Wallboard Rattle Against Studs

[bocoogto]

I cut a hole for a Dayton IB 15" woofer in the floor of my listening room. There are recesses on both sides of my HDTV recess for speakers--about 9' apart. They are 7' high, 22" wide, and 30" deep. This leaves room for the 15" woofer in the floor near the back of the recess. The back of the woofer is open to an unfinished basement, so it causes no issues.

The woofer performs very well, driven by one channel of a Hafler DH500 amplifier, crossed over at 50 HZ. The problem is the vertical drywall inside the recess that rattles against the 2X4 studs. I have drilled holes and applied glue where the rattling was most noticeable, and put extra drywall screws in many areas. At fairly high volume levels, rattling is still quite noticeable. The area behind the vertical drywall is a dead space about 8' high and a triangle about 30" by 30", forming part of the master bedroom wall.

Any ideas for utilizing this arrangement? Any clever ideas to stop the rattling? I have a second 15" IB woofer which would make the rattling worse unless there is a way to secure the drywall against rattling.

[ThomasW]

In the past we've had few reports of similar problems, but none with a system as modest as a single PE IB15.

Drywall screws and a liquid nails type glue should be adequate to the task if it's only the wallboard rattling.

The only thing I can think of is to turn on the sub, locate the offending section of drywall, then remove it. Replace the drywall with 5/8" rock glued to the studs with liquid nails and attached with screws. When the wall cavity is open check to see there aren't wires that add to the rattle.

If you can't open the wall section I don't know of any other solutions.

[bocoogto]

I'm surprised this is not a more common problem with built-in subwoofers. Even with my single 15" woofer, there is quite violent shaking of the walls at very low frequencies when watching movies at reasonable volume levels. The quality of bass until the rattling begins is awesome!! Until I have confidence that this can be overcome, however, the second 15" woofer will stay in the box it shipped in. I certainly would worsen the problem with a second woofer.

[ThomasW]

Perhaps a better approach is to add more drivers so they play louder than the rattles..

[bocoogto]

Good one, Thomas!! Until my ears deteriorate so I can't hear rattles above 50 Hz, that won't work. Perhaps more drywall screws will do the trick. Or, I'll have to break into the space from the bedroom side and figure out how to stop the rattling. Maybe a better approach would be to utilize the wasted triangular space as a large infinite baffle enclosure!!? I guess this would qualify as an acoustic suspension enclosure. A lot of experimentation with various drivers designed for sealed boxes may be necessary. My Infinity Quantum II's go down to 28 Hz fairly strongly--acoustic suspension 12" Watkins drivers. I am after the 28 Hz and lower frequencies for movie realism.

[bocoogto]

Too bad there is not more activity on this board. I anticipated getting some suggestions from other folks that encountered similar problems to mine with rattles. I've decided that houses are not built to withstand low frequency energy without making noise. What I was hoping for was a way to deal with this and make a good IB system as part of my house.

[ThomasW]

The fact that your thread didn't receive more posts is not indicative of this board having little activity. It's without doubt the largest and most widely read of any forum dealing with IB subs.

As per my original reply, in the 8+ yrs this forum has existed no other person has posted a problem similar to yours.

Given the way people post complaints about anything and everything on forums, were this an endemic situation I guarantee we'd have numerous threads and a number of solutions.

Since the majority of IB sub owners are running significantly larger IBs (some with 4 or 8 18"s) and not having similar problems, I must conclude the situation is unique to your structure and installation.

[chrisbee]

bocoogto

Despite your misgivings Thomas and the rest of us don't waste our time here. Well not deliberately.

The rules of IB building are very simple indeed. Thomas has kindly given us comprehensive FAQs. He has given us galleries galore and answered every imaginable question several times over by those trying to avoid or bend the simple rules.

If you ignore the rules or Thomas' advice then you don't have an IB. You have something else. That is your right. Just don't call it an IB if it's not. You haven't earned that right and it may put others off building their own IB subwoofer when you start moaning about your hybrid "something or other" underperforming.

You need enough displacement to make the IB safe on VLF peaks. Particularly on heavy transients like film explosions. Displacement is a handy parameter which covers all those unnecessary questions about Xmax, size and number of drivers.
You either have enough. Or you don't. I'd say 10 liters is probably a minimum safe total displacement. More is better if you have a large room or like serious levels of bass. I have just over ten liters and would prefer more for total safety on WOTW and other popular bassy films.

You need enough rear volume to match your drivers' total Vas within fairly flexible limits. More is less. The more you have the less you need to worry about sound quality.

You need to cancel mechanical reaction forces by physically opposing your drivers. Or start with a very stiff structure in the first place. If in doubt: Build a manifold.

You need enough power to keep a tight grip on all those big cones without running into clipping or using silly impedances.

We don't care how deep your speakers can dig. They will thank you for an ~80Hz crossover. As will the wimpy amp you use to drive them via resistive, passive, crossover components.

I ignored some of the rules and built up a formidable post count before satisfaction was finally achieved. That wasn't Thomas' fault or any of the other members here. It was my fault for ignoring the rules and hoping for the best. I have a horrible feeling it was my endless nagging which forced Thomas into online publishing about IBs just to shut me up.

I am a great believer in learning from my mistakes. I hope others learned something from mine. That doesn't mean the mistakes have to be endlessly repeated for their own sake. The lessons have already been learned. We move on and discover better ways of doing things from each other's personal experience while still staying within the basic rules.

Read the FAQs. Look hard at the examples in the galleries and read the blogs and websites of IB owners listed here. They all have something in common. They followed the simple rules and gave satisfaction to their owners.

[ThomasW]

Thanks Chris....

bocoogto

There are literally hundreds of people using IB subs as a result of assistance received from the members of this forum.

As a FYI, the 'total member' counter seen on the main page represents the number of people who've joined in the last 18 months. Had a counter been used from the forums inception, the number of members would exceed 10,000, but who's counting?...

[joeyskinner]

Is it possible that the rattling noise is actually the driver bottoming out?

[bocoogto]

Chrissbee,
Yes, the IB concept is simple, indeed. I have one. The Dayton 15" IB woofer is mounted in the floor of my listening room near a wall, crosed over at 50 Hz and driven by a Hafler DH500 amplifier, which is much more amplifier than this particular woofer can handle at full output. Hardly a wimpy amplifier for this application. The driver is mounted face-up, with the rear firing into a very large basement. Whether I had this driver by itself or several more drivers mounted in a manifold, the plasterboard on the adjacent wall would rattle---more with larger amounts of energy emitted by multiple drivers. I will proceed to the step of more drivers (and amps, if necessary) when this rattling problem is resolved.

My question remains: If anyone has experienced this problem, what are some fixes? Thomas answered quite helpfully.

My later comment quite about too few posters on this forum was, evidently, in error. It's just hard for me to believe structural rattles are not a major problem for IB's installed in people's homes. If this was a stand-alone woofer box, I would simply move it to another part of the room until I found a spot that didn't cause the walls to rattle.

And, to answer the last poster, the rattling of the cone bottoming is quite different from the sound of the plasterboard rattling against the building studs.

Thank you for your attempts at helping me.

[ken]

Hi bocoogto, try opposing drivers first anyway as the mechanical forces and vibrations will be reduced thus your walls rattling at a certain frequency may be reduced to an exceptable level , plus you'll get less strained output...........if that does'nt help you'll have to either locate the problem area's and glue and screw......... or rip it down and resheet and you'll get the oppotunity to check your wall studs as well for stiffness and as thomas said loose wiring etc

cheers ken

[bocoogto]

Thanks, Ken. A manifold to hold two 15" IB woofers is the way to go. I will mount the woofers on opposite ends of the manifold. Will still radiate the rears into the basement. The present cutout for the woofer will be used as the outlet of the manifold. If rattling of the adjacent wall persists, I will cut the plasterboard to remove and inspect the dead area. Repairs will be made through the hole and the plasterboard reinstalled, taped, etc.

[chrisbee]

bocoogto

You couldn't ask for a more flexible room than the attic of my old house where I enjoy my AV activities.
The previous owner clad the attic surfaces with thin decorative plywood on rather few battens.
One day I will get round to doing a decent job with plasterboard.
The disruption and heavy work puts me off changing anything in a hurry.
I used to have terrible rattles, creaks and even loud groans as the whole roof lifted on REW tests.

Then I built an apposed driver manifold.
Every surface in the house still shakes like a diesel motor.
This vibration now comes from the acoustic output of the drivers rather than mechanical structural vibration.
I changed nothing in my attic but I don't have any more rattles.
Except for the very old windows 27 feet away from the manifold.
My old double doors beside my array used to rattle back and forth by an inch on programme material and testing.
Every REW sweep started with a violent and incredibly loud shudder from the doors.

Now the doors hardly move and are completely silent on test or programme material at any level.
The laws of physics may well have broken down in my AV attic but I hardly think so.
I get far more infrasonic bass out of my manifold than from the array.
My four new drivers produce far more deep bass than the old drivers but have caused no structural vibration problems at all.
I think this is enough evidence for any reasonable person that opposed drivers work very well indeed.

Build an opposed driver manifold as I suggested in my post above.
If it doesn't work for you then you can claim our charges back for the advice you received here.

[Cozmo]

You may be able to tame the rattle with some expanding spray foam. Just drill a hole and spray it in there.

[bocoogto]

Cozmo,
Good suggestion!! I thought of doing this, but have heard foam sometimes expands too aggressively and could bulge the plasterboard. I realize there are at least two varieties of foam. There is little damage done if I use the right foam and it doesn't fix the rattles.

Thanks!!

[Cozmo]

bocoogto said:

Cozmo,
Good suggestion!! I thought of doing this, but have heard foam sometimes expands too aggressively and could bulge the plasterboard. I realize there are at least two varieties of foam. There is little damage done if I use the right foam and it doesn't fix the rattles.

Thanks!!

There is a new latex foam that might be a little more gentle as far as expanding.