[Jaytor]

I asked this question on Audiogon and got some suggestions, but I thought I'd see if anyone here has some good ideas.

My new triple OB subs generate a lot of bass energy which is causing a buzzing sound behind the drywall. If you look at the photo below, you'll see part of the ceiling that is a bit lower on the right side. This is enclosing some HVAC ducting. On the other side of this wall is the utility room with the furnace. From the utility room, I can see that this drywall box has thin aluminum framing (about 1" thick) which surrounds the ducting.

There is very little space between the aluminum framing and the ducting, and I think they are touching in front of the fire place. When I'm playing music with strong bass (e.g. Jennifer Warnes "Way Down Deep"), I hear buzzing in this area. Unfortunately, I can't get to the area that is buzzing from the utility room side since the chimney is between the two rooms.

I can set up REW to play a sine wave around 50Hz or so and easily hear the buzzing behind the drywall. If I push against the drywall above the fire place, I can get the buzzing to stop.

I am thinking that I'd drill a small hole through the drywall near where the buzzing is occurring and spray in some expanding foam insulation.

Any other suggestions? Thanks.

[Jmitchell3]

Actually I think the spray foam is a pretty good idea.

[mlundy57]

Get the minimally expanding version. Unless the cavity you’re trying to fill is really big, the regular version is a PITA as it expands too much

[Peter J]

Get the minimally expanding version. Unless the cavity you’re trying to fill is really big, the regular version is a PITA as it expands too much

Heed this advice. Low expansion is what you want.

 The big expansion stuff will potentially start to cure at the edges of the squirted blob and the center will find the path of lesser resistance to expand into. It has amazing force and can bow down your rock and push up on the duct. Been known to bow door frames and windows too. Ask me how I know...

[Jaytor]

Thanks folks. Any specific product recommendation?

[Captainhemo]

Heed this advice. Low expansion is what you want.

 The big expansion stuff will potentially start to cure at the edges of the squirted blob and the center will find the path of lesser resistance to expand into. It has amazing force and can bow down your rock and push up on the duct. Been known to bow door frames and windows too. Ask me how I know...

LOL,  this  gave me a   good  chuckle    and   brings back memories of my  dad and I  doing the cabity  between the floor  and  hull  of my boat.... ... we  avoided catastrophe but  not  by much    !!

jay