in each cab is going through the inductor, I figure they're pretty over-rated for the application.

    I hope I'm right, because you certainly know this stuff better than I do!
     
  7. groovaholic

    groovaholic The louder the better. Supporting Member

    Sep 19, 2004
    Grand Rapids, MI
    The 5.6mH inductor, at 16 ohms, sets the LPF to approximately 450 Hz, at 6dB/octave.

    This lets all of the drivers produce the lows, but reduces phase cancellation in the mids by reducing 450 Hz and up for the two drivers (in this case) on the left side of each cab.
     
  8. agedhorse

    agedhorse SUSPENDED Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    You need to know the saturation current (curve), something that should be on the data sheet.
     
  9. groovaholic

    groovaholic The louder the better. Supporting Member

    Sep 19, 2004
    Grand Rapids, MI
    Is it any better if these were used in a first-order circuit?
     
  10. silky smoove

    silky smoove Supporting Member

    May 19, 2004
    Seattle, WA
    Ah! So you're letting all of the drivers do the low end work where things are less directional, and restricting mids/highs to just one vertical pair thereby reducing comb filtering, phase issues, etc. Smart.
     
  11. Subscribed. I've been interested in this for awhile but didn't know how to do it.
     
  12. Grissle

    Grissle

    May 17, 2009
    I'd like to hear an Ampeg 810 with this setup.
     
    bassmeknik likes this.
  13. Razman

    Razman Supporting Member

    Feb 10, 2005
    Orange Park, FL
    I have a PR810H that would be a good candidate. Going to dig up parts cost as I too am curious...
     
    natw42 likes this.
  14. What about getting a couple of cheap 6" puppies to stack on top with a full crossover?
     
  15. Razman

    Razman Supporting Member

    Feb 10, 2005
    Orange Park, FL
    OP, how do these inductors affect the cabinet impedance value? Rather, are there significant changes that would cause me to be concerned about running this configuration with a tube head?
     
  16. SubNoizeRat3691

    SubNoizeRat3691 Lovin' the lows

    Feb 1, 2010
    Davenport, IA
    I am also curious how this would affect an all tube amp.
     
  17. agedhorse

    agedhorse SUSPENDED Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    Yes, you don't have the capacitive effects to the power amp to worry about
     
  18. agedhorse

    agedhorse SUSPENDED Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    I wouldn't think the impedance rise would be significant in the slightest.
     
    BrBss likes this.
  19. Razman

    Razman Supporting Member

    Feb 10, 2005
    Orange Park, FL
    Thanks Agedhorse.
     
  20. groovaholic

    groovaholic The louder the better. Supporting Member

    Sep 19, 2004
    Grand Rapids, MI
    Thank you @agedhorse!
    In my case I just have the inductor in series with 1 side of the cabinet, 1st order--6dB/octave.

    So, that inductor would add its impedance (.261 ohms, in this case) to that "branch" -- which might raise each cab from 8 to 8.1305 ohms.
     

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