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(Explain to me like I'm a 11yo) watts & ohms

Discussion in 'Amps and Cabs [BG]' started by catcauphonic, Jan 6, 2017.


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  1. catcauphonic

    catcauphonic High Freak of the Low Frequencies Supporting Member

    Mar 30, 2012
    Seattle WA
    I see amp specs that say they're usually 8, 4, & 2ohm (with 8, then 4 being the most common), and recently started hearing about 2.67ohm capable amps.

    I ask because I've recently invested in my first seperate head and cab to be used mainly as a home practice / back up setup for the Ampeg V4B / 4×10 (that I've been graciously using on loan from our drummer.)

    It's a Genz Shuttle 6.2 (600w @ 4, & 350w @8 ohm, and the cab is a 600w 4ohm Genz neo 212. It sounds fantastic and plenty loud for my purposes, but I just want to make sure I've got a cab that pairs ideally with the amp. To me, the numbers all make sense that it is, but i don't know (nor can i make sense of) ohms law.

    It was pointed out that i couldn't just add another cab w/these specs, or another 1x12, etc to this setup. Would 2 x 8ohm 350w cabs give me more or less perceived volume, headroom, or anything else??

    If you have this amp, which cab(s) make your preferred setup?

    Thanks in advance, and don't assume i know much when typing your response drool :thumbsup:
     
    fourtet102 and 12BitSlab like this.
  2. This question comes up so much that TB has a Sticky that covers the subject.
    Start there and see if it answers your questions. If not, or it generates new questions, come on back and we'll help you get it squared away.

    AMPS FAQ!! Info on OHMS, Allsize RIGS-OverUnderPowerCabs DIY TechTalk-Links
     
    Buszkock, Winoman, bdplaid and 6 others like this.
  3. two fingers

    two fingers Opinionated blowhard. But not mad about it. Gold Supporting Member

    Feb 7, 2005
    Eastern NC USA
    If you run an 8ohm cab and a 4ohm cab the load will be (give or take) 2.67 ohms. That's why they started making them that way....or at least advertising that they will handle it when they probably did all along.

    There is an inverse formula (in parallel which most amps and cabs are) for calculating ohm. No need to drag you through the math. Short version is that two 4 ohm cabs give you a 2ohm load. Two 8ohm cabs give you a 4ohm load.

    Now, most amps are rated in watts for the various loads. A common amp today is the GK MB500. It is rated at 500W at 4ohms and 350W at 8ohms.

    Hit us with specific questions if that isn't what you're going for. I did a whole semester of pretty much nothing but Ohm's Law so the topic is actually pretty broad even though it is three little letters.
     
    Winoman and Old Garage-Bander like this.
  4. lol I really hope no one ever has to explain this to an 11 year old, that sounds very painful....
     
    Spidey2112, twinjet and Smurf_Byte like this.
  5. Bob Clayton

    Bob Clayton My P doesn’t have flats or tort Staff Member Supporting Member

    Aug 14, 2001
    Philly Suburbs
    Mystic Michael likes this.
  6. 2saddleslab

    2saddleslab Supporting Member

    May 30, 2003
    Kentucky
    Watts is water, ohms is the size of the hose.
     
  7. Ohm's Law is pretty much multiply and divide. Do they still teach 11 year olds how to multiply and divide?
     
    G RICH 5, gillento, ctmullins and 2 others like this.
  8. OOD

    OOD

    Jul 29, 2009
    11 year olds are learning way more complicated things at school.
     
    G RICH 5, gebass6 and PortlandBass77 like this.
  9. You mean like how to download an app that will do the math for them? :smug:

    When I was 12, I asked my math teacher if I could use a slide rule in class.
    She said no!
    I realize now that it wasn't about doing math with a slide rule but about not getting beaten up by the jocks for bringing a slide rule to school.:thumbsup:
     
  10. One of the many quality reasons that I am not a teacher :thumbsup:
     
    OOD likes this.
  11. OOD

    OOD

    Jul 29, 2009
    I know right. You're not wrong about it being a painful process. My wife's a teacher and it seems like the worst job ever to me. Thank goodness for people who like to do it.
     
  12. OOD

    OOD

    Jul 29, 2009
    I'm not going to lie, I had to google slide ruler. It looks like something ancient Egyptians would use to predict the weather.
     
  13. JimmyM

    JimmyM Supporting Member

    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    Do I like bigger cab rigs better? Damn skippy! It's physics...bigger is always better. But that isn't to say a small rig can't sound amazing. Add that to the fact that they're easier to move, and there are some sacrifices I'm willing to make at my slightly advanced age.
     
    Bassdirty and franvarin like this.
  14. Stumbo

    Stumbo Wherever you go, there you are. Supporting Member Commercial User

    Feb 11, 2008
    Song Surgeon slow downer. https://tinyurl.com/y5dcuqjg
    IMO, Two vertically stacked 2x12 8 ohm 3-400 watt cabs along with a 300 watt amp would do you fine.
     
  15. you really are old!

    OP, you are all set with your rig unless you get into a loudness war with gui****idiots. Don't do that.
     
  16. Too young to know what a slide rule does! There would have been a whole lot of slide ruling going on with the engineers working to send men to the moon, and a decade more before electronic calculators took over completely.
     
  17. blubass

    blubass

    Aug 3, 2007
    Modesto Ca
    Current: Blackstar, DR strings, Nady. Previous endorsements with: GK, Rotosound, Ernie Ball, Cleartone, EMG, Dean, Dava Picks, Rebel Straps, Dickies
    One of the best reads I've had on the subject was from the text book, Automotive Electricity and Electronics, by James Halderman.

    Prior to that book, I learned about electricity in high school, and again when I trained to work on tanks in the Army. Simple series circuits have always seemed too basic to really grasp what's going on, but it's the only way to understand the correlation in ohms law.

    It helps to start with an understanding of just amps, ohms, and volts. When you grasp what they do, then you can introduce watts.

    This article does a pretty good job with basics- What are amps, watts, volts and ohms?

    Speakers in the case of music amplifiers, are the resistance, or load (ohms). The higher the number, ie: 32, 16, 8- the more resistance they provide, and the byproduct is always heat. The less resistance- 4, 2, 0 the more current is flowing through with less resistance. Once you get to 0, it becomes a short to ground, in which all of the current tries to return back to ground.

    Some people will never understand it, and that's okay. That's why the manuals clearly state the ohm ratings compatible.
     
    HolmeBass likes this.
  18. If Genz call it a 600w cab it must be some Uber drivers. Still need to use your ears if getting up in volume or you could blow it with excess bass EQ or excess LOUDNESS.

    If you ever find yourself adding more and more volume over a session, that should set off alarm bells. When another volume bump doesn't really do anything the best thing to do is bump it back before you cook your drivers.

    If it gets quieter you are cooking your drivers. Time for a break.

    Farting is flapping the cones caused by excess bass EQ. Turning down the bass EQ lets you get more loudness up to the point you cook the drivers.

    I would gig the V4 with the Genz cab.
     
    static0verdrive and mrb327 like this.
  19. hondo4life

    hondo4life

    Feb 29, 2016
    SC
    More is better. More cabs, more ohms, more watts. Any 11 y/o can understand that. :D
     
  20. Jazz Ad

    Jazz Ad Mi la ré sol

    I was taught Ohm's law at school when I was 13 yo.
    It always seemed straightforward to me.
    I don't understand why it seems to be such a big issue for a lot of players.
     

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