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LEGACY LW89X 8 inch Subwoofer

Discussion in 'Off Topic [BG]' started by suasa, Nov 1, 2004.

  1. okay i need speaker box dimensions for this speaker or at least a volume so here are the specs i googled it but it didnt help well thanks

    Blue Injection-Molded P.P. Cone
    Specially Treated Black Rubber Edge Suspension
    Bumped and Vented Motor Structure
    High Temperature 1.5"Kapton Voice Coil
    Heavy Magnet Structure
    Sold Individually
    4 Ohm Impedance
    Size: 8"
    Power Peak: 400 Watts
    Power RMS: 200 Watts
    SPL: 89dB @ 1W/1M
    Fs(Hz): 38
    QMS: 2.05
    QES: 0.63
    VAS(cu ft): 1.794 what exactly is Vas??
    Overall Diameter: 7.76"
    Mounting Depth: 3.54”
    Magnet Weight: 60 oz
  2. There are sine sights that will recomend the best tuning for speakers, ect.

    I think therealexcursion.com, or something like that?

    It's devoted to sub woofer stuff.
  3. Rhythmalism


    Sep 25, 2004
    WinISD is a great free program for finding it too. You'll need a Qts value though, or derive it from QMS and QES (I forget how).

    Or just go with a sealed box, maybe .75-1.25 cubic feet. Lower quality woofers behave better in larger sealed boxes like that or Free Air setups. If it was a JBL or JLaudio, I would have said .35 cubic feet, maybe a ported design. They behave better in smaller boxes.
  4. thanks for the replys but that really didnt help too much well anyone else know anything???
  5. Petebass


    Dec 22, 2002
    QLD Australia
    Your get the QTS by multipying the QES by the QMS, then dividing that number by the sum if the QES and QMS. The QTS is 0.482.

    Vas = Equivalent air compliance. The volume of air that has the same compliance ("springiness") as the driver's suspension.

    These 2 specs are crutial in determining the correct cab size.

    For best results, but this speaker in a cab that 91 litres (3.228cu.ft) and tune it to 32Hz. This will get you a -3dB point of 28Hz which is seriously low for an 8".

    If that cab is too big, go for sealed enclosure. It'll start rolling off earlier but the slope is far gentler, so it will still have plenty of bottom end. Make it 44 litres (1.554 cu.ft). It'll be -3dB at 55Hz which is more what you'd expect from an 8" speaker.

    I've been known to fool my sealed cabs by filling them with acoustic stuffing. By doing this, the speaker "see's" a larger cab. You can effectively make your cab up to 30% larger this way. So you could actually make your sealed cab about 34 litres (1.2 cu.ft), then fill it with acoustic foam to bring it up to the 44 litres specified earlier.

    Note if this is for a car, none of these calculations account for cabin gain. I personally believe cabin gain is only an issue when the cas isn't moving. Usually the car's motion creates it's own sub-sonics which cancel out any cabin gain, but that's just my opinion.
  6. sick mate sick, subwoofa.....fully sik maatteee..

    you might be the only one who gets this pete :D
  7. thanks a ton pete bass now where can i get some of this acoustic foam?? and how do i go about using it.
  8. Petebass


    Dec 22, 2002
    QLD Australia
    This is the stuff I normally use:-


    Any place that sells speakers or speaker hardware should stock something like this.

    All you have to do is stuff it in to the cabinet before you mount the speaker. Make sure you do so in such a way that the stuffing doesn't interfere with the speaker's movement.
  9. so how does that stuff work its sound dampening material how does it make your speaker think the box is bigger?? not that i am questioning your methods i just want to know exactly how it works.
  10. Petebass


    Dec 22, 2002
    QLD Australia
    I'm not sure of the exact science behind it. It's an accepted speaker designing principle that appears in all the text books. I know it works because I've used it before.

    I had a sub+cab given to me for free. A friend wanted to offload it and he gifted it to me because I helped him design the cab for it. At the time I was driving a station wagon and was worried that having the sub in the boot (trunk) in such a visible position would be an invitation to thieves. So I decided to put it behind the driver's seat where a passenger's legs would normally go, thus making it harder for a passer-by to spot. Good idea in theory, but it didn't fit. The cab was too large.

    So I knocked up a smaller cab that would fit in the desired position, then stuffed it with acoustic foam as per the text books. Worked a treat......
  11. so i figure a rectangle enclusre measuring 20x9x15 with .5 inch fiber board or possibly plywood giving me 1.23cubic feet filled with your acousitc foam should do the trick yes?
  12. Petebass


    Dec 22, 2002
    QLD Australia
    That's a bit larger that 1.23 ( I got 1.39). Sealed cabs aren't quite as fussy as ported ones though. A slightly oversize cab shouldn't matter. Actually the more I think of it, it's probably better because it's impossible to completely fill a cab with stuffing due to the speaker mass. So yep, you've got it right.

    Make sure the cab is airtight.

    Let us know how it goes OK.
  13. thanks a million pete!!! just yesterday picked up a fusion fe-402 and a pioneer deck should be pretty decent when its all hooked up but that probably wont be till the close to the end of november but i will let u know