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Sub on suspended wooden floor ?

Discussion in 'Subwoofers' started by iwatkins, Jan 22, 2003.

  1. iwatkins

    iwatkins
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    Hi All,

    I'm sure there was a thread about this a while back, but I can't find it in search.

    I'm currently borrowing a sub to see if I can live with it before handing over cash.

    The room has bare wooden floorboards suspended on joists that are suspended above a concrete floor which is about 2 foot below the joists.

    The sub is a downward firing (I think) in that the cone is open and points downwards. There is a port on the front of the sub.

    At anything resembling the right volume level, the sub seems to just make the house shake rather than making a good bass noise. If anything the noise it does make is just boomy.

    I've played with phase, input levels, cutoffs, position of sub etc. but all the energy seems to be in making the house shake rather than noise.

    For this setup what is a good way of fixing it. I do understand that the room is probably the worst when it comes to acoustics, but hey, can't have everything :)

    Any advice gratefully received.

    Cheers

    Ian
     
  2. HotblackDesiato

    HotblackDesiato
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    When my set-up was upstairs on suspended boards/joists i had similar problems.
    If it's mechanical vibration, because of the sub directly touching the floor, then decoupling the sub from the floor would be worth a try. For a cheap experiment a heavy paving slab and some spikes between the slab and the floor, and, possibly, the slab and the sub too, would at least tell you if you were heading in the right direction.
    If its just sound pressure from the bottom firing sub the slab might help a little too.
    If it's sheer SPL then tightening up the fixtures and fittings would seem the next step...or perhaps turning the gain back a notch?

    Anyway, if it works you can always upgrade the slab to something more aesthetically pleasing...


    spence
     
  3. iwatkins

    iwatkins
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    Thanks Spence.

    Yes, it is mainly vibration throughout the house when it is at an acceptable level in the room in question. I.e. it seems the floor and rest of the house is taking most of the sound and turning it into movement.

    Got a few paving slabs left over in the garden from a patio project, so I'll give them a go.

    Cheers

    Ian
     
  4. iwatkins

    iwatkins
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    Well I've given it a go.

    I've got a single slab sitting on top of four small (inch cubed) hard rubber blocks. The sub sits on top of this.

    Well, it certainly works a lot better now. I've had to turn the gain down quite a bit of get the same volume level. The sound now actually sounds like bass rather than just moving all the woodwork.

    Still have the occasional rattle of the sash windows when a very loud explosion (or similar) happens but apart from that hardly anything shakes now.

    Another upside is that you can actually feel the sound directly now. I.e. you can feel it in the chest (at higher listening levels) rather than just feeling it through the floor when all the boards move ;)

    So, thanks again Spence.

    As for making the slab more pleasing to the eye, that is something I'll work on.

    Cheers

    Ian
     
  5. HotblackDesiato

    HotblackDesiato
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    Glad it made an improvement. There's not much you can do about those rattling sashs...well if you still want then to open and close, in my experience.

    Regarding improving appearance. I set about my slabs with an orbital sander, 80grit, 120grit then finished with 240grit. I then used some car spray paint saab "odardo grey", gave them a couple of coats and then lacquered.

    spence
     
  6. Stuart Wright

    Stuart Wright
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    Fantastic - it sounds like it's doing it's job properly, then.
    You don't want the subwoofer to be producing Bass. Your speakers do that. You want your subwoofer to produce sub-bass.
    A significant role of your sub should be shaking the house.

    Boominess sounds like a problem, though. The first place I would start is settings for speakers - large/small and sub volume. Check the latter with an SPL meter.
     
  7. iwatkins

    iwatkins
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    Spectre,

    I understand your point fully, it was just excesive. I.e. I heard no difference to the sound apart from a real boomy noise and everything in the house was shaking. I didn't actually 'feel' the sound at all, which IMHO is what sub-bass is about.

    Large explosions on films (i.e. a high LFE signal) equated to sash windows shaking, lots of floor movement and then the missus shouting down the stairs that is feels like an f**king earthquake. ;)

    Now, I get the 'punch' of explosions and I 'feel' rather than hear the deep rumbles. And the house hardly shakes now. This is as far as I'm concerned what having a sub is all about.

    Cheers

    Ian
     
  8. HotblackDesiato

    HotblackDesiato
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    Just visited Spectre's web site...it looks like he has mined down to bedrock to install his REL, so vibrating floors, i hope, aren't a problem! ;)
    ...didn't the earth move in the midlands last year! ;)

    spence
     
  9. iwatkins

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    Hmmm, and wasn't that the same time as U-571 came out on DVD ? :D :D

    I'll try the making a crap looking concrete slab into something the missus doesn't swear about. Sounds straight forward and cheap.

    Cheers

    Ian
     

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