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The 4 Or 2 Ohm Thing...

Discussion in 'Bass Amps & Cabinets' started by Hetzer, Mar 22, 2020.

  1. Hetzer

    Hetzer

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    I have read all kinds of things on this topic and I would like to clear it out once and for all, and with You people.

    I am soon to get a headpeace Genz Benz 750 GBE. It gives 750 Watt @ 2Ohm, 625 W @ 4Ohm and 400 W @ 8 Ohm. Currently I am playing on Peavey Firebass 700 (which gives 700W @ 2Ohm) through two Marshall cabs (MBC 410 and MBC 115) each 4ohm which means two ohms overall.
    I plan on changing the two cabs sometime in the future with somethig better. Initialy I though with going again with 2 cabs each with 2 ohm, so that the amp can give it' full power. I did a bit of research, and apart of finding the affirmation to my idea, a lot of peapole are saying that it practicaly makes no difference if one runs hier at 2 or at 4 ohm. Allegedly is the difference in 125W here minor and in turns of loudness, nonexistent. Furthermore, some say that in these cases it would be better to run at 4 ohm because the amp does not run at ist full strain and it does not get so hot which is kind of good for the amp.

    I thought I had it all figured out but not I don't have a clue.
    So what does your expretise say?

     
  2. DiMarco

    DiMarco nutcase Good Vibe Sponsor

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    Mixing different impedance cabs will result in one cab being louder then the other. In my opinion it is not a good idea.

    That said, there are a lot of amps out there incapable of handling a 2ohm load so having two 8ohm cabs with a total load of 4ohms will give you the freedom of using virtually any amp out there (except for some old tube monsters).

    A 2ohm capable amp will not break into sweat from that 2ohm load but instead give you more clean headroom then it has with a total load of 4ohms. So if you're gonna use this amp two 4ohm cabs is the most logical choice.

    Another thing: I use a 1000w Warwick LWA amp with my SWR Henry the 8x8 which is rated 450w max. It goes LOUD without ever clipping. Much louder then it did with the Tech21 VT which is rated 500w. An amp that clips will introduce DC components in its signal which heat or even burn your speaker's voice coils.

    So having an amp that seems too powerful is actually a good thing, it gives you the clean headroom you need.
     
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  3. Florin

    Florin Warwick Forum Administrator Staff Member

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    Hi buddy,

    Marco is right. Also the advice I can give you is a no brainer IMHO. If you are planning to use two cabs, and want to invest in quality ones, do yourself a favor and buy 8 ohms each, this is the standard for two cabs, and not many bass amps are supporting 2 ohms load.
    Keep in mind that the overall loudness has more to do with the surface moving the air than the power rating itself. So the difference between 500 and 100W on the same cab will be smaller than adding another cab for the 500w one.
     
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  4. Hetzer

    Hetzer

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    What us exactly "clean headroom" in this case? Sorry but I'm nit native at English and this is like a very specific term. I have a general idea, but I could be wrong.

    Getting two cabs each 8 ohm will give me more flexibility in the future, i get that. Will it then be louder with 750 @ 2 ohm than 625 @ 4 ohm? I know the loudness is not always and only a thing of wattage. It has something to do with the speaker configuration.
     
  5. DiMarco

    DiMarco nutcase Good Vibe Sponsor

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    Clean headroom means your amp can comfortably give you the loudness you need on stage without running out of watts and distorting.
    It is better to have a higher rated nubmer of watt amp and a lower rated watts cabinet then vice versa. Just use it sensible and don't let your speakers clip.

    Also consider that some speaker cabs are really loud when feeding them only 100 watts while others are not.
    This is often reflected in the price of the cabinet.

    My 2x12" puts out 103dB at 1 watt, measured at 1m from the speaker, while my SWR Henry the 8x8" cab puts out 96dB at that one watt.
    Therefore the 2x12" is a lot louder with the same amp at the same volume setting. Since my amp puts out 1000 watts this is not a problem, it will just need more watts to make the 8x8 produce the same volume as the 2x12. Both cabs are 4 ohms so I use either one of them but never both (unless I bring my tube amp and need a really big backline - which never happens)

    ALSO, I always use a compressor to make my sound more even, and I cut all the low end below 60hz by 9dB using a graphic EQ.
    This keeps my amp from using too much energy and my speakers from flapping out in the subwoofer frequency area which I do not need anyway.
    Because I cut the lowest lows, the 8" speakers can be used REALLY loud.
     
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  6. Florin

    Florin Warwick Forum Administrator Staff Member

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    The difference in perceived loudness betwen 750 and 625 is minimal, and if you are using two cabs it will be overkill for almost any situation, so I wouldn't worry about that. And since you are still looking for a head, try Warwick LWA 1000 if you can. I liked it A LOT!!!
     
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  7. Hetzer

    Hetzer

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    The relation of wattage of an amp and of that what the cab can take is another story, but u I don't seem to find many opposing opinions on that. If I got it right, the ammount of watts that a cab can take should be a bit higher then the ammount of watts that it will be getting, right?
    If my amp gives 625W @ 4 ohm on two 8 ohm cabs that would be like just over 310 W pro cab. What would than be like the ideal wattage of each cab? Approximately 400W?

    What would be the characteristic of efficiency (loudness) of a cab or speaker? Sensitivity measured in dB?

    A good thing you mentioned low clipping. I intend of getting a device (like a pedal) that cuts everything lower than for example 25 Hz. That could reduce the strain of almost useless and hard to produce frequencies on speakes and contribute to efficiency. In the meantime I will crank up the compression of lows on my EBS compressior and reduce the far lows on EQ pedal.

    Last night I read a discussion on TalkBass forum between some IMHO pretty competent people. One is playig actively for like 40 yrs, other designes amps and there was also an engineer. It was like a km long and they did not come to a common conclusion on what would be better between pushing the amps at 2 ohms (if the specifications say it can) or staying safer and colder with insignificantly smaller ammount of watts at 4 ohms.

    I'm already getting a Genz Benz 750 GBE head. Now I'm considering what should I do with cabs and how could I best upgrade thus section.

    Buy the way, thanks!
     
  8. Florin

    Florin Warwick Forum Administrator Staff Member

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    The more competent and passionate you are about the subject the more you talk, and bring informations that not always are helping. Passionate and competent guys often are called (wrong in my opinion) corksniffers :) We like to talk a lot about wood combinations here, while others, including some very respected luthiers are saying they don't matter (which is not my experience)

    What I am trying to say is that there are so many variables from brand to brand and model to model, that you simply cannot get a straight answer, only from people that really know that particular brand, and then they will not have that much experience with other brands.
    For example it is "well known" that 10" speakers cabinets are snappier than 15" ones, still the boomiest cab I owned was 6x10, and the snappiest one was Hellborg coaxial 15".
    So if you get into really technical discussions like here, you will get very technical answers that may not fit the amp/cab combination you have.
    All you have to know IMHO is this:
    - Do not connect speakers of different impedance
    - Do not connect speakers with impedance lower than the min. recommended for the amp, or you will blow the finals.
    - If you think you will change the amp later (which is possible), buy 2x 8 ohms. Not many bass amps are dealing with 2 ohms load. The difference in loudness between 650 and 750 W is way smaller than between 1 and 2 cabinets. 650 W in 2 cabinets is more than enough for any aplication.

    Just buy what you like, based on reviews and personal experience, and enjoy the setup :)
     
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  9. Florin

    Florin Warwick Forum Administrator Staff Member

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    Nope. The fact is you will probably never push a 750W amp over 12ve o clock. Just avoid the extremes, like 1000 W amps in 100 W cab. Actually, more damaging is the oposite- 100W amp into 1000 W cab.
    If you are in the ballpark, just buy whatever you like. Cabs are seriously distorting when they are pushed over limits, you will turn the volume down before anything bad happens. I used many many times 1000 W amp into 200W cab. As far as I use it a t a volume where the cab doesn't fart it will not damage anything.
    Using a 200W amp into 1000W cabinet will make you use the amp maxed out, which creates square waves that are not always that audible as a farting speaker, but they do more damage to the speaker.
    So as I said, focus on the brand and sound you like, just have everything in the ballpark, enjoy playing, and let specialists talk about specs all day long, it is their job to do so :)
     
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  10. Luc67

    Luc67 Supporting Member

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