I'm going with Newtons law of something or other, and saying its the motor moving and tugging the enclosure along with it (since the enclosure does not have enough friction against the surface its on).
Maybe like when you have the vaccum hose and plug the one end up with your hand and the vacuum thrusts violently to one side.
EDIT: just to be on the same page, your talking about like the little Sunfire True Subwoofer and how it scoots around sometimes like an off balance washing machine??
Maybe like when you have the vaccum hose and plug the one end up with your hand and the vacuum thrusts violently to one side.
EDIT: just to be on the same page, your talking about like the little Sunfire True Subwoofer and how it scoots around sometimes like an off balance washing machine??
I'd say it would have to do with the ratio of the moving mass of the driver at high excursion to the weight of the box. I have seen a small box with the XLS jump off its feet where it had a downfiring passive radiator (not a good idea). Generally if the sub is heavy and solid, it should not be a problem.
True
One study I read showed the side panels of a poorly braced, large sub expelling almost as much energy as the woofer. This was narrow band, at or near the resonance of the panel, but very loud.
As far as the whole box moving, that is "the equal but opposite reaction" part of physics. Big motor, big excursion, big reaction.
Tim
One study I read showed the side panels of a poorly braced, large sub expelling almost as much energy as the woofer. This was narrow band, at or near the resonance of the panel, but very loud.
As far as the whole box moving, that is "the equal but opposite reaction" part of physics. Big motor, big excursion, big reaction.
Tim
The difference between those two cases seems to be that in the latter adding bracing won't help. Adding mass will help because the box will move less in recation to the force on the driver. But internal damping won't help unless it absorbs energy going from the driver's frame to the box.
Does this mean that there is no alternative to making the box really massive?
Does this mean that there is no alternative to making the box really massive?
Not at all...
You can use a wimpy subwoofer.
Or you can make thick enough sides not to bulge in/out with the woofer
If it slides around, try rubber or pointed metal feet, depending on the flooring under the box.
If it still moves with appropriate feet, you may consider bolting to the floor, but you may also consider turning the volume down!
You can use a wimpy subwoofer.
Or you can make thick enough sides not to bulge in/out with the woofer
If it slides around, try rubber or pointed metal feet, depending on the flooring under the box.
If it still moves with appropriate feet, you may consider bolting to the floor, but you may also consider turning the volume down!
Only solutions I can think of if you have the whole enclosure moving:
- anchor to floor or wall (as simple as using rubber castor cups in some cases if a wooden floor - that is what I did)
- add weight (put some heavy ornament on it that won't rattle) and stick with blu tak or similar
- if building - use a downfiring subwoofer design if driver permits or build a heavier enclosure
- check driver mounting to enclosure is secure - use tnuts to make it tight (standard woodscrews + MDF + subwoofer = useless)
Most reasonably built enclosures - esp. if 85 litres or greater for a 12" driver should be heavy enough to handle excursion forces. After all they should balance out. If not - I'd suggest if not one of the above solutions - the driver is faulty or the amp is emphasizing somehow one signal (+ or -) over the other???
David.
- anchor to floor or wall (as simple as using rubber castor cups in some cases if a wooden floor - that is what I did)
- add weight (put some heavy ornament on it that won't rattle) and stick with blu tak or similar
- if building - use a downfiring subwoofer design if driver permits or build a heavier enclosure
- check driver mounting to enclosure is secure - use tnuts to make it tight (standard woodscrews + MDF + subwoofer = useless)
Most reasonably built enclosures - esp. if 85 litres or greater for a 12" driver should be heavy enough to handle excursion forces. After all they should balance out. If not - I'd suggest if not one of the above solutions - the driver is faulty or the amp is emphasizing somehow one signal (+ or -) over the other???
David.
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