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one 4-ohm cab vs. two 8-ohm cabs

Discussion in 'Amps and Cabs [BG]' started by VifferMike, Feb 7, 2014.

  1. VifferMike

    VifferMike Registered Four Banger

    Dec 10, 2004
    Dallas, Texas
    I'm looking to move to a two-cabinet rig for portability and flexibility. I run a Genz-Benz ShuttleMAX 12.2 that can drive two cabinets simultaneously with two separate and equal power amps. Each amp is rated at 375 watts at 8 ohms and 600 watts at 4 ohms. I currently run a 4-ohm G-B Uber 212T with one of the 12.2's amps, so I'm pushing 600 watts (its RMS rating, incidentally) to that cab.

    Would it be safe to assume that, if I ran two equivalent 8-ohm cabs using both of the 12.2's amps (i.e., one Speakon to each cab) and factors such as sensitivity, etc. were also equal:

    - The head would deliver 750 watts (375 x 2) of power to the cabs?
    - The new rig would be slightly louder than what I run now?
    - Despite less power going to each cab, the new rig would have as good a sound as the old? (I don't think power delivery, resistance, etc. affects sound quality ... but a concern is what muddiness/delay/phase issues may occur by running two cabs off discrete power stages in the same amp).

    Thanks in advance for the sonic peace of mind as I consider this ...

    Dallas, Texas
  2. You will be doubling speaker area with two 212's. Yes it will be louder and most likely give deeper response while allowing you to drive each cab harder than you can with a single 4 ohm 212.
  3. VifferMike

    VifferMike Registered Four Banger

    Dec 10, 2004
    Dallas, Texas
    D'oh! I knew I left out a detail: the 8-ohm cabs would be 1x12s, So speaker area would be equivalent, too (roughly).
  4. *IF* the single 12's are the SAME speakers that are in the 2X12, then you will not really pick up any additional volume from the extra wattage. You will be in the same boat as you are now, just two separate cabs instead of one.

    If the single 12's are different then what is in your 2X12 cab, then there is no way to answer your question without knowing the specs of the cabs you will be using.
  5. VifferMike

    VifferMike Registered Four Banger

    Dec 10, 2004
    Dallas, Texas
    ... and that's OK: by "a little louder" I mean that 750 watts is not even 1db louder than 600 watts, everything else being equal.

    I'm not looking for an increase in volume (but I certainly don't want a drastic decrease). My concern is clarity and flexibility.

    Run from my head, which has two discrete power amps:
    - Will two equivalent 8-ohm 1x12 cabs, each powered by one of the head's power amps, have the same definition and quality as one 4-ohm 2x12 cab powered from one of the power amps?

    (OK, OK: I'm considering dual 8-ohm 2x10s, too. But let's not muddy up the central question any more than I already have ... :D )
  6. Jeff Scott

    Jeff Scott Rickenbacker guru.......... Supporting Member

  7. Jim Carr

    Jim Carr Dr. Jim Gold Supporting Member

    Jan 21, 2006
    Denton, TX or Kailua, HI
    fEARful Kool-Aid dispensing liberal academic card-carrying union member Musicians Local 72-147
    The two cabinet solution also has the obvious inherent advantages: redundancy in the event of failure, divisibility for small gigs and portability, plus the less obvious advantages of being more easily packed into small vehicles and easier to sell.
  8. VifferMike

    VifferMike Registered Four Banger

    Dec 10, 2004
    Dallas, Texas
    Quite true, Jim: all reasons why I'm likely about to do this now that I've got some funds available.

    I'll likely pick up a single 8-ohm cab first just to see how it fares with the 12.2. Then the search will be on for its twin ... and the Uber 212 (really sweet cab ... and with wheels!) will be for sale ...
  9. jeff7bass


    Apr 9, 2009
    More watts running into each 12" driver with the "dual full range" setup as compared to a single 212 using only one amp. Should be clearer with more headroom.

    There are other advantages also, like more focus from each driver because you essentially have a "double baffle" separating the drivers as compared to a single 212, most of which do not separate the two drivers with a baffle (a piece of wood). Also if one cab breaks, still have the other cab to finish the gig.

    The third is that you have a separate volume knob for each cab with THAT head. I run my Carvin BX1200 into my cabs this way and it helps because rooms/stages differ. On a raised wooden stage, sometimes things get boomy (stage floor acts as a sub) so I turn down the lower cab a little. If I'm on a slab concrete floor, I turn the bottom cab up a little more. Flexibility is why you bought that head, eh?

    I think the last thing is you won't be working Amp1 as hard because Amp2 will carry half the load. Actually less than that because each will see the 8 ohm load instead of Amp1 running constant at 4 ohms. The key is which 12" cabs you buy because the Uber 212 is a great cab that puts out a ton of sound and handles gobs of power.
  10. VifferMike

    VifferMike Registered Four Banger

    Dec 10, 2004
    Dallas, Texas
    ... hadn't thought about the individual-volume advantage, Jeff. Nice one ... and yep: flexibility. That's pretty much the theme of my whole rig. :bassist:
  11. DuShauh


    Aug 29, 2011
    West Michigan
    Flexibility= Your 12.2 with Hartke HyDrive HX112's. With a conservative approach on the volume control, you could run 1, 2, 3 or 4 of these 112's with that amp. :bag:
  12. VifferMike

    VifferMike Registered Four Banger

    Dec 10, 2004
    Dallas, Texas
    I'd consider a couple of those HX112s, DuShauh, but they're only rated at 300 watts @ 8 ohms. My amp puts out 375 @ 8 ohms. Recipe for disaster there ...

    ... and that's a big reason I'm considering matched 2x10s instead of 1x12s: 2x10s tend to be able to handle more wattage per cab simply because there are two drivers instead of one. The other big reason? A 2x10 will move more air than a 1x12, at the possible sacrifice of some low-frequency response ...

    ... which brings me to my big concern currently: can a pair of 2x10s deal sufficiently with a low B string? (I chiefly play four-stringers, but often tune the E to D - and I'm considering a five-string bass for a new project).
  13. tinman 1967

    tinman 1967

    Mar 6, 2010
    I have a Shuttlemax 12.0. I run 2 Orange OBC 115s (8 ohms each) out of each poweramp. So..... Amp "a" 375 watts....... amp "b" 375 watts. Basically by adding the second matching cabinet, I gained double the sound, pretty much sounds more full.
    You know, I tried running out of the amp to a cab, then out of that cab to the second therefore creating a 4 ohm load on just one of the power amps. I noticed a considerable amount of volume decrease. :eyebrow:

    Now if I could only figure out how to EQ this damned amp :oops: Just way too many choices there for my simple mind to process:(
  14. VifferMike

    VifferMike Registered Four Banger

    Dec 10, 2004
    Dallas, Texas
    I owned a ShuttleMAX 9.2 for a few months about three years ago, and the EQ frustrated me as well. I've learned a lot about EQing in the meantime, so with this second go-round with an SMAX head it's made a lot more sense. My advice: give it some time, and don't over-tweak; and a little boost (or cut) goes a LONG way.

    Interesting observation about daisy-chaining cabs from one of the 12.0's power amps. I'd be willing to bet that you were still getting an 8-ohm load somehow; that would explain the loss of volume ...
  15. tinman 1967

    tinman 1967

    Mar 6, 2010
    Yeah, I don't know, just tried it again after reading your reply and sure as heck a major volume decrease, especially on the low end. I even pumped the master up to about 5 and it was not too loud. With both cabs on each amp that volume would kill you.
  16. Depends on the 2x10 and what you mean by sufficient. From what I gather most of the new ones can produce 60hz reasonably loudly, that covers you for 2nd harmonic B, keeps me happy.

    The wattage variation between your 4 & 8ohm options is virtually immaterial.

    Headroom only exists when the speaker can handle the extra power.
  17. No need to worry about 75w of non headroom if you can hear the distortion at 250w you won't go overboard.