DIY Duct "Silencers" - Where Was That Thread??

I read a thread with some cool pictures that one of the forum members posted on building a HVAC duct "silencer" It looked like a "maze" inside and seemed to be made from 703 or something like that. Does anyone know which thread I'm talking about, or know of a thread I can read that explains this. If it's safe? Does the air flowing throw blow all the fiberglass fibers into the air, etc... Any help would be greatly apprecaited.

Hey Brad, There are a few out there but this is mine. http://johnlsayers.com/phpBB2/viewtopic.php?t=6933 Not sure what page its on but I am sure you can find it. What I remember is to make it twice the size of your ducts so not to impead air flow. peace Tom

TomVan wrote:

Hey Brad, There are a few out there but this is mine. http://johnlsayers.com/phpBB2/viewtopic.php?t=6933 Not sure what page its on but I am sure you can find it. What I remember is to make it twice the size of your ducts so not to impead air flow. peace Tom

Tom - I found it. You WERE the one! I was just on my way to update my post saying that I found it - LOL!! So Tom, how do they work when all is said and done? Are they worth it? Because (really quickly) here's my situation: I have a main HVAC-trunk that runs parallel to my sliding glass door that seperates my live/control rooms. My HVAC guy tapped into this trunk and ran a duct into my control room, and tapped in the other side, running a duct into my live room. After he left, I happen to look into the duct and almost fell off the ladder when I saw right into the live room :evil: So I'm going to close up one of the holes and make a new on the opposite side (so two ducts will branch off the same side) - in the hopes of closing off a direct path between the two rooms. I'll run my flex duct through the joists and make long baffle-boxes (maybe around 4-6 long) - just like yours! I figure that closing off the direct path between the two rooms, coupled with these baffle-boxes should eliminate and "cross-talk" noise between the two rooms. I'm not concerned with any noise the duct makes when the air is coming out. My rooms are really small (10x11 each). Any other info you can provide? Any mistakes you made? Anything to look out for? Sorry for the barage fo questions - I hope I'm not taking up too much of your time. :shock: But you really look like you know what you're doing! :wink:

Brad. Just remember to caulk the crap out of them. Its something you will probably never look at again so just make sure its tight. Once you have completed them have someone yell in one end and put your ear to the other end. You will be pleasantly surprised. As far as fibers being set free you can line the 703 with any kind of breathable fabric/material. As far as my build I haven't noticed any ill effects of floating fibers in the air. And I am a clean freak. More dirt and dust come into my space than anything else. All those long haired musicians :lol:

But you really look like you know what you're doing!

I fake it real good. Peace Tom

One more quick question Tom - will the acoustic caulk (in my case OSI 175) do a good enough job at glueing those baffle "wings" in place?

Brad, Thats what I used. But when I built mine I made sure the sides bottom and top were tight. So when I screwed the last piece of plywood in place it sandwiched the 703 pieces so they couldn't budge. Mine were so tight you could jump on them without crushing the box. I just used 1/2" plywood that was laying around from the build peace Tom