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Can i use a "dumby" speaker to get 220w @ 4ohms out of my amp???

Discussion in 'Amps and Cabs [BG]' started by ::::BASSIST::::, Jan 19, 2005.

  1. ::::BASSIST::::

    ::::BASSIST:::: Progress Not Perfection.

    Sep 2, 2004
    Vancouver, BC Canada
    In pursuit of the ultimate light rig...

    Another one of my "crazy" ideas..

    I have a swr st-220 that i am considering using with a Flite 1x12.

    Here is a question: could i get the full 220 watts out of the amp head by connecting the Flite and then "ghosting" the other speaker output from the amp somehow? Maybe connect an 8ohm speaker that wont give me any sound (ie its components are wrecked in some way so that i get no sound). That way there is 8ohms of power going to it but its not producing sound.

    I know thats probably clear as mud, but the idea is to use the 220 watts of the swr at 4ohms, which means that i have to run two cabs which are 8ohms each. I would use the Flite and then a "dummy" speaker to send the other 8ohms to.

    This would save me from having to haul two cabs.

    Is this totally impossible? :eyebrow:

    If anyone else has some creative ideas to do this please do share! :)

    I beg forgiveness if this whole idea makes no logical sense. I got 3 hrs sleep last nite. :rolleyes:
  2. Quadzilla

    Quadzilla Supporting Member

    First off, it's "dummy" not "dumby" :cool: . Now that's out of the way, the easiest fix is to just buy another 1x12 (or another 8 ohm cab). You'll get the additional wattage AND more sound from more air being pushed by the other speaker. If money is the prob, I'm not sure what else to tell you. Maybe somebody else can tell you how to make an 8 ohm cab 4 ohm. Maybe a resistor? Not sure, I'm no electronic wiz...
  3. protoz


    Nov 30, 2000
    If you really need the 4 Ohm you can use one as a personal monitor, or a drum monitor so it isn't facing the crowd.

    I did this with an old 1x15 when I wanted to show off my brand spankin new Avatar 2 years ago.
  4. Passinwind

    Passinwind I Know Nothing Supporting Member

    Get a cab or cabs with the impedance you need. A dummy resistor will let the amp put out more power, but all of that power will go into heating up the resistor, except for the part that goes into heating up the amp more. There's just no free lunch, sorry!
  5. ::::BASSIST::::

    ::::BASSIST:::: Progress Not Perfection.

    Sep 2, 2004
    Vancouver, BC Canada
    no free lunch... yeah that sucks... probably not going to work. I cant use a second cab as that defeats the whole purpose of going light.

    The whole point is extreme portability with maximum power/volume at minimum cost.

    Not asking too much am I? ;)
  6. Joe Beets

    Joe Beets Guest

    Nov 21, 2004
    A resistor large enough to do the job would function as a large heat sink. Big, heavy and expensive. What works is to take a pair of 12 volt electric heated motorcycle gloves and wire them in series. Then wire them to a jack and plug them into one of your speaker outputs. Don't let them get overheated though, because if the wiring inside the gloves shorts out it will fry your amp. I know because I smoked a Peavey Centurion bass head this way.
  7. Quadzilla

    Quadzilla Supporting Member

    Just order an new speaker for your current cab that's 4 ohm instead of 8. Prob the cheapest and most reliable solution. Flight prob uses Eminence like a lot of others out there (not positive on this). Dave @ Avatar sells raw speakers for cheap...
  8. ::::BASSIST::::

    ::::BASSIST:::: Progress Not Perfection.

    Sep 2, 2004
    Vancouver, BC Canada
    D'oh! That's the 4ohm speaker!

  9. protoz


    Nov 30, 2000
    If you want it light get a Neo speaker from Dave, he's awesome and ships very fast.
  10. Passinwind

    Passinwind I Know Nothing Supporting Member

    Ermmm, didn't I say that? :cool:

    Thing is, one highly sensitive 8 ohm cab could very well be louder with that amp than a less sensitive 4 ohm one would be. Be sure you look at the whole picture here.
  11. ESP-LTD


    Sep 9, 2001
    If your solid state amp puts out (example only) 220w at 4 ohms, it probably makes something like 180w at 8 ohms.

    So ....

    You have a choice of 180w into a single 8 ohm speaker


    half of 220w (110w) into an 8 ohm speaker and 110w into a dummy load.

    The 2nd choice is not very helpful. I would also not suggest wiring random household items into your speaker chain as a dummy load.
  12. ::::BASSIST::::

    ::::BASSIST:::: Progress Not Perfection.

    Sep 2, 2004
    Vancouver, BC Canada
    The swr st-220 is 140w at 8ohm.

    Actually, i have just come across an AI Clarus which I am seriously considering if the seller will ship to me. Its 120w at 8ohms and 200 at 4ohms, 300watts at 2ohms. So i definitely need 4ohms.

    How loud do these clarus amps get? For portability it doesnt get much better. Other than that how does the clarus compare to the swr st-220?
  13. And I thought I was the only one who smoked heads with a pair of 12 volt electric heated motorcycle gloves wired in series and stuck in the wrong output......

  14. Eric Moesle

    Eric Moesle Supporting Member

    Sep 21, 2001
    Columbus OH
    Not wise, because then only HALF of the amps power goes to the speaker, the other HALF of the power goes to the gloves. End result: less power to your speaker than when you started, and if the gloves short out, so does your amp. Do NOT try this, its assinine . . . with all due respect.
  15. ::::BASSIST::::

    ::::BASSIST:::: Progress Not Perfection.

    Sep 2, 2004
    Vancouver, BC Canada
    i have no intention of doing the gloves dealy. Bonus points for creativity though! :cool:
  16. BillyB_from_LZ

    BillyB_from_LZ Supporting Member

    Sep 7, 2000
    If you replaced your 8 ohm woofer with an identical one with a 4 ohm voice coil, you'd never hear the difference and you'd spend a bunch of money for nothing...

    You'd be better off putting the cost of the 4 ohm woofer toward another 8 ohm cabinet... An increase in cone area will gain you more volume than simply running at 4 ohms.
  17. Petebass


    Dec 22, 2002
    QLD Australia
    That's what I'd do, but he wants to travel light.

    You could sell the SWR head and get one that puts out at least at 200w at 8 ohms. But lets do the math on how much louder those extra 60watts will give you.

    Lets assume your speaker has an efficiency rating or, say 96dB. The formula to calculate maximum SPL is:-

    Efficiency in dB + 10*(Log "watts").

    1) 140 watts into that speaker has a Max SPL of 117 Decibels.

    2) 200 watts into the same speaker has a Max SPL of 119 Decibels. A maximum 2 db increase.

    3dB is considered a noticable change. Doubling your watts will give you an extra 3dB.

    To double your volume, you need to add 10dB. To add 10dB, you need to multiply your watts by 10.

    As you can see there's a big relationship between watts and efficiency that determines overall SPL. Adding more cabs adds to both your wattage and your efficiency, thus making a considerable increase in volume.
  18. Joe Beets

    Joe Beets Guest

    Nov 21, 2004
    Eric, if it weren't for the experimentation of bass pioneers like myself, you would still be playing through a Sears 15 watt bass combo.
  19. Quadzilla

    Quadzilla Supporting Member

    No offense, but I have to go with Eric on this one. Using elec motorcycle gloves on your rig to change your impedence is crazy. Maybe I'll play a gig outside my house and hook my amp up to my invisible dog fence! :p Experimentation is one thing, but using plain common sense is another. Again, don't mean to slam you, but you even said that you fried an amp while doing this... :rollno:
  20. Joe Beets

    Joe Beets Guest

    Nov 21, 2004
    You guys are too much. It was just a joke. :D