should I use a crossover?

Discussion in 'Amps and Cabs [BG]' started by Mo'Bass Mitch, May 30, 2001.

  1. I've been working on building a 2x15 speaker cab with both speakers in seperate chambers and was wondering if I should use a crossover or just wire it direct, or can I do that? My problem is that I have the cab built and I am not sure about the wiring. I was thinking it might be good to have the bottom be a subwoofer and the top full range. Is that a good idea or not. What do you think I should do and what will I need?
    Any help or info would be greatly appreciated.Thanks
  2. JMX

    JMX Vorsprung durch Technik

    Sep 4, 2000
    Cologne, Germany
    I'd run it full-range, wired either in series or in parallel (depending of the impedance of the individual speakers).
    A cross-over wouldn't make much sense, since both speakers are the same and 15s don't handle highs very well (read: bad). It'd be different with a 1x15,2x10 combination.
  3. Moderator: this should probably move to the AMPS forum.

    The cab is already built, so you are pretty much committed to which speakers you can use. Tuning and speaker selection are the only variables left to play with.

    A genuine subwoofer has a MUCH more limited response than a typical 15" bass driver. I run Rockford RFR-2215's and they are all done at 200 Hz. A JBL E-145 is spec'd to 2500 Hz, but is droopy as hell below 65 Hz. This combination would be a perfect use for a crossover.

    Consider bi-amping as a superior solution to building a high power passive crossover network. If you are already setup for bi-amping, so much the better. If not, you can score a Rane MX22 crossover for a reasonable price. This is an active crossover that you can use in your effects chain, or between your preamp and power amp. You will need a second power amp.
  4. Try it with the crossover and see if you like it. I personally do not care for it in a bass rig.
    For 2 reasons..the first, is that it's cutting out certain fundamental frequencies and second is the possibility of phase cancellation between the speakers.
  5. I have to disagree.

    A properly designed crossover is such that the drivers are down a certain amount at the crossover overlap frequency. Typically, this will be -3dB for each driver at the crossover point. The sum of the Low + High at the crossover point is the same loudness as the individuals, hence no loss of frequencies.

    If dropouts were the case, there would be no multi-way audiophile crossovers, because the listeners would not tolerate holes in the response.

    As to phase, a 2nd order Butterworth crossover is typically wired 180-degrees anti-phase in the High section. There is a phase reversal in this type of crossover that requires this. The solution was the Linkwitz-Riley 4th order crossover, which has no phase anomalies. The L/R also has a steeper slope for both bands, and provides sharper division of frequencies.

    The advantage to an active crossover at Pre Out is it does not have to handle enormous power, nor does it have a tendency to degrade the sound as a consequence of large inductors and capacitors at the speaker level. The active can be adjusted on the fly, or used with varying choices of speaker, where the passive crossover cannot.

    Last, a given driver is only good for its designed frequency range. A 6" mid-bass will blow to smithereens under low frequency load, and the highs will get lost when reproduced by large cone drivers. The crossover network lets each component work in its optimum range, without wasting power that it cannot use.
  6. Hmm.. never used an external crossover only used the one in my SWR amp. And strickly using my ears as the judge. I do undertsand the concepts of biamping and would use it in a PA application or a high power bass rig but my opinion (in most cases) is that it is not practical to do so.
    But like I said in my first post let your ears be the judge.

    Here is what SWR has to say.

    NOTE: Nearly all of SWR's speaker systems are made to be run FULL RANGE and
    biamping is not recommended except for the Baby Blue monitor system. Bi-amping
    causes a natural "suck out" at the crossover point and some phase problems can
  7. Brad Johnson

    Brad Johnson Commercial User

    Mar 8, 2000
    Gaithersburg, Md
    Boom Bass Cabinets, DR strings
    That's why when biamping it's preferable to have the ability to overlap crossover points.