I did i search but i couldnt find anything on it so sorry if its a repost.

I am currently in the process if designing and building my own subwoofer box, i have so far worked out that a 56litre ported box tuned to 33hz will work the best for my application, now the last question is.....

Should i get some sound deadening sheets and line the inside of my box?
i was thinking of using some of Jaycars sheets but i wasnt sure what one would be best, and most cost effective?

I would recommend it. The theory you see is to completely eliminate all resonances and the tar sheeting will aid a little further in doing precisely that. The Jaycar stuff is perfectly suited.


Cheers

No point really. You can line it with a fleecy material like dacron, but SD'ing a sub-box is not cost effective. The purpose of SD is to add mass to a surface. If your box is strong enough, you shouldnt need this.

The jaycar stuff is known for not having great long-term life on vertical surfaces. Ie, it likes to detach.

Dacron/sound diffusing foam, however, stops resonances inside the box. Usually, nobody can hear a difference, but it doesnt hurt to use.

Sub enclosures should use stiffness to prevent resonances, not mass, brace,brace then brace some more. An enclosure made sufficiently stiff through bracing (or stiffer materials, geometry) should not need any further sound damping if the dimentions and the operating frequency range do not allow for quarter wave interations to occur.