foward firing sealed off from the trunk??

[nicholasmccabe]

What would the pros and cons be in doing:

1. A slot ported box foward firing , sealed off from the trunk. I remove the backseat and build a box inside the car. 2 SA 15s firing foward. Should the port be in the middle of the subs or shoulld it be on the side?? I want numbers and some hard hitting shvt so i have decided to cross the boundry of just simply taking out the backseat and walling off my subs. Meca style, meter at the headrest on the passenger side seat. SO?? Port on the passenger side??

2. Leaving the back seat in and bulding either another 4th order or doing a ported box in the trunk??


I want to know if walling off the back will give me bigger numbers

[Kangaroux]

If your meter is in the passenger seat you want the port to be on the drivers side. I don't quite know the physics behind it so someone else can chime in about that, but you almost always want the port as far away from the meter as possible (i.e. the opposite corner of the vehicle).

[nicholasmccabe]

If your meter is in the passenger seat you want the port to be on the drivers side. I don't quite know the physics behind it so someone else can chime in about that, but you almost always want the port as far away from the meter as possible (i.e. the opposite corner of the vehicle).

ok cool. DO you suggest one chamber for both subs and 1 port on drivers side?? Or port in the middle with 2 seperate chambers sor the subs?

[keep_hope_alive]

i am always a fan of separate chambers so excursion isn't lost from the subs fighting each other. i also prefer ports in the middle with dual subs. simply put, you are taking advantage of constructive interference with a port. you want the rear wave to combine coherently with the front. that is what the port is doing. it also helps alleviate the natural rolloff of a sealed enclosure due to pressure.

sealing off the front baffle helps reduce phase interference from the sub output traveling to the rear of the trunk then back to the cabin, cancelling with the front output at some frequencies, adding at others, and a mix in-between.

as far as an end slot on once side or the other - keep in mind what is coming out of the port. you want each sub and port output to arrive coherently at the mic. what frequency that peaks at is both a function of enclosure design and orientation in the vehicle - i.e. path lengths of direct and reflections. it's just physics.

[nicholasmccabe]

i am always a fan of separate chambers so excursion isn't lost from the subs fighting each other. i also prefer ports in the middle with dual subs. simply put, you are taking advantage of constructive interference with a port. you want the rear wave to combine coherently with the front. that is what the port is doing. it also helps alleviate the natural rolloff of a sealed enclosure due to pressure.

sealing off the front baffle helps reduce phase interference from the sub output traveling to the rear of the trunk then back to the cabin, cancelling with the front output at some frequencies, adding at others, and a mix in-between.

as far as an end slot on once side or the other - keep in mind what is coming out of the port. you want each sub and port output to arrive coherently at the mic. what frequency that peaks at is both a function of enclosure design and orientation in the vehicle - i.e. path lengths of direct and reflections. it's just physics.

when u say seperate chambers do you mean totally seperate?? as in like building 2 boxs and sticking them side by side in the sdame shell?? or have a common area and have a port with 2 walls in the middle

do you or anyone have any links i can look at tonight and get a good feel for a a good trunk wall for a set of subs??

also, what do you guys think i need as far as cubes for 2 sundown sa 15s d4. Wired to 1 ohm nominal on a ss rubicon 2500.1 (soon to be 2 - ss rubicons 2500.1s strapped.) so i will have the power for them no doubt. so can i get away with like 3 cubes per sub or do i need the full 3.5

[keep_hope_alive]

they could share a common wall between the ports so it could just be one large box with a center divider.

when two subs share airspace, the airspace is less than if they had their own. each sub "sees" about 2/3 of the volume. so if they needed 1.5 cu.ft. each, you'd need 2.3 cu. ft. shared or 3 cu. ft. separate. that is the biggest advantage. the disadvantage is reduced output.

you can look at my build log for a trunk wall. i don't have a box on the trunk side, but i could just as easily add one. i made a rectangular opening that was reinforced so i could get an airtight seal for some IB rated subs. link in sig.

interior volume determines the Q of the enclosure. you need to figure out your actual goals for the system. you are the speaker designer. you want to perform the same calculations that a designer does when making their own home/pro audio speaker. that starts with knowing and designing for a specific Q.

[AlanHall]

In meca can you have the trunk open? I had good luck leaving it un sealed and opening the trunk. Like 1.5 gain vs. 8 or so sealing it. I have done a few fwd fire with 15s and didnt seal them and had great luck too. And if you have the room. Maybe consider areo ports too.

[Chriszle]

Generally forward firing will yield better numbers, but rear firing will sound better and have more low end authority.