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  • Boom box modification. Ramifications of removing internal divider.

  • 123toid

    Administrator
    December 29, 2021 at 6:43 am

    This is a weird one.  I can’t seem to tell is the W8 has a passive radiator on each side or a port on each side.  If it does, you do not want to remove the partition.  That can have negative effects of porting. And typically two separate cavities are better. Now it is unclear on what is causing the issue, but it might be internal resonance.  Half of 125 is 61.25, which isn’t that far from 57.5.  Typically resonance will occur at doubling the frequency.  What I would first try to do it line the internal cavities to see if it dampens it.  There’s only so much you can do about this, but you can try to lessen it’s impact. 


    Boom box modification. Ramifications of removing internal divider.

  • elliottdesigns

    Member
    January 5, 2022 at 11:56 pm

    Welcome to the forum!

    I agree with Nick, you don’t really want to be removing that divider, as you said there would be phase issues when the left and right drivers are playing different things (unless you wanted to make it mono).

    Either way there would be little to gain in removing the internal divide, removing it would give a little more internal volume, but not enough to make any noticeable difference, and while removing the divider may lower the frequency at which that resonance happens, it’ll likely also become a larger resonance since you are reducing rigidity. (Ported/passive radiator boxes generally end up with higher pressures than even sealed, unintuitive isn’t it?!), Meaning that rigidity really is key.

    I’m not sure damping would help too much at such a low frequency (for the 57.5hz peak), but if you were to try damping, try a relatively high density mineral wool as this typically works best for low frequency, but bare in mind, the more space taken up, the less efficient the bass becomes, too much space taken up and it might become peaky and one-note like.

    Another option that might be of more use and should take up less space than the thick wad of mineral wool is to add useful bracing, for instance it might be that the internal divider is flexing and could do with being replaced with a thicker divider, or gluing another sheet to it. However this may not be the cause of the resonance so other bracing might be useful, how rigid and thick are the main walls? Because that might actually be your main problem, how much does the box vibrate at these peaky frequencies? Try a tone generator and have a feel.

    Another but less likely option because of the two peaks almost being fundamentals, is that the peaks come from the bass driver’s response.

    Finally, it might still be worth lining the walls, since it may reduce the higher frequency peak at 125hz at least somewhat.