Newbie here. I’m no expert on damping materials by no means, but has anyone ever tried Acoustiblok? Amazing stuff. Converts acoustic energy into kinetic energy. Check out the video on this web site. Let me know your thoughts.
Acoustiblok Soundproofing Material - Acoustiblok Website
Acoustiblok Soundproofing Material - Acoustiblok Website
The primary goal is to damp internal eigenmodes from reflecting back to the cone, modulating it, so typically adding damping to one of any parallel surfaces as well as any that is parallel to the diaphragm is sufficient, so density is a function of the sum of all internal reflected energy and any more just starts rolling off its low end performance.
The Acoustiblok OTOH is primarily for keeping the reflections in the cab and damping them via mass loading, so guessing it's way overkill for typical speaker cab alignments. though only one way to know for sure.
Historically, [multiple layers of] acoustic fiberglass insulation has proven to be the best overall choice with O-C 703 or similar being the modern equivalent: owens corning 703 - Google Search
For vented alignments, this damping routine doesn't damp vent action unless the cab is fairly heavily stuffed, so must be 'critically' damped for best overall performance using some form of impulse response test to show/hear when there's no under-damped 'hangover'/'boom' in the system like well damped sealed except with more LF gain bandwidth [BW].
For folks that don't have REW or similar program to do this, the simple, cheap 'click' test was created: Click Test | GM210 | Flickr
For heavy stuffing, there's a point of diminishing returns: Sub Box Polyester Fiberfill
Some additional information:
What's the simple science behind polyfill stuffing? My explanation as well.
http://www.troelsgravesen.dk/cabinet-damping.htm
https://www.qtasystems.co.uk/articles/how-to-damping.htm
GM
GM, I think you are a very experienced person in audio cabinets, I would like to know your opinion about this :
Eminence Delta Pro 18 A in prism sealed 150 liters
(see post 140)
Thanks in advance !
Eminence Delta Pro 18 A in prism sealed 150 liters
(see post 140)
Thanks in advance !
Ok, then I'll start at the beginning.
It is a sealed 150-liter prism-shaped cabinet with 18mm MDF side panels. It has internal reinforcements and the deflector will be double, 36 mm. Speaker 18 inches in diameter.
The cloths are quite large and I want to attenuate possible resonances in them, although the Young's MDF module is (according to this article) between 200 and 400 hz, which would have no major impact on the subwoofer passage band I am building , (20 to 100 hertz aprox.) Since its application will be mainly for music, although it will be also welcome for some film from time to time.
So I thought about applying asphalt membrane on the inner walls to neutralize (kill, eliminate) resonances of the material of the box, not to absorb frequencies of the rear wave of the speaker, for this task the cabinet will be filled with polyfill.
I hope you understand, my limitations with the English language prevent me from expressing myself correctly, although I think I'm doing quite well, however.
" For a few years, the boxes are made with this material. It is three times cheaper than the cheapest wood and joining this to its hardness, rigidity and absorption rate make it a very suitable material to build boxes.
As a disadvantage, like all materials, it has a fixed Young's modulus and its behavior is not perfectly homogeneous and linear. It tends to resonate or reduce its absorption of sound around 200-400 Hz. This produces gray coloration. Many boxes suffer from this problem, since these frequencies are not attenuated with the materials that are commonly used (wool, fiberglass)"
Materiales para construcción de cajas - PCPfiles en www.pcpaudio.com
Squeezing a big driver into what sounds like a smallish sealed box. Pity.
With triangular sides, your internal reflections are absorbed OK by the pillow stuffing you are planning and incidentally gaining a bit of isothermal enlargement.
There's too much obsessive concern about needing more barrier from sound escaping from panels vibrating, in this forum I'd say. I've been knocking my knuckles on cabinets in stores for decades (and clapping my hands in concert halls) but not sure how much I've learned. For sure, solid cabinets seem wise in the abstract, but is the difference audible? And if audible, is it detrimental?
Cross bracing works much better than buying hood underlayer from the automobile parts store. In Canada, we just collect old hockey sticks to glue as cross braces. If your 5 cu feet is compact, the sides aren't very large.
While my grasp of engineering damping is nil, my intuition is that to damp thick MDF, you'd need real thick heavy gooey stuff, not some film as you initially thought. Bracing at strategic locations works great.
I just built a giant labyrinth with quarter-inch plywood. So granted, I'm ego-involved.
B.
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Don't know about the aluminum, but asphalt stuff like that is common in many places, I'd guess. Stiff and gooky and maybe smelly and not fun to work with except for laying big runs in hot weather, as in your video.
Important point for DIYers: figure out how to buy good materials that duplicate the expensive stuff from acoustic supply houses, as OP is showing here.
Most - but not all - fancy materials can be duplicated or fabricated on your own. My favourite is heavy aluminum foil on thick sticky stuff, 10 inches wide (for pipe insulation)*. Saves $200 in making your dishwasher walls quiet. But useless for MDF walls.
Here's the labyrinth with measurements:
17 foot pipe sub 12-230 Hz ±5dB
B.
* I wish Canada wasn't a place where temperature insulation was such a big art
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Sometimes, you just need to do the math.
So, we take academia50's 18 inch diameter choice and we add a very very necessary one inch to each side and make a cube box. And what inside volume have we squeezed that big speaker barely barely into?
Well, simply multiply 20 x 20 x20 (doesn't much matter if you do or don't leave off a few hundred cubic inches for the driver itself)?
Gotta squeeze hard to fit that driver into that box.
OK, I won't embarrass anybody by showing the number. Anybody can figure out what you get squeezing an 18 inch driver into 20 inches*. And that's the smallest conceivable cube box that will hold that driver.
B.
* OK, some folks may not remember that a cubic foot is a bit more than 1700 cu inches, but i admire Enrico Fermi who famously loved to estimate odd things roughly but wisely
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I was responding to your criticism that 5 cu ft was small. Granted, you often hear of smaller boxes, dunno why.
My point is that you could hardly make a box any smaller for that choice of driver if you wanted to. And for sealed boxes - which have only a single parameter, volume - the bigger the better.
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"Happy Q" is not a design goal, whatever your sim might produce for a simulated FR. The aim is to have the least resonance you can manage in order to get the best sound quality.
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