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counting with watts

Discussion in 'Amps and Cabs [BG]' started by JDT, Nov 28, 2006.

  1. I'm pretty bad at all this calculating watts/ohms stuff, so feel free to smack me for any stupid mistakes I realize this should be pretty basic stuff, but I just don't get it :bag:

    I'm currently using an Ashdown MAG 115 300w combo (link). This puts out 300w RMS. However, its built-in speaker only puts out about 200w, and to get to the 300w I'd have to hook up an external speaker. Minimum impedance for the speaker outputs is 4 ohms.

    The thing is: I can buy an Ashdown 410 Cab (link). This is rated at 450w with 8ohms, and I can't get my head around WHAT this will do for my sound. Will this turn into both speakers putting out 150w for the total 300w my combo can provide or is there some funky way to calculate total watts? And if I disconnect my 115, will this allow my 410 to put out 300w?
  2. Short answer: yes and no. :D
    IMO I suggest you don't get too hung up on watts. :confused:
    There's a lot of variation in manufacterer's actual power produced (regardless of what they say), and the bottom line is how loud is sounds to you.
    Just be careful the speakers you connect do not reduce the ohms below what your amp will run safely. :)

    Long answer:
    Your amp is probably rated at 300 watts into 4 ohms. Given that your 15" speaker is 8 ohms and you connect another 8 ohm cabinet (the 410) you will run 150 watts into each cab.
    This is because connecting the 410 cab to your external speaker jack on the combo will run both cabs in parallel and will reduce the ohms to 4. That should get the full 300 watts split between the two cabs.
    If you disconnect the 15 and run just the 410 cab you will only get 150 watts into 8 ohms. However, that cab may take more watts before it starts to distort, so you may be able to crank it louder than both cabs combined.
    Hope this helps :D
    Good luck :)
  3. as long as your loads are balanced (i.e. 8 ohm internal speaker and 8 ohm extension cab wired in parallel - as most amps are). you will be sending an equal amount of power to each cab, regardless of what the speakers maximum power is rated at.

    as far as volume levels go...

    if each cab is getting 150 W, the 4x10 will be about twice as lod as the 15 (assuming similar speaker/cab efficiencies).
  4. actually, if the amp is rated at 200 W into 8 ohms, you'll likely get 200 W w/ the 4x10 (unless you don't believe the rated power is correct. and we know companies never lie about their specs, do they?).

    just being picky :)

    good advice about not getting hung up on watts. i'll reinforce the point.

    general rule of thumb that i like:
    1. doubling your number of speakers doubles you volume for a given wattage.
    2. quadrupling your power output (wattage) doubles your volume for a given number and type of speakers.
  5. Thanks guys! I might just get all of this yet:)

    I'm 'fixated' on watts because its -to me- seems like a very basic indication of how loud the thing will be. I'm buying the 410 because my combo can put out more watts and I can use the extra volume.
  6. 62bass


    Apr 3, 2005

    A good 8 ohm 2-10 cabinet is probably all you'll need and will be a lot easier to haul around.
  7. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    Watts alone give no indication about how loud it will be.

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