Help designing a dual 8” ported box for a BMW Z4 E85

[Zedfour]

Hi I’m New to the forum and I’m desperately trying to build an enclosure for 2 x powerbass xl-840d 8” subs. The problem is, I have a 2008 Z4 roadster...

I’ve custom fabricated the dash and installed a pioneer avh-8500bt double din, I made tweeter pods for the A pillars and have 3 way hertz energy/ audison prima mixed components front stage run off a Helix B4 blue 4 channel & alpine 6 x 9s custom built in the rear cubby holes run off the hu.

ive removed the rear shelf so the trunk isn’t sealed!

the subs are 200 rms each and I have a massive audio b2 nanobit to run them @1ohm 

is there anyone who can help me with what size enclosure I need? The max size I have is 32” width 12” high and 14” depth 

would they be better firing up, port back? This is the sub spec

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[THATpurpleKUSH 5,000+ posts]

Coupe or convertible?

 

[Zedfour]

It’s a convertible, 32” width 12” height 14” depth is the largest dimensions I have to work inside 

 

[THATpurpleKUSH 5,000+ posts]

EBP on those subs is about 80 which indicates that a ported box should be used. I don't like the fs being so high at 52hz, don't expect much below 40hz with those. 

I would go with about .6 to .75cf per sub and tune them around 40-42hz. 

 

[Zedfour]

EBP on those subs is about 80 which indicates that a ported box should be used. I don't like the fs being so high at 52hz, don't expect much below 40hz with those. 

I would go with about .6 to .75cf per sub and tune them around 40-42hz. 

Thanks, I’ll see what I can come up with. If it sounds like mud, what choice of sub for such a small space would you recommend?

 

[THATpurpleKUSH 5,000+ posts]

Thanks, I’ll see what I can come up with. If it sounds like mud, what choice of sub for such a small space would you recommend?

SSA F8L would be a good choice