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Pairing cabs of different impedance, power and design

Discussion in 'Amps and Cabs [BG]' started by Noot, Apr 8, 2014.

  1. I didn't want to get in this position, but it happened.
    I had a Peavey 410TVX cabinet, rated at 4 ohms and 350 watts.
    Now I've bought a Music Man LH115 cabinet, which I'm told has a replacement speaker rated at 8 ohms and 500 watts (these watts could be music and not rms or program).
    I have two amps, one is rated at 4 ohms and 210 watts, the other is rated at 4 ohms and 500 watts.
    What happens if I pair the cabs on either one of the amps? Will I have an impedance of about 6 ohms? How much power will each cabinet draw? Can I bust anything? The Music Man cabinet seems to be more efficient, will I hear it louder or at about the same volume as the Peavey?
  2. dincz


    Sep 25, 2010
    Czech Republic
    Those two cabs combined will be 2.7 ohms so not a good idea.
  3. A 4X10 plus a 1X15 is a bad combination to begin with, and in your case could damage either amp you have by running below the amps minimum rating.
  4. CL400Peavey

    CL400Peavey Supporting Member

    Nov 7, 2011
    Grand Rapids Michigan
    Yep. No way of using both those cabs with either of your amps.
  5. 2.7 ohms? Wow! Good thing I asked!
    Well one of the amps supports 2 ohms load. It's a Peavey Mark III so it puts out 300 watts into 2 ohms.
    Would it work on this one? I know it's not optimal to mix cabs, but just in case I need to get loud.
  6. dincz


    Sep 25, 2010
    Czech Republic
    The Peavey will work ok at 2.7 ohms. Power will probably be around 250w. Two thirds of that will go to the 4 ohm cab and one third to the 8 ohm.
  7. Bassamatic

    Bassamatic keepin' the beat since the 60's Supporting Member

    Paralleling cabs will always result in an impedance LOWER than the lowest impedance cab.
  8. Perfect, thanks a lot!
  9. walterw

    walterw Supportive Fender Gold Supporting Member Commercial User

    Feb 20, 2009
    upshot? use the 500w/4Ω head into the 4Ω 4x10 cab on gigs, and leave the rest in the practice room.
  10. JimmyM


    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    Walter's upshot is what I would suggest, too. Or use the 115 sometimes if you like the sound, too. But I wouldn't use them together.
  11. Bassmec


    May 9, 2008
    Ipswich UK
    Proprietor Springvale Studios
    You could if you want use both amps and both cabs, assuming all the amps concerned are solid state the the 4 ohm rating is a minimum figure your amps in the original post are rated at, therefore if you run the 8 ohm 15 inch cab off the 500 watt amp the amp will deliver about 250 watts into that and the other 210 watt amp will deliver its full rated power into the 4 ohm 4x10 cab.:hyper:
    Then configure the EQ and maximum volume of each head/cab combination, inputting the amps via a splitter box.
    Would you fly a plane across an ocean with only one engine?.

    That's the setup I have used for years as a clean dirty rig, I prefer to use the distortion signal via a 2x15" without tweeter and the clean out of an 8x10" with a tweeter.

    I use 2 200 watt tube amps with my rig but your amps will output about that much, except you will just have less level due to having half the loudspeaker count.

    Do the 9v battery test to make sure all the speakers in your cabinets are going to be in phase or at least basic polarity.
    They should all move outward when a battery + terminal is applied tho the speaker cable leading to the loudspeakers red terminal.

    Always decide how loud the rig should play by defining how loud the fifteen can play fart free, then wind up the level on the amp driving the 4x10".
    That's a very well balanced well engineered twin engined setup suitable for touring reliability and built in get you home mode.:bassist:
    PS. Don't worry about the coincident phase matched loudspeaker Police round here, they will all have to find gigs in anechoic chambers, just to prove there anomalous frequency dependant phase twist graph theories.
    "Yes mate but there is a wall at an angle over there":bawl::bag:
  12. Iirc those old Peavey amps have a slave out, which might work with the other amp's fx return / power amp in.

    Or, Peavey 350w between those two cabs should be plenty loud and not a bad split of power.

    My mixed cabs sound extra good biamped high and low. So phase blending of mixed cabs is not inconsequential. If it sounds good, good. If it sounds gutless the polarity of the 15 is backwards, or the 2nd amp is out of phase, easy fix.

    If it sounds murky weird, cabs don't play well together.
  13. Think of ohms as how much resistance to flow that cab offers (a fairly accurate description). So, it's like if you are attaching two sprinklers to a hose, one using 8 gpm, and one using 4 gpm, they aren't going to present a resistance to flow 1/2 way between the two (what you were originally hoping), they're going to have less resistance to flow than either of them individually.

    (I know, they end up flowing 12 gpm, which doesn't fit with the ohm math, but you get my point, right?) :D
  14. Well, the Peavey does support bi-amping and even has a crossover knob. I will try it out to see if I can use the Hartke amp as slave, and run each cabinet with its own amp.

  15. Bassmec


    May 9, 2008
    Ipswich UK
    Proprietor Springvale Studios
    That's a very good plan, too.:D
    Although both cabs are designed to produce very much the same frequency response and so your rig will be restricted to the ability of the fifteen inch driver below whatever frequency the crossover is set at.

    You might even have more low frequency ability from the coupling of the four ten inch drivers but if it has a tweeter in the cab you will effectively mute that if you run it from the low pass side of the crossover.
    There is still a possibility that using both amps EQ to perfect a good full range sound on each you can always tell if its not going to be sympathetic, most of the phase response concerns come when you have drivers that are designed for very different frequency responses.
    Imagine a 2x18" band pass sub and a vintage Marshall or Ampeg sealed flat back 8x10".
    That's the worst case scenario that the against mixing driver sizes/cabinets Police seem to imagine in every case.:bassist:
    PS My Altec 15" drivers with aluminium voice coil caps are brighter than my Eden 10" drivers that's why the Eden needs a tweeter.
  16. Biamping gets only as loud as your low cab can put out. I wouldn't be shy to try the 15 as the high cab, but presumably you're after the extra volume that only comes with running them both full range.
  17. The Music Man cabinet has a beautiful voice with great mids, but not so much low end. The Peavey cabinet sounds like absolute crap compared to the Music Man, but it can produce very powerful lows. So I would kill the tweeter on the Peavey and use it as a subwoofer.
  18. BassmanPaul

    BassmanPaul Gold Supporting Member

    Aug 25, 2007
    Toronto Ontario Canada
    Post #9 gave you your answer. My advice would be to follow it.

    As for your musicman cabinet, it's using a driver that the cabinet was not designed for. The question would be how much power the driver can manage. Certainly not 500W unless you are very lucky and the driver and cabinet actually work well with each other.