What’s your fiberglass knock sound like?

ermmm im not sure but i think after u'v fibreglassed you have to use car body filler to add a thick layer which will strenghthen and i think shud solve ur problem. 6* Rockford T2's

6* POWER AMPs

BLACK CORRADO

BAANNGGIINN

alright you sould never use a thick layer of bondo unlease nesisary. it is not used for strengthing the box that is what the fiberglass is for. have you used the thumb test and if it flexes when you press on it than you add more fiberglass. bondo is only used for the pits and dips that you get in the process, if you dont have dips and pits dont use any bondo. what sub are you runing in it. if you can jump on it and it passed the thumb test then you are fine. and if youve layed 9 layers you sould be fine. put the sub in and try it if something dosent sound right then take it out and investigate.Want to know some good equipment- JL,Adire Audio,Mcintosh,Brax,Helix,Eclipse,JBL,RE,Dimoand Audio,Zapco, pritty much anything DYhon,Forbidden recommend

On the12volt you give some info and you get in

You can easily build up your thickness from the underside by using long strand "kitty hair" filler material. Mix up a big lump, throw on the gloves, and start smashing it in there. Easy way to add an inch of thickness that is really strong and cheap. FWIW...... the tub that is in my car right now is approx. 1.5" thick all around. Needless to say, it dosen't flex when I was standing on it (I'm 285), and when I knock on it, it is like knocking concrete. Solid. Gus Wherever I go, that is where I end up......