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Crossover Capacitor Question

Discussion in 'Amps and Cabs [BG]' started by tewnty_two, Apr 30, 2010.


  1. New to the technical side of speakers and just wanted to clarify a few things about my cab.

    This is a passive crossover capacitor right? (it reads 6.0 k 250 V MET)
    54gahz.
    Its connected to this 5"
    2dikmwx.
    and that 5" is connected to this 15"
    xmk5f8.
    and that 15" runs to the speaker output on the head

    So does this mean the 15" rolls off the frequencies above 6k to the 5"?
    And if the 5" is 8ohm will the 15" need to be 8ohm also or can a drop a 4ohm 15" in there?

    Any knowledgeable input is appreciated
    :bassist:
     
  2. johnk_10

    johnk_10 vintage bass nut Supporting Member Commercial User

    Feb 16, 2008
    Thousand Oaks, CA
    John K Custom Basses
    i that that the 6.0K means that its a 6 uf capacitor, NOT it's crossover frequency. i've enver seen a cap have the crossover frequncy printed on it since the frequency is dependent on the circuit that it is used in.
     
  3. With just a capacitor inline, it is not a crossover.

    It is a high pass filter.

    The 15" is getting full range signal.


    Is there only one 5" speaker, or are there 2 of them ?

    If there are 2 of them, how are they wired together (series or parallel) ?
     
  4. seamonkey

    seamonkey

    Aug 6, 2004
    Low tech and common in cheap cabinets.

    At higher frequencies you will be running a lower impedance as the capacitor lets signal through. You could luck out the and the impedance curve of the woofer is going up as the crossover kicks in. If the woofer is capable of outputting the same frequencies, there could be mid inference due to the center to center distance of the drivers.

    Google Winisd - it has a crossover calculator built into it. Parts express sells the parts.
     
  5. So that just lets the higher frequencies through to the 5"?

    There's only one 5" in the cab.

    Any thoughts on the new 15" being 4 or 8 ohm?

    Thanks!
     
  6. I found a pic online of the original - yes it is only one speaker. The other two holes are ports although on yours the far left one has no tube for tuning which may effect the sound of the cab ??

    How are the speakers all connected ?

    Is there only an input jack with the wires running to the 15", then from the 15" to the 5" ?


    ETA - yes, the capacitor only lets high freq's through to the 5".
     
  7. Yep thats how its connected.

    And i have the other tube for the port.
    it just wasn't in when the pic was taken.

    So then a 8ohm 15" it is then.
     
  8. I have a similar arrangment in my GK 4x12/2x10 cab. Its wired to that all of the 12's are 4 ohms, and all of the 10's are 4 ohms, but are on the other side of the cap so that they hipassed. I was given to understand this acts like a crossover in general, but looks like impedance hell to your amp. I know my Mesa isnt very fond of that cab. It works but its sounds overdriven far before it should.
    I cant remember the math off the top of my head but a capcitor when its in series with an impedance has a frequency, above which it will pass ac signals, below which it will treat AC as DC. Caps block DC or rather they absorb it for a moment and then block it.
    I'm not as good at esplainin it as I am at figgerin it out but thats the gist.
    There are a few crossover calculators on the net, but they mostly assume you are using inductors and caps for your crossover.
    IIRC older JBL/Urei/Altec designs had similar caps on their passive crossovers.

    Nice peni shirt BTW.
     
  9. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    You can use a 4 or 8 ohm fifteen, as there is no filter on it.
    What you have there is a real half-assed rig, since all of the highs going to the fifteen are wasted in a driver that can't do anything with them, while a 6uF cap is high-passing that five around 3.5kHz, which is about two octaves higher than it should be, but with insufficient slope to offer any real protection. Before doing anything else look at the fEarful 15/6 to see how it should be done.
     
  10. Question Bill..............

    When using a high pass filter like this cab is, does it act like a crossover where the amp only sees the impedance of the 15" and not the 5" speaker ?

    I thought that it did not, and the amp sees the combination of the 2 speakers together.
     
  11. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    The amp sees the woofer only below the corner frequency of the filter, both drivers in parallel above that. But the impedance of woofers rises significantly above 2khz or so, so there's no loading problem when the filter frequency is above that.
     
  12. muchos gracias Bill.

    Yea I've been looking at the fearful 15/6 as a project to do in the future possibly by September or so.
    But in the meantime I gotta get this cab up and running so I was gonna drop a eminence ca154 in there are rock it, its a 4ohm.
    I can get one for $80 shipped and thats not bad to hold me over until I get the funds for the 15/6.
    Is there any way to get a better sound out of the 5" or should I just save the $, time and effort for the fearful?
     
  13. Tim C.

    Tim C.

    Feb 4, 2010
    Chicago
    Yes.
     
  14. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    I view any investment in that cab as good money thrown away. I'd get the woofer you plan on using in the 15/6 and use it in that cab temporarily until you can build a proper cab to put it in.
     
  15. mcapote

    mcapote

    Sep 9, 2009
    Miami Florida
    +1 on that. get a 3015LF and pop it in until you can afford to do the fearful completely.
     

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