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OHM-y!!!

Discussion in 'Amps and Cabs [BG]' started by XxBassmanxX, May 28, 2003.


  1. XxBassmanxX

    XxBassmanxX

    Nov 21, 2001
    Rosman NC
    Ok, Im on the brink of FINALLY finishing my first "rig." I went to guitar center the other day for the memorial day sale and found a sweet GK 4x10 for $550. I LOVE the sound of the GK 2x10 combos so i figured this speaker would work well for what i need. I have put the cab on layaway but earlier today when i went to try my modulus through it i noticed it was 8 ohm. It had been advertised with switchable impediances so i figured that wouldnt be a problem. I dont know enough about this type of thing so ill ask you guys. How much volume am I losing by running a 600watt (at 4ohm) Mesa m2000 through an 8ohm GK 4x10 vs the 4ohm model. The bass guy at gutar center says that i am only losing about 30 watts total and it will be almost the same as the 4ohm cab. Lemme know!

    Joe
     
  2. PollyBass

    PollyBass ******

    Jun 25, 2001
    Shreveport, LA
    He is a moron, it's more toward half the power running at 8 as apposed to 4.
     
  3. jive1

    jive1 Moderator Staff Member Supporting Member Commercial User

    Jan 16, 2003
    Alexandria,VA
    Owner/Retailer: Jive Sound
    I second that opinion. The loss of power will be anywhere from 25-50% depending on the type of power amp. For example my class D Peavey DPC1000 runs at 500W @ 4 ohms, 375W @ 8 ohms. Whereas my SWR 220 runs at 220W @ 4 Ohms, and 110 @ 8 Ohms. But to your ears, decibels mean more than watts. So even though you may lose 50% of your wattage, you aren't necessarily losing 50% in decibels.

    Hope this helps.
     
  4. XxBassmanxX

    XxBassmanxX

    Nov 21, 2001
    Rosman NC
    He said it would be 270watts at 8 ohms. Is that about the same as 600 at 4? I had a feeling that they were just trying to sell it, but i didnt know. I put it on layaway so that ill still have the option of getting it at this price. Is my head made for 4ohm cabs or something? Would i be losing half my volume with the GK?

    Joe
     
  5. jive1

    jive1 Moderator Staff Member Supporting Member Commercial User

    Jan 16, 2003
    Alexandria,VA
    Owner/Retailer: Jive Sound
    No, watts and volume are related but not the same. Some of the other guys on this forum can give you better details on the technical aspects. The wattage of the speakers is how much power they can handle. More power doesn't necessarily mean more volume. If a speaker is inefficient like the Acme cabs, it will take more power to produce the same amount of volume than a more efficient speaker like the Euphonic Audio cabs.

    But to kinda answer your question 270W at 8 ohms would roughly be around 500-600W at 4 ohms. There would be a loss of volume to run them at 8 ohms, but I can't tell you how much. However, your ears probably can.
     
  6. lo-freq

    lo-freq aka UFO

    Jan 19, 2003
    The Republic of Texas
    The Mesa Boogie M-2000 owner's manual lists the 8 ohm output at "roughly" 300W (by the way it lists the 4 ohm output at 625W and peak output at 2000W).

    The difference between the loudness at 600W and 300W is approximately 3 db.

    If the GK you want is relatively efficient, you probably won't notice a lot of difference.

    If you decide you need more volume later on, you can always add another 8 ohm cab in parallel to give you max output.
     
  7. Scott D

    Scott D

    Apr 21, 2003
    Minneapolis, MN
    if the M2000 can run a 2 ohm load, you can rewire the cab to be a 2 ohm cab... which would be alot louder. i'm currently running an 8 ohm cab, but i plan to add another 8 ohm cab. if you got an 8 ohm 1x15 to add to the 4x10, that would bring the whole load down to 4 ohms... so you could try that option.
     
  8. lo-freq

    lo-freq aka UFO

    Jan 19, 2003
    The Republic of Texas
    Minimum recommended impedence load for the M-2000 is 4 ohm.
     
  9. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    Did the guy at the store say 30watts, or 30%. If he said 30w, he's an idiot. If he said 30%, he's spot on.

    Here's the thing. 600w isn't much louder than 420w. The difference is barely audible. There will be a 3dB difference at the most, and 3dB is the smallest incriment that the human ear can hear.

    Remember that to get an extra 6dB, you have to double your watts. To double your volume, you have to multiply your watts by 10. Why? Because decibels are logarithmic.

    So you won't lose out on much volume at all by getting the 8 ohm cab. In fact, you may be better in the long run because you will be able to add a second 8ohm cab. This will produce a total 4 ohm load, increase your amp's output to 600w, and increase your volume a lot more than 3dB because all those extra speaker cabs will push lots more air. The overall gain is aprox 6dB. Not bad considering the other way to add 6dB is to buy an amp that pushes 1200w.
     
  10. lo-freq

    lo-freq aka UFO

    Jan 19, 2003
    The Republic of Texas
    Sorry Petebass, but I believe that the bolded parts of your statements above are incorrect.

    The smallest audible distinguishable difference in sound pressure level is 1db.

    Doubling power increases the output of a given speaker (assuming the speaker can handle the extra power adequately) by approximately 3db.

    This means that the difference in the output from a speaker (designed to handle 600W or more) from feeding the speaker 300W and 600W is approximately 3db (which is three times the smallest distinguishable sound level change increment--definantly audible, but not a big difference).

    An example of theoretical* speaker output at 1 meter related to doubling power input:
    1W input, 93db output
    2W input, 96db output
    4W input, 99db output
    8W input, 102db output
    16W input, 105db output
    32W input, 108db output
    64W input, 111db output
    128W input, 114db output
    256W input, 117db output
    512W input, 120db output

    *There will be some losses due to entropy.

    I believe you got either misinformed or got your facts confused.
     
  11. wulf

    wulf

    Apr 11, 2002
    Oxford, UK
    Is the cab switchable? You said 'advertised as' but didn't confirm.

    If it is, then run it at 4 Ohm at the moment and then change to 8 Ohm when you want to add another 8 Ohm cab for increased speaker area.

    If not, then one of the key factors is how appealing you find the idea of getting a second cab to join the rig at some point.

    Wulf
     
  12. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    I stand corrected. Double your watts is indeed 3dB. That's what you get for posting when you should be sleeping.

    So I guess my last sentence should read "Not bad considering the other way to add 6dB is to buy an amp that pushes 2,400w".

    I stand by the rest of the post though.