Three chamber IB? An insane idea?
Feb 1, 2009 3:31:04 GMT -7
Post by chrisbee on Feb 1, 2009 3:31:04 GMT -7
Imagine you have a potential IB enclosure which is too small for best performance. Let's imagine it is a typical closet. Ideally placed at the front of the room but just too small.
Cutting a hole in the far wall of the closet to a much larger third space would need a very large hole to have much effect at low frequencies. Making such a large hole would probably be difficult to arrange in a domestic situation.
What if one were to build a second manifold into a hole in the far wall of our closet to our third space? Let's call it a secondary manifold. This secondary manifold would exactly match the primary manifold with the same number and type of drivers. (Manifolds are suggested to avoid reaction forces causing structural vibration)
The drivers of this secondary manifold would be wired in phase with the primary manifold. So whenever the drivers in the primary manifold moved the second manifold drivers would follow exactly.
The effect would be to fool the primary manifold into thinking it has a very much larger enclosure. No compression or rarefaction effects would occur because of the perfectly matched secondary driver cone movements.
Since the output from the secondary manifold is exhausted to a remote third space there is no out of phase cancellation of the primary manifold output. We'll assume that the third chamber is large enough not to be compressed by the secondary manifold drivers.
Those who have a large potential enclosure not directly connected to the HT could utilise this third space to overcome the shortcomings of their undersized IB enclosure. Usually the distance to the third space precludes simple passive exhaustion of the HT manifold to this remote space. Thomas usually starts talking about bandpass subwoofers when this is suggested.
The obvious downside is the need for twice as many drivers. I wont mention suitable ABRs at this point to avoid diluting the concept.
There may also be an increased risk of audible colouration if the primary IB enclosure is very small. Curtains of insulation batting or even a closet full of hanging clothes could probably help here.
There is no reason why floors and ceilings could not be utilised as the baffles between the three spaces if desired. I only suggest closets and rooms for simplicity and to simply the diagram below.
Any (constructive) thoughts?
Cutting a hole in the far wall of the closet to a much larger third space would need a very large hole to have much effect at low frequencies. Making such a large hole would probably be difficult to arrange in a domestic situation.
What if one were to build a second manifold into a hole in the far wall of our closet to our third space? Let's call it a secondary manifold. This secondary manifold would exactly match the primary manifold with the same number and type of drivers. (Manifolds are suggested to avoid reaction forces causing structural vibration)
The drivers of this secondary manifold would be wired in phase with the primary manifold. So whenever the drivers in the primary manifold moved the second manifold drivers would follow exactly.
The effect would be to fool the primary manifold into thinking it has a very much larger enclosure. No compression or rarefaction effects would occur because of the perfectly matched secondary driver cone movements.
Since the output from the secondary manifold is exhausted to a remote third space there is no out of phase cancellation of the primary manifold output. We'll assume that the third chamber is large enough not to be compressed by the secondary manifold drivers.
Those who have a large potential enclosure not directly connected to the HT could utilise this third space to overcome the shortcomings of their undersized IB enclosure. Usually the distance to the third space precludes simple passive exhaustion of the HT manifold to this remote space. Thomas usually starts talking about bandpass subwoofers when this is suggested.
The obvious downside is the need for twice as many drivers. I wont mention suitable ABRs at this point to avoid diluting the concept.
There may also be an increased risk of audible colouration if the primary IB enclosure is very small. Curtains of insulation batting or even a closet full of hanging clothes could probably help here.
There is no reason why floors and ceilings could not be utilised as the baffles between the three spaces if desired. I only suggest closets and rooms for simplicity and to simply the diagram below.
Any (constructive) thoughts?
