Sound deadener inside a subwoofer enclosure

[monkeymantn]

I'm getting ready to build a fiberglass subwoofer box (hidden style) for my Isuzu Rodeo. I am also going to be installing sound deadening (more than like Damplifer Pro) elsewhere in the vehicle. Can/should I install damplifier inside the sub box? If I can, should I install a paint on deadener, pad, or both?

Click to read more...

 

[Megalomaniac 5,000+ posts]

i spoke with Ant about this, you would want to use the liquid one...he recommended sludge over spectrum.

http://www.secondskinaudio.com/sound-deadener/spectrum-sludge.php

 

[helotaxi 5,000+ posts]

If the enclosure is built correctly, it will not add anything.

 

[tcguy85 10+ year member]

If the enclosure is built correctly, it will not add anything.

thats what i thought, but i had somebody argueing with me a while ago saying no matter how thick you make the fiberglass it will still resonate. but i don't know honestly, i have yet to play with fiberglass.

 

[monkeymantn]

I had read that it has to do with air displacement. I wasn't going to put anything inside until I read that the whole sound of the box could be compromised if there wasn't some sort of deadener. Sludge over Spectrum. I'll give it a shot.

 

[helotaxi 5,000+ posts]

Build the glass thick enough that it doesn't flex, and it won't ring either. Adding ridges along large flat surfaces will help with reducing flex.

What does deadener have to do with air displacement, btw?

 

[SeanDub 10+ year member]

What year Rodeo and what kind of install if you don't mind me asking. As far as the deadener in the enclosure, I would do without it. Like has been said, if the fiberglass is thick enough, there shouldn't be a problem.

 

[monkeymantn]

I've got a 99 rodeo and I've bought one of the Sony XS-L10S, so it's enclosure needs very little cubic feet. I'm putting it in the passenger side panel in the cargo compartment. I was thinking of 3-5 layers of marine (boat) fiberglass. Should I go more?

What I was meaning by air displacement is that as the woofer hits, the rear of the cone will cause the air in the sealed box to be pushed back and outward onto the enclosure. If I were to use a deadening product, wouldn't the deadener help absorb some of this air movement, thus prouducing less unwanted vibration? I'm relatively ignorant on the subject of car audio, so correct me if I'm wrong here. My ignorance is the reason I decided to join this forum.

 

[tcguy85 10+ year member]

you can use some egg crate foam or even just some polyfill to absorb the back waves if thats what you're worried about. i have never been worried about back waves in a sub box. i think it has a bigger affect on mid-bass and mid-range anyway.

 

[monkeymantn]

I'm going to be mainly using it for moderate bass. I'm not going to be entering any contests with it, but the current speakers are only 4.5" I believe. I didn't know since the entire box is going to be fiberglass.

 

[audioholic 5,000+ posts]

As said above, if the enclosure is designed and built right to begin with, adding sound deadener to the inside is nothing but a waste of time and money.

If you want uneven surfaces for wave dispersion, add egg crate foam. If you are worried about your box flexing, stiffen it properly, dont try to bandaide it with some deadening mat.

Deadening mat adds weight/mass, not stiffness. Trying to increase strunctural strength of your enclosure with deadening mat is gross inefficient.

 

[tcguy85 10+ year member]

if the rest of your speakers are only 4.5's then i would make sure whatever sub you are using can play pretty flat up till at least 100hz. you'll have to cross the sub at 80hz or 100hz because the rest of your speakers will have a hard time playing low with much output.

 

[helotaxi 5,000+ posts]

What I was meaning by air displacement is that as the woofer hits, the rear of the cone will cause the air in the sealed box to be pushed back and outward onto the enclosure. If I were to use a deadening product, wouldn't the deadener help absorb some of this air movement, thus prouducing less unwanted vibration?

Vibration isn't your concern, flex is. The deadener will have no effect on the rigidity of the box.

 

[monkeymantn]

So to avoid flex, would 3 to 5 coats of fiberglass be sufficient? I want a tight bass sound; I'm not going for overkill on the bass levels but rather just a compliment for when I upgrade the existing speaker system. Thanks for all the advice.

 

[BrianChia 10+ year member]

It is much more important for SQ than SPL. Damping material on the walls CAN help. Not to increase rigidity but to absorb backwaves which can muddy the sound. Sound pressure that isn't absorbed reflects off the walls and affects the output of the speaker itself. Also Acousta Stuff can make a box "seem" 10-15% larger than it actually is when limited space is a concern.