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  1. #1
    Forum Regular audio amateur's Avatar
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    Closed box sub designs

    -The closed-box or "acoustic suspension" enclosure, rather than using a large enclosure to avoid the effects of internal air pressure changes caused by cone motion, uses a smaller sealed enclosure, generally much smaller. The enclosure must have a very small leak so internal and external pressures can slowly equalise over time, allowing the speaker to adjust to changes in barometric pressure or altitude.- taken from Wikipedia

    'The enclosure must have a very small leak so internal and external pressures can slowly equalise over time, allowing the speaker to adjust to changes in barometric pressure or altitude'

    Is this true? Do sealed designs need a small hole or 'leak'?
    cheers

  2. #2
    _ Luvin Da Blues's Avatar
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    I'm far from an expert but I would guess that the flexibility in the foam or rubber surround would that care of any pressure differences...law of equilibrium. There would be small stresses in the surrounds but I think it would be negligible.
    Back in my day, we had nine planets.

  3. #3
    Shostakovich fan Feanor's Avatar
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    Sounds about right

    Quote Originally Posted by Luvin Da Blues
    I'm far from an expert but I would guess that the flexibility in the foam or rubber surround would that care of any pressure differences...law of equilibrium. There would be small stresses in the surrounds but I think it would be negligible.
    I've never heard that any specific provision is need to allow internal/external air pressure equalization.

  4. #4
    Loving This kexodusc's Avatar
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    Actually...

    Hmmm, good question, never thought of that before.
    There's always some leaks - I'm not aware of any air-tight, spaceworthy subs or speakers, but they are tiny, and insignificant, to the point they won't register in measurements.

    But internal pressure resulting from increasing altitude etc - I suppose the restorative cushioning force inside would be artificially high relative to the external pressure if internal pressure remained status quo and equilibrium didn't occur. That is the mass of air per volume outside would be less...

    You would be changing compliance, Vas, etc...
    I'm guessing equilibrium must occur...wouldn't take a big hole.

  5. #5
    Crank it up, dude! huh? hydroman's Avatar
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    I plan to keep my box at sea level...
    H/K AVR635 7.1
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  6. #6
    Class of the clown GMichael's Avatar
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    Quote Originally Posted by hydroman
    I plan to keep my box at sea level...
    Off shore drilling?
    WARNING! - The Surgeon General has determined that, time spent listening to music is not deducted from one's lifespan.

  7. #7
    nightflier
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    SVS said that there's no such thing as a truly sealed sub - so any plans on deep-sea HT listening are probably out. Interestingly, there's a very simple solution to the problem: adding a passive radiator like the Earthquake subs do.

    By the way, the SVS SB12-Plus is an excellent close-box performer, if you're in the market. As soon as I can free some money (probably after the holidays) I'm probably going to buy one.

  8. #8
    Forum Regular audio amateur's Avatar
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    Quote Originally Posted by nightflier
    By the way, the SVS SB12-Plus is an excellent close-box performer, if you're in the market. As soon as I can free some money (probably after the holidays) I'm probably going to buy one.
    Nah not for a while i'm afraid. I'm focusing on actually GETTING a system right now (probably be after Xmas ). No money for extras. I'm sure it does a decent job, but as I live in 'Europe' (UK & France), mostly, SVS is out of the equation. It'd be more to the likes of REL or MJ Acoustics. Small and they dig deep. Though size isn't of huge importance for me.
    I've yet to hear many, some of you have some I believe. REL plus Maggie 1.6's, anyone? I think it's JRA
    I'd be happy for some feedback. I can obviously listen to them here aswell.

    Off subject (well on really), when I would push the cone on my DIY sealed 12" at the time, It would take a little while (when I say little while it's still extremely quick, we're talking under a second obivously) to come back to normal postion (well it still does it's just it's not with me at the mo). This is obviously due to the sealed nature of the enclosure, but perhaps this is also why you need a little hole? I don't know.. perhaps that's how they are supposed to be, but I always thought it could/would affect sound. I tried to make it as air tight as possible, which I think I did succeed in doing. Whereas ported subs don't have this 'problem'. The cone comes right back to initial position, logical.

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