I just built a subwoofer box using BB and MDF sandwiching "Schluter-KERDI" waterproofing membrane the resultant panels are so dead, when hit with a hammer all I hear is "thud".
Construction: I took one sheet of 3/4 inch mdf painted one side with latex primer, while the paint was still wet i rolled out the kerdi and used a legnth of 3" pvc pipe to roll out any air-bubbles, then painted the other side of the Kerdi with the latex primer and then laid the 3/4 inch BB on top. Set a bunch of bricks on top and let it dry.
Disclosure: I am not affiliated with "Schluter" in any way, I've just used their products to tile a lot of bathrooms and have this stuff just sitting around.
Construction: I took one sheet of 3/4 inch mdf painted one side with latex primer, while the paint was still wet i rolled out the kerdi and used a legnth of 3" pvc pipe to roll out any air-bubbles, then painted the other side of the Kerdi with the latex primer and then laid the 3/4 inch BB on top. Set a bunch of bricks on top and let it dry.
Disclosure: I am not affiliated with "Schluter" in any way, I've just used their products to tile a lot of bathrooms and have this stuff just sitting around.
CharlieLaub,
Yes, it is expensive. I'm a contractor so I get the stuff wholesale...
I've been thinking about using 2-3 mm Pond liner. it's basically inner-tube rubber my local pond supply shop has it for 85 cent per sq ft. with the appropriate adhesive should deaden any enclosure. must test. must learn.
Yes, it is expensive. I'm a contractor so I get the stuff wholesale...
I've been thinking about using 2-3 mm Pond liner. it's basically inner-tube rubber my local pond supply shop has it for 85 cent per sq ft. with the appropriate adhesive should deaden any enclosure. must test. must learn.
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CharlieLaub,
Yes, it is expensive. I'm a contractor so I get the stuff wholesale...
I've been thinking about using 2-3 mm Pond liner. it's basically inner-tube rubber my local pond supply shop has it for 85 cent per sq ft. with the appropriate adhesive should deaden any enclosure. must test. must learn.
Dead is good, but proper bracing can make panels quite dead without all the weight and expense.
If the stuff that is deadening is absorbing energy, output is reduced.
What sound is a thud? Was the hammer blow on the inside of the box. MDF on the inside or outside?
LF, low Q is not the kind of sound you want back, particularily a woofer box.
dave
planet10,
When hit from the outside, It's the good thud or "thunk", think of a "thunk" ~300hz with a very very fast roll-off.
When hit from the inside the impact is damped so transmission to the outside is negligible (the "thunk" from the inside of the box is louder than the sound transmitted through the wall (I put my ear really close to the side being hit...)).
The MDF is on the inside, the edges were beveled and glued. Two shelf braces are used to split the top/bottom and the sides.
When hit from the outside, It's the good thud or "thunk", think of a "thunk" ~300hz with a very very fast roll-off.
When hit from the inside the impact is damped so transmission to the outside is negligible (the "thunk" from the inside of the box is louder than the sound transmitted through the wall (I put my ear really close to the side being hit...)).
The MDF is on the inside, the edges were beveled and glued. Two shelf braces are used to split the top/bottom and the sides.
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Think of it this way, the inner top is split in half, the largest open space is 12in X16.5in with a resonance of ~600hz the outside pannel has a resonance of 300hz so only the second harmonic has a chance of making it trough, on top of that the wave has to make it through 4 density shifts before it gets to the air.
MDF-acrylic-polyethylene-acrylic-BB
MDF-acrylic-polyethylene-acrylic-BB
inner
used a plunge router to cut to 3/4in depth on the outside, radius of 5.5-7in. then flipped the pannel over and cut 3/4in depth radius 5.5in. to get a 11in cutout on the inside and a 14in cutout on the outside. prettied it up with a 1/4round on the outside.
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Sounds like it will fo the job well.
That's the way it makes sense to me. I'd probably use particle board thou... this application would make use of what it did well, and not care about what it doesn't.
Pictures?
dave
Not really. What is adsorbed is the resonances in the panel, and this does not change the compliance of the air or add any appreciable dampening of the air inside the enclosure. So output is not reduced any appreciable amount.
Although you can add lots of bracing, once you hit about 200 Hz the panel's resonances start to add an extraneous source of sound outside the boxthat bracing doesn't really attenuate much. The only real way to stop it is to dampen the panel. There are several ways to do that, of which the sandwich construction using stiff and flexible layers is good approach.
-Charlie
would auto/variable box or port size help subs in any way ?
depending on power/air flow/pressure the box or ports expand and contract.your multi layer dampening gave me the idea.
as power is increased the box gets larger to prevent port noise etc. simple way u could have a inner and outer layer of mdf with something inbetween that compresses.
thinking it could be a very good gimic for retail subs, a little plastic window showing the actual box moving .
This subs so powerful the box expands ,otherwise it would explode.:}
depending on power/air flow/pressure the box or ports expand and contract.your multi layer dampening gave me the idea.
as power is increased the box gets larger to prevent port noise etc. simple way u could have a inner and outer layer of mdf with something inbetween that compresses.
thinking it could be a very good gimic for retail subs, a little plastic window showing the actual box moving .
This subs so powerful the box expands ,otherwise it would explode.:}
There is no "real" latex in paint ... latex is a natural rubber and is not found in paint at all (but if they say it's a latex glove, it's latex rubber). It's just a common term used in North America ... in Europe they call the exact same formula "Emulsion" paint.
What is there is acrylic resins and vinyl resins. The acrylic is twice the material cost of vinyl, so cheap paint has more (or all) vinyl whereas expensive paint has more, or perhaps all, acrylic. Some kind of blend is extremely common.
Acrylic has better properties than vinyl (for example, it's more resistant to staining, more washable, holds pigment better, etc). A pure vinyl paint in a can will actually lose a shade of colour if you simply add a bit of water. It will also grab and hold any water-based topcoat you apply, which makes certain decorative paint effects difficult or impossible.
Commercial paints have varying amounts of both, to balance performance versus cost. I suspect, based on using different paints, but don't know for sure, that some large retailers also sell modified exclusive versions of name-brand paint that contain more vinyl than the paint-store version. You can't go by the label to determine the exact amount ... they're not ordered in % like food labels are, and are deliberately jumbled by manufacturers to hide proprietary information. The list is comprehensive, however, because of safety issues (MSDS, etc).
Because of that, it's a guess (unless vinyl resin isn't listed at all) as to the quality of the BONDZ product ... they might just call it acrylic because that represents a premium product, and that is a common practice in paint labelling and product naming ... but you're OK to call it latex. Having said that the properties the BONDZ product claims to have are consistent with a high acrylic content.
As an aside, pigments are also expensive, relatively. Pigment and the percentage of acrylic versus vinyl essentially form the basis for different paint costs per gallon of latex paint.
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Been reading some good things about Green Glue. You might try to glue the panels together with this.
Noiseproofing Compound | Active Noise Reduction Systems – Green Glue Company
The problem with green glue is that it never really "dries/cures", It's designed to be used between layers of drywall that are linked together with screws. In layer damping you don't want a strong connection between the inner and outer layer that a screw would create and allow direct transmission of energy between the inner and outer layers. Plus, Silicone would work just as well and cost a lot less.
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