# Vibration isolation....?



## Vader (Jul 8, 2006)

Hi all,

I am running dual SVS 20-39 PC+ cylinders, which are co-located a few feet from a gas fireplace. I have chased down and eliminated every rattle I can get to, leaving only one left. At certain frequencies and volumes, I hear a rattle coming from the fireplace, and I have determined that it is actually the aluminum flu (which I cannot get to). I believe it is the mechanical transmission from the sub, through the floor, to the wall, to the flu that is the cause, not the air movement (I "sealed" the front plate with weather stripping and it still rattled). Since moving the subs is not an option (due to space restraints), I am looking at putting a large marble slab (still working on where to actually get one cheap) under the subs to dampen the vibration (big mass = small acceleration). Am I on the right track?


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## basementjack (Sep 18, 2006)

I have a hunch that physical isolation is not going to solve this.

Can you put the sub on a couch temporarily to validate the vibration goes away before you embark on the marble slab?

if it is vibration related - check for a heating and cooling distributor in your area - my local one had some waffle like rubber sheets for isolating things like furnaces, etc... it wasn't cheap, but it might be good to get few small squares and put them under the marble if you go that route.


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## Vader (Jul 8, 2006)

Jack,

If I move the sub away from the "pseudo-corner" next to the fireplace, the rattle from the flu(?) stops. Because of the room configuration, I really have the subs placed in the ideal (and only) spot available. I was extremely lucky that it was not a null or anything, and actually works with the room gain well. My only choice, for the time being, is to de-couple the subs from the floor. Another route I am considering is using spiked feet to minimize contact with the floor....


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## Fincave (Apr 20, 2006)

Vader said:


> Another route I am considering is using spiked feet to minimize contact with the floor....


 Soundcare is a manufacturer of spikes that seem to have quite a good reputation, prices are not too bad either here in Europe.


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## drf (Oct 22, 2006)

I heard a rumour that those spikes actually assist vibration into what ever surface they are on. apparently it works similar to a gramaphone horn only in reverse. I'll try and see if there is any truth or whether this is just some snake oil like hype. 

Is the vibration being caused by the sound hitting the flu or is the vibration traveling through physical mediums (e.g floor->hearth->heater) before it excites the flu?


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## Vader (Jul 8, 2006)

I think the vibration is travelling through the physical mediums, since the vibration continued after I sealed the front panel of the fireplace (with weather stripping) so that the air movement would not ever reach the flu...


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## Josuah (Apr 26, 2006)

Spikes will couple your subs to the floor as well. You need an isolation riser, like the SubDude. Or you can build your own. I built mine by placing a wood disc on top of two feet of insulation styrofoam, with some semi-rigid fiberglass in the middle as a "trap". Don't know if that semi-rigid fiberglass did anything, but this did succeed in insolating the sub from the house.

pics


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## drf (Oct 22, 2006)

I would definately look into something that will decouple the subs physically from their surroundings. mayby try some matress foam or rubber and see if this makes a difference and if so how much of a difference.

heres an article on spikes but I don't know about its validity.

http://www.st-and.demon.co.uk/AudioMisc/cones/speak.html


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## Kipp Jones (Oct 19, 2006)

Does it make a difference if the flue is open or closed???


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## Vader (Jul 8, 2006)

> Does it make a difference if the flue is open or closed???


It does not seem to make a difference one way or the other. I'm gonna see what a riser will do for me, first using a setup that I used to use to isolate my tape deck from vibration: two boards seperated by two layers of shag carpet (the bottom layer has the carpet up and the top layer has it facing down). If that doesn't help, I'm gonna try what Josuah suggested (with the insolation styrofoam)....


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## yphs_mst (Nov 11, 2006)

One of my thought is raising the subwoofer from the floor with a box filled with sand, and covered with thick rubber (like tire rubber). Sand is a good vibration isolation, but putting foams on the top of sand doesn't make a good surface for the subwoofer to stand on, so we can make the box a lil rigid covered with somekind of rubber (not carpet/foam, they don't do anything to vibrations). Any thought on this ?

As far as the spikes, I don't think they work well, from the law it self that pressure equals force over area (P=F/A), when the area is smaller (spikes), the force is greater. That's how I understand this spike 'phenomena'

Hadi


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## l´Blundt (Jul 6, 2006)

Try putting a couple of pieces of cork under the subs. It should do the trick and is pretty cheap to.

l´Blundt


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## Josuah (Apr 26, 2006)

If you build a box and fill it with sand, the box will still act as a transmission device to the floor. I put sand in my riser so it will absorb acoustic energy that gets into it, but the frame itself still vibrates when sound hits it. You'd still need to decouple the box from the floor.

Spikes can help for a couple of reasons. The first is that they raise the tweeter so your ear is more on-axis, or even more off-axis if that's how the tweeter gives you the best response. The second, to my understanding, is they prevent horizontal movement because of the additional friction. That's why you kind of need them on carpet, otherwise the box has more freedom to move back and forth, although you might not notice physical movement.


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## Guest (Nov 21, 2006)

Tighten all screws and secure all fixings, and once done, play a sine wave frequency in the low range from 20Hz up too 200Hz at varies sound pressure levels and careful listen for any buzzing sounds rattling sounds anything that is being excited by the air being disturbing objects within or outside the rooms confines!

The smallest solution is to use Blu Tack this is a user friendly substance with lots of uses.


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## yphs_mst (Nov 11, 2006)

> If you build a box and fill it with sand, the box will still act as a transmission device to the floor. I put sand in my riser so it will absorb acoustic energy that gets into it, but the frame itself still vibrates when sound hits it. You'd still need to decouple the box from the floor.


That's why we can wrap it with rubber/synthetic rubber .. spikes under all of that, will be great I think ...

Hadi


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## russ.will (May 10, 2006)

Do a Google search on "Sorbothane isolation feet". Sorbothane has massive energy absorbtion characteristics as it's about 90% water. It has a resonant frequency of about 8Hz so at audio frequencies it's effectively rigid, unlike rubber.

I have a rather lively laminate floor and have been using Sorbothane under my sub and speakers for years, ever since I realised spikes don't and never have, isolated anything.

Spikes are an extremely efficient way of transfering energy. Nice if you have a concrete floor as a massive energy sink, but rubbish under almost any other circumstance.

Russell


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## Vader (Jul 8, 2006)

Well, the big experiment begins… I put together what I believe will isolate the subs based largely on recommendations from you guys, and Mr. Newton. I started with a plank of particleboard, on top of which I placed several shag carpet pieces in two layers (the top layer is facing downward so that the carpet is facing each other). On top of that is a 150 lb slab of granite, followed by more carpet padding, and finally another plank of particle board. The real test will be the beginning of Serenity, which always excited several rattles (including the master pole – or whatever it is called - that runs up the middle of the house). Thanks for all of the responses!


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## yphs_mst (Nov 11, 2006)

russ.will,



> Sorbothane has massive energy absorbtion characteristics as it's about 90% water. It has a resonant frequency of about 8Hz so at audio frequencies it's effectively rigid, unlike rubber.


What do you think of neoprene ? Do you think Sorbothane material is more effective ? I'm just curious.



> Spikes are an extremely efficient way of transfering energy. Nice if you have a concrete floor as a massive energy sink, but rubbish under almost any other circumstance.


I agree ... :T 

Hadi


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## Vader (Jul 8, 2006)

Well, first impressions after building the platform: It did not completely solve my problem, but it diminished it somewhat (leading me to conclude either that mechanical transmission through the floor to the walls is not the only culprit, or my de-coupling was not effective). The overall sound was warmer, less "rumbly", better defined. I re-ran my room EQ using the Room EQ Wizard, and the results were somewhat unexpected (though they should have been). I lost a significant amount of room gain, that apparently was coming from the coupling with the floor. The largest discrepancy (relative to my earlier room EQ) was in the low end, below about 14 Hz. Previously, the response had remained quite strong in that area, but now, it falls off as I would expect. A couple of other places had similar losses, though nowhere near as significant. As for the low end, I am thinking that it was the rumbling of the walls that remained strong, and not output from the subs themselves. So, my de-coupling seems to have done it's job after all. I still need a BFD, though.....


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## Vader (Jul 8, 2006)

OK, after testing with some of the most brutal bass monsters around, I have come to the following: First, the de-coupling is nearly complete. During several sequences that normally would have peeled the paint from the upstairs walls, my wife confirmed that the foundation is no longer "pitching a hissy-fit". The pictures actually stay straight, and _on the wall_. During these sequences, I also felt both the base of my makeshift platform and one of the subs. While the sub was shaking significantly, the energy was not transmitted to the base (at least not that I could tell). This did nothing to solve my fireplace problem, however. Therefore it must be something other than mechanical transmission through the floor. After some experimentation, I succeeded in dampening it by wedging a roll of shag carpet between the aluminum(?) back and the fireplace itself (yes, I know that is a fire hazzard, but the fireplace is completely turned off - I never use it). Now my only problems are the creaks in the walls themselves - which there is no way short of tearing them down to quell those.... Next house will have an unfinished basement so I can take care of that as well. Thank you all!


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## Guest (Nov 27, 2006)

Vader said:


> OK, after testing with some of the most brutal bass monsters around, I have come to the following: First, the de-coupling is nearly complete. During several sequences that normally would have peeled the paint from the upstairs walls, my wife confirmed that the foundation is no longer "pitching a hissy-fit". The pictures actually stay straight, and _on the wall_. During these sequences, I also felt both the base of my makeshift platform and one of the subs. While the sub was shaking significantly, the energy was not transmitted to the base (at least not that I could tell).



I always wondered about that. Some of these subwoofers (like IB units) seem to be mechanically shaking the houses. Sometimes I am not sure if the house is the "driver" of the "house shaking" rather than the output capabilities of the subwoofer itself.





Vader said:


> After some experimentation, I succeeded in dampening it by wedging a roll of shag carpet between the aluminum(?) back and the fireplace itself (yes, I know that is a fire hazzard, but the fireplace is completely turned off - I never use it). Now my only problems are the creaks in the walls themselves - which there is no way short of tearing them down to quell those.... Next house will have an unfinished basement so I can take care of that as well. Thank you all!



You never use it? Famous last words. How about in the future (if you move, get senile or simply die)? Get rid of that fire hazard before you forget about it. There has to be a better permanent solution to this problem. A bundled bit of raw fiberglass insulation can be used.

Funny thing is I am installing a zero clearance gas fireplace in my new HT room (unfinished basement). I can get to everything (not a sealed area), but I am going to be more aware of potential for "rattles" when I do the work. Just another potential headache to be concerned about (in my case).


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## Josuah (Apr 26, 2006)

Properly installed, one would hope the IB drivers are not creating much vibration in the mounting frame. The same way you extensively brace a non-IB enclosure so that it doesn't vibrate even when the drivers are running hard.


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## Vader (Jul 8, 2006)

> ...if you move


Planned in a couple of years.... I have it set up quite obvious that they are there if I ever want to light the pilot light and/or turn on the power, and a way to "fish" them out easily.



> ...get senile


Too late.



> ...A bundled bit of raw fiberglass insulation can be used.


Now that I had not thought of. I will give that a shot (granted, it _would_ be a lot safer)... Thanx!


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