Displacement Question and More...

[Shagarello]

...from a first timer.

Hey guys (and gals),

New to the forums here.  Hang out mainly at CAM, but I've been looking into an IB implementation for a while now and am getting close to pulling the trigger.   Some background on my intended use...What I'd like to do is bring some sort of passive pre or equalizer with selectable channels so that I can toggle between my HT and my 2-channel listening system.

But for now the question is really around the drivers.  I keep coming back to Fi Audio and AE.  I'm looking at 18" drivers.  The AE IB18HT and the Fi IB318v2. Both have similar SD (1218 vs 1210. The AE lists an Xmax of "18mm (peak)" and the Fi "34mm one way". But the Vas for the AE is claimed to be 632 litres, while for the Fi sub it is 246 litres. What gives? What am I missing? Is there another spec I need to take into consideration to account for the 2.5 times difference?  Does the 18" AE really displace 2.5 times the amount of air that the Fi Audio does?

And if so, do the merits of having two drivers (Fi) with which to balance the bass outweigh the simplicity (and more displacement) of one AE driver?  If I implement two drivers, one will be wall mounted on the left, and the other floor mounted on the right.  If I go with one, I will like choose the floor mounting option on the right (but could go with either.)

Any advice, input or feedback?

And no, i can't go as far as two AEs...(not unless they do some crazy black friday sale)

edit: room size approx 1800-2000 cubic feet.

[ThomasW]

Hi, and welcome .....

Sorry I can't address the Xmax vs Vd as far as AE computes them.

The AE driver has a more sophistated motor design, and it should offer more linear operation. That would be a consideration if the driver were operating higher in the bassband that an IB sub operates.

Since we limit the driver's operation to a narrow passband at very low frequencies it's highly unlikely that a sophistated motor design is worth the cost of admission.

FWIW, the Vd spec tells us how much air a driver displaces. Vas references the compliance of the suspension.

So IMO go buy a pair of the Fi drivers

[Shagarello]

Hey thanks Thomas.  Perfect answer.  I will be ordering two Fi 318s in the next week or two.  Will see if there's any more to be saved for black friday, but going to order either way.

does lead to another question or two, but that's for another thread!