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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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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.

brownsfan
1,508 posts
 
I treated my listening room with pretty good results.  I agree with auxinput's comments.  I will add the following.  Before you do anything, download REW (room equalization wizard software) and optimize the results around the room without treatment.  Get your speakers and your listening chair optimized, then play with the location of other furnishings that may be in the room.  While you are doing this, listen for improvements in vocal clarity and stereo image.  After all of this is done, then begin judicious introduction of room treatments.  As auxinput indicated, it is usually good to focus on the tricorners first.  You will almost certainly find that the measurements show accumulation of bass in those corners.  Also, be patient, and let your ears be the final judge.  Don't get fixated on ruler flat response.  Be reasonable.  I've been told it is hard to do better than + or - 10 dB in a room that is not custom built for a stereo room.    The next time I move, I intend to custom build a home with a room designed for listening.  That will be a fun project!  
brownsfan
1,508 posts
 
Anyone have any experience with the SR black box?  I'm thinking about trying one of these in my living room where room treatments aren't going to be permitted by my beloved.
folkfreak's avatar
folkfreak
1,349 posts
 
@brownsfan my experience with the SR Black Box was not positive. I have a full suite of SR ART, HFTs, FEQs and Atmosphere which work well and add to the air and space on recordings but for me the BB sucked the life and energy out of the room -- if anything it controlled the bass too well (i.e. killed) and no amount of moving it around helped. It also imposed a certain thin tone that was very audible. Now this is in a room that has built in bass traps in the walls and soffits as well as ASC traps in each corner i.e. already has very well defined and controlled bass -- in a more acoustically open situation your experience may be very different
brownsfan
1,508 posts
 
@folkfreak , thanks for the info.  I don't have, and won't have, any other treatments in the living room.  It is too alive.  No carpet.  Hardwood floors and lots of windows.  The room has almost no symmetry, so I wouldn't think room nodes would be that bad.  One of these days I will run REW to see what I've actually got going on.  Without measurement,  I think it is excessive decay time that is causing my problems.  I guess I should look for a vendor that is OK with returns.  I don't want to run a $2K experiment. 
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