Sub Calculations

Discussion in 'Subwoofer Box and Custom Fabrication' started by schizted, Feb 18, 2012.

  1. schizted

    schizted New Member

    Pyramid (PW677X) 6.5"

    FS -55
    QTS -0.72
    QES -0.84
    VAS -0.448
    QMS -5.01
    SPL -86

    EBP -65.48

    Can Some one throw this in WinISD and tell me what the VB and FB for a portted box.

    I get that i need to tune it lower than my Fs, but does this mean with a fs of 55hz i cant tune the box super low like 32hz.
    When i run it in WinISD i get a Box volume of 2 cubic feet and a port of 3 inches at 2.6 inches long tuned to 44hz
    it gives me a f3 around 35 and 0dB at 38hz


    I dont understand winisd, am i trying to make a smoothe curved line or ...?
     
    Last edited: Feb 18, 2012
  2. Ranger SVO

    Ranger SVO Full Member

    Two cu ft for a 6.5 inch speaker is a bit too big and trying to tune a box with a 6.5 inch in it to 30 Hz just isnt going to work, lets be real.

    Lets try something much more reasonable. Like maybe 1 cu ft. Also set your tuning around 50 Hz. Just looking at those specs, tells me that the graph your looking at is all over the place. Setting the size to 1 cu ft and 50 Hz should smooth it out. You should see a gain in the low frequencies, but that OK and the graph should be smooth

    That QTS of 0.72 is pretty high, looks like a speaker designed for free air. Thats why WinISD is going to have problems making an accurate box size recommendation.

    Anyway, 1 cu ft, tune to 50 should work great. A 2.5-inch diameter port around 4.5-inches long should work
     
  3. schizted

    schizted New Member

    Yep, that makes things smooth out more. I get a F3 at 40hz and 0dB at 44hz and a peak of 66hz at 4dB.

    Just to get my bearings the F3 is the drop off, the 0db is the FB of the box right?

    and if i wanted to look for another woofer that could be tuned lower, would i look for a lower qts or a lower fs.
     
  4. Ranger SVO

    Ranger SVO Full Member

    For a woofer, that would actually be a very good performing speaker. And yes your right, f3 is the beginning of roll off, so we don't pay much attension to anything lower. The fb of the box is the peak frequency. So I'm going to assume its 66, and for a 6.5 inch speaker thats really good. And for a woofer thats really good

    For a subwoofer we want a little more, so an 8-inch woofer would be the minimum I would look for. But most people would need a 10-inch

    I just recently built a downfire, ported 8-inch woofer tuned to 45Hz for a friend. It peaks at 54Hz. That thing rocks. His favorite test track is "Fergalicious" and it has no problem handling the lower frequencies in that song.
     
  5. schizted

    schizted New Member

    I have 3 speakers im looking at the

    Pyramid PW677X 6.5"
    Legacy LWF8X 8"
    Dayton Audio SD215A-88 8"

    Im throwing it into a home theater to upgrade the old one. Its a 400watt system. So the sub would probly get around 150 to 180 watts of power from the amp.

    Am i trying to find the lowest F3 with the smoothest curve to 0db to get the best SQ and bass?
    Im confused at what i need to get the peak to be at on the dB
     
    Last edited: Feb 19, 2012
  6. Ranger SVO

    Ranger SVO Full Member

    Because of the way we hear, we want a slight gain (above 0dB ) Typically around 3dB is prefered. If you want low make the box larger. Just keep the graph smooth. Tune higher or lower depending on whether you want more or less gain (louder-more gain, less loud- less gain).