Power Amp insanity!!!

Discussion in 'Amps and Cabs [BG]' started by BigBohn, Nov 14, 2001.

  1. BigBohn


    Sep 29, 2001
    WPB, Florida
    I just don't understand how all these things in a poweramps specs relate or what they are??? Whats damping factor? Whats slew rate? Whats signal-to-noise? Input impedance? Can anyone refer me to a link that would help me about this? :confused:

    I'm looking at Carvin, QSC, Crest?(maybe), and Mackie. I play new rock stuff and relatively loud. I want atleast 1800W RMS @4 ohms bridged mono. I want as clean as possible, with little to no distortion, and as much headroom as possible. I try not to crank my cabs to the max, so the full RMS wattage is never put into them. The rig is an Eden Navigator and an Eden D-410XLT, with the possibility of adding another 1 of these to it or an Eden 15" cab. I'm looking to spend under $1000 for it. The Carvin was the best price, $600 for 2000W RMS@4 ohm mono. Anything close to that? Thanks for the help. :)
  2. BigBohn


    Sep 29, 2001
    WPB, Florida
    advice would be greatly appreciated. :)
  3. jasonbraatz


    Oct 18, 2000
    Oakland, CA
    well...i'll go on what i have experience on.

    i have a carvin DCM1000 that i used paired to my old SWR bass 350 before i got my IOD, and it sounded exactly like the bass 350 did, just louder. now, with the IOD, it sounds ridiculous. i'm sure with the navigator it'd be a great match as well.

    i HIGHLY recommend carvin's poweramps.

  4. FalsehoodBass


    Jul 22, 2001
    Denver, CO
    ok.. not an amp tech.. but this is what i know..

    slew rate... I THINK has something to do with how quickly it responds to an input signal..

    input impedance... it has to do with the minimum output impedance of your preamp.. it won't really matter if you have the IOD... if you're getting a standard poweramp

    signal to noise ratio... every amplifier is going to make some sort of hiss.... this tells you how loud this hiss is going to be... normally not a problem, especially in a live situation.. as a sidenote, this can be reduced if you turn the volume on your preamp all the way up, and then use the controls on the poweramp to control your volume.

    that said.... i like mackie.. esp if you have the extra cash... get a 1400 or 2400... but i promise the 1400 will be more than enough... even with 2 cabs, and against a pack of gnarly mesa-fied guitars and loud drums
  5. Here's is a post I wrote for another forum on damping. hope it answers some of your questions....

    Punchy is a word we use to describe a tight, quick responding, well defined sound. It has as much to do with speaker damping as the actual tone. 10 inch speakers sound punchier than 15 inch speakers because of their inherently higher damping factor.
    When a speaker cone travels either out or in, its own inertia tends to keep it moving in that direction unless something stops it. A speaker's resistance to it's own inertia is called the damping factor. 10 inch speaker cones have less mass than 15's so they are less victims of their own inertia.

    Speaker damping can be increased in two ways, mechanically and electronically. You can increase the damping factor mechanically buy placing the speakers in sealed box (infinite baffle). As the speakers move outward, a vacuum is created inside the box that helps snap the speaker cones back to their rest position when the audio signal oscillates or stops. Infinite baffle cabinet designs (like the SVT or Acme) benifit from a much tighter or punchier sound, but there is a trade off. The speakers cones have less freedom of movement and it requires more power from the amp to achieve the same sound pressure levels as in a ported cabinet design.

    Electronic damping is handled by the amplifier. The damping rating on an amp is a gauge of the amp's ability to stop the speaker cone's inertia from moving it in one direction when it should be going in the other. Unfortunately, most bass amps don't have spectacular damping factors and are heavily reliant on the type of speakers and cabs they're plugged into for a punchy sound. This why 15 or 18 inch speakers sound loose and "woofy" compaired to the punchy sound of 10 inch speakers when played through your typical bass head.

    You've probably noticed at some time or other when at a concert how tight and punchy the PA sounds even though you know they must be using huge speakers for bass reinforcement. It's largely because the amps they use have damping factors high enough to whip those big 15's and 18's into submission. It's also why more and more bassists are moving toward using PA amps in their rigs and getting away from the traditional bass head.
  6. leper


    Jun 21, 2001
    thanks mudbass, I had actually thought that about pas and wondered how that came about...knew about the speakers end (ie sealed cabs are punchier), but not how power amps contributed

    but i thought acmes were ported...maybe im wrong.
  7. ACMEs are sealed. Very low effeciency. It takes at least 1000 watts to drive them, but once you get em moving...look out! :) The sound they make is truely remarkable.

    I use a Crest V1100 PA amp. It's 700 watts x 2 into a 2 ohm load. It has a damping factor of 1000:1. I bi-amp it into an EV 215 cab and an Eden 210 cab. Even the EV 15's sound incredibly tight with the Crest. If I thump a note it kicks you right in the chest. The only power amp I know of with a higher damping factor than Crest V series is the Crown K1 series with 3000:1.
  8. leper


    Jun 21, 2001
    i guess i just assumed they were ported to get down that deep.
  9. Acmes are ported on the back side.

    As far as amp specs: don't look at them. Not even for a second. Throw all the tech jibberish away and hook up the darn thing. Drive it insanely loud and LISTEN. If it sounds ok, buy it.

    I'm a technician and I know what all these specs mean, and I don't look at them. They say nothing about how it sounds. Because the sound of an amp is pretty much totally subjective.
  10. BFunk

    BFunk Supporting Member

    This folks is trully a moment of sanity in an otherwise insane, (spec driven), world! :D

    The only exception is make sure your amp can handle the speakers impedence.
  11. Joris is 100% correct on the amp specs: ignore them and just play it. All the top quality amps have specs so tight I doubt an A/B test would discern the differences. Cheap amps are... cheap amps. You get what you pay for.

    As for speakers, the punch comes from control of the speaker cone. This can be quantified by the ratio of the Bl (force factor) and the Mms (moving mass) ratio. The math is Bl / Mms = arbitary number. The higher the arbitrary number, the more control the motor assembly exerts over the cone.

    The king of ratios in 15" drivers is the JBL E130. Funny how it is also the most efficient. In 15" bass drivers, the JBL E145 is the highest ratio bass driver I have catalogged.

    In 10" drivers, the JBL K and E series 10" are the kings of punch.
  12. BigBohn


    Sep 29, 2001
    WPB, Florida
    wowsa! tons of replies. the community has come together as a one to help out. i'm speechless. thanks for all the info. you guys have influenced my purchase.

    :D :D :D