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Bass trapping - corners or walls?

I've been reading articles on the ASC website and it seems that they contradict themselves regarding placement of bass traps. Most of their placement articles discusses placing bass traps in the corners. But the article below actually says that traps in corners are not that important and that traps along the mid point of opposite walls are more beneficial. What gives?

http://www.tubetrap.com/bass_traps_articles/iar89.htm
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handymann
380 posts
 
@geoffkait   Sounds interesting, but I don't have the space. @auxinput I would never buy the absorber from Foley-can't afford the shipping for one thing. Sounds like u solved your problem. Mine has too many problem frequencies for that. Although it may not sound like it from what I'm saying, my room sounds pretty good. RTA says the frequencies I mentioned are a little hot. 
swingfingers
44 posts
 
@auxinput,

I am considering GIK soffit traps to help me with a bass null, and I would be grateful if you could expand upon the comment you made above:
The thick GIK soffit traps really don't do much here.
It would be great to hear your experiences with these traps, their pros and cons, and why you don't think they would do much.  Thanks in a advance for your thoughts.
auxinput
2,920 posts
 
I tried the extra large soffit traps once.  They did not seem to do much with the very low 50-70hz area.  And since they were broadband, they seemed to suck the life out of the room (too much mid/high frequency absorption).  I have since moved onto the GIK Monster Bass Traps with Flexrange Limiter.  This seems to work well for 80 to 150hz absorption, but still allows some reflection of minds/highs.  I really love the Owens 703FRK panels, I think they work better than Monster Bass Trap for 80-150hz, but the foil definitely reflects upper mids and highs very much, so you need to be careful and experiment with placing.  

If you look at the testing results document for soffit, you will see that it does do limited absorption down in the 50-60 hz area, but it’s not very much (even for being 14” thick!).  Convention soffit and even Monster with Flex Range Limiter will not do much down this low.  Flex Range Limiter and Owens 703FK are really on,y good down to about 90hz (maybe somewhat at 80hz).

If you really have sub 80hz Bass nulls, the only way I have found to fix them is using limp mass tuned membrane bass traps.
swingfingers
44 posts
 
I hear you, @auxinput.  Thanks very much for sharing your impressions.  If you have a chance, I would be curious to know how many traps you used and for how large an area.  Interesting to hear that you feel the Owens panels are more effective than the GIK. 
auxinput
2,920 posts
 

My room is 11 feet wide, 17 feet long, 9 feet tall. I have:

6 - 2’x4’ 703 FRK panels (various corner edges)

2 - Rockboard 80 2' x 4' panels (on side wall for speaker SBIR)

2 - GIK Monster bass traps 2’x 4’ with Flexrange Limiter (back wall)

2 - 63 hz limp mass tuned membrane 2’ x 3’ (back wall at corners)

2 - 50 hz limp mass tuned membrane 2’ x 3’ (side wall at back corners)


The two 50hz limp mass tuned membrane seemed to make the biggest difference in bass response. I also did a measurement on this and this really improved the 40-60hz area where nothing else did (even the 63 hz panels).

It’s really just a gut feeling that the FRK performs better than the GIK Monster Flexrange. It could just be additive. However, I did definitely hear 90hz boost when I put up certain FRK panels (like the front wall/ceiling edge). If you play 90-150hz test tones, you can feel the foil on the FRK resonating. On the Monster Flexrange, it’s a very stiff and solid front board panel. It’s somewhere between cardboard and actual wood (stiff but flexable panel, probably 1/8" or 1/4" thick). You cannot feel it resonating as much as the FRK foil.

The idea on the Owens 703 FRK. The front foil will resonant/vibrate with sound pressure waves in the 90hz to 150hz area. The pressure will resonate/push the foil and the fiberglass behind will absorb that energy. The same general principle works for the limp mass bass traps, except the front panel is 1/8" or 1/4" neoprene rubber with a fairly empty cabinet (just 1" of loose acoust-a-stuff glued to the back wall to improve Q). The limp mass is also a very narrow band trap, where the 703 FRK works well beteen 90 and 300hz.

The Monster Flexrange does well and doesn’t absorb much mid/high frequency, so it does not suck the life out of a room as much as a full broadband trap. The Owens 703 FRK reflects a LOT more mids/highs than the Monster Flexrange. On four of the FRK panels, I have a towel covering about 30% of the panel because it actually reflects too much and the mids/highs became overly powerful. It’s a fine line tuning exercise.

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