Question on frequencies

Alright, I have 2 10" mclass subs in place of the center console downfiring in which i want it to hit the mids and highs of the lows. I have a 15" HPO with a box i made myself being tuned at 38hz, square ported, and 3 cubic feet. Im putting that in the back. I want the 15 to hit the low lows only, so that i dont have any cancellation between the 10's and the 15. So either the 10's are playing or the 15 is playing. the 15 is going to be powered by an st-500D, the 2 10's are being pushed by a jbl-600.1. What frequency should i tune each amp?

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03 F150 on 24's
HU:Pioneer DVD5700
Frt:MC57
Subs:(12)S12L7
Amps:(3)KX2500.1's, MC-2004

With that much seperation between your sub and your woofers this could end up sounding really weird, so you need to make sure the sub plays only non-directional low bass. Normally I'd say lowpass your sub at the standard 80Hz, but with this kind of setup you'll want to go lower so it is only active for very low non-directional rumble and is sufficiently cut up in the directional range.  I suggest using a low-pass on the sub at around 60Hz, and a band-pass on the 10's between 60Hz and wherever you are high-passing the components, say about 250Hz.  Use at least a 2nd order crossover, 12db/octave.  Then high-pass your components and your rear speakers at the same frequency (250Hz) and be sure you are using the supplied crossovers with your components.

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Yes the components were professionally installed with the crossovers. What is a 2nd order crossover? And what should the freq on the amp be set at? on both amps. Thankyou dyohn

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03 F150 on 24's
HU:Pioneer DVD5700
Frt:MC57
Subs:(12)S12L7
Amps:(3)KX2500.1's, MC-2004

With the 10's and the 15, I would drop those both off real quick (crossover frequensie) so they cant "join" in what will sound very dissapointing. Dyohn was sugesting the 15 get cut off at 60 cycles. The 10's are gonna sound odd. If your componants are cut off at 250 (wich I think is TOO high) youll need the 10's at or between 80 and 250. 250 is reaching a bit on the 10s. I would have a band pass crossover built for the 10's with narrow Q slopes stick with 80 to 250 on the crossover points.....man this is gonna sound interesting

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You're planning on using just the crossovers built into the amps?  Hmm, well this could create a problem. 

With both woofers playing the same frequencies from different locations and from different amps you could end up losing bass not gaining.  About the best you could do is try setting the Memphis LP to 50-60Hz and the JBL LP to whatever frequency your HP for the components is set to.  But you now have the perfect setup for cancallation in the frequencies where the sub kicks in below 50-60Hz.  A better solution would be to get an external crossover like an Audio Control 4XS so you can actually create a bandpass filter for your 10's.

Complex setups like this require the correct control equipment, I'm afraid.  And it just gets more expensive all the time!

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