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Bi-Amping Cabinets

Discussion in 'Amps and Cabs [BG]' started by Jeff Corallo, Sep 28, 2000.


  1. Jeff Corallo

    Jeff Corallo

    May 30, 2000
    I'm relatively new at configuring bass rigs and have thought about bi-amping some cabinets. I currently own an Ampeg B2R which puts out 350 watts at 4 ohms. The Ampeg literature suggests the use of a crossover in a bi-amp situation. If I added another comparable amp putting out 350 watts at 4 ohms utilizing a crossover between the two heads (and each head is driving its own cabinet), at any one time, I would be putting out a maximum wattage of only 350 watts and not 700 watts. In essence, the crossover will act as a "power limiter". So, why is a crossover necessary if you want the 700 watts? In addition, why should you limit the frequency to a cab? (Although a high frequency is not in the proper range of an 18" speaker, so what. This would mean that a person with a combo amp with one 18" speaker should not be able to play the entire range of sounds thru this amp...it is only good for very low frequencies.)
     
  2. White_Knight

    White_Knight

    Mar 19, 2000
    USA
    Ok, first of all, the point of spliting the sound between two cabinents is because some cabinents handle different frequencies better than others (as you said). Now, the reason to limit the frequencies to some cabinents is because some don't handle certain frequencies well. An 18, for example, doesn't produce what most people would consider to be clean, responsive, and articulate highs. Thus, if you send the highs elsewhere (say a 2x10 or a 4x10) then you free up the 18 to do it's work of producing the low notes only. Sure, a really good 18 might be able to handle some of the higher stuff, but if you send it only the lower end of your frequencies then you'll get it's full effect since it would have to be diciding itself up and producing the higher frequencies.

    If using two 350 watt amps, yes, you would be putting out 700 total watts, however each cabinent would only be getting 350 watts. See you'd only send the output of one amp to each cabinent, thus giving each cabinent 350 watts. Two cabs and two amplifiers would double that to 700 watts.

    A crossover isn't necessary. What a crossovwer would do is allow you to split the frequencies so that you can send them to the approiate cabinents. You could, alternatively, run your entire rig full range with the full frequency spectrum going to each cabinent. It's just going to depend upon the sound that you're going for.

    I personally don't know of any 18" combo amps, but yes that's true. My 15" combo technically, doesn't reproduce the entire sound spectrum. It does however, cover the spectrum adequately for me and most other people. You have to remember that there are both overtones and fundamentals to a note. You'll still get the fundamental, you'll just be missing out on some of the upper overtones. Kinda like the difference between a cab without a tweeter and a cab with a tweeter.

    BTW, the Big Ben (18") cabinent from SWR produces frequencies up to 3kHz, which is pretty high for an 18"! You could use that standalone, but it's reccommended that you add another cab to it for the higher overtones.

    Hope this has helped somewhat.
     
  3. Phat Ham

    Phat Ham

    Feb 13, 2000
    DC
    Bi-amping with a crossover not only splits the frequencies between the speaker cabinets, it also splits the frequencies between the amps. By making one amp only amplify the low frequencies and the other amp only amplify the higher frequencies each amp can produce a cleaner sound. You also usually want more power going into the low end than the high end.
     
  4. I run full range stereo with three way cabinets and cross over only my 18" sub. (I don't play loud) with only 140 watts a side stereo and only 30 watts going to a very efficient sub. Part of the signal chain has no effects (the sub) and the rest has effects. This produces a huge sound but its a lot to carry to gigs.
     
  5. White_Knight

    White_Knight

    Mar 19, 2000
    USA
    Good point, Phat Hamm, I didn't really think of that until I read your post, but now it's obvious.