Damping/Absorption material in cabinets

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#24
If you go to canadian tire or any hardware store get a can of liquid rubber for under panels for cars etc...it easy to use it's called a sealer also because you use it to block the end of a branch on a tree when you just cut it.so the tree does dry up because of the cut.Same principles as dynamat but in a can, sprayable!🙂
 
#25
Extensional layer damping (free layer damping) involves a damping material applied to one surface of a panel. Constrained layer damping is essentially sandwich damping with outside panels and an inside substance (usually flexible). Lower frequencies are best attenuated by stiffer boundaries while mid and higher frequencies are best attenuated by less stiff boundaries. Jim Moriyasu in AudioXpress Feb 2002 compared these types and other box styles. A good source of explanation is also Acoustic Behavior of Sandwich panels from a technical bulletin by DIAB.

HTH

Jay
 
#27
newfinish said:
If you go to canadian tire or any hardware store get a can of liquid rubber for under panels for cars etc...it easy to use it's called a sealer also because you use it to block the end of a branch on a tree when you just cut it.so the tree does dry up because of the cut.Same principles as dynamat but in a can, sprayable!🙂
Click to expand...

its called sureseal
 
#29
Morbo,

You're correct, many fail to grasp that there are two distinct phenomena related to stuffing:

1. Damping, energy dissipation via conversion of acoustic energy to heat

2. Effective volume increase by absorbing the heat of compression and reducing the pressure rise

" if the material in question is air-permeable, it will increase volume "

Actually I believe if 2. is the goal, closed cell foam might be better.

Open celled will allow air movement through the cells and dissipate energy, whereas closed cell will not.

I built a sub once and IIRC I used closed cell and got about a 25% volumje increase based on reduction of Fb.

I was just looking at the stuffing section in Dickason's LDC 4th edition and noticed for the first time what I would have previously considered a discrepancy between the freq resp curves and Fsb.

I'd assumed that the lowest Fsb would correspond to the biggest effective volume increase and lowest Qtc, and give the greatest output at lowest freq.

But this is not the case; the 50% filled boxes with middling reductions in Fsb and Qtc had several dB more output at 20 Hz.

The 100% filled boxes (single materials and various combinations) were equal or only slightly better than the empty box for low freq.

The Qm of these were very low, indicating a lot of absorption, so I conclude that for a subwoofer box the 50 % fill is best.
 
#31
panel dampening

here is a material you might want to try instead of those costly
little pads, a product used in roof covering known as "ice and water shield'
it is a rubber and asphalt composite and comes in 36 inch by 250 foot roles it si about $90(us) but you get a lifetime supply.
or you might look for some roofers using it and beg for some roll ends.
I have used it to line the inside of car doors with great results.
just dont let it touch itself or you will NEVER be able to seperate
it
 
#32
Not me. However, it seems as if it's a high density foam might be betterr suited towards low frequencies. Pure speculation though, which I'm good at. 🙂

Hey, it's created by NASA right? I'm sure they have specs on their site of it's acoustic properties.
 
#33
amp-guy said:
here is a material you might want to try instead of those costly
little pads, a product used in roof covering known as "ice and water shield'
it is a rubber and asphalt composite and comes in 36 inch by 250 foot roles it si about $90(us) but you get a lifetime supply.
or you might look for some roofers using it and beg for some roll ends.
I have used it to line the inside of car doors with great results.
just dont let it touch itself or you will NEVER be able to seperate
it
Click to expand...


Although he doesn't post much anymore TTBOMK, Ed Heath over on the old Bass List has used this, and many other compounds, potions and goo. He really liked this stuff, not only for cabinets, but if memory serves, but also for damping speaker baskets.

Another cabinet damping material is a mixture of Aleene's Original Tacky Glue and drywall mud. This is nearly the same, or identical, to the "Glop" that North Creek used to sell.

Another Wonder-Goo that has been used is Latex Roof Sealer, the white stuff that you roll on an existing roof to waterproof it. Mixed with sand you pour it in and let it set up. You can only do one panel at a time as it wants to flow, but we're DIYers and have all the time in the world.

Another of Ed's favorites is to use oil-based modelling clay and apply it to the cabinet wall (on the inside!!! :^). Rolled out with your wife's favorite rolling pin to the desired thickness, it is just pressed into place. Additional mass can be added in the form of lead birdshot mixed into the clay before rolling it out. If you contemplate a thick application you can always staple window screen to the surface before pressing the clay into place. The oil-based clay never dries up and can be reused 5 or even 10 years later. I've used this method and it really works well. Ed recommended Dick Blick oil-based modelling clay, a google will probably get you to an outlet for this stuff.

As for Black Hole, I have a story that I'd love to relate, but as it concerns people still living amongst us, I will refrain out of respect for the parties involved. However the final outcome was, for a short space in time, you were welcome to haul away as much of it as you wanted.

Hope this is of some use.

Best Regards,
TerryO
 
#34
I must admit that I have never taken a definite aproach to the stuffing of the box, for industrial speakers I tend to use fiberglass, at home a mix of polyester and open cell foam, preferably pointy egg crate style which I place a small amount directly behind the driver on the back wall, the rest of the surfaces polyester stapled.

My main aim has been to try as many different materials as possible and I vary materials for different sounding rooms.

Most of my foam has been bought from Clark Rubber stores, and they have a range of different styles, my favorite is the yellow matress underlay, followed by the gray coloured cut to order one.

I find the pointy ones great for improving the clarity of the woofer in a standard style of box, so that it sounds a bit more like a better shaped box, ie 7 or 11 sided box, but without the effort.

well thats my 2 cents worth, all I can say is enjoy the difference that this can make🙂
 
#35
I used some foam-bitumen laminated material at work with cloth coating, don't know the brand since I got to work with only a piece of left over... and for a whole different goal (reducing the sound of a generator.....) But I would figure it works fantastic in a speaker cabinet...

And I think it wouldn't be very hard to DIY the material.. Just a thin layer of foam than a 3mm layer of bitumen, than a thick layer of foam (with eggtray-texture...) maybe a little floating piece of 'BAF' or wool behind the woofer or midrange.....The laminated part glued to the rear and sides offcourse....

How about it?
 
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