How does an Acoustic Suspension Subwoofer work?

Discussion in 'Speakers' started by Pablo Abularach, Sep 9, 2003.

  1. Pablo Abularach

    Pablo Abularach Supporting Actor

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    Hi,

    I just wanted to know how does Acoustic supended speakers and subwofers work? I have read that they are more accurate but have lower SPLs but how do they work and why does this happen?

    Thanks,
    Pablo
     
  2. LanceJ

    LanceJ Producer

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    I like acoustic-suspension designs myself, though some people don't because they think they sound too "reserved" or "soft" sounding. They weren't popular for almost thirty years for nothing......

    Their only real "problem" is they are less efficient compared to a comparably sized bass-reflex (ported speaker), but power is cheap nowadays so IMO this isn't a big deal.

    Here's where acoustic-suspension started.

    Accuracy? Comparing an electroncially equalized/corrected ported speaker to a plain sealed design is not a good comparison, so make sure you know how each speaker is built first.

    LJ
     
  3. Sasha_G

    Sasha_G Agent

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    Interesting section from the article you referenced:

    "He placed the musicians (the Fine Arts String Quartet, among others) on the stage, with a pair of AR-3 loudspeakers behind them. At various points, they would stop playing and the taped performance would take over. Most reviewers of the day could not tell the difference between the live and recorded sound. 'I thought that these concerts defined what we meant by high fidelity,' commented Villchur with pride. He took care to use the best equipment possible at the time, including an Ampex tape deck, two 60-watt Dynakit amplifiers, and number 18 zip cord." (Birchall 1993)"

    Villchur's Lab:
    [​IMG]
     
  4. LanceJ

    LanceJ Producer

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    Amazing what can happen with just 60 watts per channel & some skinny lamp cord........

    LJ
     
  5. RISUG

    RISUG Stunt Coordinator

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    Brett you forgot the most important factor - SVS rules!.[​IMG]
     
  6. RISUG

    RISUG Stunt Coordinator

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    By the way Brett, - Hi.

    Long time no talk. My pc was in the shop for a week or so.
    I posted in the "AR Speaker Help" thread on my friends pc;
    I read your progress report on the line arrays, needless to say we all wait with bated breath for the completion of the project.

    One other thing - what a sweet shot from your new cam, I darn near got a cavity from scoping that pic.
     
  7. ColinM

    ColinM Cinematographer

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    What's the difference?

    To be acoustic suspension, the cabinet can only be so big? A certain % of Vas?
     
  8. Brett DiMichele

    Brett DiMichele Producer

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    Reese,

    Hey Bro! If you get a chance IM me on AOL sometime...
    Yeah I can't wait for the LA's to be finished either.. And
    at least with this kickin new cam I can document my progress
    on the build... (I am ordering a WideAngle and Telephoto
    extender lens this week.... [​IMG]

    The cam is definatly sweet!

    And we now return you to the previously scheduled conversation
    about Acoustic Suspension Sealed Speaker Systems.
     
  9. Phil Iturralde

    Phil Iturralde Screenwriter

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  10. LanceJ

    LanceJ Producer

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    Infinite baffle eh? I think some old Bozaks used that design. Basically they used a really large sealed enclosure (compared to the woofer’s size) simply to absorb the woofer's back wave.

    Here's a good example. I actually saw these at an estate sale a couple years ago for eighty bucks a pair. I honestly thought they were large end tables at first, then I noticed the dark tan grilles with brown vertical stripes had faint shadowy circles the size of a 12" woofer. [​IMG] They were in excellent shape & I wanted to buy them, but they didn't take checks or credit cards, only cash, and I only had seven dollars on me at the time. Damn!! They used metal cone tweeters and midranges but people that have heard them say they sounded quite warm--neat!

    LJ
     
  11. ColinM

    ColinM Cinematographer

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    Found on the net:

    There are two types of sealed enclosure systems: the infinite baffle (IB) system and the air suspension (AS) system. The IB system normally uses a large enclosure where the compliance (or "springiness") of the air within the enclosure is greater than the compliance of the driver suspension. The AS system normally uses a small enclosure where the compliance of the air within the enclosure is less than the compliance of the driver's suspension by a factor of 3 or more.
     
  12. Mark Seaton

    Mark Seaton Supporting Actor

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    Real Name:
    Mark Seaton
    To quickly translate some of that to more simple terms, in what is typically referred to as an acoustic suspension system, it is the air in the box which dominates the "spring force" behind the speaker, whereas in what was originally called an "infinite baffle" design, it is the suspension(spyder & surround) which dominate the spring force behind the cone. More recently, DIYers tend to use the term infinite baffle for the most extreme case, where the box not only does not dominate this spring force, but is in fact almost negligible.

    For what it's worth, the reason for, and the benefit behind the acoustic suspension design was that certainly at that time, the air spring is/was more linear than the suspension of the driver, thereby resulting in less distortion.
     
  13. LanceJ

    LanceJ Producer

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    The "ultimate" infinite baffle design is a wall-mount speaker (where the back is completely open). Then you have to make sure the woofer's suspension can control the cone completely by itself. This is the same idea with most car speakers too.

    Just a FYI for people considering reconing their old acoustic-suspension speakers (like older Advents, KLHs, Infinitys, Boston Acoustics, etc): make SURE you use an identical surround to the one the woofer came with. As Jack mentioned "real" acoustic suspension woofers have a very loose suspension system and I've seen reconed AS woofers that have too-stiff generic surrounds on them. This will result in a lack of bass! So don't believe those ads that say their replacement surround will work with any woofer--sure, it will FIT, but it won't sound right. And the same goes for bass-reflex woofers. There's a lot of subtle things going on in a speaker so don't take anything for granted.

    LJ
     
  14. Jack Gilvey

    Jack Gilvey Producer

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