Duct Work issues and Dip/Null

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DTB300

Duct Work issues and Dip/Null
« on: 29 Apr 2013, 02:53 pm »
So I was at a friends house over the weekend helping them setup their new sub.  Got things sounding pretty good, but during our testing there was a 125Hz suck-out occurring.   After playing around for a bit trying to find a better place for the sub, we then looked at the 125Hz issue.   First, It is not the sub as the cutoff is around 40Hz with 24dB slope and the dip is still there even with sub off and just main speakers playing.   We did many different things, with placement, seating etc with no changes to the dip.   Then by accident as the pink noise was playing, and we were walking around room with FFT results, I put my hand up against the duct work and saw the dip raise slightly.  I then tapped the duct and saw that 125Hz dip come up with each tap.

My friend cannot replace duct work with something like Duct Board, or even put a lining in the duct - way too much work and cost for them to consider. 

Is there any other type of fix they could try?  I thought of maybe Dynamat on the outside?   If Dynamat could be a solution, what else could be used to cover up that awful silver backing they use?

Thanks....

Atlplasma

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Re: Duct Work issues and Dip/Null
« Reply #1 on: 29 Apr 2013, 03:31 pm »
Could he access to the duct and paint it with this:

http://www.acousticalsolutions.com/vbd-10-damping-compound
« Last Edit: 29 Apr 2013, 05:31 pm by Atlplasma »

DTB300

Re: Duct Work issues and Dip/Null
« Reply #2 on: 29 Apr 2013, 05:19 pm »
The DUCT in located in the room, partly below a dropped ceiling, so there is access to it.