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Standing waves in my subwoofer box

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  • billfitzmaurice
    commented on 's reply
    Resonance only matters if you can hear it. If you can hear it, or even if you can't, you can measure it, not only via FRD but also impedance.

  • bassman_soundking
    replied
    Is B&W using dual layer walls?

    Leave a comment:


  • Thephantompsychic
    replied
    Is it unreasonable to expect inertness similar to what I hear about in cabs like what B&W makes? They have a pretty insane process.

    I'm obviously not putting in near the time or effort they are, but is a cab that dead really worth it? For a "spare no expenses" speaker yes, but practically speaking? Should every DiY person spend every waking minute trying to get a "dead" cab?

    Leave a comment:


  • billfitzmaurice
    commented on 's reply
    Here again, dowels. Have four of them connect to the baffle at the spots where driver mounting screws are, the other ends to the cab back. The driver mounting screws go through the baffle into the dowels.

  • fpitas
    replied
    Originally posted by bassman_soundking View Post
    I always felt the most important panel to brace was with drivers on it,
    I have either under braced or over braced most enclosures 😂
    Well to the point, the panel with the drivers has huge holes cut out of it. So yes, an effective plan for bracing it is an excellent idea.

    Leave a comment:


  • bassman_soundking
    replied
    I always felt the most important panel to brace was with drivers on it,
    I have either under braced or over braced most enclosures 😂

    Leave a comment:


  • billfitzmaurice
    replied
    Originally posted by bassman_soundking View Post
    If you look at Parts Express Knock-down sub enclosures. they have an elaborate bracing scheme.
    .
    They look impressive, but rail bracing is far less effective than panel to panel bracing. The same applies to window bracing, where the sections that connect the opposing faces do all the work, while the rails just add excess weight. The last place that requires bracing are the cabinet corners, being the strongest part of the box. Anything within six inches of the corners is wasted material and unnecessary weight.

    Leave a comment:


  • fpitas
    commented on 's reply
    Yes, in general you have a point, although some people roll subs as high as 120Hz.

  • mobius
    commented on 's reply
    I think maybe what you mean to say here is that the harmonics of any subwoofer note can activate the natural resonant frequencies of the box walls when they are the same, which is true if there is enough energy to the harmonics. But if you are rolling the sub frequencies off 2nd order LR at 80Hz, well then there really isn't going to be that much SPL/energy to any harmonic frequencies above about 160Hz maybe even lower. The fundamental at 160Hz with the 80Hz xo is going to be down about 12dB or so to start with and the 160Hz 1st harmonic of 80Hz is going to be much lower in SPL than that to start off with. It'll be down even more if the receiver happens to use a 4th order LP filter. Or you set your sub xo lower than 80Hz.

    So just make sure that the sub wall natural resonances are above about 200-300Hz and there shouldn't be a problem.

  • fpitas
    commented on 's reply
    That is true, it doesn't need to be fancy. I've used window braces as well as scrap pieces of 3/4" plywood, 1" wide. The window braces do look cool.

  • devnull
    replied
    Decent bracing doesn't have to be really fancy. I use simple stick built plywood window frame bracing. A double layer of plywood with offset joints glued and brad nailed together. Doesn't take that long to put together, a lot less waste than one piece braces.

    If you want a quick and dirty test for panel vibrations throw a couple of bags of sand or cement on top of the subwoofer. That adds mass to the top horizontal panel and puts the vertical panels under compression making it harder for the panels to vibrate. The sound shouldn't change.

    Just a couple of thoughts while I have my morning coffee.....

    Leave a comment:


  • fpitas
    commented on 's reply
    Yes, it's obvious why the box walls shouldn't weeze in and out with the sub excursion. The sub panels can and will resonate at harmonics of the sub frequencies.

  • mobius
    replied
    Cubes are generally fine for subs because of the reason billfitzmaurice stated above - standing waves are of no consequence in a small sub box.

    Because in order to generate a standing wave, you need that frequency to actually be produced in the box. Even without bracing, the standing waves inherent to small boxes are going to be above the frequencies a sub is producing so it doesn't matter if the standing waves between all opposite surfaces in a cube are all the same frequency, they won't be activated.

    More important is to brace the sub so the panels don't deflect due to the changes in internal air pressure from the sub's cone excursion and to a slightly lesser extent, to also keep the natural resonant frequencies of the subs panels above the frequencies the sub is producing.

    Leave a comment:


  • bassman_soundking
    replied
    Originally posted by Serenitynow View Post

    I have the capability to make cabinents, but all of the internal electronic components are way over my head unfortunately .

    I'm really looking for a good stereo pair to build, but finding a proven design with all the information that fits my needs is daunting to say the least.
    Im planning to build several sets of speakers.
    Like you my issue is one of crossover design.
    Learning cant be done overnight, and the price of the parts isnt low.
    Starting my projects off with prefab XO networks is what Ill do on most.
    Later Ill go back and work on the crossovers with help from the forum hopefully.

    Leave a comment:


  • Serenitynow
    replied
    Originally posted by bassman_soundking View Post

    If only I had a CNC.
    I would be bombarding this forum with builds.🤔
    I have the capability to make cabinents, but all of the internal electronic components are way over my head unfortunately .

    I'm really looking for a good stereo pair to build, but finding a proven design with all the information that fits my needs is daunting to say the least.

    Leave a comment:

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