Bass trapping - corners or walls?
I haven't read their other articles nor do I have any direct experience with their products but what they say in this one regarding standing waves and the need for whole room treatment is true. Treating only one end of the room isn't enough. Of course this is a general statement, final determination depends on the individual space and system. david |
I have experience with the ASC Tube Traps as I've been using them now for over 10 yrs. in my room. I love them & despite the fact that they do not have a high WAF I would not replace them w/ any other trap device. I agree with Drummermitchell that bass loves the room corners where the floor-wall, wall-ceiling interfaces are. So, tube traps must be placed in the corners & yes, the diameter of the tube trap does make a diff with a 16" trap doing the best job. Pay attention to how much you absorb the mids using this round 16" tube trap. The articles give you a very good education on how-to. Full room coverage is required so you would also need traps at the 1st reflection points & traps between the 1st reflection pt & your chair + traps behind your chair. Panels are used to absorb mid freq & compliment a tube trap but do not replace them. Absorbing bass is about controlling low-freq standing waves while absorbing mids is about absorbing/reflecting higher freq waves in motion. That's why you find panels a few inches off the wall & never flush with the wall. When the mid freq hits the wall, the orig wave motion stops (& uncontrolled reflections commence) & then a panel cannot do anything to that stopped wave. when the panel is off the wall you treat the wave in motion before it hits the wall to degree you desire & also control its reflection(s). hope this makes sense.,.,,,, thanks. |
I have followed the method outlined in the article above and it worked well for controlling bass resonance issues. Bass traps place in the corners behind my speakers actually resulted in less ambience eventhough the reflectors were aimed into the room. With the bass traps directly behind me, against the rear wall, brought life back to the room and solved resonant issues. ASC are expensive but they work. |
I have made four "ASC" type of traps, going by their diagram. They have helped with general slap back immensely, however, IMO, if you have a bass problem, you will need to go with either a parametric eq, or something besides ASC type devices. It all depends on your room. Some say any tone controls detract from the sound. I'm running all analog and even though I have many absorption panels, believe I either need to get a very expensive parametric eq, or make some diaphragmatic absorbers. I have a problem with 30-150hz. I've put so many panels of 1" 2x4 703 compressed insulation, I have begun to suck the life out of the music. I'm going to put some wood facing over about half of my panels and make a couple of diaphragmatic absorbers. IMO, if you have a heavy bass problem, anything else will be a waste of time and money. I'm very open to any suggestions. I have a good quality graphic eq in the mix( Samson S-curve 231), it just doesn't get the job done. My room is 19x21x10 and has 'knee" walls. I realize tone problem is my room dimensions-too square. I keep saying I need to post some pics, but don't have a wide angled lens. Equipment used: VPI Scoutmaster w/ DRT XV-1s cart, Theta Miles CD transport, Aesthetix Rhea Signature, Aesthetix Calypso Signature, Krell EV-600 monoblocks and a couple of Wilson Maxx II's. All suggestions welcomed!! As Milla Jovovich once said "please help." |
As fate would have it the standing waves associated with room corners do not (rpt not) always manifest precisely in the corners. That’s why it’s a good idea to map out the standing waves using a test tone and SPL meter. You may find in some cases the standing wave is located a foot or more from the actual corner. Placing the tube trap in the precise location of the standing wave makes all the difference. In addition to the corner locations, there usually are other places around the room where a tube trap is beneficial such as at the reflection point on side walls. |
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. |
@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. |
@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? |
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. |
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. |
@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. |
@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. |
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. |
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. |
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 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 |
@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. |
@brownsfan all SR products (and the BB is no exception) come with a 30 day no questions asks return policy so you should only be out return shipping costs (and possibly outbound shipping as well, at least I got charged that when I returned mine). If you are within driving distance of an SR dealer this won't be an issue I wouldn't be surprised if the BB did not work well for you -- my original intro to SR was via the ART system which I installed in my old room which was just like yours. Your wife may be very open to the ART system, it's not cheap but it works really well and looks very classy (unlike the HFTs or even worse the UEF panels) |
