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Subwoofer in the roof?

Discussion in 'Subwoofers' started by riprip, Aug 26, 2003.

  1. riprip

    riprip
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    Before I discuss my (possibly) crazy idea, I should point out I have only a basic grasp of sound dynamics and a vague understanding of how my subwoofer does what it does. Please bear this in my as I tell my story.....

    Just moved into my new flat. It's very nice, thankyouverymuch. Detached house, converted into two flats, one up one down. We're upstairs, and the chap who lives downstairs seems like a nice bloke.

    Last night put The Two Towers on. This is the first DVD I've watched since moving in that gives the subwoofer anything meaty to do. Sounds great.

    We get to the Helms Deep battle and there's banging on the front door. As you've probably guessed, it's the man downstairs complaining about the noise. He's not really complaining - I explained when I moved in that I've got a surround system that can go pretty loud, could he please let me know when it's too much so I'll get an idea of the maximum volume I can go to. He says that he can't hear any normal sound - like dialogue or music, nothing like that. But the bass is making his glassware rattle.

    I switch the subwoofer off, watch the rest of the film at the same volume, then ask him if he heard anything after he knocked on the door. Not a peep, he says.

    Since this is a converted house, rather than a purpose built block, I'm guessing that it's just wooden floorboard between us and him. I havn't taken the floor up yet, but there's probably little or no insulation between my floor and his ceiling, judging by the way the bass from the sub travelled. So I think that laying some sort of insulation between the two flats (just in the lounge - let's not go mad) should sort this out. We're going to put a laminate floor down, which I know is bad for sound but the girlfriend really likes it. This should also muffle some of the bass.

    Then I had a genius idea. Could I put my subwoofer in the loft? The roofspace is totally open, so I could place it directly over my lounge. Then turn it up to 11 to drive the bass down through my ceiling.

    What I'd really like to know is would this work? And would it solve my neighbour problem? I'm not entirely sure that if I had it at a sufficient volume to sound good in the lounge, the bass would still be loud enough to rattle the guy downstair's crockery.

    Any suggestions? Or am I mad?
     
  2. Stellavision

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    A subwoofer needs to be on the floor to get the proper effect.
    I wouldn't even consider putting my tiny pc sub at ear level.
    I'm affraid your idea of having your sub above you would be about as useful as putting it in the back garden.
    Sounds to me like you will need to stick to enjoying your system at modest levels or when the neighbours are out.
     
  3. Apocalypse

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    Just had to check the date to make sure it wasn't April 1st :devil:
     
  4. SeaneyC

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    I don't think it would sound particularly good, more pure boom i would imagine, you wouldn't be moving the air in the room, just moving the air in the loft.

    On a side note, i think the best place for a sub is actually half way between ceiling and floor, at least this is what my physics brain tells me, and i'm sure i've read this somewhere too.
     
  5. buns

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    The sub doesnt necessarily need to be on the floor. There are guys using infinite baffle subs which are placed in their ceilings........ do a search on avs and you'll find some links.

    But if you are talking of putting a standard sub into the roof space, it wouldnt work, or i strongly doubt it

    Ad
     
  6. Stellavision

    Stellavision
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    Bass and sub bass especially is something that is often felt not just heard. To this extent the optimal position for any bass speaker, be it in the home or in a proffessional set up, is on the floor. Similarly a lot of subs are made with downward firing drivers to help with room coupling.
    An elevated sub simply wouldn't provide the same vibrations you should expect to feel from low frequency's.
     
  7. Dom36

    Dom36
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    I live with my parents (only 16) and i'm upstairs with my 1st home cinema sytem.
    The Yamaha YSTSW315 might not get the reviews and the high scores but for me it works better than nothing and gives an excellent effect when mixed with the rest of my system. But the shop I bought it from suggested buying a paving stone from my Local hardware store to cut the bass out downstairs.
    I havn't actually tryed this yet but in theory it will work a treat for the both of us...
     
  8. riprip

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    See, I knew I was talking crazy talk. Can someone please explain to me (in words of one syllable, I guess) exactly how a subwoofer does what it does? Like the actual physics of it - how does what only appears to be a simple boom at such and such a frequency translates across a floor..........

    Perhaps if I can understand exactly what's going on after the sound leaves the sub I can work out the best way to get around this problem. The sub isn't really turned up that high - the crossover's set to about 80hz and the volumes about 40%. If I turn it down any more I might as well turn it off. I guess I'm looking at insulation in the floorboards. Which could get pretty expensive.

    But Dom's paving stone is sounding pretty good - and cheap......
     
  9. Dom36

    Dom36
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    The real physics could depend on the sub itself.
    I myself have a downfireing sub which adds to the problem of keeping the noise upstairs.
    I normally run my sub at cut off 50Hz and 3-5 out of 10 volume. If anything lower than 80Hz cut of isn't doing much your speakers must be good enough?
    But I understand your logic for a sub.

    I you remove the Grille off the front of one of your front speakers. Touch the cone - gently!
    Turn the bass up on your amp - turn it down - add volume - turn up the bass till it is moving quite alot - you can probably see and feel the difference...
    The end result is effectivly what a Subwoofer does...except it is made to handle more bass at higher volumes than standard speakers...as the cone inside is larger.
    Also a sub will have an air outlet. This is because when the speaker comes backwards where is the air gonna go? It has to get out - I used to think it was this moving air that created the bass and i'm still not sure but i'm sure its the cone...

    Your front speakers may also have these air outlets on if they are powerful and move alot...and my newly purchased centre also has it on.
     
  10. SeaneyC

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    See i do kind of agree with this, but also, my inquisitive mind is thinking that getting the sub to try and move all that solid rock/wood/whatever must be an awful waste of energy. Surely it would be more efficent to move 100% air than 50% air and 50% solid material (based on the assumption that the solid material would lose quite a bit of the kinetic energy by the time it reached you sat on your sofa)

    Also thinking laterally, putting a sub near walls of a room can make it sound overblown and boomy, and surely the place furthest away from the walls would be the very centrepoint of the room. Clearly not practical, but maybe would give the cleanest bass possible? I'm a bit out of my depth here, just kinda throwing ideas about.
     
  11. riprip

    riprip
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    This is where my understanding of the subwoofer starts to get pretty ropey. I thought that bass, like all sound, is carried in a wave. And bass is pretty much non-directional, which is why placement of the subwoofer in the room is important, but no where near as important as precisly positioning your other speakers.

    So taking the above (incorrect?) assumptions to be true, I began to wonder if my sub would also work the same if I put it in the roof. I turn up the volume to drive the wave through the floor below it (my ceiling) then down through the total height of the lounge below. Other than the loss of bass as it hits the ceiling, it can travel through the total height of the room, a bit like the 100% efficiency that Seaney mentions. I understand you'd lose out of the vibrations in the floor that you get with a sub - replacing these with vibrations in the ceiling! But I was wondering if losing the vibrations but still keeping the bass would still sound good, or whether the two functions of the sub are just as important as the other.

    I should probably just stop now - I've already shown myself as a woeful inadequate newbie as far as this is concerned. I didn't think my idea would work - but I really wanted to know why my theory was wrong.....
     
  12. eviljohn2

    eviljohn2
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    Bass notes themselves are as "directional" as any other frequency (ie. mid-range & treble), it's just that the ears can't pinpoint the direction they come from as easily.

    With regards to wall placement, ported speakers (with the air vents) are often designed as such so that you can deliberately place them nearer a wall and get some extra bass out of them - my Paradigm PDR10 sub says in the manual that it's supposed to be placed against a wall.

    Bass frequencies are low and thus have a long wavelength, higher frequencies have shorter wavelengths. Sound travels at approx. 330m/s in air so here's an example to deal with the attenuation using the old equation
    VELOCITY = FREQ * WAVELENGTH

    A bass note of 30Hz thus has a wavelength of 11 metres.

    A mid note of 3000Hz has a wavelength of 0.11metres (11cm).

    A treble note of 18kHz has a wavelength of 0.018metres (1.8cm).


    From that you can clearly see that by the time a single wavelength has passed of the bass note it can be through your floor and into the next room with little attenuation from your floor (which will only be a few centimetres at most), and that for a similar distance many wavelengths of the other 2 will have occured so more attenuation again - the treble will be stopped short at the room boundary!

    I should imagine that installing a sub in the ceiling itself would certainly not be a problem and add reasonable bass if the driver actually encroached into the room since there'd be plenty of air movement which is nice to feel.


    It's a bit of a ropey explanation but it covers some of the main questions that have been brought up using not much more than GCSE level physics.
     
  13. JonLeach

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    Have a look here its all about tweaking your hi-fi and some stuff on room acoustics

    here

    i'll be doing the mains stuff tonight.

    i don't live in a flat but putting a slab of marble under my sub made a HUGE difference

    Jon
     
  14. alexs2

    alexs2
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    I think you will find that whatever the position of the sub in the room(or loft!),if it loads the room sufficiently,your neighbour will be able to hear it....low frequency sounds are fairly poorly attentuated by carpets and wood flooring,whereas higher frequencies are absorbed pretty well...hence his complaints about things rattling,which then went when the sub was turned off.
     
  15. riprip

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    OK - I'm getting a better idea of what's going on with my sub now. Eviljohn, thanks for that explanation. I never could work out how bass could be non-directional. I'm read this in What Hi-Fi, which might explain a lot.

    What effect would sitting the sub on a slab of concrete have? Obviously the bass wave wouldn't travel through that so easily, but what effect would it have on the sound produced in my lounge? And what as the bass radiates out from the sub - surely that is still going to pass through the floor?

    I may be clutching at straws now, a slab of concrete (or marble) might be the answer to my problems.

    Not sure the girlfriend will approve of a paving slab in the lounge. Could I pass it off as an 'architectural feature'? Maybe a piece of 'modern sculpture'?
     
  16. alexs2

    alexs2
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    riprip...the slab will provide a nice solid support for the sub,but will not stop radiated bass energy passing through the floor over the whole of the rest of the room.
     
  17. Dom36

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    Just the fact that it is a very solid "object" that will prevent the noise going downwards...
    JonLeach has used a piece of marble and said it makes a big difference (not sure what he means - noise downstairs reduction or making sound better but even so...)

    Not sure the girlfriend will approve of a paving slab in the lounge. Could I pass it off as an 'architectural feature'? Maybe a piece of 'modern sculpture'?

    LOL! What other way is there...?
     
  18. JonLeach

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    the slab made the bass much tighter it was sounding very woollie before. but also....

    i have a very thin wall between my av room and my neighbours, thin enough to here the tv as though your in the room.

    i asked them what noise they could here and i ended up installing some sound proofing between us, after this all they could hear was the sub, the peice of marble sorted that.

    i have a top quality carpet n underlay, the slab stopped most of the noise going next door

    Jon
     
  19. riprip

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    OK - I've just 'borrowed' a couple of concrete slabs from work. I'm going to conduct a highly scientific experiment in sonics by putting them under the sub. Let's see what happens.
     
  20. Respectamonkeee

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    a paving slab is the thing to plonk ur sub on. this works a treat if you are above your neigbour as it will stop a lot of the vibrations traveling thru the joist.

    get down to ur local wicks/B&Q/Hombase to get a cheap slab before getting a rather expensive marble slab.
     
  21. avanzato

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    riprip: If you're putting down a laminate floor it'll be worth looking into getting a good acoustic underlay.

    As well as the slabs try putting the sub on cushions or pillows, anything that will isolate it from the floor. Just to see what that does to the sound transmission.
     
  22. riprip

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    Tried the paving slabs. They did improve things, but it's still not really good enough - he says it's still quite loud. Grrrrrrr.

    Now I've tried turning the on it's side and upside down. I know this is absolutely sacrilegious, but I was getting a bit desperate. On the side the sub produces the best sound, but it's still a bit loud in the flat below. Upside down the bass is adequte, and the man downstairs is happy. I guess it's a success of sorts......

    I'm still yet to tweak the bass with the old MCACC on my VSX2011 amp, which will hopefully improve the bass a little. It'll certainly do for the time being, until I decide exactly how I can improve the sound proofing of the floor.

    Thanks to everyone for the advice and help in this problem. Plus the science bits (concentrate) were invaluable in helping me understand what's going on with the sub. Cheers to all.
     
  23. Stellavision

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    Rip Rip, I'm affraid some neighbours will never be happy.
    I live in a purpose built flat and I used to have neighbours below me who would feel the uege to complain if I farted too loud.
    Different neighbours have since moved in and they say they hardly notice the noise from my system.:eek:
     
  24. Andrew_B

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    Just a thought, but how about adding a tactile transducer to your system and fixing it to your sofa? You'll still get the 'feeling' of powerful bass without the associated low frequency soundwaves. You could then run your sub at a reduced volume just to get the audible frequencies in the room. How do you sell the idea of a tactile transducer to SHMBO? Sorry, bad idea.
     
  25. riprip

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    What the hell is a tactile transducer? Sounds like the sort of thing you get delivered in brown paper packaging.

    And what is my SHMBO? Dammit, I thought I recognised most of these new-fangled acronyms.
     
  26. Ian J

    Ian J
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    Obviously not a fan of Rumpole.

    She Who Must Be Obeyed
     
  27. Andrew_B

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    I haven't got one of these yet, but it's sure on my list. The 'brand leaders' are Clarke Synthesis and Butt-Kicker, but you can make one yourself from an old speaker...

    www3.telus.net/gwolanski/Htheater.html

    She Who Must Be Obeyed (oops, sorry, got the 'W' wrong in the last post) might even like the good vibrations which will emanate from your couch! The home-made jobby would have to be hidden away and you will need somewhere to stash the extra amp to drive it.
     
  28. avanzato

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    A tactile transducer is basically a speaker without a cone attached. It puts all it's energy into vibrating your sofa where as a speaker puts it's energy into vibrating the air in the room. So a transducer give you loads of effect for very little effort.

    You can get some cheap and effective shakers 'Bass Rockers' from CPC for about £30 each and you will also need a subwoofer amp panel as shakers need to be low pass filtered like a subwoofer.

    TTFN
    HTH
     
  29. Andrew_B

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  30. GavT

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    (Gonna try and re-awaken this old thread :hiya:)

    I am asking myself the same question - can I place a sub in a roof space? I don't have the same neighbour problem, just that SHMBO does not like the size of my Paradigm PS1000.
    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 ports face down) and cut a hole in the ceiling for the ports to 'breathe' through? Will it mind being on its back?

    What d'ya reckon?
    GavT
     

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