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crossover help

Discussion in 'Amps and Cabs [BG]' started by Insighted02, Oct 11, 2002.


  1. This is what I want to do. I was wondering if it was feasible.

    I have an SWR 4x10 (goliath III) 2X12 (twelve pack) and a trace elliot 2X15.......What I want to do is set it up so I send my lows to the Trace elliot, my lower mids to my 2x12 and the rest to the 4x10.

    The SWR's toghether make a 4 ohm load (combined they can take 1100W)
    The Trace elloit is 4 ohms and can handle 400W.

    To do this I am purchasing a Crown K2 power amp (800w per side in stereo @ 4ohms). I haven't brought a crossover yet.

    Is this possible?
    Is it a good idea?
    What do I need and how do I do it?
    Am I insane?!.............(little voice: Of course not! :) )
    Oh my achin' back...lol.

    -insighted
     
  2. Yes it's quite doable. It's called tri-amping and it's done with PA systems all the time, but you're going to need 3 power amps. You can use each side of the Crown and then get a smaller power amp (the RMX 850 ought to be about right) and run it bridged for the third amp.
     
  3. Do yourself a huge favor and buy an inexpensive active crossover. The Rane MX23 is a three-way crossover that does the job 100%, and they are cheap and plentiful on eBay.

    Only an active crossover will allow you to vary the crossover frequency and volume as needed. You will need this feature to match the sensitivity levels of the drivers.

    An active crossover is also totally independent of driver impedance. A passive 24dB L/R crossover is VERY intricate and requires precise construction and matching to the exact impedance of each driver at the crossover frequency. If you miss, it won't work properly, will sound like hell, and expose your drivers to damage. It will cost you more to build a 3x passive than you will spend on a Rane MX23.
     
  4. Mudbass..........

    I was thinking of using the channels in the crown power amp to power each side of my cabinets........

    swr 4x10 and 2x12 on one side (which equals 4 ohms) and the trace 2x15 on the other.

    I figured eight hundred watts split in between the 4x10 (700w by itself) and 2x12 (400w by itself) would be plenty to power the cabinets. (The trace elliot would just not be cranked in order to protect the speaker.)

    Are you saying that I won't be able to use just one side of the crown to power the SWR's?

    If there is a way to it would seriously help me out........

    What brand of power amp are you referring to?

    Thank you for you help.

    -insighted
     
  5. Ooooh, I see. Yes you can do that, but you'll have no control over the volume of the 2x12 cab and 4x10 cab individually and one is bound to be louder than the other. Also, you have no way of splitting the bass signal in to seperate low, low-mid and high bands for each of the cabs. The most practicle way of going about it is to do like bgavin said and get an active crossover. Your preamp plugs into the crossover and the crossover splits the signal into low, mid and high frequency ranges and then feeds each to a different power amp and each power amp in turn connects to each cab. Most stereo crossovers will do either stereo bi-amp or mono tri-amp configurations. With a stereo crossover you can easily bi-amp with the Crown and the cabs you have, but that leaves the problem of what to do with the 3rd cab. Even in a bi-amped system, if you hook two cabs up to one side of the Crown you're going to have problems balancing out the cabs. Personally, what I'd do is sell off the 2x12 and the 4x10, buy an active crossover and a great 2x10 cab to run with your 2x15 box and run a bi-amped system with the Crown. That's my basic set up right there (except I use a Crest) and it sounds HUGE and tight as hell. :D
     
  6. Hello again........

    Sorry to trouble you again......but:

    Even with the active crossover I STILL can't do what I'd like to do? The crown is in the mail! NO!! :O

    What do I need to make this happen?

    And what kind of power amp is the RBX450?

    sorry, I don't mean to pester.

    -insighted
     
  7. No problem. Let's see if I understand what you're trying to do correctly. You want to run three cabs and have each cab handle a different frequency range...right so far? A crossover will handle this but you'll need three power amps. The crossover splits the signal into low, mid and high bands.

    You wire your 4x10 box and 2x12 box to each side of the Crown. The K2 will deliver 500 watts to each of these cabs because they're both 8ohm cabs. Feed the HIGH output from the crossover to the side of the Crown with the 4x10 box on it and feed the MID output into the side of the Crown with 2x12 box hooked to it. That takes care of your mids and highs.

    For your deep bass, you get yourself a QSC RMX850 power amp (830 watts bridged @ 4ohms) and plug your 2x15 cab into that and the LOW output from the crossover goes into the input of the QSC.

    What you have now is tri-amped bass system and complete control over the volume and crossover frequency of each cab ...and enough power to knock objects out of low Earth orbit. :)

    Does that sound pretty much what you're trying to accomplish?
     
  8. Mudbass is right on the way to tri-amp by adding another poweramp and a stereo crossover but it might be more practical to just bi-amp your system.If you ran the 2-15 cab on one side of the Crown crossed over around 125Hz.and the other two cabs on the other side,both from 125Hz.up I think it would sound fine.The differance in frequency responce between the 10s and 12s probably isn't enough to bother splitting them up.If you tri-amp you will always have to take all three cabinets to the gigs unless you want to re-wire your rig for smaller jobs.Also with another amp in your rack(for triamping)you'll be stuck with more weight.
    If you bi-amp you aren't stuck with all three cabinets for every job,you can do with just two if you want.Maybe the 2-15 and the 410 or maybe the 2-12 and the 410 in rooms that don't need that much bottom.Also you won't need to buy another poweramp,just an electronic crossover.You can get a stereo crossover,you just need to use one side,and if you still want to tri-amp you can add a power amp later.I'd try that first to see if it works.
     
  9. Yes, that's exactly what I'm getting at. I think I'm going to need a bigger rack..........(happy sigh)

    It's a shame there isn't an easier way to tri amp but I guess that's just what I have to do.

    Blues Bass has a good point in his post. I think before I go with the tri amping, I'll try bi amping it first. Buying power amps is too expensive sometimes.

    Thank you all for your help!
     
  10. I have trouble understanding the need to tri-amp. Many good 10s will hit 8,000 Hz, and this is the very upper limit of non-distortion harmonics on bass guitars. Even the most restricted of subs will hit 100 hz, and cross over to the 10s.

    Tri-amping introduces a 3rd amp channel, which I see as problematic because the other channel is unused. I can even see bi-amping with two power amps and running one set of speakers on each amp channel.
     
  11. What I was really trying to do is use the speakers in my cabinets to there full advantage. I love the lows in my 2X15. I love the mids in my 2x12 and 4x10 (etc.).

    I also was looking for one hell of a rig, one that could be louder then I ever really needed. All I'm looking for is more power than I'll ever need at my fingertips (damn, that sounds so sinster.....:) )
    I could compete with a growing trend in most metal bands, the ever present presence of two guitarist and their screaming rigs. Sometimes even three in fact!

    I don't know, call me a fool but yeah it's going to be a bit of trouble making this happen. Luckly I already bought a equipment dolly, That thing is great!

    Anyway.........your thoughts..........

    -insighted
     
  12. In a tri-amped system, I like the idea of a 2x15 and 2x12, but I think the 4x10 cab is way overkill for the job it's going to be doing. A 2x10 box would fill the bill better and be much easier on your back. I run a bi-amped 2x10 and 2x15 box and when I really pour on the power, it's the 2x15 cab that starts complaining first even though it's rated 150 watts more. The two cabs are rated fairly close sensitivity wise, 103db for the 2x10 and 101db for the 2x15, but it's the 2x15 which has to do the grunt work while the 2x10 cab just happily blasts away. Once you cut the low frequencies to a 2x10 cab, as in a bi or tri-amped system, they can go really loud.
     
  13. Multi-level amping is the ticket for efficiency, for sure. That is why all venues of any worth are bi or tri-amped. A driver is more efficient when the range of frequencies it receives is entirely within its produceable range. For example, presenting a subwoofer with highs won't hurt it, but the highs are completely wasted.

    My reluctance about tri-amping for bass is because there is no 3rd band required. The highest non-distortion harmonics are 8,000 Hz. This is within reach of 10" drivers, and certainly the 8" that are becoming increasingly popular.

    As for a monster power rig, that is easily done. Add amplifiers and add more speakers. Bi-amp for more efficiency and clean tone. Each of my PLX 3002 weighs 21 pounds. This is the same weight as my PLX 1202. The only difference is output power, and finding a capable wall circuit... A pair of PLX provides sufficient power to drive LOTS of speakers with clean tone.

    Chelsea , my daughter's bassist, used my stage rig at their high school battle of the bands in a large gym. This was bi-amped as two 1x15 subs, and a 2x10 for the highs. A single PLX 3002 provided the power, left channel for lows and the right for the highs. This gave her a completely clean tone with no distortion, and a massive amount of bottom.
     
  14. You're gonna need a good bass pre-amp, 3 power amp channels and a 3 way cross over. The K-2 can handle 2 of the channels but you're gonna need something else for the 3rd one. Maybe you have another amp head around rated into 4 ohms. The other thing you will need is a 3 way crossover. There are many 2-way stereo/3 way mono that will fit the bill nicely for around $100 or so. The real trick is gonna be crossover points. I'd cross the 15's at between 70 to 100 into the 12's and the 12's into the 10's at anywhere from 1000-3000 for starters. This system is gonna be a real pain to setup and break down. You're gonna need a rack case for the amps, pre-amps, and crossover. Your also gonna need a lot of good patch cords. But, it has been my experience that a bi-amped or tri-amped system doesn't sound all that great at a close distance like on stage. You have to get far enough away from it to let the drivers sounds merge together to form one sound. Bass volume beyond you normal bass amp is better handled by the PA and a "competant" sound engineer. Trying to run high volume from stage is a war you can't win and usually ends up sounding bad out front to boot. If you are wanting more stage volume to compete with the drummer or guitar player, get a good 4X10 cab and put it up on something so it is behind you head. Also, have the engineer fold back some of your bass into your monitor. jmho
     
  15. hey there, thanks for the post.

    I do happen to have my Workingman's 4004 (SWR) head around. That's what I use now and it's minimum load is 4 ohms@400W. The trace elloit 2x15 has the exact same impedance and watt voltage! Not sure if I'll be able to connect it to the crossover though. It has an effects loop and the standard two speaker outputs.

    How many patch cords am I going to be needing? What kind? I already have the rack (ten space). What's the skinny on good patch cords? How much? What kind? What kind of connection?

    I already have an EQ that I'm going to use with it that uses speakon jacks exclusively. (Behringer Ultra Curve Pro........very cool EQ)

    -insighted
     
  16.