subwoofer moving on the floor...

[JaRoD]

I have a peerless xls 10" and a 12" passive radiator in a 36 liter box and it starts moving around on the floor when there's bass under about 25 hz. The passive radiator is tuned to about 22 hz, not exactly sure. I have it in a corner and there's a large peak (~5 db) at 25 and the responce falls faster under that.

I have put on some rubber feet but that only helps a bit. Sitting on the box also helps but that's not practical in the long or short run But even sitting on it doesn't help at some frequencies and at loud enough spl... Having a downfiring passive radiator might help but then again since the weight of the membrane is about 600g it will dip down something like 3-4 mm and I'm not sure if it will dip down even more in the long run. It does have an xmec of 24 mm so loosing 3 mm isn't too bad.

The moving on the floor isn't the most annoying part even if it's annoying, it's the noise that comes from it moving that's bad Using 2 pr's on opposing sides might work since the mechanical movement will take out eachother but that would require alot more weight on the rp's. Probably something like 2 times more since I can't make the box any bigger or I'll get a huge peak at resonance.

So, anyone have any ideas? Or any experience with a similar setup?

[AKN]

Hi Jarod!

If it is just right otherwise, you can just make the whole box heavier so you increase ratio between moving mass and box.

[JaRoD]

To add 20 kg of weight to the box I'd have to build a box with about 6 cm thick walls... Then again, it might get more stable if it has more contact with the floor. And it would be nice to be able to move the box too.

But 20 kg might not be enough considering that it was still moving when I was sitting on the box...

[FastEddy]

I would guess that the distance between the subwoofer drivers and your floor is quite small.

Consider: the way heavy machinery on a machine shop floor is sometimes moved, is by squirting air pressure under the base plate, thus suspending the machine on a thin cushion of higher pressure air. It might be that the distance between your drivers (and radiators) is such that increased air pressure at certain low freq. is enough to "suspend" or lift the whole box. Adding weigth (mass) to this box would probably have a very small effect.

I would suggest giving your box taller feet, increasing the gap btween base and floor. Laying down some heavy carpet would probably do it as well, but would also interfer with bass response.

This is all quite interesting. What is the gap distance between edges of your box and the (bare) floor? What at the outside box deminsions? ... Gap times area times pressure (differential) would equal upward thrust ... sound pressure being quite mechanical in nature.

[richie00boy]

How thick material have you built it from? Does the sub house the amp as well? Is the drive unit facing the floor?

[FastEddy]

richie00boy: " ... How much space around the drive unit to 'breathe'? ..."

So, richie00boy guessed the answer as well ...

[AKN]

JaRoD,

Is the floor steady when sub start to moving around?
Adding solid weight to box is not the same as sitting on the box.
Some pictures or printings would be nice..........

[AndrewT]

Hi,

How much space around the drive unit to 'breathe'

sub start to moving around

Mom, Mom come quick. It's alive!

[AKN]

[AndrewT]

Here sis, come and sit on this!
The rest will get censored.