Pairing an 8 ohm and 4 ohm cab

Discussion in 'Amps and Cabs [BG]' started by MattGreer, Nov 22, 2013.

  1. MattGreer


    Jan 27, 2013
    Denver, CO
    Not sure how this works, newbie here.

    If I pair a Markbass Standard 104HR (which can be purchased in either an 8 Ω or 4 Ω variet, and a Markbass Standard 151HR, which comes only in 8 Ω, and I plug those into a LM III, which puts out 300W @ 8 Ω, or 500W at 4 Ω, what power output am I going to get? Or is this not a possibility? I have to get them both as 8 Ω cabs? Or can one be 4 Ω and the other 8 Ω?

    Thank you for your help!

  2. You should get the 104HR in the 8Ω variety. Otherwise, your amp will see a load of 2.7Ω which could be hazardous to its health IF it has a minimum impedance rating of 4Ω. I don't know what it is rated for - you will have to determine that.
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  4. MattGreer


    Jan 27, 2013
    Denver, CO
    Thank you for the reply!

    How is that calculation performed? Are the resistances in parallel or series?

    The amp is rated for either 8 or 4 ohms.
  5. B-string

    B-string Supporting Member

    You can run one 8 ohm cab or two 8 ohm cabs (=4 ohm load). You can run one 4 ohm cab with no other. If you run a 8 ohm cab and a 4 ohm cab that will equal a 2.667 ohm load and either damage the amp or it will shut down.
  6. B-string

    B-string Supporting Member

    The IMPEDANCE will be a parallel formula available in the FAQs /stickies.
  7. In addition to worrying about the amp, different ohms in the speakers will cause the amp to send more power to the lower impedance speaker so they won't sound even.
  8. One thing to be aware of is the 104HR has a rated sensitivity of 103dB while the 151HR is rated at 100dB. This means the 151HR is likely to have trouble keeping up with the 104HR. The 104HR is also rated to play lower than the 151HR (35Hz vs 40Hz). While that may not seem like much, it tells me that there is little point to getting the 151HR. I think two 104HRs would be a better choice.

    I have nothing against the combination of a 1x15 and a 4x10 in general but sometimes a given set of cabinets might not be well-suited for each other and that seems to be the case with these in my opinion.
  9. MattGreer


    Jan 27, 2013
    Denver, CO
    Guys, I can't thank you all enough for the help and advice. There's more to think about than I realized.

    There's definitely a difference when listening to the 104HR and 151P (I know, not the one I mentioned above, but very similar). There's just such a smooth bottom end that fills out the sound so well, at least to my ear. I can't explain how it sounds different considering the fact that the 104HR goes down to 35 Hz and the 151P only goes to 40 Hz. Dunno.

    That being said, based on the sensitivity, it would be better to pair the 102HF with a 101 db SPL and the 151HR with 100 dB sensitivity. I know the dB scale is logarithmic, but that's as close as I can get to match the sensitivity with the MB product line (I like the light weight and it sounds quite good).

    The rooms I play in are small, so power is not a necessity really, but I want a balanced full sound, and I just felt the combination of the 10's and 15 gave me that. But there's a big advantage to the two 4x10's, as I can leave one at home to practice on and one at church so all I have to do is transport the amp back and forth.

    It's hard to pick this stuff out! I'm an intermediate-level player with better ears than skills, heh.
  10. walterw

    walterw Supportive Fender Gold Supporting Member Commercial User

    Feb 20, 2009
    that's "listening with your eyes", and not a good idea. the "balanced, full sound" comes from matching good cabs, while differing cabs can actually cancel some of each other's sound.

    this is a well-worn topic around here, just search "4x10 and 1x15" or "matching cabs" for endless hours of reading fun!
  11. MattGreer


    Jan 27, 2013
    Denver, CO
    Walterw, I appreciate your comment, but honestly, playing back and forth the combinations of 4x10, 4x10+1x15, 2x10, 2x10+1x15, there was a big difference. But, I shall follow your advice! On to the search engine! :)
  12. walterw

    walterw Supportive Fender Gold Supporting Member Commercial User

    Feb 20, 2009
    no doubt, adding the 15 to whatever will indeed make it bigger and louder; the question is whether it would be as good as adding the identical matching cab instead.
  13. MattGreer


    Jan 27, 2013
    Denver, CO
    I found some threads and I see what you're saying Walter. Seems like there's new folks like me that come across this subject quite often.

    The issue, is seems, is power balancing between the cabinets? I'm sure it's more complicated than that. Put the 15 on top and listen for cries of help, heh.

    Perhaps the 102HF (rather than a 4x10) and 151HR might be well matched? Power, impedance, sensitivity all match well, no?
  14. One more thing - the cabs don't have to total either 4 or 8 ohm. It's OK to run between the amp ratings so a 16 and an 8 running in parallel will be between 4 and 8 and won't hurt the amp but it probably won't sound good. Two 8's in parallel making a 4 ohm load is a much better combination.

    The amp manufacturers rate them at 4 and 8 because those are standard impedances that can easily be built a variety of ways. The modern amps (class D) I've seen are designed to operate between 4 and 8. They also have special circuitry to sense if a load less than 4 ohms is connected and self-protect.

    There was a time when many amps were designed to operated between 2 and 4 ohms. I just sold off a bunch of tried-and-true Old School Peavey amps that were designed for these loads.
  15. RickenBoogie


    Jul 22, 2007
    Dallas, TX
    Here's one thing you can bank on- 2 identical cabs will always outperform a mixed set. In your "experiment", the combinations you did NOT try were 2x the 115 cab, or 2x the 210 cab. 2 identical cabs will "couple", increasing everything, including low end response. I would go with a pair of the 15's.
  16. Whenever you drive multiple speakers of different specifications, the results are always unpredictable. Two speakers that separately sound good can sound dreadful when paired together even if their electrical characteristics match. Two different size and different impedance speakers can behave very oddly. The amp won't care as long as the impedance is within it's driving ability, but the sound can be very odd. It's very similar to when somebody swaps just one pickup on a guitar for another brand and style and suddenly finds the tone control works strangely and the volume controls behave very strangely, often with all the action squeezed into one end of the travel.
  17. BassmanPaul

    BassmanPaul Gold Supporting Member

    Aug 25, 2007
    Toronto Ontario Canada
    I wonder where I've heard that before. :D
  18. walterw

    walterw Supportive Fender Gold Supporting Member Commercial User

    Feb 20, 2009
    eh, no.

    the point would be (if you like that brand and they're similar ballpark size and price) to listen to each one, decide which one you like better by itself, then just get two of them.

    for me it's two little LDS single 15 cabs. one for small gigs, two stacked for big gigs.
  19. MattGreer


    Jan 27, 2013
    Denver, CO
    Thanks again to everyone that provided helpful comments in this thread.

    In the end, I decided to go with two 4x10 cabs and the LM III head. The reason I went with the 410s was due to the feedback from folks when I played the Jeff Berlin combo vs my existing 210.

    Should be here in a week!
  20. walterw

    walterw Supportive Fender Gold Supporting Member Commercial User

    Feb 20, 2009
    that'll be a monster stack!

    you probably won't often need more than one 4x10, but the pair will crush all your enemies.
  21. You made a good & wide choice my fellow bassist. :cool::thumbup::thumbup::cool:
    You say you could hear a distinct difference when listening to just a 410 then adding a 115. or a 210 & adding a 115 cab. Did you try adding a 410 to a 410 or a 210 to a 210. or a 115 to a 115???
    I'm sure you'd have noticed a big difference if you did too.
    I'm glad you picked 2 identical 410 cabs. That sure will be a monster stack. Be sure to post a pic or two :thumbup: