Crossover/Power Amp question

Discussion in 'Amps and Cabs [BG]' started by mattwells, Aug 1, 2003.

  1. mattwells


    Mar 19, 2003
    I am considering adding a 15 to my 4x10 and would want to use a crossover to send the lows to the 15. My problem is I do not know how this will work with my current setup. I have two preamps running into a stereo poweramp (one in each channel). When I use a crossover [like the one built into my preamps], however, I will need to use both channels for each preamp. 2 preamps x 2 channels a piece = 4 channels needed. I would rather not invest the money (and weight) into a second power amp. So is it possible to do this any other way?
  2. redneck2wild


    Nov 27, 2002
    Memphis, TN
    Why are you using 2 Preamps?

    Normally one would run a Biamp configuration this way:

    If Preamp has crossover:
    Bass -> Preamp -> Preamp Low --> Amp Channel A -> Low Speaker (15?)
    --------------------------> Preamp High -> Amp Channel B -> High Speaker (4x10?)

    If Preamp does not have crossover:
    Bass -> Preamp -> Crossover
    Crossover Low -> Amp Channel A --> Low Speaker (15?)
    Crossover High -> Amp Channel B -> High Speaker (4x10?)

    Both only use a single Preamp and a stereo poweramp.
  3. mattwells


    Mar 19, 2003
    I use 2 preamps because I have a regular fretted bass and an electric upright and a fretless. I run different EQ settings on the two so I have one for the Electric upright and one for the fretted (if I play the fretless I change the EQ's on the fretted's preamp).
  4. redneck2wild


    Nov 27, 2002
    Memphis, TN
    In that case you probably want something like a A/B box between the two preamps and a crossover.

    Bass1 -> Preamp1 -> A/B input A
    Bass2 -> Preamp2 -> A/B input B

    A/B box output -> crossover -> poweramp

    Rolls has a cheap 2-way crossover that works well for a bass crossover since the frequency can be set as low as 50hz:

    Cheap A/B boxes:

    You could also use a small mixer instead of an A/B box:
  5. You do not necessarily need a crossover. You might like the sound of the 4x10 and 1x15 running both full range.

    You should also consider running the 4x10 full range, and running the 1x15 as a subwoofer crossed over around 150 Hz. So you would just need a low pass filter for the 1x15. It could either be passive, connected between the power amp and speaker, or it could be an active crossover in your preamp.
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