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 Post subject: Acoustics Project Update
PostPosted: Thu Aug 31, 2006 10:29 am 
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Joined: Mon Dec 19, 2005 12:07 pm
Posts: 27
Location: Ithaca, NY
Earlier this year I began upgrading my home studio acoustics. This thread describes what I did earlier:

http://www.johnlsayers.com/phpBB2/viewtopic.php?t=6010

I redid my absorbers, making them all 4" thick, and edited a post in the first thread to describe what I did and where they're hung.

Here's where we left off:

knightfly wrote:
Your room undoubtedly IS resonating at that frequency; 71 hZ is the first harmonic of both your height and width's axial modes. One way to verify this is to put your head exactly halfway between ceiling and floor, and exactly 4 feet from the front wall; this should be the minimum effect of the 71 hZ peak.

Although more absorption in corners and on walls may help, there's not a lot of room in that size room; perhaps another way would be (if you're up for it) to build two panel resonators 4 feet wide and nearly ceiling high, tuned to 70 hZ - this will pull out much of the room's axial problems without affecting much else.

If floor space is REALLY tight, building four such panel traps TWO feet wide by 8 feet long and placing two of them on the ceiling with their long dimension running front to back, and two more on the upper section of wall, also running front to back, can work as well or better. This would affect BOTH of the 8 foot dimensions which are causing the problem.

To build these, you can use Ethan's plan for a LOW bass trap with one change - instead of 1/4" plywood for the face, use 1/2" ply instead. This will lower the trap's center frequency to your modal problem range.


I used Ethan Winer's stuff to measure what frequencies were acting up in my room. I measured from my listening position with a small diaphram omnidirectional condenser mic, located at ear's height, aimed directly to the front. Ethan's pink noise sample was dialed in at 90dB, then I ran the test: I copied his sound files into Pro Tools. Without drawing a chart, here's the news:

+5.0 dB rise at 65Hz
+1.3 dB valley at 78Hz
+20.8 dB rise at 135Hz
+8.4 dB valley at 147Hz
+12.4 dB rise at 152Hz
+5.1 dB valley at 197Hz
+9.6 dB rise at 215Hz
+6.1 dB valley at 250Hz
+12.4 dB rise at 274Hz
+10.3 dB valley at 284Hz
+12.2 dB rise at 290Hz

The 135Hz rise is incredible. This needs management. But how would I go about figuring out what type and size of resonant panel I need, and where would I place it. I know it needs to go where the pressure is the greatest, and I used http://www.hunecke.de/english/calculato ... modes.html to help figure this out.

Just wanted to check what y'all would do.

Thanks,

Nick


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 Post subject:
PostPosted: Fri Sep 01, 2006 4:53 am 
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Joined: Mon Dec 19, 2005 12:07 pm
Posts: 27
Location: Ithaca, NY
Here is a chart of the low freqencies from my mix position:

Nick


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