Stuffing my sub

Discussion in 'Archived Threads 2001-2004' started by BrentPollard, Nov 22, 2002.

  1. BrentPollard

    BrentPollard Second Unit

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    I have been doing some net surfing concerning adding more insulation to ones subwoofer. I popped the 12" driver out of my PSB Subsonic II to check it out. The inner cavity is divided in two the left side which houses the amp is stuffed with pink fiberglass. The right side is empty with two ports. Would adding poly fiber fill to this area affect to port tuning? A rough estimate as to volume on the right side is 1.3 cubic feet. Thanks.
    [​IMG]
     
  2. Geoff L

    Geoff L Screenwriter

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    I am not familar with the GUTS of the PBS so proceed with caution...

    Is it "completly air tight" when you say the 2 sides are seperate?

    That is,, the driver/port side as opposed to the amp/insulation side is "totaly seperate and air tight"????

    That is a very small space for a 12" to operate ported (aprox-1.3ft^3)...I would suspect the tuning to be quit high if this is truely the case.

    If it ("IS seperated") from the amp side a 1/2 to as much as 3/4 pound might help of Polyfill=Kmart or pillow, or Acousta Stuff=Parts Express.
    I'd try around 3/4 of a pound fluffed up to start. (don't block the ports) Then work back from their.

    If their (NOT totaly seperate sides), then 1 to 1-1/2 lbs same stuff. Remove fiberglass "unless" it's their for a reason, and replace with fill on that side too.
    You would have to experiment to see if you like the desired results. You can have to much of a good thing.
    Fluff it up and definitly keep it out of the ports ability to breath.

    It can help 2 things, tighten up the sub and or lower the tuning slightly if "done properly". Don't expect SVS performance out of stuffing you PBS!

    If you ave a spl meter and a frequecy disc you can plot the performance, (from as is, to with fill).
    DON'T change the subs location, the volume you have the receiver set at, or the gain and crossover on the sub between measurments!!!
    This will give you an idea of what your stuffing is doing to the performance of the stock sub.

    YMMV
    Geoff

    Edit:
    Based on Tom N testing of adding fill to both Sealed and Ported enclosers.....
    =========================================
    A rule of thumb, is 1 pound Acousta Stuff to 1 cubic ft of internal cabinet volume. This will gain you a average of up to 25-30% cabinet volume that the driver sees. Your "fooling" the driver into performing as if it is in a larger cabinet.
    After 3-cubic ft starting internal volume, the % gain in what the driver sees (following the same rule of thumb) begins to drop. In small enclosers this can work quite well especialy in sealed enclosers.
    There is also to much of a good thing and over stuffing will produce just backwards results.
    A reduction in internal volume the driver sees.
     
  3. Neil Joseph

    Neil Joseph Lead Actor

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    Neil Joseph
    I see you have found my thread (stuffing a PSB Subsonic 6)...
    http://www.hometheaterforum.com/htfo...96#post1166362
    Another consideration is that the rattling you hear could be caused by the cabinet itself and it sounds similar to a sub bottoming out. You can use lead lining on the inside of the enclosure, in effect, to add weight to the box. I am looking into this as well. Also, I am building another box with a built in plate amp that should blow away the sub6.
     
  4. Jaime B

    Jaime B Stunt Coordinator

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    Brent:

    My experience with stuffing ported designs is that you will lose volume output. The sub will be less efficient and will probably not go as low. Do test it for yourself.

    Mr. Barton knows how to design speakers. If you are not getting good sound, try re-locating your sub. Also play with the volume and frequency cut-off controls. The lower the cut-off frequency, the better.

    -Jaime
     
  5. Geoff L

    Geoff L Screenwriter

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    Jamie,

    Might you be clearer with your experience is stuffing ported enclosers!???

    When talking larger volume ported encloser (say 3-4ft and up) I would tend to agree to some extent. Line-ing the walls with batting is the best approach and having the right internal volume and porting correct to start.

    But dealing with small internal volume ported enclosers, (much higher tuning usually also) fill can a dose have an affect, and positive if done properly.

    You may loose a little punch/output in the 30-40 hz range (minior at best) and tuning will drop slightly. Also a tightening of the sub sound can be sometimes noticed due to it.

    Start with a small amount, 1/2 pound. ~{I say this as I have no idea how much, what kind, and where exactly Neil stuffed his PBS}~.

    ~{You should PM him and ask about this, you don't need a dead sub}~!

    Tom N testing, (can't find link right now), shows this with measured data in small ported & sealed enclosers.
    Tuning droped a few HZ's on the smaller ported subs, getting a little more extension. Nothing changed cabinet wise, except for adding the fill!

    I am not saying that his PBS will absolutly perform better,! but experimenting cetainly would not hurt and is dirt cheap to try.
    Definitly measure the sub before and after filling, this would prove what is or is not happening....! If you can't measure, play sines (low to med volume coil heats fast) and when the cone stops moving, at what ever frequency, this is your tuning point or very damn close. Once you go by it continueing down in HZ's the cone will begin to go crazy as it offers no protection for the driver.

    I built two 1.25ft^3 ported cabinets a year + ago (volume is less driver and amp) with 12" divers, and with aprox 1-pound of fill in the encloser it droped the tuning point 5hz. That 5 more than I did have and it sounded better and measured flatter....

    Again, YMMV
    Geoff
     

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