Subwoofer Vibration...suggestions?

[backtothemusic]

I recently added a sub to my setup and it's placed under my desk. I would like to keep it there if possible. The floor is carpeted. I have a few bass traps which have helped define the bass a lot better but I'm getting awful vibrations from the furniture and nearest wall. Anyone have any subwoofer isolation tips to share?

[Ethan Winer]

Originally Posted by backtothemusic

Anyone have any subwoofer isolation tips to share?

I suggest you first determine for sure if isolation will help. It may be the problem is sound traveling through the air. Invite a friend over and have him lift the sub 1/4 inch while you listen. If that helps, then isolation will be useful. You can use 2-inch thick 705 rigid fiberglass, and Auralex sells the SubDude that's meant just for this.

--Ethan

[backtothemusic]

Thanks Ethan. I did try the sub with the feet on and off and it didn't seem to make a difference but I will take a look at the subdude. Not sure though if it will help.

[Factory101]

My sub wasn't rattling but I placed it on largish balls of Blu Tac onto two concrete blocks (onto carpeted concrete 1st floor) - seems to work fine for me (I make music for pleasure).

I wouldn't mind trying out an isolating pad before purchase to check the difference...I couldn't find the SubDude in the UK.

[jayfrigo]

True vibration isolation is rather complex, and is far more than just putting something soft beneath your noise source (subwoofer in this case). However, it is something a DIYer can still tackle if you are willing to put in a little effort.

Transmissibility is the ratio of the transmitted force to the driving force, where a 1 would represent all force transmitted into the structure, and 0 would be no sound transmitted (0.02 is about the real world limit). A resilient isolator's job is to reduce the transmitted force, but the wrong choice can actually resonate with the force, thereby increasing the transmitted force above 1. So a worst case scenario is not that the isolator will simply be ineffective, but that it will actually amplify the transmission.

The "driving" or "forcing" frequency (Ff) is the lowest frequency generated by the source. A piece of equipment with a fan rotating at 1650 RPM would have a Ff of 1650÷60 s/min=27.5 Hz. A subwoofer with a low frequency extension to 25 Hz is simply a Ff of 25 Hz.

The natural frequency is that which the resilient element tends to restore itself after displacement, or the spring-mass system will bounce if displaced from its resting place. Imagine the Jack-in-the-box bobbing up and down after it is opened. The rate of the bob is the natural frequency of the spring, or Fn.

The basic goal is to choose an isolator that, under load (with the equipment in place) will have a Fn of less than 1/10 the Ff. Again, it can get quite complex, but this starting point satisfies most simple applications.

Unfortunately, we are not done yet. we need to consider static deflection next. Static deflection is the distance in inches by which the resilient element (the isolator, whether various neoprene pads or pucks, spring mounts, or some other more esoteric materials) will compress under the load of the equipment. The proper static deflection can be calulated with the following simple equation:

S.D.=9.8/Fn^2

That is 9.8 divided by the natural frequency squared. You also want your desired static deflection to be in the middle of the range of your isolator. If you need 1/4" S.D., you don't want it to be 1/4" of a 4" spring. If you need 5/8" S.D, it'd best not to be a 3/4" pad. If it is compressed nearly all the way, or barely at all, it likely won't have the springiness and travel you are looking for. You also want an isolator that isn't damped very much. Things that don't spring back quickly, like carpet and foam, don't make very good low frequency isolators.

Steel springs, neoprene mounts, and neoprene pads are common choices. Springs offer S.D. of about 1/4" to 4" for Fn of 6.3 to 1.6 Hz. Mounts run from 1/10" to 1/2" S.D. for Fn of 10 to 4.4 Hz. Pads run 2/100" to 1/4" for Fn of 22 to 6.3 Hz.

Sometimes (often) you will see springs in line with neoprene isolators. These help to further isolate the equipment from vibrations travelling down the helix of the spring. You don't want too rigid a connection as it will prevent the bounce and offer a structure-bourne vibration path to the building. Low frequency energy, especially from speakers, will also radiate directly into a room, exciting surfaces and other objects in the room, so it is not appropriate on it's own for transmission loss into adjacent spaces, AKA soundproofing.

Here are some links to some sources of isolators or isolating materials:

http://www.kineticsnoise.com/
http://www.sorbothane.com/

Good luck!

[Anderson]

A few more for EU people:

REINICKE BRINGT RUHE.

(Sylomer is also distributed by lots of local providers.)

Solutions Elastomères - Acoustique - Anti- Vibratoire - Etancheité

One that was pointed to me recently:

CDM - home

[auxpot]

Originally Posted by Factory101

My sub wasn't rattling but I placed it on largish balls of Blu Tac onto two concrete blocks (onto carpeted concrete 1st floor) - seems to work fine for me (I make music for pleasure).

I wouldn't mind trying out an isolating pad before purchase to check the difference...I couldn't find the SubDude in the UK.

the subdude is literally the same as auralex´s gramma (just the size is different, but performance is the same)

i just got one recently...installed it today and i couldn´t believe it...but really it works..i had a mate with me in my studio, he said let´s try the subdude..and the we realized a big difference....the wodden floor underneath stopped vibrating, not totally but significant..and the sound got much much mire tight.....
i still don´t believe that such a basic mdf + foam thing could make that huge difference....i thought it´s voodoo, but it´s not....
don´t know of a simple piece of foam would have the same result, but really i don´t care, it works and i have a big smile on my face....

i am not related to any company nor do i have any interest in making people buying any stuff...except my records though