Using My Infinity 12s for IB, What Can I Expect?

[SmoothSQ 10+ year member]

Hi, me again. lol.

I was gonna get an AV15-X, but they keep pushing the in stock date back.

In July it was mid August. In mid August it was mid September. Now the date given is mid October. I don't wanna keep waiting. So...

I have a pair of Infinity variable-Q dual 4 ohm 12" subs that I'd like to try in an Infinite Baffle configuration. I'm thinking of having them mounted behind my folding rear seat.

When I switch the pole pieces, that changes the sub's specs significantly.

If I remove the pole piece that I'm using at the moment, here is what the sub's specs will be changed to..

SPL: 84db

Le: .81mH (parallel)

BL: 8.28Tm

Vas: 3.31 cubic feet

Cmd: 275.39 uM/N

Mms: 189.8g

Fs: 22.01Hz

Qms: 10.52

Qes: .64

Qts: .60

Xmax: 16.75mm (one way)

In a volume of 17 cubic feet, WinISD shows the F3 being 26hz. That's pretty low.

I'm guessing with an Infinite Baffle configuration, the low bass, 50hz and below, is gonna be very pronounced, but above that output will be relatively weak. Does that sound about right? After listening to my Infinity 12s with their "low q" insert in a small sealed box for the past few months, I'm starting to miss the low lows. So maybe IB would be just fine, if I upgrade my cabin speakers to some speakers that have good mid-bass response.

I've read some articles which said that IB doesn't get loud. I'm not worried about that though. I'm not trying to impress other motorists, or trying to set off car alarms. Surely dual 12s would be plenty to fill in the low end.

Is IB transient response usually better or worse than sealed?

Should I wire my subs in series to achieve a higher amplifier damping factor, to help control my subs since they won't be in a box (unless you consider my trunk to be a sealed box)?

I've heard people say that IB is good for SQ systems. What makes IB good for SQ-based systems?

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[T3mpest 10+ year member]

Ib and sealed are the same thing all an IB setup does different is teh box is so big that it offers the suspension no compliance. That makes it more effecient than a smaller actual box would. The Q of the system IB is the same as QTS since their is no airspring to raise that value so your overall Q will be .6, which is fine. Power shouldn't be an issue no matter which way you go, you'll probably have enough power to reach mechancical limits either way. Damping factor really wont' make much of a difference, the motor will control the cone movement,that's what it's there for.

 

[SmoothSQ 10+ year member]

Hey, there's something I need to know before I get the custom work done for the Infinite Baffle...

As shown in the aforementioned specs for my Infinity 12s, their Qms is 10.52

I was looking at the Fi Car Audio Infinite Baffle subs and their Qms is 4.00

That's a big difference. Performance-wise, what difference will that make?

Most IB subs that I've seen have high Qms specs. Is a high Qms advantageous for my application?

Or would it be better to have the lower Qms?

I'd really appreciate it if someone who knows how this would effect IB performance would answer these questions for me.

Thanx.

 

[whitedragon551 5,000+ posts]

Your questions would be better addressed at DIYMA.