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Discussion Starter #1
Hello all,
I have finally gotten my subwoofer system up and running, so now it's time to EQ my subs.
Here's a little bit of background on the equipment.

AVR: Pioneer Elite - SC-65
Front L/R Speakers: 1963 Bozak (2x12" woofers in each cabinet) *I know, not the best choice for home theater
Subs: 4x18" FiCar - These are installed in the ceiling in manifold configuration (Infinite Baffle), one at the front of the room and one at the rear (near the peak of the vaulted ceiling).
Sub Amp: iNuke NU3000 (running in stereo mode for 880 watts going to each manifold).
Sub EQ: MiniDSP 2x4 Balanced - Connected with composite cable from AVR and input jumper set to 2V.
Mic: Cross Spectrum Labs UMIK-1

Both manifolds have been gain matched and time aligned.

Last night I took a few measurements:
1) The front L/R with the sub amp turned off
2) Both subwoofer manifolds on with the front L/R mains turned off

This allowed me to see the crossover point and see how things performed without everything playing at once.
 

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Discussion Starter #2 (Edited)
That was my baseline testing.
Things start to get weird when I turn on both L/R and both Sub manifolds at the same time though.
I start getting a dip near the crossover point (~85Hz), so I started messing with the phase on the subs and tried a couple of different settings (Inverse Polarity on MiniDSP)
Things seemed to get worse, so I put them back to default.

This dip is not present when measuring the sub by itself, and not when measuring the mains by themselves.
It's only happening when the mains and sub are both playing. This would indicate some sort of phase interplay issue right?
 

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Discussion Starter #3 (Edited)
Now, here's my questions.
When I begin EQing this system, should I EQ the subs with the mains disconnected or should I have everything playing when I EQ?

Should I do mostly cut filtering and try to get my sub response as flat as I can get it?
I think I want a rising low end where at 80Hz it is the same SPL as my mains, then Low Pass Shelved raising SPL towards 10Hz.
My subs seem to start rolling off around 12Hz.
Do I EQ flat, then put the shelf filter on?

My 2x4 has 6 slots for parametric EQ, which should be more than enough.

If one of my subwoofer manifolds is behind the listening position, should I invert the polarity on that one?

Should I start by posting some of my graphs?
 

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Discussion Starter #5
This graph is the starting point. I measured the L/R Mains without the sub amplifier on.
Then I measured the Subs without the L/R Mains connected.
No EQ was applied to the subs at this point.
 

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Discussion Starter #6
And this is the where I have landed with the EQ so far.
It doesn't seem like I'm going to be able to get much flatter than this, although the shelf filter may be messing things up.
There are four cut filters applied to flatten response, then a shelf filter applied.
I put a shelf filter on at 80Hz, with a Q of 1, and gain of 5db.
 

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Looks pretty good. :T

There’s no reason to go with all cutting filters, if it’s more efficient to use boosts and cuts to get where you want to be. It’s a myth that cutting saves headroom, if that’s what you’ve heard.

That’s fairly flat response for the sub, which a lot of people like more in theory than in practice. How do things sound to you?

Regards,
Wayne A. Pflughaupt
 

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Discussion Starter #9
I'm not buying the cut filters only. I realize that when you only use cut filters you are reducing your gain, and so you have to jack up your trims to compensate.
It sounds good now, but I'm sure it could sound even better.
Bass heavy music sounds a little weak, but action movies sound pretty awesome in the lower registers.
I just bypassed the low shelf and will watch a few movies and see where that gets me.
 
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