Why face drivers towards eachother in IB?

[NoDestiny]

Researching the topic, I couldn't find this answer about anywhere. I notice almost every install has a manifold with 2-4 drivers, all facing eachother. Wouldn't this lose efficiency doing it this way? Would it be better to just angle and have both drivers facing into the room instead of eachother?

[Space]

Opposed cone motion will cancel vibration, so you don't rattle the floor too much. And this manifold design allows a smaller opening in the floor. At very low frequencies it doesn't matter too much which way the driver is facing, in terms of sound output. The output is basically up, into the room either way.

[A9X]

Plus if you set them in push-pull, then you'll also get a degree of cancellation of the even order suspension non-linearities.

Edit: the efficiency is the same as for two drivers mounted flat on the ceiling wall, also in IB, that is, the manifold makes no difference here.

[NoDestiny]

Interesting... I figured two drivers facing eachother would "push" on eachother as they moved, making them less efficient. Guess that makes sense on the vibration cancellation.

[Space]

It's also good to have the drivers mounted facing horizontally, so the moving mass doesn't stretch out the suspension over time.

You may have a point about multiple drivers impeding each other in a manifold, but only if the gap inside the manifold is very snug. Generally the air resistance should be a lot less than what you'd have inside a typical subwoofer box.

ThomasW has said that the number of drivers needed in an IB is much more than with box speakers, like 3-4x as many. I've wondered why that would be true, and all I could think of is that there may be leaks that cancel output between the front and back of the drivers, like with an OB. But maybe the manifold design is inherently inefficient, as you were thinking.

[ThomasW]

Researching the topic, I couldn't find this answer about anywhere. I notice almost every install has a manifold with 2-4 drivers, all facing eachother. Wouldn't this lose efficiency doing it this way? Would it be better to just angle and have both drivers facing into the room instead of eachother?

Wall mounted subs place a surprising amount of strain on the wall itself. We've had people post they saw 1/2" of flex with standard 2"X4" stud wall construction. When the wall flexes the output from the drivers is decreased. With the drivers mounted in opposition in a manifold the wall flex is eliminated.

The effect of the sub on the rest of the room is the same with a manifold as it is with surface mounted subs.

ThomasW has said that the number of drivers needed in an IB is much more than with box speakers, like 3-4x as many. I've wondered why that would be true, and all I could think of is that there may be leaks that cancel output between the front and back of the drivers, like with an OB. But maybe the manifold design is inherently inefficient, as you were thinking.

IB specific drivers have smaller motor structures therefore less ability to tolerate high amounts of power (heat). The reason they have smaller motor structures is when mounted in an IB any driver will become more efficient as as the frequencies they're playing go lower (this is the opposite of other types of subs) So paying for big motors when a driver will be used in an IB is a waste of $$$$$

To compensate for the inability to apply huge power to a single driver we use multiple drivers. This cuts the workload on individual drivers and gives us more total output.

BTW lots of answers to the standard questions about IB sub at the IB FAQ link in my signature..

[NoDestiny]

Flexing... that makes sense to me! Flexing would lose far more, I didn't put that into thought at all. I didn't see this question in your FAQ (Didn't SEE it, doesn't mean its not there though )

Just looking out for future ideas