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simple x-over

Discussion in 'Amps and Cabs [BG]' started by Chris_AtariDoll, Jul 16, 2002.


  1. Chris_AtariDoll

    Chris_AtariDoll

    Dec 8, 2001
    UK
    I was just wondering if anyone has tried using a simple cap and coil arrangment to make a passive x-over to split the freq between 2 cabs (ie a coil on the 1x15 and a cap on the 2x10).

    If so... has anyone got any suggestions of what values to use?

    Chris
     
  2. BlacksHole

    BlacksHole

    Mar 22, 2000
    Rockville, MD
    I am also switching to a 2x10 + 15 combination. So far, I've considered adding a cap to the 2x10 to reduce the notes below 100 Hz going to it, but not a coil (as of this time) for the 15. Note that prior to this switch, I've been running a biamp setup, so I've had an active crossover. What I have found for a high power cap (for 500 watts or so power) is product 027-616 at parts express. Most 100 mf caps are for much lower voltages and cost much less than this one, i.e., a buck or two. This cap is currently priced at $31.10.
     
  3. Chris_AtariDoll

    Chris_AtariDoll

    Dec 8, 2001
    UK
    thanks for the info... do you think its worth putting a coil on the 15 or will the cap be enough?

    Chris
     
  4. BlacksHole

    BlacksHole

    Mar 22, 2000
    Rockville, MD
    I honestly don't know. It probably depends on the 15" itself. AFAIK, most 15s will be fine with a full range from a bass. I'm only concerned (in my case) about overdriving the 10s with a low B.
     
  5. IMO, you are going to spend $31 and be seriously disappointed. Using a 100 uF cap as a 1st Order high-pass crossover will reduce most of the fundamentals from reaching your 2x10, so it will be working mostly with the harmonics.

    100 uF will give you a 6dB slope at 200 Hz for an 8-ohm load and 400 Hz for a 4-ohm load. This means it will be down -6dB at 100 Hz, and -12 dB at 50 Hz, and -18dB at 25 Hz. If your 2x10 is a 4-ohm cabinet, it will start to cross over at 400 Hz, which is far too high.

    Assuming your 2x10 is an 8-ohm load, a 250 uF cap would theoretically start crossing over at 79.5 Hz. This assumes a perfect 8-ohm impedance at this frequency. If your cabinet is vented, it will have two impedance peaks, and the upper one may be close to your crossover frequency. Without first plotting an impedance graph of your 2x10 cabinet, you are just guessing when picking a passive crossover component. If your $31 cap doesn't give you the sound you want, you'll have to buy another and another... it gets expensive quickly.

    I suggest connecting your rig to an active crossover and vary the frequency to see how it sounds to you. Active crossovers are independent of speaker impedance and work with any stereo channel power amp.

    When all is said and done, you will find the price of large, pricey passive components isn't much less than a nice Rane MX22 active crossover. These are plentiful on eBay every day.

    Welcome to bi-amping.

    :D
     
  6. Chris_AtariDoll

    Chris_AtariDoll

    Dec 8, 2001
    UK
    ill give you a run down of what ive got.

    Warwick 2x10+tweet
    Warwick 1x15
    Warwick Pro-fet IV head

    I was thinking of buying a pre-amp and seperate power amps, but i liked the warwick too mutch. ive noticed the 15 is a hell of a lot quieter than the 2x10... would it we an idea to use a seperate power amp to drive the 15? i felt the 2x10 was having problems handling some of the power... but the 15 wasnt doing mutch.
     
  7. BlacksHole

    BlacksHole

    Mar 22, 2000
    Rockville, MD
    Thanks, BGavin. I currently biamp now but was considering switching away from this approach but have had some concerns about the 2x10 handling the low notes. In my current setup, I crossover frequently at 400 and despite that freq. a lot of sound still comes out of the upper speakers since the first overtone is so well represented on a bass. For a larger set of upper range spkrs, such as the 2x10, I was figuring that 200 or 100 Hz would be better. Since I am currently looking for a new amp, perhaps I'd be more comfortable staying with a biamp rig.
     
  8. I twiddle with the crossover frequency on my rig during live gigs. My Rane MX22 crosses over between 100 and 3200 Hz at the twist of a dial. The more expensive Rane AC22B range is 70 ~ 3600 Hz. Typically I run around 325 Hz for more thud, then down to 100 Hz for more sharpness. Running up to 400 Hz or higher puts almost everything through the subs, and the whole tone is lifeless and dull.

    This is the benefit of active crossovers: on the spot tweaking for the best tone.

    The tone of my subs is fine, but I'm still not happy with the highs. Listening to program music though my rig shows a very high amount of coloration introduced by the JBL E110s (I hear this as "yellow"). It's almost like what you get from a wah-wah pedal at half-wah.