Dynamat sub box

[new-yorker]

Would it be a good idea to dynamat the inside of a box..preferrably a sealed box? any opinions? i know MDF lets air leaked out because its wood, well compressed saw dust. I am thinking the dynamat will help.

[1996blackmax]

If the box is properly sealed it should not leak air.

[swerve]

no - there is a huge discussion about this somewhere... i'd have to hunt it down.

[hellohello]

if ur worried about the mdf leaking air, put a couple coats of a sealer/paint on the inside, dynamat will still have gaps/seams, and its hella expensive

[VR3]

Dynamat will make the woofer think the enclosure is bigger than it actually is. This may be in ur favor or against it.

Just use caulk or a liquid nail of some sort and put it on the inner seams and take your finger and run over it... this "seals" it...

[skydeaner]

Fiberglass resin coating the entire inside of the box works awesome. Make sure it is dry before you put the subs in.

[VR3]

Do you folks use multiple pieces of MDF per panel?

Why would you need to coat the entire panel?

[1996blackmax]

Dynamat will make the woofer think the enclosure is bigger than it actually is. This may be in ur favor or against it.

Just use caulk or a liquid nail of some sort and put it on the inner seams and take your finger and run over it... this "seals" it...

I think you are refering to polyfill.

[VR3]

No...

Dynamat absorbs vibrations...

IE: Slows them down.

Polyfill slows them down, just not as much...

So Dynamat... Foam... - all they do is dampen things... and inside the enclosure would make the woofer think it is bigger.

Anything spongey/absorbant inside an enclosure acts as a "insulation"

If hes talking about doing the outside of the box... I say sure... but why? Whats the point...

Adequate bracing would be much more effective...

[exalted512]

the only thing dynamat will do is absorb vibrations from your box rattling. It will not make the box think its bigger. It will actually hurt your sq due to its outside barrier. You want something more along the lines of ensolite or the foam second skin makes. If your worried about your box leaking air through the wood, dont. The only place it would leak is where the sides meet. You can slap some resin on to stop that...or seal it with gorilla glue.
-Cody

[VR3]

"Would it be a good idea to dynamat the inside of a box"

The way he wants to use it. It will add volume to the box.

[audiobliss]

It will add volume to the box itself, meaning the box's materials. However, it will reduce the volume in the box. It makes perfect sense to me that it would act much like polyfil, slow the backwave, and so make the sub act like it's in a bigger box.

[swerve]

just someone hunt down the old thread. we've argued about this before!

[audiobliss]

I know it's fun to re-read old arguments, but it's more fun to make them again!! :D:D

[neomagus00]

well, i see where vr3thingy is coming from... to a sound wave, dynamat and polyfill do exactly the same thing, slow it down, so in this particular sense, i'd say they're identical... now, how much dynamat you need to equal 1 pound of polyfill, that i have no idea... and yeah, putting a layer of dynamat inside a box would decrease its volume, by a very little bit, but the acoustic effect would be much larger than the physical effect...

one of the reasons mdf is used is because it is inherently resistant to vibration and resonance, so dynamatting the inside to get rid of such things shouldn't be necessary... sealing the inside using the caulk-and-finger along each seam is a good idea... i'm not sure why you'd resin the entire inside of a panel, but i don't see a problem with it as long as you let it get completely dry...

and vr3... no, we don't generally use multiple pieces per panel, unless it's a wicked huge sub and it needs a double layer on the front to mount onto...

[VR3]

I have used multiple pieces per panel before... :p

I like to use foam on the inside of my enclosures... instead of Polyfill...

It helps dampen the panel and increases the volume a lil bit - but I think its important to have something in there to dampen the backwave from the driver to... (learned that one from Russ)



Uses a total of 12 panels (not counting the top and bottom cap)

Here is how I seal the inside...

[new-yorker]

For some time now, I have used Wood Putty to seal up the inside of a box. does anyone agree wit me that wood putty is very effective?

[swerve]

I've always used liquid nails...

[audiobliss]

I don't see why wood putty or liquid nails wouldn't work.

[swerve]

That's just how I do it.

Man Juice works best though

[MacLeod]

Its not a terrible idea to use Dynamat on the box to add mass to it which would make it more rigid. I had a severe space problem with mine so I had to use 1/2" birch plywood to get the volume I needed to fit in the space I had. I was concerned about the box flexing so I covered the outside with Dynamat simply to make it a little more rigid.

If you dont have a space issue tho it would be stupid to do this cause all youd have to do is use thicker wood.

Bottom line: Its not a bad idea to use Dynamat and it wont hurt anything. The only benefit from it is it will add mass and density to your box but you could use thicker wood and get the same results for about $100 less.

[VR3]

I wouldnt use wood puddy to seal a box...

Wood puddy as a tendency to shrink and crack - even if it says it dosnt.

For instance... wood puddy dries VERY hard and can be knocked out of place on a surface its not dug into... it just dosnt leave "intact" to a flat surface... its meant to fill in holes.

Liquid nail gets in there... and it sticks and will last a long time and you can count on it to stay.

Just use liquid nail...

Caulk gun - 3 bucks... tube of caulk... 1 buck... sealed box... priceless

PS: Make sure you let the caulk fully dry and no "smell" is left behind... if you put the driver in there and its a sealed enclosure, the acid content from the glue will eat away at the driver materials...

[exalted512]

dynamat DOES NOT SLOW DOWN WAVES IN THE BOX
that is all...if you want to know why, use your common sense, if you still cant figure it out, ill let you know
-Cody

[VR3]

How can dynamat... INSIDE of a box... a "dampening" material (which eliminates/slows down sound waves) NOT double as a polyfill material when placed INSIDE a box... NOT OUTSIDE... but INSIDE (just incase you arnt getting what I am saying)...

Inner...Within...Inside The Woofers Container...Inside The Boomers Crate... WITHIN...INNER... Ya know... INSIDE... slowing down the waves directly before hitting the outside walls... taking away mass from the box - but adding much more in theory...

Explain to me how it dosnt work that way... INSIDE the box. Not outside the box. BUT INSIDE.

[swerve]

It doesn't work. a marine biologist told me this afternoon.

[lackeyb]

If your looking to have a sealed box, use the liquid nails or wood glue and a nail gun or wood screws. Then give the box a coat of fiberglass resin, mixed according to directions of course. Let the box cure and dry without the speaker, I'd give it at least a day. The fumes some of these products give off when curing can eat away the surrounds of your speaker. If your really going for airtight you should think about a gasket of some kind between the basket and the enclosure.

As for dynamat vs polyfill vs foam. Take your pick. Since the enclosure is sealed and you don't have to worry about blowing fibers everywhere I would recommend a half fill of loose polyfill. Better yet try your options out and see which one works better with the acoustics of your box and car. The speaker makes an wave in front and an identical but 180 degrees out of phase signal in the back. So if these wave mix you get a significant cancelling out a lot of your bass. The effect your enclosure is trying to achieve is to cancel out the wave created from the back of the speaker cone and provide air suspension to the woofer. See what fits in the budget and test them out if you can, they should give a similiar effect but your ear may like one better than the other and in the end that's what matters.

[PoweredByDodge]

RE - Wood putty.
-------------------------------------
Junk dude. As stated above, it'll shrink, crack, etc. It's meant for finishing cabinets and stuff, not sealing anything. 100% silicone caulk to seal the corners up. Don't worry about anything else. If you're overly insane, as stated above you can do it up with an ENAMEL based paint.

RE - dynamat inside box
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No opinion - never tried it, probably never will. I'd be worried that it would fall off the insides of the box. If i wanted to make a box "bigger" i would simply use polyfill or foam... or just straight up make it bigger.

As far as what dynamat does... I am not so sure it 'slows down' waves as it absorbs vibration (waves). absorbtion and "slowing down" are two different things. absorbing a wave in a box i THINK (am no where near sure) would just keep it from rattling. I dunno - freaky ****.

RE - Box building
---------------------------

I hate MDF - i have never used a more ****ty material in my life. Jstas said a long time ago that if i ever made a box out of cabinet grade birch ply that i would never go back - and he was very correct. joints should be coated with carpenter's wood glue prior to being nail-gunned or wood-screwed in place. If you're lazy like I get most times, you can just screw the bastard together with screws every 4 inches and then caulk the **** outa the seams inside. Glue gets too messy for me, however, glue is the proper way to do it.

[exalted512]

How can dynamat... INSIDE of a box... a "dampening" material (which eliminates/slows down sound waves) NOT double as a polyfill material when placed INSIDE a box... NOT OUTSIDE... but INSIDE (just incase you arnt getting what I am saying)...

Inner...Within...Inside The Woofers Container...Inside The Boomers Crate... WITHIN...INNER... Ya know... INSIDE... slowing down the waves directly before hitting the outside walls... taking away mass from the box - but adding much more in theory...

Explain to me how it dosnt work that way... INSIDE the box. Not outside the box. BUT INSIDE.

think about it for a second, let it soak in, what is the backing of dynamat made of? The shiny part. Answer that and if you still cant figure it out, ill let you know
-Cody

[exalted512]

heres a hint:
http://secondskinaudio.com/products/...hp?productid=1

they both use the same type of material in their shielding
-Cody

[audiobliss]

Good point, Cody.

Also, I hadn't thought about the dynamat absorbing the waves more than slowing them down. Good point, PWD.