Quick question about ohms and my setup. (Parallel?)

Discussion in 'Amps and Cabs [BG]' started by Corvette19, Feb 24, 2013.

  1. Corvette19


    Oct 10, 2010
    Greenville SC
    Alright! It's tax return season so I have purchased my first head/cab and I have decided to grab the Ampeg PF-500 head.


    it pushes 300 watts at 8 ohms and 500 watts at 4 ohms.

    Alright so I also picked up a Hartke 4x10 cabinet (which sounds great!) which is rated for 400 watts and is 8 ohms. I'm wanting to get another cabinet (I'd really like a 15 inch speaker.) So here is the real question. I have the amp running one line to my 4x10 cabinet which is rated at 8 ohms. It has a "Parallel" output jack beside the input. What would the 15 inch cabinet need to be rated at in terms of watts and ohms in order to make my impedance 4 ohms?
  2. It will need to be 8 ohms and it will get a maximum of 250W. That's the max though. It will not get that all the time so you could probably get by with a 200W speaker if you wanted to as long as don't play at max volume all the time. If you get a Hartke 15 cabinet it will be able to handle at least 300W, depending on the model. Some of them handle 500W.
  3. two fingers

    two fingers Opinionated blowhard. But not mad about it. Gold Supporting Member

    Feb 7, 2005
    Eastern NC USA
    8 ohms. But here's the thing. There will be uneven power distribution between the speakers. Please do some reading in the sticky section of Amps. It's truly an education. The short version is that your best bet would be another 4-10, preferably just like the first one. A 15" speaker doesn't "sound more bassy" than 4 10s. You will get more volume, and more even power distribution with another 4-10 and frequency wise they will probably be the same.

    This is as far down that road as I am willing to go because the subject of mixing drivers quickly turns into something ugly around here.
  4. Cab would be 8 ohms and you'd get 250 watts per cabinet, but I would make sure the 15 is rated at least at 300 watts so you could use it stand-alone.

    Also the point about mixing disparate cabinets is a good one, speaker cabinets do not have an inherent sound based on the size of the drivers in them. Many 410's go lower than many 115s. Check out the efficiency of each cabinet to try and get some handle on their relative loudness, most 410s just bury 115s in terms of efficiency, which ends up leaving your 115 making very little overall contribution to your sound/volume. I agree, check the stickies for more in depth information.
  5. RickenBoogie


    Jul 22, 2007
    Dallas, TX
    I'll just add, the topic of mixing a 410 with a 115 is a very tired subject. Bottom line, it is NOT a good pairing. There are literally millions of threads on this topic, and the educated among us have given proper scientific evidence of this being a bad idea. Do some research, and do yourself a favor. If you want more volume and low end then you have currently, get a 2nd identical 410.
  6. CL400Peavey

    CL400Peavey Supporting Member

    Nov 7, 2011
    Grand Rapids Michigan
  7. Corvette19


    Oct 10, 2010
    Greenville SC
    My main question is how does this "parallel" output affect my ohms? Will my setup still be at 4 ohms if I connect an identical cabinet? They are both at 8 ohms.
  8. GrowlerBox


    Feb 10, 2010
    Nude Zealand
    Yes. Two 8 ohm cabinets connected in parallel will provide an impedance of 4 ohms (all complications aside).
  9. BogeyBass


    Sep 14, 2010
    mega face palm

  10. Corvette19


    Oct 10, 2010
    Greenville SC
    Sorry for ensuring the safety of my newly purchased amp. Good day to you :p

    And thanks for the clarification. You guys have been a huge help.