It should work - somewhat. It’s effectiveness will be limited based on the diameter of the Sonotube compared to frequency. Once the frequency is low enough, it will just bypass around the tube as if it’s not there. If you’re trying to duplicate a tube trap, it’s essentially a hollow tube made from a wire mesh that uses two solid ends (like a piece of wood) to hold it’s shape.
You should also put ‘ribs’ between the top/bottom discs for rigidity and support around the perimeter of the mesh. Stiffer fiberglass (like Armstrong) is used to line inside the mesh. There are also some versions that cover half the tube (before covering with cloth) with a plastic sheet.
The air in the tube column actually increases the effectiveness. By covering half the tube with plastic, you can control how much absorption occurs versus reflection/diffusion from the plastic.
The plastic sheeting happens assist absorption somewhat at lower frequencies by acting as a mild resonant absorber, along with reflecting frequencies back into the fiberglass from the backside.
Yes. I have seen the half plastic covered tubes as u mention. What the DIY video showed was drilling holes in the cardboard in a pattern …using a dowel run up the middle for the top and bottom to screw in along w glue to attach. …and placing fiberglass inside Then wrapping with material. Seemed like a simple project. I just don’t know if my room needs it. I was trying to use this as a test of some sort.
So he’s making a Helmoltz resonator in with a tube. The effective frequency/band of the resonator is determined by the percentage of the surface perforation. One has to be careful to not drill random holes of random size, or the Helmholtz effect won’t work.
Get the cheap Dayton IMM-6 mic (about $30 from Parts Express - I think you can also get it on Amazon). Every mic is individually calibrated, so when you get the mic, you can download the calibration file from Dayton and load it into an App such as AudioTool on your phone.
In conjunction with a pink/white noise file playing through your speakers, you will then have a pretty decent/cheap way of measuring the frequencies that your room needs help with.
I wouldn’t bother drilling holes for your purposes. You want diffusion not absorption with those Maggie’s. Only place you might want bass absorption is the corners or the head end of the room. Plus the self made tube traps just don’t look that good and they don’t work as well as ASC’s.
One way to test the effect of bass traps is to straddle bed mattresses across the front corners. It will give you an idea if they would improve things.
Or get some polyester roof insulation (fibreglass is too scratchy) - it often comes in cylindrical packages and put them in the corners.
In the case of diffusion- just purchase some and try unless you are good at DIY then look up the plans online.
A good, boring read (but highly informative) is The Master Handbook of Acoustics by F. Alton Everest. I think it’s in its 7th edition, but you likely want the 5th edition (I recall) if you can find one, because it has more information relative to what you are trying to do as far as things that are more relevant to people’s home listening environments versus commercial such as recording studios, etc. - though there’s plenty of that in the 5th too.
It give more info on stuff like bass traps, Helmholtz resonators, calculating room modes (as it relates to bass frequencies), etc.
@minnesotafats is correct if you are trying to control an overabundance of bass (usually the biggest problems in a home environment) because the corners of a room is what causes the biggest problems. But be aware that if bass is your problem there is simply no way around the fact that it takes a large surface area depending on the frequency. This is why the tube is round and hollow - they are designed to a have a lot of surface area (inside/outside) without being big and flat. If you opened a Tube Trap flat, it would be stupendously large.
If you are trying to get diffusion behind the Maggies (maybe with a little absorption) in the upper bass/mid/lower highs, it will be a little less “obtrusive” and nicer looking because diffusers are better looking.
The book (5th edition) does a fairly good dive into quadratic residue diffusers, how they work, and even how to calculate the dimensions - though as stated earlier, there’s a lot of free calculators online for that these days.
Here’s a breakdown of what’s in an ASC Tube Trap (it’s NOT from the book):
I forgot to mention. Helmholtz resonators and panel absorbers (flexible panels, usually made of something like thin plywood that “absorb” bass frequencies by flexing with an air gap behind) can be effective as well, without being as visually obtrusive as a bass trap - if it’s bass that you’re trying to control. Both types are also covered in the book.
No, I have no financial interest in the sales of the book.
Note in the image above, what is listed as the “sturdy exoskeleton construction for strength and durability” is also what is pointed to as “treble range reflector.” Note, as stated previously that it only covers half the circumference so reflection can be adjusted by how it’s rotated. I believe that ‘sturdy exoskeleton’ used to just be a thin film of plastic sheeting in older models.
I believe most people find that putting it in the corner, with the reflective area facing directly away from the corner gives the best combo of reflection/diffusion of upper frequency while also giving the best absorption of lower because the membrane assists in reflecting lower energy back into the absorbing structure to be absorbed even further.
The reason to fill them is so they don’t ring and act like organ pipes from vibration… if they are a long term solution I would fill them with insulation but you won’t get effective bass absorption…just a cylindrical diffuser…which works depending upon the diameter of the tube and distance from the speaker.
Tests have shown that an air gap combined with absorptive material works better than all absorptive material (depending on the design), which is why the Tube Trap is not completely stuffed.
Even panel absorbers will tend to work better with an air gap behind the absorptive material (between the wall/back panel and the back of the material.
What also makes a difference is the density of the material. Nice fluffy stuff does not work as well as nice dense stuff. But of course, there’s a limit. Generally, something in the range of about 3-4lbs per cf is good - so much denser than just getting the pink stuff from the borg (or you could do that and pack it more densely.
Fibrous absorption works by converting the sound waves into heat (the fibers vibrate and rub against each other - no, it’s not going to start a fire. If the material is too ‘loose,’ there’s little to none of this action. If it’s too dense, it starts to become reflective.
@timm. I agree with @tak1313 synopsis with respect to bass absorption. Your application isn’t as concerned about bass absorption but diffusion. For diffusion on your Maggie’s you basically have a choice to put diffusers on the wall behind the speaker or use some sort of portable stand mount diffuser behind the panel. Bass would best be absorbed in the corners with real Tube traps.
As @minnesotafats states, with Maggies (I have the 1.6QR myself), depending on the size of the room, you LIKELY need upper low to mid diffusion more than low absorption since Maggies start dropping pretty drastically from about 40Hz (depending on model). The caveat being many room DO have a hump at around 60-80Hz because of common dimensions used in US construction - but many Maggies are already starting to go down by then especially because it’s a dipolar source, and the panels aren’t big enough to prevent front/back leakage of the waves.
If you keep the Maggies close to the corners, you MAY need bass absorption, but it’s always best to at least make rudimentary measurements with the cheap Dayton mic I mentioned earlier. To me, throwing absorption around without at least some measurement is a waste of time/money, because you might think you need absorption, but if you’re guessing at the frequency, it’s like using a parts cannon in fixing cars. You may absorb the wrong frequency(ies) and make things worse. Then you’ll think that you didn’t use enough, then you’ll start dumping more, etc., etc., etc.
These are surprisingly good diffusors / reflectors. About $125 each for 36" x 80" at Menards prefinished in white and very easy to move around.
Not necessarily an audiophile solution but maybe cheapophile one.
I have hurricane shutters on the windows behind my speakers. I can attest to them being very effective diffusers. What’s interesting is tweaking the shutter angle to hear what they do.
Depending on aesthetics, one choice a lot of folks make is placing a tall bookshelf with books on it, or if windows set behind, using curtains with denser materials on the backside.
I bought them as a sort of portable noise curtain to go between the TV room where my wife hangs out and the living room where the stereo is. They allow me to listen at a little higher volume and not bother her.
The nice part is they fold up and go in the corner when I am done listening and want to join her for some TV watching together. I wasn’t expecting any sonic qualities but they do make surprisingly good diffusers.
