Any suggestions on how to keep my twin SVS PB12+2's from shaking my JVC RS1 projector and causing my image to shake as well? Besides obviously turning them down :(

Projector is ceiling mounted 22' away from subs at back of 24' (by 15') dedicated (air-tight) room. Ceiling is double 5/8" wallboard on 2 X 12 joists.

Maybe tip toes would help keep the vibrations out of the walls/ceiling?

Maybe Bass traps would help? Bass does build up somewhat at the back of the room. I do have approx 3' behind the 2nd row to the rear wall.

Try using Auralex Subdude's under your subs. That should help at least somewhat.

Here is a suggestion which may help. Run some tests to find out what frequencies are causing the problems. If you are lucky, they will be occuring in a relatively narrow band. Use a parametric eq as a notch filter to reduce that narrow band to the point that it no longer causes a problem. If it is narrow enough, you won't notice much loss in the sound.

Here is a suggestion which may help. Run some tests to find out what frequencies are causing the problems. If you are lucky, they will be occuring in a relatively narrow band. Use a parametric eq as a notch filter to reduce that narrow band to the point that it no longer causes a problem. If it is narrow enough, you won't notice much loss in the sound.THAT is an excellent idea!


Tim

This will fix your problem, but you must follow the instructions very carefully:

Pack up your subs and send them to me :)

No, seriously, go to a local HomeDepot type store. In the flooring dept
they sell 12" x 12" squares of ruber floor tiles. Use that between your projector and it's mount. Should help reduce vibrations.

I've used them under our washer and dryer and they make a big difference.

Thanks for the tips. I tried several of them last night - but to no avail.

What I discovered is that my ceiling was not really shaking after all (I have a floating floor-so the floor the subs are sitting on doesn't come in contact w/ the walls). The problem seems to be standing waves. Bass is accumulating at the back of the room. When standing at the back of the room - you can actually feel a wave of Bass roll past you and into the very back of the room where the projector is mounted.

What did work, although not a cure all, was turning the phase control to 90 degrees on one of the subs.:)

T

What did work, although not a cure all, was turning the phase control to 90 degrees on one of the subs.:)


And all that did was kill the response of that sub. Take a look at GIK acoustics. They make some nice corner traps and sound panels. they are not cheap, but they are very inexspensive compared to some other companies out there.

And all that did was kill the response of that sub. Take a look at GIK acoustics. They make some nice corner traps and sound panels. they are not cheap, but they are very inexspensive compared to some other companies out there.

Interesting response because I was thinking the same thing, but was not quite sure if it would help resolve this gentleman's issue.

Is the thinking here to flatten the response curve and keep those untamed frequencies from radiating in all directions in the room?

I'd recommend GIK as their pricing is very fair compared to the rest of the competition. My room was an echo chamber even with rugs and items on the walls. High volume meant a disarray of all frequencies radiating all over the room. However, after recommendations and treatment from GIK, the room is now absorbent. It's a vastly improved listening environment. I've never done the frequency sweep protocol, but my system sounds so much better even though a larger room would be best.

It is amazing how when I walk from one room (hardwood floors/9 foot ceilings) which is untreated and then into the treated room how the echo just dissipates with the room treatments.

I second GIK. Just put up four of their 2' x 4' x 4" panels in my 16 x 18 room -- bass resonances and slap echo greatly reduced.

You usually want to kill reflections off your back wall anyway -- start with either 4" thick panels all along the top of your back wall, or if you can afford it, run corner traps all along the top of the back wall first and then a line of 4" panels below the corner traps. 2" thick panels down to 36" or so off the floor would be a typical finish to a completely treated back wall but would not address your current problem.

I know what you're thinking -- it's your living room not a studio -- still, it helps to see a complete solution even if you can't do all of it.

Try to get as many 4" panel or corner traps in up high as you can, and if you can treat the upper side wall corners from the rear wall forward to where the projector is that will help too.

2' x 4' x 4" panels mounted at a 45 degree angle across the corner work very well, but are very difficult to mount securely to an upper horizontal corner -- you'll need a helper for sure. Make sure you know where your studs are before attempting this mounting method.

I'd try solidifying your projector mount before buying traps (you do need some traps in any case).

One problem you have is the 1 1/4" of sheet rock your projector mount screws have to pass through -- that gives them enough unsupported length to flex a little.
Another problem would be if you are mounting to just one ceiling joist -- the screws have to be in a line, which can allow a rocking motion.

To solve both these problems you need to use a mounting board securely attached to two ceiling joists to hang your projector mount from. You'll need a total thicknes of 1 1/2" -- a piece of 2x12 18" long (I'm assuming 16" centers on the joists), or two pieces of 3/4" plywood at least 12" wide by 18" long, or you can buy prepainted decorative shelf boards -- try to find 3/4" thick ones, if you get 5/8" ones you'll need three stacked. I don't really recommend MDF/particle board, use wood if at all possible.

Now mount the mounting board(s) across two joists using 1/4" lag screws. If you have to flush the heads for appearance reasons, try to find #14 wood screws. You'll need to predrill the holes, pass through diameter in the board(s), screw shank diameter into the joists.

Now screw your projector mount to the board using the largest screws you can.

The mount itself may also need to be changed -- try to flex it and see what happens. Generally speaking, mounts that extend down less far, with wider mounting plates, and fewer adjustable joints (short, squat, and welded up solid :) ) will be less likely to allow projector movement.

Let us know how it works out!

ggunnell:
Thanks!
Actually my ceiling mount is only supported by the 1 1/4" sheet rock (using large fender washers in the attic). The mount is right inbetween the joists. So I wasn't able to drill into any ceiling joists. So no wonder I have flex. I'm gonna re-do the mount this weekend using your plan.

Question: Wonder if there is a way to reinforce the projector from inside the attic - so the mounting board is not visible inside the room??? Plus I hate to lower the projector by 1 1/2.

Sure, John -- here in Missouri it's roughly 140 degrees in my attic so I didn't think of it. :)

Just cut your board to fit between the joists. Although you could use angle irons or joist hanger type angle brackets to attach, I'd be tempted to just try toenail-angle screwing it to the joists with 2 1/2 to 3 inch deck or drywall type screws, and see if that immobilizes it enough.

I had another thought -- you did check that it's not your screen moving?
I'd hate to do all this work . . . :eek:

Hey John I have a solution for you-just give them to me.....:o:o Just kiddin of course. But, hey if you are going to dream why not go all out.........right? Anyways, there are some really good suggestions here. Good luck as I hope you figure out a way to tone down the vibration. Be sure to keep us posted.

I had another thought -- you did check that it's not your screen moving?
I'd hate to do all this work . . . :eek:

I thought about the screen too today! Both subs sit directly in front of it. I'm sure that screen wall and screen take quite a pounding. What the heck am I gonna do if that's the case???

If your subs' ports are blowing on the screen, you may have to reposition the subs. Try some bassy scenes while watching the screen from the side.

On third thought, this may not be that likely, as you said out-of-phasing one sub greatly reduced the problem -- 'port puffs', even out of phase, would still move the screen if that were the problem.

I agree you need bass traps, but they won't fix your problem.

Stiffen up where the PJ is mounted for sure. I think that will help the most.

I would also try to do a frequency plot of your room , maybe even where your projector is mounted. Even if you have calibrated your subs, there may be a huge room-mode slamming into the PJ. You can try moving your subs a few feet in either direction to experiment. I like the idea of running different frequencies to find the one that's shaking it the most.

If your ports are hitting the screen you can try a piece of cardboard between the sub and the screen. I'd think its the direct air hitting it, not the whole area being energize.

My $0.02

Did some more testing last night. It's definitely not my screen shaking. It's my mount. Utilizing the tips above - I'll try and stiffen up the area where the projector is mounted. If need be - I can also mount my Chief projector bracket directly to the ceiling - eliminating the ceiling bracket and 2" long 1½" pipe. Although I'll have to use a little more lens shift to compensate.

Sounds good, John!

A few inches of 1 1/2" pipe should not be a problem (assuming the pipe mount flange at the ceiling end is large enough to prevent rocking).