Im considering eithet a 15" or an 18" Fi BL. I have an alpine mrd-m1005 amplifier (approx. 1100 watts rms @ 2 ohms). I want to stick this thing in a ported enclosure in the trunk of my cutlass, facing backwards.

What would be the absolutely optimal enclosure size for these applications (both sub sizes)?

18" in trunk ? Very difficult.

Get the 15".

Ooh, and what car is it ?

Look for enclosure designs on the Fi forum. They are free and well done.

You could probably squeeze this in the trunk:

For the 15": Sub facing upwards

H: 14"

W: 38"

D: 25"

Port:

H: 12.5"

W: 5"

L: 25"

Net Volume: 4.82 ft^3

Port Area: 62.5 in^2

Tuning: 32.04 hz

For the 18": Sub facing upwards

H:14"

W: 38"

D: 30"

Port:

H: 12.5"

W: 6"

L: 23"

Net Volume: 5.95 ft^3

Port Area: 75.00 in^2

Tuning: 32.00 hz

It's a bit on the small side but it should fit a majority of trunks. Hope this helps!

Hey guys. Its a 1994 olds cutlass ciera. My dimensions in the trunk are as follows:

38 inches of width to play with

15 inches fromt he trunk floor to the bottom of the magnets of the 6x9's, 17 3/4 inchs if i took the 6x9's out of the equation (which i may do sooner than later because they are infinity kappas and they absolutely suck)

several feet of depth so that isnt an issue.

I really prefer not to have the subwoofer firing upwards.....i have done this in the past in this car and i have found some bass cancellation occurs.......

How are you going to put a subwoofer that's 18" tall in a trunk that's only 15" tall? You just answered your own question. It must fire upwards or downwards. You couldn't fit a 15" vertically either as you'll lose 1.5 in from the thickness of the board.

Sounds like you need a smaller subwoofer or a change of plans.

Get the 15 unless you want to get into something that you most likely don't have the experience to do properly.

Im having a shop custom build my box around my driver.....what about having the driver slanted upwards.....like the front of the box would be at a 45 degree angle....anybody done this? I really want a 15" at the smallest.

Asides from the bass cancellation form a sub firing towars the rear deck, i also get concerned about the cone or surround hitting stuff during excursion.

Im having a shop custom build my box around my driver.....what about having the driver slanted upwards.....like the front of the box would be at a 45 degree angle....anybody done this? I really want a 15" at the smallest.

Asides from the bass cancellation form a sub firing towars the rear deck, i also get concerned about the cone or surround hitting stuff during excursion.

cramming an 18 into your trunk might present other problems. for example some have observed that if the box is too large, the box effectively blocks the sound from traveling into cabin.

if the rear seats fold down then walling off the trunk might be a better option if you want to stick with a large sub. i remember an install were the sub was down-firing and port forward ( or simply angle the baffle).

chances are that a 15 would avoid such problems. and if your inexperienced this might be a safer option. Just because an 18 could be theoretically louder then the 15 does't mean that it will be the case in your install.

your dimensions didn't say if you could actually get the box into the trunk. perhaps you could through the back seat but you would have to account for that as well.

Both my specifications I gave you are pretty perfect for your application. If the port faces the rear of the trunk and the box is built properly, then there should be minimal bass cancellation.

PS: Why don't you have the people that are building it design it? You're going to fork out $200-$500... Might as well make them work for it.

2 12's would be wayyy louder than an 18" as well. You should have more power just for the single subwoofer as it's rated at 1500 RMS.

Edited April 5, 201213 yr by z3nor

2 12's would be wayyy louder than an 18" as well. You should have more power just for the single subwoofer as it's rated at 1500 RMS.

What makes you say that?

I dont have enough cash to get 2 subs......through Fi, the cost of subs is minimal going from a 10 to a 12 to a 15 and so on, but to get 2 subwoofers would exceed my budget. Plus I only have one amp and about 1100 watts rms to play with so i just want to pump all that into one sub. Just gonna kinda keep it simple yet effective, know what i mean?

And i was planning on having the audio shop do most of the work, i just wanted ya'll' s opinion on if a trapazoidal shaped box owuld present any issues....

Oh yeah and the seats in my cutlass dont fold down. The ciera wasnt built for a sound system, but i do love my car so much....