View Full Version : Advice for dual 8" ported build

02-28-2009, 08:01 PM
Hey guys, I'm new here and have been trying to do a bit of research on getting a ported box made. Depending on how confident I feel, I may attempt to do it myself, or have someone else do it for me.

I'm doing a stereo build for my 1991 BMW 325i coupe. The car currently has rear deck speakers, but they will be going out and I'd like to aim the ports so they fire from the previous speaker cavities.

The setup is going to be 2 e3.8 woofers by Elemental Design.

They will each be getting about 100rms from a nine.4 amp, also be eD.

I'd like to keep the enclosure as narrow as possible, and here is what I came up with for the box dimensions. What I need help with is finding the port size and type, and the placement of the ports as well as the subs.

Here is what I came up with.

Rectangular Box
Height 15"
Width 35"
Depth 7"


The sub specs are as follows:

Qts: .30
Qes: .38
Qms: 3.5
Fs: 23.00Hz
Re: 7.4
Vas: 45L
Mms: g
Bl: 15.34T*m
Sd: 231cm²
Xmax: 14.1mm
Voice Coil: 38mm

Magnet Width: 4.800"
Cutout Diameter: 7.250"
Mounting Depth: 4.375"
Weight: 10lb
Total Height: 4.900"
Displacement: ft³
Outside Diameter: 8.375"

And the recommendation for box sizing is:

Vented ( ideal )
.5ft³ Tuned to 30Hz

Vented ( DDLoud)
.7ft³ Tuned to 35Hz

I see a lot of people going with the slot/square ports now, and not so much the round plastic ports. Is there a reason for that? I'd like to stick with the round ports, as they seem to be more idiot-proof. What I need is dual ports, and also having them as close to the edge as possible so I can aim them into the factory deck opening.

I'd appreciate any pointers or help. If you need more information, I'll do my best to provide it to you.



03-01-2009, 12:32 PM
is there enough room on the rear deck to fit (2) 8 inch subs and (2) 4 inch aero ports? and port length changes depending on box size. the box won't be all that deep (up/down) if it is stretched across the entire length of the rear deck, which will probably pose an issue with having to bend the round ports. i personally don't do that. if the port is too long to do a straight shot with an aero, i use slot ports instead. your design would work fine also, but you'd possibly lose the rear cushion to the back seat. i haven't seen the interior, but firing those subs too close to the back of the seat would be an issue.

03-02-2009, 02:06 AM
If you need anymore help just hit me up, but I think what we came up with is the only way to go really

03-02-2009, 02:08 AM
2x 4" aeros? That's ridiculous. That's the full area of a single woofer. Bigger enclosure, smaller ports :imo: