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newbie headroom question

Discussion in 'Amps and Cabs [BG]' started by tysonlb, Mar 9, 2006.


  1. tysonlb

    tysonlb

    Mar 9, 2006
    Long Beach, CA
    Hey all!

    I am in the market for a new amp and I've read just about everything in the faq's. While I think I understand the basic idea of headroom and why it's necessary, I still need some help.

    So here's the situation:

    I'm looking at buying an Ashdown Mag300H, which is rated at 307W RMS or 550W peak @ 4 ohms, and pairing it with either a 2x12 or 4x10 cab........what wattage rating (for the cabinet) should I be looking at to make sure I have adequate "headroom?"

    I am thinking (right now, at least) that I'll probably end up with a 4-ohm cab.

    Thanks in advance
     
  2. The Ashdonw MAG300H gives about 150-200W at 8 ohm and probably somewhere between 300-400W at 4 ohm. I would buy two 8 ohm cabs, each one 300 watt. So you can use one for rehearsals and connect the additional one for gigging.
    E.g. the 112's from Avatar are pretty good for the money.
     
  3. wolfs

    wolfs

    Jan 18, 2006
    nyc
    Provided you're not in the noise scene or that you don't play ear-bleeding metal or that your guitarist(s) is a reasonable person, I would say that a 4 ohm 4x10 would probably move enough air while getting the maximum wattage from the amp. That said, I like the above poster's suggestion of two cabs if you can afford it (2 8ohm 2x10's would be really easy to transport)... If you have any doubts about how loud you'll need to be, an 8 ohm 4x10 would be best, that way you can add another 4x10 or 1x15 or 2x12 later to move more air. But in that instance, you would of course have less headroom whilst having more volume.
     
  4. GSPLBASSDC

    GSPLBASSDC

    Jan 25, 2005
    Phoenix, AZ
    I agree...2 - 8 ohm cabs would probably be the best way to go, but I would suggest getting a 2x12 right now and a 2x10 later. That way you have 3 distinctly different configurations for more versatility.

    Two cabs with the same speakers in each doesn't make much sense to me....:eyebrow:
     
  5. Richard Lindsey

    Richard Lindsey

    Mar 25, 2000
    Metro NYC
    Headroom has nothing directly to do with your cab's power handling capacity, and you can't get more headroom merely by getting a cab with different power handling. You get headroom by having a bigger amp than you need to do the job you want to do.

    If a 300 W amp is enough to do the job you want to do, your headroom is basically the same whether your cab handles 200 W, 400 W, or 600 W (assuming equal cab efficiency and frequency response). If a 300 W is not enough to get the job done, you're out of headroom whether your cab handles 200 W, 400 W, or 600 W, and simply going to a cab with different handling won't give you any headroom.

    You can get more headroom by going to a more sensitive or efficient cab, because for a given volume, that will allow you to use a smaller percentage of your amp's rated max power. But that's a separate issue from power handling.

    Again, headroom has nothing to do with the ratio between the amp's rated max power and the cab's power handling, and everything to do with the ratio between the amp's rated max power and the amount of power you actually need to use to get your job done.
     
  6. Richard Lindsey

    Richard Lindsey

    Mar 25, 2000
    Metro NYC
    No, if you have more volume, you have more headroom, not less, because it means that for a given acoustic output, you need to use less amplifier power. The smaller the percentage of the amp's max power you need to use to get the volume you need, the more headroom you have. Headroom in an amp is defined by the amount of power that you don't have to use.
     
  7. wolfs

    wolfs

    Jan 18, 2006
    nyc
    I stand corrected... sorry for misleading :)
     
  8. wolfs

    wolfs

    Jan 18, 2006
    nyc
    I guess I got confused -- it was 5a -- when I trying to let him know that between two large 8 ohm cabs, instead of one 4 ohm cab, he would have the potential available watts split between the cabs. Certainly, you're right: if 300 watts is enough to the job, then a couple big cabs will provide enough volume by moving a lot air and, thereby, not requiring the master to be cranked...
     
  9. Willem

    Willem

    Dec 26, 2005
    Belgium
    So if I add a 1x15 cab to my 4x10 cab (both 8Ohms) I will not gain volume?
     
  10. ghindman

    ghindman

    Feb 10, 2006
    Not necessarily. I believe most 410s are generally wired in series/parallel - two pairs of series wired cones, wired in parallel, which would be the same wattage split as running two 2x10s, or two 2x12s, etc..

    The advantage of two cabs is portability, the advantage of one cab is additional low-end due to greater cabinet cubic volume.
     
  11. ghindman

    ghindman

    Feb 10, 2006
    If the cabs are the same Ohm rating, the amp's power will be evenly divided between the two cabs. Assuming your amp has enough wattage to adequately power both cabs, it'll be louder. But, if the result is two under-powered cabs, it won't.

    However, if you're running a SS head, you'll be getting more power at 4ohms than at 8ohms, so the extra power drain usually balances out nicely.
     
  12. wolfs

    wolfs

    Jan 18, 2006
    nyc
    No, you will definitely gain volume, you'll be pushing more air... watts does not equal volume... speaker area and sensitivity are much more important to volume than watts of the amplifier.
     
  13. wolfs

    wolfs

    Jan 18, 2006
    nyc
    I was talking about two 8 ohm 4x10's versus one 4 ohm 4x10 (or 2 8 ohm 2x10's) with all other factors being equal... I'm just providing more confusion than it's worth so I'll just shut up now ;)
     
  14. Richard Lindsey

    Richard Lindsey

    Mar 25, 2000
    Metro NYC
    It will be louder because of mutual coupling, and "underpowering" is a nonissue for those purposes.

    Two speakers in parallel don't create more "power drain," they create a lower impedance.
     
  15. GSPLBASSDC

    GSPLBASSDC

    Jan 25, 2005
    Phoenix, AZ
    +1 watts equals power. Volume is a measure of sound pressure levels (in db's). The two aren't interchangable, but often get mixed up.