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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
 

Your room will have bass nodes at different frequencies and spots.  Some of these "room nodes" will be loaded on the left/right side walls.  Some will be loaded on the front/back walls.  Others can also be loaded on the floor/ceiling points.  However, putting bass traps in the tri-corners of the room (such as where floor meets back wall meets side wall) will treat all three types.  It's a good compromise unless you need to specifically treat a certain frequency more so (in my room there is 50hz node loaded on the side walls, so I put 50hz membrane bass traps on the side walls to help).

@handymann - try using 703FRK panels instead of normal 703.  The foil cover on the FRK will reflect the mids/highs and will not suck the life out of the room as much.  It will be a fine-line balancing act.  Too much FRK panels will create brighter and harsher highs.  Your normal 1" 703 panels will do absolutely nothing to treat the 30-150hz areas.  The FRK foil panels will actually work well in treating frequencies down to about 80-90 hz.  The foil cover on the FRK will act as a "membrane" and will resonate to the 80-150 frequencies.  The fiberglass behind the foil will absorb the energy from this resonation and you have a nice 80-150 bass trap.  Anything below 80hz really requires a tuned membrane type bass trap (such as the GIK Scopus traps).

your 19x21x10 room appears to have 3 significant nodes at 53hz, 56hz, and 59hz:

https://amcoustics.com/tools/amroc?l=21&w=19&h=10&ft=true&r60=0.6

An idea would be to contact GIK Acoustics and have them make some custom T55 Scopus bass traps (figure on about $1,000 for four traps).  Them put them in the four tri-corners of the back wall.  That should really help treat the 50-60 hz area.  You have two other nodes, 80hz that load on the front/back walls, and 88 hz that load on the left/right walls.  You can probably treat these with some 2" 703 FRK place in the rear corners maybe just on top of the Scopus on the floor. 

auxinput
2,920 posts
 

@handymann - alternatively, you can make your own tuned membrane bass traps.  Requires some woodworking (sealed box) and neoprene rubber sheets and some acoust-a-stuff.  I can help advise on design of this if you want.  I have made two sets of tuned membrane (one pair at 50hz and another pair at 63hz).  They are very effective and work better than any other broadband type bass trap.  The thick GIK soffit traps really don't do much here.  I have even tried Helmholtz resonator boxes and they didn't do much either.

handymann
383 posts
 
@auxinput@geofkait:  My tubes have 12” of sheet metal, facing toward the listening position and are out between the listening position and the side wall on the same plane.  The other two tubes are straight out from each speaker, up against the side wall.  I used 1” compressed fiberglass panels and most do have the foil.  They’re placed 2” out and mounted on my knee walls with extension brackets, so the back of the panels will do work too.  I’ve considered building some diaphragmatic broadband traps, like acoustic fields advertises. I need something in a wide range of lower frequencies.  I do have a higher build up around 60 hz, but think the absorbers mentioned from Dennis Foley will take care of this.  BTW, I read where he’s going to have a traveling room, where he will pick cities to demonstrate his absorbers.  Does anyone have any direct experience with his products?  I have my 2 subs coming out of my line stage tape monitor loop and connected to a Sony E 2000esd, so along with the room correction program on the subs, I can remotely control the volume for the subs, as well as control the frequency, with the parametric eq on the Sony, depending on the album/CD played.  I’m seriously considering a Manley Massive Passive, but the cost is high.  Any thoughts on this?
geoffkait's avatar
geoffkait
23,365 posts
 
For a stubborn 60 Hz standing wave in my room I once built a 15 foot long folded S shape Helmholtz resonator using 6” diameter PVC PIPE, PIPE ELBOWS, END CAP, pipe fitting nozzle, PVC purple prep, PVC cement and a grapefruit size ball of hollow fiber wool inside for internal damping. Problem solved.
auxinput
2,920 posts
 

I don't know enough about your 12" sheet metal tubes (which I assume are your DIY version of ASC).  I have no experience with ASC traps, so I can't comment.

I don't have any experience with Dennis Foley's product.  It might be good.  It could be another variation of tuned membrane, but he really doesn't say.  Keep in mind that they are $1,000+ each and are very huge.  They have a really large 16" depth (which means they are going to stick out in the room like a large footprint speaker).  They do have a very large 30x60 face, which would be good for low frequency capture.  If you have the money and the room to place them, they might work out well.  DIY tuned membrane panels at 55hz would be 6" to 7-1/2" deep depending on thickness of membrane (either 3/16" or 1/4").  You can build them as large as you want.  Mine are 24" x 36".  It is definitely an interesting design using dual damped front wall diaphragms and carbon damping.  Could work out very well.  Shipping will probably be very expensive (maybe 300-400 dollars each) because they are oversize and very heavy (I've read 150-225lbs each).

You would need 3 GIK Scopus traps ($750) to match the area of a Dennis Foley.  Or two of the 24x36 DIY panels.

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