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What does power really mean?

Discussion in 'Amps and Cabs [BG]' started by Trevorus, Oct 26, 2002.

  1. Trevorus


    Oct 18, 2002
    Urbana, IL
    I hear so many people talking about getting a 750 watt amp, over 400, 500 or something like that. Everyone is always wanting that extra hundred watts. I want to set something straight. If you are going to increase your power, to actually double your sound output, you must multiply your power by ten times. But, if your amp can handle it, you can double your sound output by doubling your speakers. Speakers move air, moving air = sound. So, when you think of spending an extra couple hundred dollars for 100 more watts, remember, your only making it about 10 percent louder, allowing for physics. Of course there are amps that sound louder, even if they are lower power than others, but remember, and efficient amp will be louder. So the numbers pretty much mean nothing, because they are subjective to the companies anyways. So just remember all this when buying an amp.
  2. Get an amp that goes to 11. It's one louder.
  3. Trevorus


    Oct 18, 2002
    Urbana, IL
    they make some that go to 12, that's 2 louder. yay!!
  4. Actually, you get about 3dB from doubling the speakers and a max of 3 dB from any extra power the amp puts out due to lower impedence. That's about a maximum of +6dB which is considerably less than double sound output ( +10dB). But it's still better than the 3 dB you get from just doubling amplifier power..... I've been preaching the "adding speakers is a more effective way to get louder than adding amp power "for years.

    The early versions of the QSC mx-1500 had input attenuators that went to "11"...................
  5. So presumably if I sand out the numbers, and write new ones in with Twink that go up to 15, I'll be way louder. Perhaps I could get some of those number transfers, that'd make it look really professional......
  6. lneal


    Apr 12, 2002
    Lee County, Alabama
  7. You're right that adding an extra 100 watts, coming from 300 watts isn't going to make it louder.

    But what you said earlier, is not entirely true.

    If you tenfold you amp power, you'll tenfold the sound output. But your ears will perceive it as only twice as loud.

    If you double the cone area, you'll get an increase of maximum 3 dB due to mutual coupling of the cones (only in the lower frequency band BTW) and about 2 dB max. of increase in power from the amp. That's 5 dB at most, which is a clearly audible increase in volume, but not nearly twice the volume.

    The best way to get a good deal on amplifier power, is to determine how much power you need at one point, and then buy a power amp of four times that rating. That way you won't have to buy a new power amp for years. The price of a 1200 watts amp vs. that of a 600 watts one of the same specs is negligable.

    My 2 cents.
  8. Trevorus


    Oct 18, 2002
    Urbana, IL
    That's what I meant. With the way our ears work, it will be twice as loud while it's really ten times the sound energy. But who cares about all that physics stuff. We just want it loud, right?
  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
    Any way you cut it, less power is less power and more power is more, but most of the time power amps are running at less than full power. You can have a less powerful amp set to a higher gain than a higher-power amp, and it'll sound louder with the same input signal. But the more powerful amp will be able to go louder before it clips.

    But that's why there are knobs, so you can adjust gain to what's appropriate for the situation.

    You mean a more efficient loudspeaker will be louder.
  10. Having enough power to play as loud as you need too with out clipping your amp or frying your speakers. That is what power is. How much you need is relative to your speaker efficiency and the amount of db you need to generate in relation to the other instruments in the band. I've used a 200 watt amp with a Hartke 4.5 for the last 6 years and it has been plenty. But if I were trying to power an Acme b4 it would probably sound way too soft. That is because my 4.5 is something like 99db efficient and the B4 is like 96db efficient. That is 3 db softer. 3 db may not seem like alot but it would take appr. 400 watts with the B4 to produce the same db 200 watts will produce with the 4.5. In fact most of the people I read in this forum wouldn't power the B4 with anything less than 1000 watts just for good measure. I'm not exactly as to what the efficiency ratings are of both cabs and my calculations for power needs are based on power doubling ever 3db, however, I think you get my point. You need enough power to get the job done. I always like to have a little in reserve to boot. :D
  11. Trevorus


    Oct 18, 2002
    Urbana, IL
    true. It is always good to have headroom. Your gear lasts longer anyways, since you don't have to push it so hard. The more gain before clipping you can get, the better.
  12. ihixulu

    ihixulu Supporting Member

    Mar 31, 2000
    South Shore MA
    power is being able to cast hypnosis on any one with the wink of an eye.

    Oh wait wrong forum....

    I stated out pushing 100 Watts into 1 18. Then I upgraded to 200 watts into that same doofy 118. Then I got a 410, and got an SM400 which I run bridged (400watts). I haven't been in a situation yet where 400 hasn't cut it for me. Once for the heck of it, I borrowed a friends 410 (also 4 ohm) and ran my head in stereo, 410 on each side. I couldn't turn the amp past 2 without drowning out the rest of the band..... so moral of the story is:

    you are getting sleepy, sleepy, you wil send me all your money and gear and when I count to 3 you won't remember a thing.....
  13. zzzzzzzzzzz

    {Capt Kirk voice on}
    I must.........keep my gear
    {Kirk voice off}
  14. Or a pair of PLX 3002...

  15. Rockbobmel

    Rockbobmel Supporting Member

    And so she wandered through the door-way, Just like a shadow from the tomb............... She said her stero was four-way, An' I'd just love it in her room......
  16. Larry Kaye

    Larry Kaye Retailer: Schroeder Cabinets

    Mar 23, 2000
    Cleveland, OH
    What I'd like to see more speaker cab makers have is rating a cab by a range....x to y watts recommended, minimum wattage recommended and maximum wattage recommended.

    Just saying that my Epifani 310 is a "600 watt" cabinet means nothing by itself. Bottom line, how much volume do you need in the band, room, for the type of music, stage volume/fill the room volume, etc. etc.

    Also, if you and your bandmates like the sound of an EBS 410 cab with your 5 string, why concern yourself with whether the cabinet's effective frequency reproduction range, +- 3 db is 62hz. Again, it's what the bass sounds like in relation to the other instruments, style of music, types of songs, PA support, your role as bassist in that band etc. etc, not whether you and one other person out of 1000 can actually hear fundamental rolloff at 62 hz.

    3000, 2000, 1000, rms, peak, tube power watts, all is useless information in a sense without someone hearing and listening to the volume and tone produced by your equipment. How loud do you have to be? How clean do you have to be? How bassy must you be? Does the combination of your bass, head, and cabinets get you there or not? If not, you may want to first try a more efficient speaker cab and/or adding another cabinet. If that helps and still doesn't totally cut it, consider getting as much power as you can afford, 2 more cabinets, a personal roadie, and a hearing aid.


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