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4ohms Versus 8ohms??

Discussion in 'Amps and Cabs [BG]' started by Irie01, Feb 19, 2002.

  1. Irie01


    Jan 22, 2002
    i was talkin to a guy in guitar center once and he explained to me the difference between 4 and 8 ohm's. Well, here it is time to get a nice rig, and I totally forget what the difference was between them.I feel like he was saying that the 4 ohms was better but I cant remember exactly.I am looking for a 600 watt cab, probably a 350watt head to start.Could anyone please expalin to me the ohms and differences/advantages of both.Also, I would like to know some people's opinion on the difference between a 15" and 4x10's as far as the cab. If it helps at all, I play a lot of reggae, jazz, and ska kinda music.Thanks a lot..
  2. BassPlayerGush


    Sep 23, 2001
    to make a long story short, ohms measure the resistance of impedance. therefore it will take less power to drive a 4 ohm cab over an 8 ohm. depending on the contrsuction on the 4 ohm cab, it may be more vulnerable to blow. that doesnt mean that it will, but just has more of a chance. please dont criticize the way i explain it:p . but thats the way i like to put it. everyone has there own opinions on everything. i personally like a 15" cab of a cab of 10"s or 12"s. im a firm believer that each instruement or part of a band has its very own frequency range. a 15" cab has a lower punch frequency, thus if it is set up right, the audience will feel it more and get that entire beautiful and complete concert sound that leaves your stomach pumping. why must you need so many high frequenies when thats the guitarists job? afterall the bass guitar is a BASS guitar, lol. therefore you should have more bass then high frequencies. i think its more effective for the audience to feel your bass guitar then hear it. some people may disagree with me, but o well;)
  3. PICK


    Jan 27, 2002
    Sydney, Australia
    Stuff the rest of the band! Cover as many frequencies as possible! Guitarists have been using too much bass for years so why shouldnt we take their frequencies!! jk :)
  4. BassPlayerGush


    Sep 23, 2001
    hahaha........good point;)
  5. abaguer


    Nov 27, 2001
    Milford, NJ
    Another point in the 8ohm vs 4ohm equation is whether you want to use a separate cab or not. A 4 ohm cab is good if you're only planning on using it as a stand along cabinet. Since many amps handle 4ohm minimums you can't easily add a second cab to that. If you have an 8ohm cab you don't get the maximum power out of your amp if you use the cab by itself; BUT if you want to add a second 8ohm cab then the load is a 4ohm load and you get the full wattage out of your amp plus the added coverage of two speakers.
    When I buy a cab the first question I ask myself is how will I use it. If I'll use it by itself it makes sense to get it in 4ohms; if I wanted the flexibility of sometimes adding a second cab, then I would get it in 8ohms. The impedance that your amp can handle is a big consideration.
    As far as tens vs 15s; I've always used fifteens in the past, usually in conjunction with a 210 cab for louder gigs. Over the last few years however I've made the switch to only tens, either 110s or 210s. Since I play upright as well as elec I like the control that the tens give me over the sound. When I play a louder electric gig I'll usually stack 2 210s or a 210 and a 110 and I have no problem getting a very deep sound, what I like about the 10s is that they are very focused in the low end. Having tens doesn't necessarily mean that you have to play in the guitarists frequency range. You can still get very deep bass just with a little more focus; especially if you play a lot of different rooms.
  6. chucko58


    Jan 17, 2002
    Silicon Valley, CA, USA
    I paid for all my gear myself. Well, me and MasterCard.
    Here's the way I understand it.

    First, the basics. Multiple cabs are usually hooked together in parallel. If you have two cabs, and each is 8 ohms, the combination is 4 ohms. Likewise, if you have two 4 ohm cabs and you parallel them, you get a 2 ohm load. A 4 and an 8 together give you a 2.66 ohm load. Etc.

    With tube amps (specifically amps with POWER tubes!), there's usually a choice of impedances, so it really doesn't matter what impedance your cab is.

    With solid state it gets interesting. In general, the lower the impedance of the load (fewer ohms), the more power an amp can deliver to it. But there's a limit, and that limit is usually either 4 or 2 ohms. This rating is usually on the back of the amp, right next to the speaker jacks.

    But pushing that limit can cause trouble. Some very reputable amps will eventually overheat and shut down if you drive them hard into a minimum impedance load. Others will freak out and shut down quickly for no apparent reason. So you have to take that rating with a grain of salt.

    I won't even talk about stereo amps and bridging here.

    Here's the simplest advice I can give and still respect myself. ;)

    If you are only ever going to use one cabinet, 4 ohms is probably OK. But if you think you might want to add a cab later, and your amp isn't stereo, you should think about an 8 ohm cab instead.
  7. Irie01


    Jan 22, 2002
    Thank you all very much. I feel much better now that I have that knowledge of the amps. I couldnt ask for it any better.
  8. RAM


    May 10, 2000
    Chicago, IL
    All very true! A way to think about it is like a garden hose. A thicker garden hose will theoretically allow more water to pass through, right?

    Well, the lower the number of ohms in a cabinet, the THICKER the "hose". That said, 2 cabs put side-by-side that are otherwise equal except one is 8 ohms, the other is 4 ohms: the 4 ohm cabinet will be louder.

    This loudness will make the amp work harder, which is why amps are often rated with different wattages at different ohm levels. But, bringing that number down below the ohm limit on the amp will cause the amp to fry.
  9. Bob Lee (QSC)

    Bob Lee (QSC) In case you missed it, I work for QSC Audio! Commercial User

    Jul 3, 2001
    Costa Mesa, Calif.
    Technical Communications Developer, QSC Audio
    For a given output voltage from the amp, a 4-ohm cabinet will draw twice the current--and therefore twice the power--that an 8-ohm one will. That's 3 dB; noticeable, but not a blistering boost in volume, and if you're comparing an inefficient 4-ohm cab with a more sensitive 8-ohm, it might not offer any advantage in sound level.

    Tube amps are usually optimized for a particular load impedance, so changing from one impedance to another might require you to change taps on the output transformer.

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