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View Full Version : dynamat on the inside of box....



waNtsumBuMP
10-25-2004, 12:21 AM
since everyone is using it to seal up the trunks/hatches, and it usually helps the number increase, what would the effect be of puting dynamat, or peal and seal on the inside of the box.... i think it would look preaty **** cool too....

nosaj070
10-25-2004, 01:36 AM
Erm, well first no one can see the inside of the box, second, sound deadening is used to keep sound waves in, and to rid of rattles, two things the mdf doesn't have a problem doing. All it would do is take up space.

Naxis2k1
10-25-2004, 01:55 AM
Erm, well first no one can see the inside of the box, second, sound deadening is used to keep sound waves in, and to rid of rattles, two things the mdf doesn't have a problem doing. All it would do is take up space.

GOOD ANSWER! :handclap:

waNtsumBuMP
10-26-2004, 12:02 AM
yeah that was exactly what i was thinkin, the only reason i was askin, was becuz on pimp my ride, they always put dynamat on the indisde of there plexiglass boxes, but i didnt know if it was just for looks or not.....

DBfan187
10-26-2004, 12:10 AM
Aso, if its ported. It will raise your tuning.

tommyk90
10-26-2004, 12:21 AM
Aso, if its ported. It will raise your tuning.

Actually, i think if it takes up space it would lower your tuning.

Smaller box and the same size port=lower tuning. No? :confused:

Moe Lester
10-26-2004, 12:23 AM
Actually, i think if it takes up space it would lower your tuning.

Smaller box and the same size port=lower tuning. No? :confused:


if your port size/length is constant, but the box size decreases, the tuning goes higher.

tommyk90
10-26-2004, 11:00 AM
if your port size/length is constant, but the box size decreases, the tuning goes higher.

Hmm, i dont know why i thought otherwise. Oh well.

idiot
10-26-2004, 03:46 PM
Isn't this useful if the box is made of fiberglass rather than MDF, though?

squeak9798
10-26-2004, 03:54 PM
yeah that was exactly what i was thinkin, the only reason i was askin, was becuz on pimp my ride, they always put dynamat on the indisde of there plexiglass boxes, but i didnt know if it was just for looks or not.....


First off, do not base your stereo design/choice off of what you see them do on "Pimp my POS". They appear to know about as much as *** hair about stereos.


But, they plexi isn't nearly as strong as MDF. You need really thick plexi to get much strength from it (which isn't cheap), so they are probably using some fairly thin/flexible crap, and so they use the sound deadening to help reduce some resonance problems with the box.

squeak9798
10-26-2004, 03:56 PM
Isn't this useful if the box is made of fiberglass rather than MDF, though?

What, sound deadening? Fiberglass can be just as strong as MDF if the box is constructed properly. 'Glass is extremely strong when curved, and rope and such can be added to help strengthen the flat surfaces.

RattlinStratus
10-26-2004, 03:56 PM
They do that to the fiberglass because it sometimes is prone to rattling. If you have a fiberglass box you are most likely not going for SPL, so they are probably going for show or SQ, and the box is sealed so when they put the dynamat on it, it keeps it from vibrating and it may actually help to stiffen the glass.

RattlinStratus
10-26-2004, 03:58 PM
Squeak is right fiberglass can be as strong as the mdf. They probably use that sound deadening stuff to compensate how ****** their boxes sound and how bad they rattle.

idiot
10-26-2004, 07:39 PM
What, sound deadening? Fiberglass can be just as strong as MDF if the box is constructed properly. 'Glass is extremely strong when curved, and rope and such can be added to help strengthen the flat surfaces.

So is there no reason to spray rubberized undercoating inside a fiberglass box, or line the sides with modeling clay, or apply deadening material, or any of a thousand other ways to manipulate box resonance, if it was built properly? Because I’ve seen all of these done and recommended.

I’m building my first glassed box, and don’t really know if it’s constructed properly or not (due to lack of experience). I will have finished putting about 10 layers of Bondo brand mat down soon, and it still will just barely be ¼” thick (which many people consider too thin, apparently)… so I’m not sure if I’ll have to be one of those who will have to slap something on the insides to compensate for poorly-built box. This was why I was wondering.

squeak9798
10-26-2004, 07:58 PM
So is there no reason to spray rubberized undercoating inside a fiberglass box, or line the sides with modeling clay, or apply deadening material, or any of a thousand other ways to manipulate box resonance, if it was built properly? Because I’ve seen all of these done and recommended.


It completely depends upon how thick you make it. If you don't have enough layers of 'glass, then sure it's going to be weak. And as I mentioned, you can lay ropes and such inbetween the layers to strengthen the 'glass. If anything, bracing it would be the best way to go.

The spray-on undercoating I seriously doubt will be heavy enough to do anything. But, Read This (http://forum.soundillusions.net/showthread.php?t=37294), pay close attention to Dan Wiggin's posts, and it should give you a good idea of the best ways to go about it. The thread is aimed towards kickpanels, but the same concepts can be applied to sub enclosures. Notice what he says about what is required to change the resonance

idiot
10-26-2004, 08:51 PM
I've read that post before, which led to a discussion (on a different board) regarding the benefits to layering cement on the inside of a box as a mass-loading device.

But if you're arguing that matting is an insufficient means of adding mass and lowering resonance, why is sound deadening the door panels seen almost as a required action, here and on other boards? I doubt a few layers would come close to doubling the mass of the effective door panel area (I'm excluding anything above the window, which is not part of the enclosure, once covered), yet it seems to be effective (lowering vibrations merely one of many claimed benefits).

squeak9798
10-26-2004, 09:40 PM
But if you're arguing that matting is an insufficient means of adding mass and lowering resonance, why is sound deadening the door panels seen almost as a required action, here and on other boards?

Because we can't change the construction of the door panel to better suite our needs ;) Have you ever tried bracing your trunk, or trying to build it out of thicker material? No, because it's impossible, so we have to do what we can. Whereas when we build 'glass enclosures, we can do things such as brace them and build them differently (like the rope inbetween layers thing) to stregthen them.

rumydad
10-26-2004, 09:48 PM
i am doing my first glass box also and i am constructing the entire box of mdf and just glassing the front(the only side to be seen due to construction) for looks that is ok right?

idiot
10-26-2004, 10:26 PM
Because we can't change the construction of the door panel to better suite our needs ;) Have you ever tried bracing your trunk, or trying to build it out of thicker material? No, because it's impossible, so we have to do what we can. Whereas when we build 'glass enclosures, we can do things such as brace them and build them differently (like the rope inbetween layers thing) to stregthen them.

I don’t deal with trunks; I have a wagon. ;)
Alright, I understand what you’re saying. I guess I’ll just use some rope, then.

squeak9798
10-26-2004, 10:41 PM
I don’t deal with trunks; I have a wagon. ;)


I don't deal with trunks either. I put all my speakers (and subs) infront of the front seats :D

rx7vert
10-26-2004, 10:53 PM
the rubberized undercoating inside a figerglass box helps keep the smell of the resin down.

The dynamat/peel and seel keeps the door panels and trund from flexing, and causing resonance. In physics, if you take it, you learn about mass and inertia. Basically, something with less mass has less inertia, and it is easier to move. Added mass, means higher inertia, and more difficult to move. A bare door panel is fairly thin, flexible, and light. The pressur and vibration of the speaker move it easily, causing rattles and resonance. dynamat is put on to add mass to the panel. When you add the mass, it increases the inertia, and makes the panel more difficult to move, therefore reducing rattles and resonance.

plazman
10-27-2004, 08:59 AM
What, sound deadening? Fiberglass can be just as strong as MDF if the box is constructed properly. 'Glass is extremely strong when curved, and rope and such can be added to help strengthen the flat surfaces.


how would you add rope to a fiberglass box?

nosaj070
10-27-2004, 10:03 AM
how would you add rope to a fiberglass box?

Resin the rope to the sides...

plazman
10-27-2004, 08:47 PM
Resin the rope to the sides...

like make 1 wrap around?

any special way?

rx7vert
10-27-2004, 11:35 PM
fray the end of the rope, smash it against the side of the box, apply resin, I like to put a layer of cloth around the rope, and over the frayed end.