The No.1 Website for Pro Audio
 All  This Thread  Reviews  Gear Database  Gear for sale     Latest  Trending
How’s these HVAC baffles look?
Old 11th August 2019
  #31
Well i guess I used the wrong crap. Wow what a faceslapper. Duct wrap is definitely NOT the same as duct liner and now I need to scrape of 65 feet of dangerous (and expensive) fiberglass duct wrap.

Can We just snake insulated duct through these boxes? I know sharp turn are better (with duct liner) but If snaking duct will also work we’re inclined to just finish the job that way. Thoughts?
Attached Thumbnails
How’s these HVAC baffles look?-image_7457_0.jpg   How’s these HVAC baffles look?-image_6878_0.jpg  
Old 11th August 2019
  #32
Lives for gear
 

Quote:
Can We just snake insulated duct through these boxes?
Nope! Unfortunately not. That would greatly reduce the internal cross-sectional area, which you carefully calculated originally when you designed the silencers, to produce the correct flow rate and flow speed while not increasing the static pressure too much. Reducing the cross sectional area would increase the flow velocity, reduce the flow rate, and increase the static pressure drop. Not a good idea. You would also lose the benefit of the impedance mismatch due to the sudden change in cross sectional area where the duct enter the silencer, and where the solid sleeve exits the silencer directly to the register.

Sorry. No shortcuts here!


- Stuart -
Old 11th August 2019
  #33
Lives for gear
Quote:
Originally Posted by jml designs View Post
Can We just snake insulated duct through these boxes? I know sharp turn are better (with duct liner) but If snaking duct will also work we’re inclined to just finish the job that way. Thoughts?
Online you will find people doing it and saying "it works" but no real qualification of how much it works. Considering it's pretty easy these days to get a free app, play some noise and get another free app and measure the noise on both sides of the baffle, that's not very promising...I considered it because it would save about $2000, but it was just another might-as-well-do-it-right (or rightish at least) moment in studio building. The thought of having to go back and fix this later wasn't appealing to me.

If you're going to put a booster fan, then you probably don't have to worry about static pressure too much, because you can just upsize the fan until you get enough airflow into your room. The downside though is that the more CFM you cram down a 6" duct, the louder and louder it's going to get. I would get fans that are adjustable.

I'm still confused on the EPS here. It seems to be taking up space in that duct with no sound absorption properties (unless I'm missing something in this application). You want the cross sectional area to be as big as possible/practical...
Old 12th August 2019
  #34
Quote:
Originally Posted by RyanC View Post
...”I'm still confused on the EPS here. It seems to be taking up space in that duct with no sound absorption properties (unless I'm missing something in this application). You want the cross sectional area to be as big as possible/practical...”
Hi! Thanks (and thanks soundman2020!) for all your info! Very very much appreciated. So I used the green EPS thinking, more insulation between sharp turns the better. The gaps are 8”x8” spaced with 1” duct liner being installed to create 6”x6” final mouth. I just figured the green insulation over the plywood would add a guaranteed isolation between turns. Maybe not necessary? No harm tho right? Thanks again you guys rock
Old 12th August 2019
  #35
Lives for gear
Quote:
Originally Posted by jml designs View Post
Hi! Thanks (and thanks soundman2020!) for all your info! Very very much appreciated. So I used the green EPS thinking, more insulation between sharp turns the better. The gaps are 8”x8” spaced with 1” duct liner being installed to create 6”x6” final mouth. I just figured the green insulation over the plywood would add a guaranteed isolation between turns. Maybe not necessary? No harm tho right? Thanks again you guys rock
EPS or any closed cell foam has no real sound absorbing properties. No harm per se, but you want the cross sectional area to be double or more the area of the duct that feeds it. This causes a sudden impedance change, which increases the insertion loss. Also the larger size helps keep the static pressure and velocity lower, meaning less loss of airflow and less duct noise.

I would take the EPS out too. Are you feeding the baffle box with a 6x6 or a 6" round duct?
Old 12th August 2019
  #36
Lives for gear
 
avare's Avatar
 

Quote:
Originally Posted by jml designs View Post
d. So I used the green EPS thinking, more insulation between sharp turns the better.
I am confused. You were given recommendations in another thread. Most EPS is closed cell and USELESS for sound absorption.
Post Reply

Welcome to the Gearslutz Pro Audio Community!

Registration benefits include:
  • The ability to reply to and create new discussions
  • Access to members-only giveaways & competitions
  • Interact with VIP industry experts in our guest Q&As
  • Access to members-only sub forum discussions
  • Access to members-only Chat Room
  • Get INSTANT ACCESS to the world's best private pro audio Classifieds for only USD $20/year
  • Promote your eBay auctions and Reverb.com listings for free
  • Remove this message!
You need an account to post a reply. Create a username and password below and an account will be created and your post entered.


 
 
Slide to join now Processing…
Thread Tools
Search this Thread
Search this Thread:

Advanced Search
Forum Jump
Forum Jump