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Need help matching head to cabs

Discussion in 'Amps and Cabs [BG]' started by BassmanMrEd, Oct 21, 2009.

  1. Good afternoon everyone. I was trying to figure out how this is done. I have the GK Backline 600 head rated 300 Watts. What I want is to run 1x15 and either 2x10 or 4x10. Given this head, how would I match up speakers to use that I can benefit from? At present I am using at 300 watt x 15 woofer. How do you go about matching all this up. I am thinking of moving up to either 400 or 500+ watts as the others tend to drown me out a bit. But then again, HOW do you match it all up? Oh, it's an 8 ohm head too. I'm new to all this technical stuff. Any help would be greatly appreciated.

    thanks and have a nice one,
    Ed :cool:
  2. Hmm you've got some facts backwards there, a head cannot be any one particular amount of ohms, a head has a minimum ohm rating for safe use. I'm fairly certain that the minimum ohms on the backline 600 is 4, not 8. perhaps you meant your cab is an 8 ohm 1x15?
  3. i've always been told to think of it this way.
    you want to have more watts in your head then your speakers need, to have clean tone at volumes. if you 4ohm cab needs 700 watts, you should have a head that put out more then 700 watts to a 4ohm load.
    now if your amp can only support 300 watts at 4ohms, you'll be overdriving you head and getting a dirty sound, and will shorten the life of your head.
    if you have a 8ohm cab that takes 700 watts, with that same 700 watt 4ohm head. it would be the same as powering a ~1400 watt cab at 4ohms. so again you will be overdriving.
  4. BillyB_from_LZ

    BillyB_from_LZ Supporting Member

    Sep 7, 2000
    Stick to 8 ohm cabinets and use two of them. That will operate the amp at 4 ohms, which as it has been posted, is the minimum load impedance for the BL600. To my ears, a 2x10 and a 1x15 are always a good mix and 2x10s are easier to haul than 4x10s.

    If you have efficient enough cabinets and you're still not loud enough...get the others to turn down.

    And, you might want to re-examine your EQ settings. When set flat, the EQ section of the BL600 provides some healthy bass boost, bumping it up more just eats up amplifier power.

    I'd recommend that you take some time read Fdeck's paper on the BL600 EQ section. http://personalpages.tds.net/~fdeck/bass/gkbl600.pdf

    Oh, and going to a 400 or 500 watt head won't really help as the loudness increase would be negligible (given the same speakers).
  5. Sorry, but almost none of this is right. You might want to search on underpowering and overpowering, particularly with reference to the sticky thread at the top of this forum. Look for posts by BobLee, Mark Reccord, and billfitzmaurice, for starters (there are other good ones as well; don't want to forget anybody).
  6. RickenBoogie


    Jul 22, 2007
    Dallas, TX
    +1 the BL600 is a 4 ohm minimum head, so you want 2- 8 ohm cabs. If your 15 is an 8 ohm, get an 8 ohm 2x10. A 410 paired with a 15 is not a great match, though many people use that combination. Fact is, most 410's will handle alot more power than most 1x15's, so the 15 limits you. 210/15 with your head should be fine.
  7. thank you
    i'll look that up. thats just always what i've been told, and what i put together for through electrical engineering
  8. Do a bunch of reading in the faq and you'll find some good info that can help with your decision. [Also note that the difference between 300 watts and 400 is minimal. Depending how the amp is voiced, you may hear no audible difference, or even possibly *less* volume output (all other things equal).]

    You're currently pushing about 180 watts through a single 15" speakers. To get more volume, you would benefit with more speakers. A 2x10 cab (8 ohms) to match your 8 ohm 1x15 cab would help. Stack the 2x10 vertically for best results (though it may "look" funny). You should be able to keep up with a rock band with this setup. Don't boost the low frequencies too much though - they eat up wattage (and thus reduces your amp's headroom), and overall don't help increase your volume in the mix. Can get muddy in a club with too much lows too.
  9. Steveaux

    Steveaux Safe-Guardian of the Stoopid Supporting Member

    Jul 1, 2008
    The Wilds of NW Pa.
    Read this ...

  10. so i read your suggested information and found my post to be true.
    the only difference is the grammar in mine sucks and was talking in respect to the head and not the cab.
    if you still disagree then please post the correct information
  11. JimmyM

    JimmyM Supporting Member

    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    It seems to has calmed down a little, but there has been an epidemic of people blowing their small cabs because some dunce told them that you need twice the power that the cab can handle so you don't underpower it. If you have 32 ounces of water, are you going to put it in a 16 oz cup?
  12. If you thought it agreed with what you said, then I'm sorry, but you misunderstood it, or what you posted was the opposite of what you meant to say. No disrespect, but I've posted about this so many times that I don't feel inclined to do it again right now. Maybe later. Or you can reread Bob's, Mark's and Bill's posts to see why cab ratings do not in fact refer to what a cab "needs" but rather to what it can take, and why over/underpowering has absolutely nothing to do with the ratio of the amp's power rating to the cab's power handling.
  13. Sahm


    Dec 18, 2007
    Delaware, OH
    There might be something lost in translation here, but without even addressing your statements on under/overpowering, I don't see this statement as anything but incorrect! Again, you said your grammar might be wrong, so maybe you meant something else, but if you added an 8ohm cab to a head that puts out 700watts at 4 ohm, it would NOT be like adding a 1400watt rated 4 ohm cab. What would actually happen is the amp would put out less watts, say 400, since it's now at 8ohms.
  14. what i ment to say is the amp would see this as a load that is twice as big as it actually is. the amp will run at full tilt trying to give the speakers what they need. this will cause the amp to clip and give a distorted tone (i guess overloading should have been used instead of overpowering). this doesn't mean you can use a 2000W head into a 400W cab (well at least not at full tilt) but you could use it to get all the volume clean volume available by your cab.

    the output wattage would not change to something less then what the amp puts out. but the wattage available to use through that speaker would not be enough to operate the load efficiently.

    by no means am i trying to debate, this is what i learned in electronics engineering.
    its possible that we are talking between coventional current flow and flow of electrons. but we are saying the same bottom line. using an amp with more wattage then the cab will work better then the opposite. running an 8ohm cab with an amp designed for a 4ohm load won't sound clean
  15. your facts are ALL WRONG, heads are not "designed for" any particular amount of ohms, they have a minimum. Running an 8Ohm cab with a head that puts out 700 watts at 4 ohms will cause the head to put out about 300 or 400 watts at 8 ohms, the speakers determine the impedance, not the amp.

    And secondly, the theory that underpower causes clipping or distortion is a myth, my phil jones head is running about 400-450 watts into cabs that are rated at 1500 and I can turn my gain and master to 10 and not hear distortion through the active input.
  16. i ran my ampeg througha 8 ohm for years and could never get a clean tone, soon as i ran it through 4ohms the sounds was crystal clear

    the cabs are the only impedence through the entire system, the amp is the power sorce. the power across the load is what changes not the power the amp can supply. if you plug an appliance into your house outlet there will always be 120V supplied from the outlet, but the appliance may only use 90 at any given time. but it can never use 150V
  17. Nope:)

    Quickly.... first, you are confusing the power rating of a cab with 'what the cab need's. The power ratings of cabs are nothing more than the manufacturer's suggested MAXIMUM power rating that can be applied over a reasonably amount of time before thermal damage is done to the drivers. Since amps rarely put out their rated power for any more than short bursts, this is where the 'you can safely use more rated power from an amp than what the speaker maximum rating' comes from. Cabinet SPL (i.e., loudness per watt) is a totally different thing, and some cabs, regardless of impedance, can require a lot of juice to get up to their full volume potential due to the cabinet tuning (i.e.,... very low), etc. This is a different issue.

    Second, your 4 versus 8ohm issue is most likely a proxy for increasing the power output of an amp. If you are driving an amp to its limits at its lower 8ohm output, adding another 8ohm cab will result in more power and more cone area, resulting in an almost shocking increase in volume and clean, open low end in most cases (i.e., with moderately powered solid state heads).
  18. But was it the EXACT same model cab except 4 ohms? with the same wattage rating? otherwise this observation can not be blamed on the impedance.
  19. If I understand this.....you were running your tube amp on the wrong setting which sounds terrible, when you ran it on the right setting it sounded fine. All I picture is a tube amp on top of a 810 with the impedance switch selecting 8ohms. If this is the case.....you're doing it wrong.


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