Fibreglass sub box HELP

[Nick Read]

Ive decided that the wedge shaped MDF sub box in the back of my Clio is a bodge and I want to make something different that will fit into the rear footwells. Ive just bought a fibreglassing kit to keep me busy over the winter LOL

The plan is to have a shape that basically fills the two footwells completely and comes across the central tunnel with a totally flat top. One side of it will contain the 10" sub firing upwards, with whatever volume it needs underneath, probably around 1.5 cu ft which is what my present sub box has, then the other side will either be a cubby hole or hold my amp.

Now Ive never been particularly happy with my subs performance, its a JL 10W0 and is great until you really crank it up. When I initially set it up with my JBL 4 channel amp, both rear channels bridged into it which is something like 100W RMS IIRC, I tweaked it to get the most out of it I could without distortion, but when I turn my head unit up to a decent level for motorway driving I start to get farting from it so have to turn it down. Is this a limitation of the sub, the sealed 1.5 ch ft box, or the amp? The amp seems perfectly happy driving the front speakers so loud that its unbearable, and theyre little 5 1/4 coaxials.

Lastly, will a fibreglass box with the same volume as an MDF one sound sh*t and plasticky? Or will it sound better?

 

[audio one]

sounds like your box size is to big... usually wouldnt go much bigger than 1cu ft for a 10"..

Fibreglass boxes sound the same if not better than mdf as if built correctly they are totally sealed..

What did you get in the fibreglass kit and i can tell you if you need anything else before you start..



Paul

www.audio-one.co.uk

 

[Rorrie]

box. i got one for my brother car, put it in a .7 sealed, or 1.25 ported, .5 is far too big, and its going to start flapping.

 

[BRUN]

yup id say the box is too big aswell

less than 1cu ft for a 10"

 

[Rorrie]

sorry mine meant to red 1.5 is far too big sealed

 

[Nick Read]

Right, cheers for the replies. I just said 1.5 cu ft off the top of my head, let me think...the front face where the sub is mounted is about a foot square. The bottom is a foot deep. Then the back panel goes up at an angle but not at 45 degrees, so there is a flat top bit as well, probably 6" deep. So in other words its halfway between 1 cu ft and 1/2 cu ft. 3/4 cu ft then.

WIthout having it in front of me and measuring it (Ill do that tomorrow) I cant be sure but it sounds like its not too big...is there any other reason why it could be flapping? Thats a very good description by the way, flapping is exactly what it does when you crank it up. Its weird cos most of the time its totally solid and punchy, but you just cant turn it right up or it just gets all ragged.

 

[BRUN]

well 100W RMS isnt much for a sub Nick.....

 

[midge]

sounds like your amp isnt powerful enough.. i dont know much though..

 

[Nick Read]

Yeah maybe thats it. Ive found the manual. Its a JBL P80.4 which apparently gives 40w x 4 into 4 ohms, 80w x 4 into 2 ohms and 160w x2 bridged into 4 ohms. Im pretty certain all my speakers are 4 ohm jobs, so that means 2 x 40w to the front and 1x160w to the sub. Is that enough power for the sub?

 

[BRUN]

is that RMS power ?

ive checked the spec on that sub and the RMS figure is 125W, so if your amp is 160W RMS then it isnt the amp, and if your box is under 1cu ft then it isnt the box

hmmmmmmmmm

 

[BRUN]

i presume you have decent quality power, earth and RCA cables, and your battery is in good condition etc etc

 

[Nick Read]

Maybe I just like my music louder than anyone else and Im being unreasonable? Its an old Pioneer MD head unit with its pair of preouts running straight to the amp under the passenger seat, I think theyre Monster Cable or something, then Ive got some big thick power and earth cable (about 6 or 7mm in diameter of actual wire, not counting the sleeving) running less than a couple of feet directly back to the battery which is in the boot anyway. So it cant be that.

The head unit I think goes up to 30 on the volume, once it gets to about 22 the sub starts flapping. Should I recalibrate the gain and see if that helps? If the gain for the sub channel is set too low, am I making the head unit do too much of the work and the amp not enough?

 

[Rorrie]

just like to add, the w0 can run off HUs (if its one of the HUs that the rears can be bridged!!) ive seen it done, and not sound bad!!

100rms is still a little low, my brother is giving his about 220rms and its nice for a cheap setup!

 

[BRUN]

maybe try setting the gain again mate

there is a guide to it on car audio direct website

 

[Nick Read]

OK cheers for all the help everyone! Ill get right on it