port placement in a car trunk

[rp]

I am building a ported box for a friend this weekend with a 12" sub in a trunk. I am going to be using dual 3" ports. I am wondering how it will sound if I run the ports up through the rear speaker holes (the rear speakers are already taken out). Will the balance of frequencies be off due to there being less resistance from the ports into the cab than the subwoofer. In other words, will the ports have more output at the lower frequencies (sub 50Hz), than the woofer ouput (above 50Hz) into the cab of the vehicle due to the sound from the subwoofer having to go through the seat and whatnot. Would it be better for me to just port the box next to woofer and forget about anything fancy.

Hopefully, my question makes sense.

[madrok]

I think the best way is to remove not just the rear speakers but the entire rear deck, and vent the ports and the woofer through the large space that results. You should not restrict the subwoofer to only moving air through the back seat. It might work for a bandpass system though.

Also, you can always lower the rear seats.

-Has a 10" sub under the driver's seat for the most accurate bass.

[rp]

I like your way of thinking.

That would be my ideal enclosure, but he is only giving me saturday evening to build the box. So I won't have time to build a bandpass box, but I could easily slap together a ported one. The woofer I am using has very good parameters for a bandpass enclosure.
Qts=.35
Vas=4.18cuft
Fs=25Hz

I would love to isolate the cab area from the trunk and put the ports through the existing speakers holes. That would sound incredible if I only had the time to do it. Right now, he has a couple of older 8"ers sealed. So, I figure a 12" in a ported box should make a huge difference.

> I think the best way is to remove not just
> the rear speakers but the entire rear deck,
> and vent the ports and the woofer through
> the large space that results. You should not
> restrict the subwoofer to only moving air
> through the back seat. It might work for a
> bandpass system though.

> Also, you can always lower the rear seats.

> -Has a 10" sub under the driver's seat
> for the most accurate bass.

[trevorg]

> I am building a ported box for a friend this
> weekend with a 12" sub in a trunk. I am
> going to be using dual 3" ports. I am
> wondering how it will sound if I run the
> ports up through the rear speaker holes (the
> rear speakers are already taken out). Will
> the balance of frequencies be off due to
> there being less resistance from the ports
> into the cab than the subwoofer. In other
> words, will the ports have more output at

> the lower frequencies (sub 50Hz), than the
> woofer ouput (above 50Hz) into the cab of
> the vehicle due to the sound from the
> subwoofer having to go through the seat and
> whatnot. Would it be better for me to just
> port the box next to woofer and forget about
> anything fancy.
> Hopefully, my question makes sense.

All i can say is thatif you want to port the sub and port through the back deck you will need to seal it from the backof the trunk. if you seal it so that the port and subs are playing into the cab of the car and the cab of the car is seperated from the trunk of the car you will get soo much more bass. We do this all the time where i work.
They last car we did had two 12's mounted to the rear deck mouted up playing towards the back window and the ports playing right into the back seat and it bumped beyond belife. We were concerned about how much we were flexing the roof of his car. The subs used were 2 memphis 12" m3 mojo's.