Im going to make a box for a DD2515 soon and was wondering what thickness mdf i should use? would 25mm do it.....?

25mm would do fine, probably an overkill but thats debatable. I take it its just for general driving? 16/18mm would be fine depending on the box and the bracing used.

yeah its just for general driving, it was just that i built a box for a cheap crappy kenwood 12" sub outta 18mm mdf and it seems to vibrate it a fair bit..the dd2515 will vibrate it a crapload more so i was thinking going to 25mm would be best.
The thicker the box/less vibration the better it sound and output it produces right?

25mm will give you optimal results but the box will be that heavy you'd notice it when driving.

FYI, I'm about 90% done on a box for a 3512 and i'm using a combo of 6, 12 and 18mm and f/glass.

If you take your time, build it right and use some clever bracing you'll get away with 18mm.

A 18mm box was vibrating? Sounds like it either wasnt sealed properly (but that wouldnt really 'sound like vibrating') or it was resting on something and the bix itself was vibrating against that. I know if I put my sub box in the floor of the shed (running it outside of the car to test for leaks and stuff), unless I sit on it or put carpet underneath it vibrates against the concrete like all hell.

18mm sides, base, front and back then 25mm sub baffle or even double up on the 18mm for a 36mm baffle.

How big is the actual box? (L x W x H)

how much power do you have?

The difference in weight between a 16mm box and a 25mm box would be less than 5kg. If you can "notice it when driving" your car must have around 20kW.

The more dense, the more rigid, the more solid the box, the better it will sound. Honestly worrying about 5kg is nothing. If you must try and set a world record at the drag strip, you can always take the box/woofer out.

Phil

Depends on the size of the box though, having a huge 'taking up your whole boot' 25mm slot box you would notice. Dunno about notice a difference but you would notice a difference between it being in and out. Its like when you have all your mates in your car and then just yourself. Guess it depends what your driving.

I gave it a good look over when it was playing a bass tester song and it seems to be fine actually, but ill think ill go for the 25mm anyway.......