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Crossover for 15" + 6" box

Discussion in 'Amps and Cabs [BG]' started by jock, Oct 20, 2005.


  1. jock

    jock

    Jun 7, 2000
    Stockholm, Sweden
    I´ve got plans for a 15 + 6 box with Beyma 15G40 and beyma 6MI90. Where do I cross them over? How about a Second order Linkwitz- Riley @ 500Hz? Im not so excperiensed with this so please no tech talk. ;)
    Also how important are the components? A 20uF cap varies bretween $90 and $1. Is there really such a big difference in sound?
     
  2. Doug Parent

    Doug Parent Supporting Member

    May 31, 2004
    San Diego, Ca.
    Dealer Nordstrand Pickups.
    I'm not the one to answer your question, I'll leave that to Bill and the usual suspects who are qualified. However, if your in need of an input panel for the back of your cab you might find pre-made cross-overs from allparts.com that might do the trick. I know Eminence also makes a few "cabinet ready" cross-overs already pre-wired that are decent quality that might be at the right frequencys for you. They usually come with two speakon inputs and two 1/4 inputs and an attenuator for around $85.00 -good luck.
     
  3. My suggestion is purchase a used Rane MX22 active crossover. This allows you to vary to crossover region from 100 ~ 7000 Hz. The slope is 24dB/octave and FAR superior to passive components. An active crossover is also independent of driver impedance, which is very important. The MX22 allows for adjusting gain between the Low and High channels to compensate for drivers of different sensitivity. The Beymas mentioned here are already closely matched.

    Once a passive crossover is constructed (from expensive parts) it is fixed forever. Passive crossovers are very sensitive to impedance in the crossover region, so an accurate measurement must be first done of each driver, before building a passive crossover.

    In short, a huge pain in the ass.

    :D

    Using a 24dB/octave slope, you can place the crossover point as little as 1/2 octave below the point where the bass driver begins to roll off. This point has to be lower when using a passive crossover of a lower order.

    Using the Beyma 15G40, the driver upper frequency is about 1800 Hz before it starts to roll off from flat. For the 6MI90, the lower rolloff is about 150 Hz. This is a large overlap of the flat response areas.

    I'd set the active crossover around 600 Hz for a starting point. This means your 6" driver will be down -48dB at 150 hz, safely protecting it from bass frequencies at high power. The woofer will be down -36dB around 1800Hz where it begins to roll off. This provides a generous overlap in the flat region of both drivers, and keeps the 6" far enough out of the bass range to prevent damage.

    The highest fundamental on a 4 string bass (G, 22nd fret) is 349 Hz. The 6" driver takes over at 600 Hz, so it is handling only the upper harmonics while the woofer handles the power.

    The 15G40 is fully beaming (directional) by 1058 Hz, so crossing over at 600 Hz makes your rig less directional. The 6" is fully beaming by 2500 Hz.
     
  4. jock

    jock

    Jun 7, 2000
    Stockholm, Sweden
    Thanks. I´ll look into the Rane and see whatit might cost me.
     
  5. I find 'em on eBay for $35 to $50 USD.

    I use one for my PA, the other for my bi-amp bass rig. Rane is very good equipment, especially for the used price. It sells for FAR less used than it sells for new.
     
  6. jock

    jock

    Jun 7, 2000
    Stockholm, Sweden
    On second thought I´d rather not have to carry an extra rack space to my gigs. So is a passive crossover really that hard to make. I meen how bad can it sound if I cross over at 600Hz with the right components? :meh:

    Also I would like to be able to bridge my poweramp into this cab as it is not powerful enough with only one channel driving the 15G40.
     
  7. Buy an Eminence crossover at 500 Hz, unless you have a strong need to DIY/tinker.
     
  8. I agree with the Eminence Crossover, however if you want to build Dayton Caps are just fine. I have used more expensive, such as kimbercaps..yes...they are minimally better with a horn but with a speaker you will not hear the difference which is mostly in hiss levels that horns pickup.
     
  9. I'm thinking if they're that cheap on Ebay, get the active crossover, try it, try different freqs. That lets you experiment until you find a good freq. Then build you're passive crossover at that freq.

    You don't just have to balance the freq response of the 2 drivers, you should also match power handling. The higher the crossover point, the more power goes to the woofer, the less goes to the 6". You want to find a good balance between freq response and power handling. You may need more than one 6" to handle the power if you cross over lower, or may not.

    The active crossover also lets you play with relative volume levels of each driver. Because yes, you also have to match the relative efficiency of the drivers. If you have to attenuate the 6" a lot cause its more efficient than the woofer, you may want to put 2 6" in series instead of just having 1.

    There's too many variables to worry about, I think the active xover is a great idea to experiment first, before you pick the passive crossover point out of thin air as a guess and find it doesn't work so well.


    Randy
     
  10. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    Jock, my advice is to try the 15 without the 6" first. The idea is to work out where your ears think the 15" is lacking. Be agressive with your EQ'ing and work out exactly which frequencies the 6" will need to cover to give the 15" good assistance. For example, If you find yourself boosting 500Hz and above, then that's proably a good place to cross it over. If you find that the 15 works quite well up to 1.5K, then cross it over at 1.5K.

    The beauty of DIY is that you can crossover it over exactly where YOU like it without having to cater for a broad cross section of tastes. Keep EQ-ing until the 15 on it's own produces a sound which makes YOU happy.