a sub Q
 

how much room do i need behind a sub
there is a hole for air to the VC and i need to let air in and i need to know how fare i need to keep off the wall

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You don't want the back of the sub rubbing against anything, I would think that about 1/2" to 1" would be ok. Why do you need it so tight?

Non vented pole piece can pretty much touch, vented should have an inch or more.

Standard rule of thumb is usually to keep the driver (on all sides) 1" away from any walls/obstructions.

^ Agreed.