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Arx A3's mass-loading chamber

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  • Arx A3's mass-loading chamber

    Hello All,

    Has anyone tried filling in the A3 chamber?

    I picked up a 20lb bag white silica assuming i Could fill up my pair [ looking to get tighter bass ] only to realize thats not sufficient to fill one A3.
    Questions I have now is :

    1. Whats the right amount to fill these chambers with?
    2. Should i fill them to brim or not?
    3. Has anyone tried this out, please share with me your experiences...
    4. Is white silica right material to fill or ?


  • #2

    I filled mine with white purified playground sand. I put one 20lb bag (from Lowe's) into the base of each. I suspect I could have divided a third bag between the two with little excess left over, but I left it as-is.

    I'm ashamed to say that I did that only days before the A5 prototypes arrived at my door (Jon surprised me in the best way). So, I have essentially zero critical listening with the A3's being mass-loaded. I have since emptied them of the sand due me having to move them more often than expected.

    I am confident that 20lbs of any dense material (sand, silica, lead shot, etc.) will have a noticeable effect on tightening-up the bass and in damping overall cabinet resonance at higher frequencies as well.


    • #3
      Assuming you can wrestle a 65# speaker around, filling them is well worth it. The difference in image focus and bass slam is impressive.

      Spend time getting the stock (empty) pair positioned as well as you can, then tape off the outline on the floor, flip and fill them, and taking care not to stress the bolts holding the base on, carefully put them back where they belong and settle the pointed feet home.

      You should notice a remarkable improvement in "blackness", where images and sources emerge with more focus from a sense of greater space. Some of this will happen because the bass will have become harder and deeper at the same time - removing blur really improves the sense of timbre.

      Silica sand was recommended because it's clean, dry, dustless, available, and cheap. Lead shot works but weighs an awful lot - again watch out for the bolts holding the base on if you twist the heavy filled speaker around by the base. Any clean, dry, dustless heavy granular material works.