Crossover Question, please help

Discussion in 'Amps and Cabs [BG]' started by onusx, Feb 15, 2005.

  1. onusx


    Feb 15, 2005
    Hi, i'm new to the forums. i'm using a sunn 300t as my main amp and an 8x10 nemesis cab. the cab gets a tad flubby on the very low frequencies, and i'm going to be picking up a 15 or 18 to try to tighten that up.

    i recently snagged an old traynor active crossover for $15 to experiment with. i want to use the sunn and just send lows to the 15 or whatever sub, and highs/mids to the 8x10.

    as i understand it now, after a little reading, most of the time active crossovers are used in a biamping system, so i'd have the option of running the bass directly into the crossover, then sending highs only to the sunn connected to the 8x10, and lows only to an acoustic 370 connected to the 15 or 18.

    that's a cool option and i'm definitely going to try it, but is it still possible to just use one amp and split the frequencies from the speaker output to different cabs? i thought i could run from the sunn's speaker out jack into the crossover, and from there to two separate cabs, one driving lows and the other driving highs.

    if i can do it that way, what are the impedance considerations? i couldn't find any info on the impedance of the crossover; so would i just use settings on the sunn as though i were just running into two cabs (i.e. set the sunn for a 2 ohm load if i'm driving 2 4ohm cabs after the crossover?)

    please help me out if anyone understands this. i don't really know if the crossover was designed to take a guitar signal directly or a speaker line level after the power section of an amp, or if it was somehow designed to withstand either. i just don't want to fry anything when testing different configurations. ideally i want to improve the performance of my amp, not explode it!

    thanks, brian
  2. IvanMike

    IvanMike Player Characters fear me... Staff Member Supporting Member

    Nov 10, 2002
    Middletown CT, USA
    when using an active crossover you need 2 amps (if it's justa 2 way crossover). that crossover takes instrument or line level only - if you put speaker level into it, kiss it goodbye. a passive crossover is used after a power amp and is generally located within the speaker cabinet.
  3. ESP-LTD


    Sep 9, 2001
    No, it was probably not designed to accept a guitar signal directly. It was most likely designed for 'line level' which is about 1v.

    If you put it after your power amp, it will surely fry.
  4. onusx


    Feb 15, 2005
    thanks for the help, that's what i feared based on the articles i was reading.

    where can i get more information on passive crossovers, then? are they relatively cheap, and i could i do what i was planning with two cabs instead of having the crossover work within the cab? any recommendations on which ones to try?

    i've already spent a little time messing around running the crossover and biamping my guitar into two amps-- i've been meaning to try this via an a/b/y box for a while, but there's definitely something cool about being able to split the high and low signal and run different effects on each, so i'll use this option, just not all the time.

    i'd really appreciate any suggestions on where to pick up an outboard passive crossover and thoughts on how well these systems usually work. i'd like to keep all the tone from the sunn and improve efficiency by sending lows to a sub and keeping the bright/grisly sounds in the 10"s.
  5. onusx


    Feb 15, 2005
    ok, i did a little searching and found that peavey and others sell simple passive crossovers-- but they all look like they're supposed to be installed in a cab and used to divide frequencies within one cab, like if you have a 2x10 and 1x15 cab.

    can i use the same type of crossover to send lows to a standalone 1x15 and high+mid to an 8x10? does anyone make a passive crossover with an input jack that would come from the speaker jack on my amp, and then two other output jacks, one for the bass and the other for high+mid? level controls would be great;

    basically i like the way the active crossover i got is set up, and i just want to find something that would work the exact same way, but be able to handle a level post-power section on my sunn.

    all help appreciated, thanks, brian
  6. IvanMike

    IvanMike Player Characters fear me... Staff Member Supporting Member

    Nov 10, 2002
    Middletown CT, USA
    i could be wrong, but i doubt you'd find the performance of a passive crossover that great for your specific application.

    here's a thought. if you find yoru 8x10 is falling apart at the lower frequencies. is this perhaps due to you boosting bass frequencies on your bass or amplifier? maybe if you ran both cabs off of one head (assuming that one of them can handle 2 ohms) you would find that you could leave the bass knob flat and the larger diameter cab would give you the bass response you want while the 8x10 won't freak out from extra bass being pumped into it.
  7. Petebass


    Dec 22, 2002
    QLD Australia
    I agree, try it this way first and see if you even need a crossover. I call it Natural Frequency filtering. I often add a 15 to my 10's whenever the gig needs it. Straight up, I find it necessary to wind off some bottom end from the EQ. So your 10's get fed less of those flab inducing low frequencies, and you sound fatter overall than before. Don't you love win-win situations!

    Just make sure you can run the extra cab on that head without creating an impedance problem. Chances are that 8x10 is a 4 ohm cab. If it is, you can't add another cab unless your amp is capable of a 2 ohm load. You'll have to check.
  8. nonsqtr

    nonsqtr The emperor has no clothes!

    Aug 29, 2003
    Burbank CA USA
    Sounds like good advice. Passive crossovers that handle bass instrument power levels, are difficult to find, and difficult to make reliable. I have one, but I built it myself. It's about the size of a shoebox, and it handles around a kilowatt. Those types of passive crossovers are very difficult to find on the open market, and the ones that exist, aren't all that reliable. For bass, it would probably be far better to take the active route. I don't use my shoebox very often, but when I do, it's just like a little heater. That darn thing gets so hot, that I have to put it on a Teflon pad. (Not really, but you get the point). :)