My god are you picky!!
"Foam is foam and none of it works very well at LF."
Did you not understand that "LF" means LOW FREQUENCY! Or is this just another one of those "let's see if we can make a mountain out of a molehill by being anal."
Hi guys, I have used LDF with great success. Low density fibre board, also called pin up board. It is 12mm (1/2") thick and I line the larger internal sides. I use it combined with normal types of other stuffing. Tends to be better at low freq. Just a caveat, make sure you seal it against moisture.
Terry
Terry
Way to cherry pick. The obvious point of contention is that "foam is foam", which is in direct conflict with both your choice of foam for your waveguides, and reality.
Open cell acoustic foam is open cell acoustic foam, and none of it works very well at LF.
Interesting....
I think I know the stuff you mean. There is something like it here in the US that is meant for under flooring. A sort of very soft fiber board. I actually have some on the floor in one room of the workshop. Never thought of using it inside a cab.
What carpet padding? In general the new stuff is foam and useless in this role. The old stuff was used quite a bit, IMHO it is just too thin to have any real benefit.
Terry
We need to understand what the stuff we put in enclosures is supposed to do.
In general terms, not down to the last joule,
The amount of energy that is propogated into the room is equal to the amount of energy sent to the inside of the enclosure. Lets not get too technical.
We want the energy in the room, we call it music.
We DONT want the energy that goes into the box. It stuffs up the music.
In my experience I use the following.
Layer 1, next to the walls, 12mm LDF, moisture proofed. Absorbs lower freq well. Glue it in.
Layer 2, on top of the LDF, 25-35mm of some sort of material. Some use ordinary insulation (Batts - these are carconagenic, they cause cancer. In a ported enclosure this stuff is sprayed into the room by the port. Your children can suffer.) Use a natural fibre, many to choose from. I use a product made by Tontine. It is called TBL and comes in many sizes and weights. It is not natural but is non-alergenic. The longer the fibres the better. Many other types of material are available. Lastly and only if necessary I will use a lighter weight material if I need to fill more of the enclosure.
Now, anything that gets passed this has to be dealt with by the enclosure walls. The less sonic energy that hits the walls, the better.
http://www.diyaudio.com/forums/construction-tips/152459-guide-using-acoustic-concrete.html
Hope this helps
Terry
I love acoustic concrete, it is both stiff and absorbs energy.
In general terms, not down to the last joule,
The amount of energy that is propogated into the room is equal to the amount of energy sent to the inside of the enclosure. Lets not get too technical.
We want the energy in the room, we call it music.
We DONT want the energy that goes into the box. It stuffs up the music.
In my experience I use the following.
Layer 1, next to the walls, 12mm LDF, moisture proofed. Absorbs lower freq well. Glue it in.
Layer 2, on top of the LDF, 25-35mm of some sort of material. Some use ordinary insulation (Batts - these are carconagenic, they cause cancer. In a ported enclosure this stuff is sprayed into the room by the port. Your children can suffer.) Use a natural fibre, many to choose from. I use a product made by Tontine. It is called TBL and comes in many sizes and weights. It is not natural but is non-alergenic. The longer the fibres the better. Many other types of material are available. Lastly and only if necessary I will use a lighter weight material if I need to fill more of the enclosure.
Now, anything that gets passed this has to be dealt with by the enclosure walls. The less sonic energy that hits the walls, the better.
http://www.diyaudio.com/forums/construction-tips/152459-guide-using-acoustic-concrete.html
Hope this helps
Terry
I love acoustic concrete, it is both stiff and absorbs energy.
This is not entirely true. The two paths - inside and outside - are in parallel, but they are distinctly different impedances so the net flow through each leg will be substantially different - not the same at all.
Syntex is not foam. It is like industrial carpet, about 5mm thick. Slightly stiff on the underside.
Instead of trying to absorb the internal standing waves, another approach is to break them up. Short of building an irregular shaped box, an easy way is to cut an oversized piece of syntex and line the four side walls. Because the width is oversized, it will not lay flat (which is the objective). Do the same for the back panel with enough excess behind the woofer so that it is not a flat surface. The internal walls are now no longer parallel to each other. Greatly reduces standing waves. Mineral fiber or other materials can then be added if desired.
Mike
I agree, even though the link you provided is hosted by the industry that it's trying to promote.
In any case, IMHO, FG and even asbestos with it's history of health related issues were the result of long, heavy exposures to asbestos by those who worked in the construction industry. The limited exposure whilst stuffing a speaker or a few spurrious fibers ejected from a speaker port are infinitesimaly smaller exposure in comparison to what causes a health issue. Simply wear a dust inhalation protectioin device like a peanut mask while stuffing your speaker and all will be fine.
A common falicy. For a given closed shaped volume, not too much different in any direction, the number of modes in a given band is fixed no matter what the shape or how many baffles you have. The mode shap will differ, but there won;t be any more or less due to a shape change.
thank you.
The product planet10 is using looks to be around 25kg/m3 if my calculation is correct:
Natural Cotton Fiber Insulation, Natural Cellulose Insulation
The product planet10 is using looks to be around 25kg/m3 if my calculation is correct:
Natural Cotton Fiber Insulation, Natural Cellulose Insulation
The bonded logic cotton comes in different densities. The big bales made for in wall seem to be the least dense. The small rolls that you can order from Home Depot are denser and thinner. And the type with a foil backing is densest yet. The foil will peel off if you are careful.
Good stuff. Many thanks to Gary Pimm for turning me on to this stuff.
http://www.pimmlabs.com/
Good stuff. Many thanks to Gary Pimm for turning me on to this stuff.
http://www.pimmlabs.com/
It seems folks here are confusing the density of the stuffing material with the density of the stuffing in a speaker cabinet. They can be VERY different things.
Take R13 Owens Corning pink fiberglass batting for example. It's sold here in the US in rolls with backing to be used betwenn wall studs 16 inches on center. It's thickness off the roll is about 3 inches and it's about 15 inches wide. 5 feet of it weighs about 1 lb with the paper backing removed. That's a calculated density of .64 lbs/cu ft.
If you stuff an acoustic suspension speaker to a density of about 1 lb/cu ft (not uncommon), you've compressed the FG 1.56 times in 'unstuffed' density.
Take R13 Owens Corning pink fiberglass batting for example. It's sold here in the US in rolls with backing to be used betwenn wall studs 16 inches on center. It's thickness off the roll is about 3 inches and it's about 15 inches wide. 5 feet of it weighs about 1 lb with the paper backing removed. That's a calculated density of .64 lbs/cu ft.
If you stuff an acoustic suspension speaker to a density of about 1 lb/cu ft (not uncommon), you've compressed the FG 1.56 times in 'unstuffed' density.
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