mickb
New Member
Posts: 13
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Post by mickb on Aug 26, 2008 6:53:57 GMT -7
Hi, Having recently been 'hooked' by the thought of building an IB, and doing lots of reading, I have a dilemma with placement. My HT room has an alcove opening at the rear, which leads into a small office-space (approx 8x6). This also has a door at the far end. I thought I'd be able to place the IB in the alcove, then close it off, thereby venting the IB into this room. However, reading up on placement, it sounds like placing th IB at the rear will cause issues. Should I therefore stick with my SVS sealed unit, and give up on an IB solution....
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Post by ThomasW on Aug 26, 2008 8:25:59 GMT -7
Having any sub work properly at the rear of the room requires the ability to very closely match phase with the mains. It also requires the mains being able to quite low so that a low crossover point can be used.
All this means yes it can be done but doing so requires significantly more expertise compared to having a sub in the front. For example it's almost impossible to accurately match phase without the use of an oscilloscope.
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mickb
New Member
Posts: 13
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Post by mickb on Aug 26, 2008 11:10:30 GMT -7
Thanks Thomas.
My main pair should handle a low cut-off (B & W 802D), what sort of freq do you suggest?
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Post by ThomasW on Aug 26, 2008 11:22:47 GMT -7
As a general rule I don't think having only a rear firing sub is a good idea.
Take your existing sub, put it behind you and give a listen. See if that's what you want. Experiment with differing XO points, see if there's one you can live with.
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mickb
New Member
Posts: 13
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Post by mickb on Sept 3, 2008 4:44:43 GMT -7
Thanks again.
A quick question on drivers:
my HT room is approx 1300 cu ft, and I'm looking at IB 15's, would 2 suffice or should I go for four?
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Post by ThomasW on Sept 3, 2008 11:03:03 GMT -7
Did you experiement with your existing sub behind you?
Do you have access to an oscilloscope and a way to adjust phase?
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mickb
New Member
Posts: 13
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Post by mickb on Sept 3, 2008 11:36:56 GMT -7
My existing SVS PB12 is in roughly the same position, slightly in front of the alcove where I'd put the IB.
I don't have an oscilloscope, do you think phase issues will be a big problem?
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Post by ThomasW on Sept 4, 2008 8:29:42 GMT -7
If having the sub behind isn't a bother, (it drives me nuts) then build away.
You'll have to deal with the phase issues if they occur.
If the finances are such that the $200 difference between 2 drivers and 4 is problematic start with 2. I always recommend making a manifold that will hold 4 drivers just in case...
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