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Help! Projector Vibrating During Heavy Bass! How to Decouple from surface its sitting upon?

post #1 of 13
Thread Starter 
OK, I need some help here.

I recently completed a hush-box installation in my theater. Before the hush box i had the same vibration issues but to a lesser degree. There is a lot more background into that in my build thread but I need help damping the vibration of the projector or otherwise decoupling it from the projector.

Since moving my projector to the projector box, I have some serious vibrations in the projector image during intense low bass sequences. I notice it mostly on music since the image is static but its still annoying.

The hush-box is very rigid and mounted solidly. However the old ceiling mount was quite flimsy and I could elicit movement with a single finger! So what gives with all the vibration now!? I did place rubber grommets between the projector box, wall, and soffit into which its mounted at all contact points. See the Mounting here:

D5CFE378-29B8-43D1-BEC8-63CC5C7E785A-4441-00000B0D42EAB665.jpg

My guess is that since the box is so rigidly mounted the room vibrations are being transferred to the projector. Its not the upper bass range thats the problem, but like 25Hz on down when the room really starts to breathe you can see the projector shaking.

A couple thoughts:

  • mount a plate on some medium density foam to place the projector on in the projector box to de-couple it from the box
  • mount a plate on some springs to place the projector on in the projector box which would decouple the projector from the box.


I've seen both those decoupling methods used in commercial offerings for projector mount de-couplers but not sure if they will work here or how well.

Thoughts? Anyone else solved this?
post #2 of 13
You might want to take a look at ccotenj's solution. You might be able to modify to suit your application:

http://www.avsforum.com/t/1332917/ccotenj-finally-gets-a-projector/120#post_22324622
post #3 of 13
Thread Starter 
^ Thanks, It looks like Sorbothane is highly recommended and its cheap.

After some reading It looks like adding mass to the object that needs isolation is also used.

I am thinking I will use a slab of granite or marble(probably tile) with sorbothane feet placed into my hush-box. I'll put the projector on that and make sure to get the proper feet for the weight of the projector and added mass.

Looks like the 30 durometer is most effective in the lower frequencies so I'll try that.

Does that sound reasonable?
post #4 of 13
Thread Starter 
UPDATE: SOLUTION!


ive been battling with projector vibration on the really low stuff. I tried adding mass to the projector itself and that didnt work. I tried adding rubber grommets to hush box and feet of projector, didn't work. I was all set to buy some sorbothane and put it under a marble slab in my hush box until I FOUND MY SOLUTION!

It all started when I saw this:


Notice the springs....... It just so happens i had seen those same springs in my local lowes in the conduit area.

So my solution is to attach those springs under a platform with bolts and place projector on platform "levitated" with springs. Now i started with only 4 springs but they were over-compressed and I was still getting vibration. Four was close so i added a fifth spring in the center. BLAM! No vibrations even with the bass cranked on the heaviest material!!! The picture stays crystal clear even when the walls are breathin' Guess I need more subs now!!!

Important note for other applications: Getting the spring count right is critical. Five worked for me but a heavier or lighter projector will need more or less to get the springs into their "happy" zone.

Total cost $13. No more fuzzy picture=priceless!





Hope someone else puts this to work bc it made my day!
post #5 of 13
Can you show a pic of the compete installation so we can see how you put that platform into play.
post #6 of 13
Thread Starter 
yeah, i can get a shot tonight.

That platform just sits in bottom of my hush box with projector sitting on it.

I did add felt feet to the spring feet.

This is proof of concept, i want to build the platform more recessed in the future so i have more room to reach the lens shift dials.
post #7 of 13
Since I wasn't familiar with that product I looked for it at my local Lowes today on my daily errands circuit, The name of the product is Super Strut - Spring Nut by Thomas and Betts.

It is on HD wed site in both 3/8 and 1/4 sizes.

http://www.homedepot.com/buy/superstrut-3-8-in-channel-spring-nuts-5-pack--za100-3/8eg-10.html#.UOXL6HdOV8E
post #8 of 13
Thread Starter 
Nice work Big!


I spend so much time in Lowes, they are my second family............ You know its bad when they all know your name!rolleyes.gif


Oh, forgot to mention: Remove the plastic covering on the springs.
post #9 of 13
So it's like suspension for your projector smile.gif. Two boards, with the springs in the middle and the projector attached to one board and the other attached to the mounting points. Will this work for an inverted projector though? I see how it works when the projector is mounted up right on the top board and the springs below. I am just trying to visualize it when the projector is hanging by these spring bolts essentially.
post #10 of 13
Thread Starter 
Quote:
Originally Posted by KanosWRX View Post

So it's like suspension for your projector smile.gif. Two boards, with the springs in the middle and the projector attached to one board and the other attached to the mounting points. Will this work for an inverted projector though? I see how it works when the projector is mounted up right on the top board and the springs below. I am just trying to visualize it when the projector is hanging by these spring bolts essentially.

I don't see why it wouldn't work for suspended projectors too. I'm only using one board but you could reconfigure to make the springs hold the weight of the projector in any number of ways.

Its kinda unnerving bc the projector bounces and sways around when you touch it to do lens shift or something but once it sets still the bass doesn't get transferred to the projector. I never would have guessed it working if I'd not seen it work.

My largest problem was actually the vibrations vibrating the lens assembly in the projector. i could see the lens assembly shaking around due to the play in the power zoom assembly. Since I zoom to 2.40 I couldnt stabilize the lens so I had to remove the energy from the projector.
post #11 of 13
Thread Starter 
Double checked focus and lens shift today. After the beating last night and 24hrs to settle its still dead on.......

I cranked it for a bass session just for good measure and we are successfully decoupled. Woot.

8DF3F453-64D9-4465-BD11-6523CDEE5A3D-8978-000010D55215386A.jpg

FE744D17-1E35-4F9F-8A04-1CD8A4FD83E6-8978-000010D5541EE270.jpg

D6BFAD35-5C87-4544-8744-FD849FECD9BF-8978-000010D5688968CD.jpg

BA45DB93-D742-4D93-AA28-6D244E689918-8978-000010D587CA8FAE.jpg
post #12 of 13
I see, so for that method you would need a projector that can flip the projection angle, if its mounted high or low, but not upside down. Guess the higher end models probably all do that.
post #13 of 13
If you can attach a projector to a piece of plywood I would imaging you can make a variation of this spring mount system work for you even if inverted hanging from the ceiling. In my gut I also think that if your projector is a lightweight adding mass will help.
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