Thanks for allowing me to get info in this thread and all who tried to help.
37 responses Add your response
My guess is that one panel will make no or just barely perceptible audible difference in the bass unless it is in the corner and you are physically less than three feet from it. I think that two panels and you will just begin to hear improvements (barely). I would say that four panels and you have a modest improvement in most rooms (worthwhile but not a total cure). I would think you need to be up around 8 panels to make a serious impact. If you go membrane or resonators such as tubes rather than broadband absorbers then provided you know what you are doing then you can get the same benefit (at a specific frequency) for 1/4 the treatment. So two membrane panels tuned to your specific problem might be as effective as 8 broadband minitraps. The disadvantage of "tuned resonators" is that they don't help as much outside their "tuned" range. So in my mind broadband bass trapping is the way to go if you can find an aesthetic solution that is acceptable. This is all "rule of thumb" YMMV but in the case of acoustics size actually does matter. |
Onhwy61 If you're treating reflections properly, you're treating both nulls and peaks. For treating 61 Hz, I would consider 1/4 to 1/2" membranes, 3 to 4' wide and 6 to 8' tall. That would be with a practical 4 to 6" depth and 703/705 dampening. I haven't done the math yet but that's based on my work with 4' by 2' membrane panels which were efficient around 100 Hz. Not likely to buy anything that size off the shelf because it's just too big to ship. I wouldn't even consider "soft" traps for this frequency. I wonder if there's a market for membrane trap kits? Just the unassembled frames (Ikea style). The rest can be obtained from building stores. |
This shows a before and after where a suckout at 75 Hz is completely removed Minitraps The entire demonstration is on the Minitraps Demonstration video Since this room is probably particularly bad -I don't think you can typically expect a dramatic 15 db improvement but you get the idea. Broadband bass absorption will normally improve suckouts but each room will behave differently. There are some articles on how to determine placement on Realtraps site too. Note that minitraps are not the most you can apply for bass absorption as they are 3 1/4 inches thick. The minitraps are very practical and useful for both corners and walls - a great all round product. However, specifically for a corner, the Tri-traps I use are actually thicker as they fit all the way into a corner. |
if you have a wide null centered at 61 Hz, your best bet is to try and cross a sub over a bit higher than 61 Hz and boost that null. just be careful not to create other issues with the added low freq energy released into the room. if you use a RTA while you are tweaking the sub settings to properly mate the sub to your main speakers, you can see the results with each turn of the knob. in the end, you will find this to be a very tedious process that can drive you insane. |
Now I'm really confused, not that that is an usual state of affairs. Can bass traps solve frequency response suckouts, or not? I maintain they can't. For those who maintain that bass traps are the solution, please estimate how large a trap would be necessary to deal with the 61Hz problem in the original question. |
It is a while since I visited Realtraps website. There is a wealth of information here. I think Ethan does great service to audiophiles everywhere whether you buy his Realtraps or another acoustic company's products. I got GIK Tri-traps becuase I decided that the biggest thickest "superchunk" equivalents was what I needed most (of course I should have done much more if I wanted anytthing more than a very modest improvement but aesthetics will ultimately limit us all). Nevertheless, my choice to go with GIK did not stop me learning an awful lot from the material that Ethan has shared... you have to respect that! |
after i treated my room with bass traps, the nulls were not measurably better. Good point - I hope nobody goes away with the impression that bass traps can cure suckouts. I agre that it takes a significant amount of broadband bass trapping to make even a small difference. Tube traps (resonators) can do nore at specific frequencies but you really need to know what your doing - in this case best get an expert IMHO (I wouldn't dare play with tube traps given my limited knowledge and amount of time/effort I expect it would entail. Sticking large thick broadband absorbers in the room corners is a simple easy fix but designing tuned tube traps is a whole other matter...) |
What would need filling in? Below 16hz? Those nasty suckouts. If you place the sub closer to the listening position and further from a wall/corner then you can hope to provide some "fill" where the main speakers produce a terrible suckout at your listening position. It won't completely cure a suckout but along with bass trapping it may help just enough to make an improvement. In this situation with full range speakers one could easily end up with overall too much bass - this is where a PEQ with notch filters can help on the sub to avoid adding to both peaks and troughs...you just add to the troughs and the sub peaks are EQ'd down. Of course you could notch filter the whole lot (mains and Sub) with a PEQ also (depending on the specific issues) or you could EQ each speaker and sub seperately...indeed the possibilities are many with the only caveat being that it is all too easy to overdo things and try to get ruler flat by placing dozens of filters which I suspect is a bad idea. At some point diminishing returns and the KISS - Keep It Simple Stupid rule of thumb applies....less "tweaking" may actually be better sounding than more. |
one improvement has been achieved as I found one speakers woofers out of phase so it is much better but not as ideal as I hope for. Upon discovering the speaker was internally out of phase now I have a new noticable problem, the bass is behind me and to the sides but at my seat it is way down so again I am lost. I suppose bass traps behind me in corners will tame that but suspect it may further steal bass from my sweetspot.......signed confused and bewildered |
I dont run a sub as I run speakers that have usable bass to 16HZ but I may try to add my sub to fill in suck out if nothing else works If your speakers are very symmetrically placed with respect to the room and listener (as most people) then you can assume they are exciting room modes in much the same way. A sub off to one side will also suffer from the same room modes - no doubt - so you will still have problems but not in quite the same way - especially if the sub is closer to the listening position than the speakers and at a different distance from floor and walls - so the combined effect of the mixing of the bass signals may help a little. Again the abundance of bass means you can use EQ to tame peaks which should better help you hear the troughs - just don't expect miracles as room modes are there whatever you do and they always dominate unless a room is extensively treated acoustically. Since you have bass down to 16 Hz then you can think of the subs role as "fill-in" duty... |
Bob, Sorry ....not laughing at you but the plots that Ethan shows have huge differences over a few inches in a real listening environment. It has to make one "laugh" and put things in proper perspective when one looks at a Stereophile set of pristine measurements! What are we actually getting at home - even the best of us - and how much 'processing' is the brain doing to compensate for these peaks and troughs. Certainly Ethan's arguments seem to support the contention that a device that produces modest amounts of additional even harmonic distortion may very much help improve the sound in a typical room with nasty suckouts. As in the case of nasty suckout at a particular fundamental, it will be all the other harmonics that still allow our ears/brain to interprete, fill-in and hear the note with a fundamental that actually isn't there...perhaps this is why even harmonic distortion is often pleasing and adds warmth and detail that we could not appreciate before in our less than adequate surroundings... |
LOL. Bob is quite correct - bass traps can help suckouts. The others that chimed in against Bob are of course making what superficially appear to be logical statements. A very understandable misconception. The same understandable thing happens when an audiophile attributes magical properties to a speaker cable when differences are mostly due to equipment design and matching (or slight change in seated position). Again superficially it seems like the cable is the only thing changed therefore it has "caused" all the change. Whereas poor equipment match and design or your head movement are the real culprits, as a cable should NOT cause dramatic changes if the equipment worked well together in the first place or you sat in the exact same spot with exact same volume levels. Here is what Ethan has to say on Why we believe and here is an article that suggests that bass traps can improve nulls and suckouts ...in fact this may be the biggest benefit of traps...it matches my limited experience with Ratschack meter and GIK Tri-traps - I trap mostly for nulls and use a PEQ (only on the sub) for taming peaks. It seems to work well and can probably fix almost any room - the key is to get rid of really bad suckouts and get reasonably flat - I would never recommend you go for ruler flat as I think the actual room sound is something to be enjoyed too, after all it is real and you can't hide it from your eyes and ears completely. Of course, just two cents worth and I respect that often no agreement can ever be reached on these type of opposing views. For some, cables have had a huge impact and are clearly seen as having special properties and wires are worth treating cryogenically and all manner of other tweaks, such as raising them off the floor. |
Onhwy61 said "A bass trap is a passive device that can only dissipate acoustic energy from a room. As such it can never eliminate a null in room response since it cannot add energy into the room." The energy is allready in the room (if your speakers/equipment are capable). The problem is a null is created when the waves come back to you and meet where you are positioned and those freq are cancelled and therefore not heard. Just the opposite of a peak where you are positioned at the peak of the waves coming together to reinfore that freq. A bass trap decreases the wave strength (reflection) and therefore decreases the null and at the same time brings down the peaks. Onhwy61 said "But in that case you didn't really have a bass null, but two bass peaks." So, have can you have peaks only and no nulls? Bob |
A bass trap is a passive device that can only dissipate acoustic energy from a room. As such it can never eliminate a null in room response since it cannot add energy into the room. However, if you have two bass peaks it's possible that room traps can eliminate the peaks to generate smooth bass response. But in that case you didn't really have a bass null, but two bass peaks. If you measure room response in narrow enough bands you'll typically find any number of very deep and very narrow nulls. As a practical matter they cannot be eliminated. Fortunately, they usually aren't a noticeable problem. Broad band nulls are a major problem. Repositioning the speaker and/or listener is the best way to address that type of problem. |
Hi Holeneck, you said "bass traps cannot fix a suck out, but you should still treat your room to achieve other benefits." That is a completly false statement. Bass traps do indeed flatten peaks and raise nulls IE: fix suck outs. They also narrow the width of the peaks and nulls among other benefits. Bob |
bass traps cannot fix a suck out, but you should still treat your room to achieve other benefits. you can equalize a bit by overlapping your main speakers with a subwoofer, then adjust the phase control and sub level until you reach a desired result. you may not be able to completely solve the issue, but this has worked for me in the past. also, you can try active room correction too. |
No one note bass at one point I am down about 13db so its there just not flat but not ideal for sure, and I never said to myself it doesnt sound right but the seating and speaker positiion are both new so maybe I could trim that a bit but I know not completely. With one note bass wouldnt that would be more of an issue with peaks masking things right? I know its my room but have only been here in new house for a few months so I knew before I even did the test that it was highly impossible that things would be perfect, its a double edged sword to know of the issues, one hand being it ofcourse it stinks to see you have more work to do then you planned but its great to atleast know the issue and have the ability to try to change things. Tomorrow I am going to get back to measuring and will have help to move things around so I hope to trim that enough that I can insert Behringer into my bass amp and electronically raise the dip. Having a bi-amp system is perfect for this. |
When I move the SPL around even a foot or two it changes everything but the suck out cant be cured to any huge degree so I am curious as to possible solutions This kind of result is quite normal - you may not even realize that you were getting "one note bass" for years. If you get it right then the bass riffs anchoring much music will take on a whole new world - a balanced sound where each note is audible. The problem is your room. finding out the Emperor has no clothes isnt fun but is needed to get to the performance we all strive for. Yes and perhaps it would change some peoples attitude towards the gear merry-go-round if they realized what a major effect the room plays. The only real solution is to have way too much bass..so add another sub....then you can cut the peaks down to get a flatter response. Going from -15 db trough to -6 db will make all the difference...don't try to get flat and avoid boosting unless you have extremely powerful amps and huge woofers....most systems would distort terribly at modest levels with a 15 db boost in the hard to drive bass. Bass traps help suckouts but you need a lot of big traps to have significant impact - nevertheless every trap will help provided it is large and at least 4 inches thick and placed in a corner. |
I have a big suck out from 46hz to 60hz which at max xuck out is -15db with a correct meter calibration and measurement software that I just verified last night. When I move the SPL around even a foot or two it changes everything but the suck out cant be cured to any huge degree so I am curious as to possible solutions. I think if nothing else I will install my Behringer and use it to give me a 6db gain at 50hz as this is closest frequncy I can manipulate and 6db should be ok for my amp, I bi-amp so I wont add any sonic signature of real consiquence with this limited to only the bass amp. I strongly advise folks to measure room even if they may not like what they see, use REW (Room Eq Wizzard) software which is free at Hometheatershack.com along with your SPL meter which is calibrated and compensated for within this program. It is my strong belief that most have serious issues with the room they dont even know exist and they only logical resistance to taking advantage of this program is related directly to the fragile ego of many Audiophiles.....finding out the Emperor has no clothes isnt fun but is needed to get to the performance we all strive for. |
61 Hz; that's specific. Before getting into room accoustics, experiment with the positioning and integration between the sub and the speakers. Sounds like a phase issue to me. Of course, it could be just the microphone or SPL meter you used. They are notoriously inaccurate at lower frequencies. Even the testing labs don't certify below 100Hz. After playing around with positioning and settings and you still have the same issues, come back and discuss bass traps. A null at that frequency would indicate a fairly large room volume and, probably, an unusual ceiling. |
