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Differing Ohm Load Ampeg Cabs

Discussion in 'Amps and Cabs [BG]' started by Pickinator, Jan 8, 2012.

  1. Pickinator


    Dec 28, 2011
    Eagle River WI
    I have the opportunity to buy an Ampeg stack with a 4X10 and a 1X15. The 1X15 is rated as 8 Ohm (200 watt) and the 4X10 is rated at 4 Ohm (400 watt). The Ampeg head is rated at 500 watts, but not at all Ohm loads.

    Can the system run with differing Ohm load cabs?
    Will the head read a total Ohm load of:
    3.464 (square root of 12 {4 + 8})?

    Forgive me if I'm off Base (get it) :D with my math or worried about Ohm loads unnecessarily.

    The amp was sold together as a package at a music store, but that probably doesn't mean much. I am looking to use this set up for the living room and possibly small clubs someday if I make the purchase. It is lightly used and was made in America.
  2. punkrocko


    Jun 18, 2002
    Nashville, TN
    The load will be 2.67 ohms.
    Your amp will need to be stable at 2 ohms to run both cabs together.
  3. Rockman


    Mar 2, 2006
    Bolded is incorrect. That is not how you calculate total impedance of parallel components.
  4. RickenBoogie


    Jul 22, 2007
    Dallas, TX
    The good news is that IF you were to run a 15 with a 410, they should be @ the impedance your 2 cabs are. The bad news, 8 ohms plus 4 ohms equals 2.67 ohms, so your amp would need to be 2 ohm stable.
  5. I'm with him on this.

    Which specific Ampeg cabs are they? I ask because if the 4 ohm 410 is the SVT-410HLF, I don't think you'll get much synergy between that cab and a 15; I think it's best to run that cab on its own or with another one of the same cabs.
  6. Pickinator


    Dec 28, 2011
    Eagle River WI
    The amp head is the B5r and it's tech specs read:
    675 watts @ 2 Ohms (500 watts continuous)
    380 watts @ 4 Ohms (310 watts continuous)
    200 watts @ 8 Ohms (180 watts continuous)

    The Cabs are:
    BSE 115 T
    BSE 410 HLF

    I believe the 115 is rated for 200 watts and the 410 is rated for 400 watts. Each cab has a horn in it too.

    Is this bass package a mess or can it work. I'm looking at $600 for the works.

    How is the Ohm load of the 2 cabs combined determined. I thought it would be the square root of the combined 4 + 8 thereby the square root of 12? (about 3.464....). Again, please forgive my ignorance; I'm still learning. And I'm a drummer.

    Thanks for the input (get it):D
  7. In a parallel connection, the impedance is:

    1/I(total) = 1/I(1) + 1/I(2) + .......
  8. For mis-matched loads Parallel: ZT = (Z1*Z2)/(Z1 + Z2)
    For 2 matched loads ZT= Z/2
  9. Turock

    Turock Supporting Member

    Apr 30, 2000
    Since the head can run a 2 ohm load, it shouldn't hurt anything. If it were me, I'd see if I could buy just the head and the 4x10 cabinet, the 1x15 would probably be useless in that set up.
  10. BassmanPaul

    BassmanPaul Gold Supporting Member

    Aug 25, 2007
    Toronto Ontario Canada
    +1 The 1x15 will be barely audible over the 4x10. It's a waste of time and money.
  11. RickenBoogie


    Jul 22, 2007
    Dallas, TX
    Yes, agreed. Skip the 15, buy the head plus the 410. Run that, it'll be plenty loud- but if you need even louder, find another matching 410. That would kill.
  12. Smooth_bass88

    Smooth_bass88 Groove it

    According to Ampeg's website, running 2 cabs, each with different loads (impedances) is NOT RECOMMENDED.

    Don't do it!
  13. The amp (SS) is not going to care. A 4 ohm 115 will blow before a 8 ohm 410 even gets warmed up though when paired that way. ;)
  14. will33


    May 22, 2006
    I would imagine that's due to uneven power distribution. In this, you'd want uneven distribution with the 15 recieving the least power, or better yet, leave the 15 out all together. The HLF is already a very deep sounding cab, the only thing a 15 would hope to add to the blend would be if it was a very bright sounding 15, adding response the 410 doesn't have. It'd be best to run the 410 by itself. One reason to buy the whole stack would be so you could leave the 15 at a separate location, like a rehearsal space to be played by itself....just carry the amp back and forth.
  15. Pickinator


    Dec 28, 2011
    Eagle River WI
    Unfortunately, it all comes as a package for $600.

    Could a guy buy a new 15" 4 ohm Ampeg speaker and swap it with the 8 Ohm that's in it. If so, how much would it cost and any recommendations on where to purchase. Is it an easy job to change the speakers?

    Would this sound good?:bassist:
  16. Foamy


    Jun 26, 2006
    Sac Area
    Or....can you buy the package, and then turn the 115 for more money?
    Buying a replacement speaker is going to be expensive.
  17. WHY? That is the LAST thing you would need to do if you run it with the 410! :rollno:
  18. BassmanPaul

    BassmanPaul Gold Supporting Member

    Aug 25, 2007
    Toronto Ontario Canada
    That's even worse. You'll almost certainly lose the 15 that way. Do a search on 4x10 plus 1x15 topic. If you buy the package sell the 1x15 and be done.
  19. will33


    May 22, 2006

    Changing the 15 to a 4ohm would be a step in the wrong direction and money wasted.
  20. walterw

    walterw Supportive Fender Gold Supporting Member Commercial User

    Feb 20, 2009
    $600 is a good deal for that collection of gear; just think of it as a half-stack rig with a 15 thrown in for other uses.

    sell the 15, keep it in the practice space, use it for small gigs where that big ol' 4x10 would be too much, whatever. (were it me, i'd sell the 4x10, get another 15, and rock 2 15s old-school.)

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