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How I built my bass traps...
Old 25th July 2017 | Show parent
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chrismeraz's Avatar

Originally Posted by jcjr View Post
In my small room lots of thick absorbers had to be added to achieve noticeable low bass improvement.
When you say "lots," are you talking like 25% coverage of the room? 50%?
Old 25th July 2017
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chrismeraz's Avatar

I want to mount 4" thick Rockwool panels with a 4" gap.

The easiest way to mount them on the wall involves a 3mm MDF backing. How will this affect the LF absorption?
Old 25th July 2017 | Show parent
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Originally Posted by chrismeraz View Post
When you say "lots," are you talking like 25% coverage of the room? 50%?
Hi chrismeraz

I never calculated it and perhaps I would calc it wrong. Probably less than 50% if including ceiling and floor surfaces. Perhaps more than 50% if only considering walls.

When I finished absorber building a couple of years ago, posted a pictorial overview of the end result here on my website that time forgot--

Last year I hobby-built some coax studio monitors and the most recent measurements are shown here after installing/tweaking the homemade monitors. The rest of the room and location of absorbers is the same as that earlier overview. Only the speakers and amps were changed.--

The room has two always-open interior doors in the rear wall, an un-covered window on one side wall and an exterior door on the other side wall. The remaining worst null around 37 or 39 Hz is almost certainly caused by reflections between the side walls. I suppose that bass null could be improved by putting deep absorbers over the left-wall window and the right-wall exterior door, rendering the exterior door useless and blocking natural light from the window.

To get serious about it, I would need to move some furniture out of the room to allow more absorbers. The big thin absorbers in the pictures and the frame of the front "speaker enclosure" are 3" thick safe'n'sound brand rockwool. They seem to measure effective for highs and mids, and possibly a dB or two "total" improvement in bass. That is, all the thin absorbers added together might be responsible for leveling bass peaks and nulls by one or two dB. I doubt if they do more than a dB or two all together, in the low bass. But seem to work quite satisfactory in mids and highs.

The "speaker enclosure" is three inch thick safe'n'sound rockwool on both sides, back, and top. All surfaces open on both sides. All coverings are burlap.

The hanging ceiling absorbers and several other small absorbers are the same rockwool but thicker than 3".

The front-left corner is 2 foot X 9 inches safe'n'sound rockwool, as is the absorber seen sitting a foot in front of the right exterior door. Those two 6 foot X 2 foot X 9 inch rockwool absorbers were the first two I built when started experimenting with room treatment. Not knowing any better, I expected to measure better improvement than reality dictated. Placed in both front corners, the room decay time was measurably reduced but no useful change could be measured in frequency response. That was my first hint that maybe I needed to build a lot of absorbers to expect much improvement.

One corner is floor-to-ceiling 2 foot square of pink fluffy. Another corner is 2 foot X 3 foot floor to ceiling pink fluffy. The front left wall is 8" thick Pink Fluffy, and the absorbers sitting on-top of the rockwool speaker overhang up to the ceiling are 12" thick pink fluffy in the thinnest "top to bottom" dimension. They are about 3 foot X 2 foot X 1 foot pink fluffy.

All the absorbers are built "as open possible" to present to the room as much absorber surface possible. Most of the fluffy absorbers open on all four sides and the top, with thin wood frames holding them together.
Old 25th July 2017 | Show parent
Originally Posted by chrismeraz View Post
I want to mount 4" thick Rockwool panels with a 4" gap.

The easiest way to mount them on the wall involves a 3mm MDF backing. How will this affect the LF absorption?
It would diminish its efficiency. Check out High Sundry's construction tutorial on YouTube. I followed their design method and recommended it. It's a low profile yet sturdy frame that is easy to mount with a gap.
Old 8th August 2017 | Show parent
Gear Head

Ikea hacking

Billy bookcases and some Isopond WLG035 wool
Attached Thumbnails
How I built my bass traps...-20170808_174548.jpg  
Old 13th August 2017
I sometimes see frames with holes in it but isn't it tricky to use less wood? The trick with bass absorption is the wood resonating because of air waves which the isolated material will then absorb, right?
Old 13th August 2017 | Show parent
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Originally Posted by Raaphorst View Post
I sometimes see frames with holes in it but isn't it tricky to use less wood? The trick with bass absorption is the wood resonating because of air waves which the isolated material will then absorb, right?
Some kinds of absorber rely on damped panel vibrations.

The simple fiber absorbers just present friction to sound waves, diminishing the room sound build-up by converting some of the audio to heat. They also slow down sound passing thru and can act like delay elements, which could be useful in some tasks.

In some uses you get best absorption with the biggest surface area of fiber. If the fiber is in a completely sealed heavy stiff box it wouldn't absorb much unless the sealed box would act like a helmholtz or panel absorber. If one side of the box is open it will absorb more than the sealed box. With two sides open it will absorb more than just one side open (depending on what a person is trying to accomplish, maybe some constructions would work best with only one side open.)

Testing for instance a few rolls of attic fiberglass in a reverb room, it should test most effective just laid out on the floor without enclosures, fluffed up as much possible. And then if you maybe make a chicken wire stand so you can lay out the same amount of raw fiberglass suspended a foot or three off the floor, then the reverb test would probably work even better, because you added absorptive surface area by raising the absorber, exposing the bottom surface to air.

Fiber absorbers also do some of the attenuation by diffraction, when sound waves scatter off edges of the absorber.

I made absorbers with as little wood possible and as much surface area possible. It seemed wasteful and time consuming to use big pieces of wood then drill lots of holes in the wood. I just used little pieces of wood as "open frames".

I drilled random sized, random location holes in a few nearfield absorbers, but in that case it was not to increase surface area. The nearby flat pieces of wood would be likely to reflect sound and hurt the frequency response. So the holes were intended to diffract sound so that there is less sound reflection, and the reflected sound is scattered.

Any "regular repetition" of features such as holes, for instance a nice long straight row of identical 4 inch holes, could possibly act as a filter and affect the sound in unanticipated ways. That is why I tried "pseudo random" hole size and location to minimize the odds of accidentally making an undesirable audio filter in the nearfield.
Old 20th August 2017
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What do you guys think about these bass traps...any good?
Old 12th November 2017
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Cantona999's Avatar
I've been building quite a few broadband panels this week with 100mm Rockwool RWA45. I am moving onto the basstraps this week but I have a couple of things which are still confusing me.

I wanted to build some superchunks in the beginning, but I seem to generally find people are putting the more rigid battens like RWA45 or similar in there. I keep reading though that for traps it is better to go with something less dense. If that's right why would people be using the more rigid insulation for chunks?

Finally, I have only have access to two different types of insulation that I can get for quite cheap, would any of these be good for building my traps? I have tried to search to find the more details to see if these are suitable regarding there absorption but I cant seem to find much on these Knauf rolls.

Knauf Eko Roll Loft Insulation, (L)4830mm (W)1140mm (T)200mm | Departments | DIY at B&Q

Knauf Full Fill Cavity Insulation 1200mm 455mm 100mm | Departments | DIY at B&Q

Last edited by Cantona999; 12th November 2017 at 11:51 PM..
Old 7th December 2017 | Show parent
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Originally Posted by buttonjaw View Post

Backed them with SoftTouch™ Duct Wrap HVAC commercial duct insulation (one layer mylar, one layer MLV, one layer insulation)

Setup in the live room
Did you do anything to the Air Duct itself?

I have a small, heavily treated production room in my basement which has exposed duct work. Theres an air duct running lengthwise across the ceiling which runs parallel and then connects to the main air duct. That duct runs straight the length of the house. It creates a HORRIBLE, almost plate reverb sounding tail. Are you having resonance or reflection issues with the air duct in your room?

I used a pack of vibration dampening sticky pads (used for cars) on the exterior of the duct but I think I need to treat the inside of it to halt reflections. It did nothing

most info online is geared towards silencing the AC unit itself or minimizing transmission between rooms. Im hoping for a simple, inexpensive DIY solution so I can get my tight bass decay back!
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