Off-the-shelf subwoofer in the roof

Discussion in 'Subwoofers' started by GavT, Jan 23, 2008.

  1. GavT

    GavT
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    I have been reading a number of threads here which talk about infinite baffle and mounting DIY subwoofers in the roof, which all look very tempting but its not really what I am trying to achieve.

    In a nutshell my Paradigm PS1000 takes up a little too much floor space in the cinema room so can I place the entire subwoofer in a roof space?

    My cinema room is a single story extension with a pitched roof so enough space up top to hide the sub. Because the Paradigm is a ported sub with no visible drivers I'm thinking...

    ... can I place the sub in the roof, on its back (making the 3 ports face down) and cut a hole in the ceiling for the ports to 'breathe' through? Will it mind being on its back? Alternatively should I sit it on its feet and construct some kind of 90 degree bend port extension to an exit in the ceiling (worried about de-tuning the bass notes with this though)?

    What d'ya reckon?
    GavT
     
  2. Peter314

    Peter314
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    There is a thread about this sort of thing here.

    Although if you wait a while, I'm sure the Wise Old Polar Bear will soon be along to help out. ;)
     
  3. GavT

    GavT
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    Hey Peter,

    Tried to hi-jack that thread last week but the responses were a little wide of the mark for my particular issue (the focus was still on the noisy neighbours problem rather than relocating an entire subwoofer enclosure).

    Thanks all the same.
    Gav
     
  4. AngelEyes

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    There is nothing to stop you placing the sub in the roof on its side or whatever, it shouldn't effect the way it works.

    More importantly though is the location and how it interacts with your room. Having a sub in your room means you have some chance to move it around to get the best possible reponse (cure and nulls or booming peaks in the listening position). Having the sub in the ceiling really doesn't give you the chance to test the ideal place and you would be left to guesswork at best and reliant on where the joists allow, at worst.

    I am sure there are ways of testing, perhaps by placing the sub at ear level where you sit and placing your spl meter at various points around the ceiling and running some test sweeps with REW you may be able to determine a good location but I defer to others with more experience in this sort of thing.

    Adam
     
  5. Nimby

    Nimby
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    GavT

    Adam has covered some of the likely problems.

    You should also consider the deterioration of the sub enclosure due to damp and rapidly changing temperatures in a typical loft.

    Getting the ports to work properly would involve making a large hole and getting the enclosure panel flush with the ceiling. That would involve fixing the sub firmly to the joists somehow.

    I am not familiar with this sub. Are there really just the ports visible? That would make it a bandpass design. If the driver is hidden by a spaced bottom plate in the usual downfiring position then you have serious problems trying to adapt it to the above ceiling mounting. It could be inverted and fixed to the ceiling joists without real loss of performance. The ceiling would take over the boundary gain duties normally supplied by the floor.

    Have you considered hanging the sub on strong wall or ceiling brackets somewhere up at the front of your HT? The ceiling brackets would need to be screwed to the joists not just the plasterboard. Fixing the sub to the wall above your screen would be far easier than trying to use the loft. The height would hopefully make little difference as long as the front speakers offer some bass output of their own.
     
  6. GavT

    GavT
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    Thanks for the input, they have certainly opened up more considerations.

    Hanging the sub off the wall / ceiling is probably not an option here since the ceiling is quite low and will not really work with look / feel of the room.

    Nimby - you say the ports should be flush with the ceiling (yes it is a bandpass design). Would the depth of the floor joists (4 inches I think) disrupt the soundwaves that much?

    With regard to placement, if I've understood other threads on here correctly, sounds generated by subwoofers are omnidirectional and the ear cannot identify from which direction the sound eminates. On that basis could I place the subwoofer centrally safe in the knowledge that I will enjoy at least, say, 90% optimal performance? When a subwoofer is located on a floor, placement is important if you want to load the bass by putting it nearer the wall, no?
     
  7. Nimby

    Nimby
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    It's all to do with tuning. The ports are calculated and tested to be a particular length and area. You can't mess about with these calculations by sinking the sub behind a solid surface with a hole to "breathe through". To do so would almost certainly spoil the tuning.

    The location of the ports relative to the nearest wall, floor and corner are all vital statistics in the sub's designed and actual performance. I built some bandpass subs of my own and found that just rotating the box (still with the ports facing upwards) made an enormous subjective difference from the listening position. This was in a room nearly 40 feet long x nearly 20 feet high at one end.

    Even placing a conventional sub flush with a room surface will add an extra baffle effect to the driver which it wouldn't normally enjoy when sitting on the floor as designed. You are in unknown territory whenever you try alternative subwoofer situations.
     
  8. GavT

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    I think that is what appeals to me :)
     
  9. Nimby

    Nimby
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    Subwoofer experimentation doesn't usually involve making large holes in the house. (unless you're an IB nut)

    It doesn't give you much of a chance to get it right first time.

    At the very least you should be testing the sub on top of a high stepladder before you start burrowing.

    Be careful your don't drop the sub on anything or anybody! :eek:
     

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