Couple Questions About IB?

[Chicago]

Ok , I been reading about IB. And im sold!!!!!! Ive been reading threads but my problem is. Each thread i read, I kinda get a partial answer to my questions , So ill just ask mine, and then hopefully ill understand a little better. Ok here goes Does a IB have to be 4 Subs, ive read a guy has 1 and he says works fine? To be honest most of the ones ive seen in here i would love to have , but wife wouldnt allow me to spend (at least not all in one shot) and the bass that must come from them has to be out of this world, but right now would be a little mcuh for the wife, Id slowly have to introduce her to the world of bass. Next what determines what makes a SUB a IB sub? Also how do you find out what the VAS is on a sub?. 2 more questions . How do you determine to point sub in or out ?(some are in and out ) . And the last is i did ask in diffrent post but i want to ask in a diffrent way . I have a Cerwin Vega 15 was wondering if i could at least try this sub to see the type of sound i could possibly get,(Anyone know the VAS to this sub?) Then buy a diffrent sub designed for IB (like 2 of the FI 15's or 18s'). My guess that would be plenty for wife. But if anyone could kinda hit on all these questions id be able to get a better grasp on the other threads and understand them a little quicker . Thanks for any help

[Chicago]

Ok after spending hours reading ,here and the cult. I still would like to know what VAS means? And why you couldnt take a sub out of a SVS, Cerwin Vega etc etc and put it into a IB? Any help here would be great. Thanks

[Mike P.]

VAS is the stiffness of the suspension, there is a definition here:

http://www.hometheatershack.com/foru...arameters.html

Since the recommended enclosure size for an IB is 10 times the VAS of the driver, it would take a reduced amount of input power to reach the Xmax of the driver in an enclosure that size. Reduced power input means reduced SPL output. Since low end bass is all about moving air, (displacement), the use of multiple high Xmax subs is required to move the air necessary to produce the required low end SPL. You could use the subs from SVS, Cerwin Vega etc, if you had enough of them to move the required air to produce the SPL.

[hddummy]

Chicago wrote:

Ok here goes Does a IB have to be 4 Subs

No an IB doesn't have to be 4 subs. The problem is that since there is not cabinet acting on the back side of the sub, there is very little to resist its motion. Because of that, it doesn't take much power to push an IB sub to it's excursion limits and therefore the volume output is limited. The common way to get more volume if you cannot apply more power is to add more drivers.

Chicago wrote:

Next what determines what makes a SUB a IB sub?

I believe you mean what makes a particular driver suitable for IB use. Since the only resistance to motion in an IB is it's own mechanical resistance (spider, mass, and surround), IB drivers have different values than drivers intended to be in a cabinet. Also, IB drivers don't require much power to reach their excursion limits, so the motor structure is generally not a large, powerful motor. Start a dialogue with the guys over at Fi for more design specifics.

Chicago wrote:

Also how do you find out what the VAS is on a sub?.

When you buy a driver, the manufacturer will list its T/S parameters. When you buy an already built subwoofer, there isn't any way to find info on the driver unless it is sold independantly on the market. There is also a do-dad from partsexpress that will measure the T/S parameters of any driver.

Chicago wrote:

How do you determine to point sub in or out ?(some are in and out )

I don't think it matters, but someone else may know better.

Chicago wrote:

I have a Cerwin Vega 15 was wondering if i could at least try this sub to see the type of sound i could possibly get,(Anyone know the VAS to this sub?)

No one can tell you what to do, but you are risking the health of that driver and ruining an already fantastic sub.

What does VAS mean. Don't know for sure...I would guess Volume of Air Suspension. From wikipedia "It represents the volume of air that has the same stiffness as the driver's suspension when acted on by a piston of the same area (Sd) as the cone"

[Chicago]

Ok Thank you , I am kinda figuring it out . And i do think im gonna try to build one. Thanks again HD