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Why is one rig louder than another when both are rated for 400W?

Discussion in 'Amps and Cabs [BG]' started by pokey, Mar 23, 2002.

  1. pokey


    Mar 9, 2002
    I was considering a Firebass head, but at 600$, I shopped around. I found a used Peavey Megabass for 350$ with a small rack and speaker cord included (head is ~10 years old). I liked this head quite a bit, only a few scratches and clean inside. Is is a bi-amp with 200W at 4 ohms per channel (400 full range), 7 band eq, and built in chorus. Looking at used gear it sounded good biamped to a used Hartke 210 and used Ampeg 212 cab. I compared this to new amps with comparable power, a Hartke 4000(400W) and a WM4004(400W). The Megabass going thru only the Hartke 210 was louder than both the Hartke 4000 going thru a Hartke 410 and the WM4004 going thru an SWR 8x10 or 6x10? All the heads were rated 400W at 4 ohms, so at 8 ohms they should be close as well in Watts. All of the cabs were 8 ohm cabs except maybe SWR. I would have thought that the larger cabs would have produced more sound, but the opposite was true. Why?? Is the wattage ratings of the speakers the difference? The 210 was overpowered while the 4x10 and 6or8x10 were underpowered. I am new to these larger setups and do not understand how everything works together yet. Any advice is appreciated. Thanks.
  2. well i'll tell you one thing i've learned about the hartke aluminum cones definately project more and are cut through more, like their punch and attack, compared to other cones, IMHO.
  3. :confused: Ah, one of the greart mysteries of the universe! Why indeed? Shouldn't 400 watts be 400 watts and have the same volume into the same cabinets? Unfortunately, it's so much more complicated than that. I'm not an electrical engineer or anything, but the variables involved with producing something like the combination of a preamp, power amp and speakers preclude any consistency in performance.

    Perhaps some of the more technical types out there can throw some light on this often pondered dilema.
  4. Stupidnick


    Mar 22, 2002
    ...my room...
    I think it has to do with ohms...
    I once heard "its not how many watts you have but the ohms".. hmm like think about those small surround sound speakers... how you get that much power out of something that small?
    search for Ohms..
    i know that might sound bad.. i hope not dood i just dont know much about ohms at all really but ive heard that
  5. Christopher


    Apr 28, 2000
    New York, NY
    Power specs are always approximate. The lone fact that an amp is rated at 400W RMS doesn't really tell you much about how much power the amp at any given moment in time and where it maxes out (peak power).

    Factor in differences in speaker cabinet efficiency (SPL), cabinet and cone design, room acoustics and EQ, and things are no longer comparable on paper. The only way to really tell is to test the equipment.

    A 400W head ideally should be putting the same amount of power into two different cabs with the same ohm rating. Halve the ohm rating of the cab, or connect two cabinets in parallel, and the RMS power increases by about 60% (or the amp blows up). Conversely, double the ohm rating of the cab, and the power goes down by about the same amount.
  6. ihixulu

    ihixulu Supporting Member

    Mar 31, 2000
    South Shore MA

    The human ear is more sensitive to mids so if an amp puts out more mids it will sound louder even if it is putting out the same amount of watts as the amp that has mucho lows and highs.
  7. John Davis

    John Davis Guest

    Mar 27, 2001
    Houston, Texas
    Volume on the head was louder than the other? I dunno....
  8. brianrost

    brianrost Gold Supporting Member

    Apr 26, 2000
    Boston, Taxachusetts
    For one thing, if two amps are rated the same you can only tell which is really louder by hooking them up to the same speaker (you did) and run them flat out until they start to distort (I bet you didn't).

    As someone else noted, the more midrange in the signal, the louder the amp will sound. Many "old school" amps like the SVT are extremely midrangey which makes them sound louder than modern "hi fi" amps which go for a flatter midrange.

    RMS wattage is measure by passing test tones through the amp. Music is not test tones, it has harmonic complexity and also is dynamic. This means that two amps with the same RMS wattage could sound a lot different in terms of volume when playing real music through them.

    As far as the MegaBass I'd say it's an OK amp IF you will be using two cabinets most of the time. You can't bridge the power amp, so you get a lot less power into one cabinet than you can get into two (or more). I've used it for shows on large stages in full range mode and it does the job, nice and loud.
  9. JMX

    JMX Vorsprung durch Technik

    Sep 4, 2000
    Cologne, Germany
    You can't really compare different amps without using the same cab. Even with the same impedance and power ratings differences in frequency response can make one cab louder than the other.

    Apart from the differences in how the ratings are measured, amps with more prominent mids and more subdued lows will also sound louder at similar settings.
  10. 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
    Why was one louder than the other? Because you probably were using more power from one than the other. In other words, you run one hotter than the other, it's going to sound louder, regardless of its power rating. For example, a 1000-watt amp putting out only 10 watts isn't going to sound as loud (into the same speaker) as a 300-watt amp putting out 50 watts. The 1000-watt amp will have the capability of getting about nearly 5 dB louder, but whether you use it to that extent or not is a different matter.

    Power amps will be pretty identical in loudness if you compare them with the same speaker in the same location and have them putting out the same signal levels. If you don't, who knows what you'll get.

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