Brain Teaser

I would like to run all of my subs off of my bd1000.  however, i have a 6" bazooka tube that plays best from 70-110Hz, two 8" rockford wedges that play best from 50-90Hz and 4 15"lightning audio subs that play best from 55Hz and down.  the impedence of the bazooka tube is 4 ohms, the wedges together are 2 ohms and the 15's are down to one ohm. the amp can handle one to four ohms.   good luck!

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Eric Sigman

Hi Eric, while this is not an extremely difficult problem to solve if you remember that impedance is relative to frequency, it is likely to give you undesireable results. If you do intend to run the multiple woofers you described you're going to want better control than you'll get with passive crossovers and L-pads. I'd suggest using more than one amplifier and an electronic crossover, but here's the simpliest solution to your brain teaser:

Connecting all speakers on a single mono output using 6dB per octave passive crossovers wiring them as you described above...

Bandpass filter for Bazooka (80Hz - 110Hz, 4 ohms): 5.8 mHy coil and 497 µfd capacitor
Bandpass filter for Rockford wedges(50Hz - 80Hz, 2 ohms): 3.98 mHy coil and 1592 µfd capacitor
Lowpass filter for 15" Lightning Audio subs(50Hz and down, 1 ohm): 3.18  mHy coil
Nominal Impedance at amplifier = 1 ohm 50Hz and down, 2 ohms 50Hz to 80Hz, and 4 ohms 80 to 110Hz

You can attempt to overlap frequencies with the Rockfords and the Bazooka, but you're likely to get an unwanted peak between 70 and 90Hz. To do so, instead of using 497 µfd capacitor on the Bazooka use a 566 µfd capacitor, and on the Rockfords instead of using a 3.98 mHy coil, use a 3.5 mHy coil. This will give you a nominal impedance of 1 ohm 50Hz and down, 2 ohms 50Hz to 70Hz, 1.33 ohms 70Hz to 90Hz, and 4 ohms 90 to 110Hz.

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the12volt • Support the12volt.com

Errr.... if you want to run the Lightning Audio subs at 55Hz and down and not 50Hz and down, use a 2.8 mHy coil instead of the 3.18 mHy coil.

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the12volt • Support the12volt.com

...and if you run the Lightning Audio subs at 55Hz and down instead of 50Hz and down, you'll also need to use a 1459 µfd capacitor instead of the 1592 µfd capacitor on the Rockfords, if not, the nominal impedance will be .67 ohms between 50 and 55Hz.

thank you very much for your help!  i am going to get the caps and coils today.  i'll let you know how it turns out.  thanks again,

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Eric Sigman

Hi Eric, you're welcome, glad we could help.

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the12volt • Support the12volt.com