I've kinda already got an idea of what I wanted to do for the sub box. I wanted do build a ported box tuned around 27Hz, but maybe I should do something else idk. Here's some info.

1. Make/Model of Subwoofer
Hifonics BRZ15D4 (15")

2. Subwoofer's T/S parameters (Qes, Qms, Fs, Vas, Sd, Xmax, and RMS Power handling)
Qes: 0.58
Qms: 3.5
Fs: 21Hz
Vas: 200L
Sd: 0.08sqM
Xmax: 15.5mm
RMS: 600W (I'm pushing 500W to it)

3. Where in the trunk you plan on placing this sub
Plan on making a rear-firing box. Want the back of the box to be up against the rear seats inside the trunk, perhaps even have a slanted back to the box.

4. Make and model of your subwoofer amplifier
Kenwood KAC-8105D (1000W max, 500W RMS @2 ohms)

5. Types of music you primarily listen to
Rap/Hip-Hop, Electronic/Dubstep/Trap/House/EDM/etc., music with heavy bass in the 25Hz-45Hz range

6. Primary goal for performance (Sound quality, SPL, best use of a box you already own, smallest box possible, etc.)
The box can be as big as is necessary, pure SPL for longer and heavier bass notes (rap&electronic bass) from around 25Hz-42Hz.

What do you guys think? Right now I'm looking at building a ported box of 6cu. ft tuned to 27Hz.

 

http://www.audiocontrol.com/t34/c298/1262/Support.html

There are two adjustments on the unit. One is by the RCAs that I believe is the "thresh hold" ****. This tells the unit when to start bringing the bass back, then there's the accubass **** that controls the volume you want to bring the bass up to. We use these all the time at our shop and it's nothing short of fantastic.

Is this before or after displacements? If it's after then this box will be HUGE. IMO too big for the sub as well as the trunk. I'd also tune slightly higher to around 29, 30 or a big higher yet. This will bring the box size down quite a bit because the port doesnt need to be nearly as long and will still be able to play the lows quite well.

 

^^^ what he said.

there is not need for a box this large.

it'd probably be more cost effective to get a different sub and save $ on MDF, time, trunk space, a huge amounts of weight in your new fuel economy ride.

 

Okay so I changed my schematics up a bit and now I'm looking at either a 4-5cu. ft box. The 4 drops below +0dB at around 30.5Hz tuned to 28Hz, the 5 drops below +0dB at around 28Hz tuned to 28Hz. Which one do you guys think? I will probably work with both 1/2 MDF and 3/4 MDF so the box is not as heavy. Here's the info:

Box type : Vented
Box size : 5.000 ft^3
Tuning frequency : 28.00 Hz
Vent : 1 vent(s)
5.54 in length for each
4.00 in round


Relative
Freq Gain SPL
[Hz] [dB] [dB]
20.00 -8.85 106.14
21.00 -7.51 107.48
22.00 -6.25 108.74
23.00 -5.06 109.93
24.00 -3.94 111.05
25.00 -2.88 112.11
26.00 -1.89 113.10
27.00 -0.96 114.03
28.00 -0.09 114.90
29.00 0.70 115.69
30.00 1.41 116.40
31.00 2.04 117.03
32.00 2.58 117.57
33.00 3.04 118.03
34.00 3.40 118.39
35.00 3.69 118.68
36.00 3.90 118.89
37.00 4.04 119.03
38.00 4.12 119.11
39.00 4.15 119.14
40.00 4.14 119.13
41.00 4.11 119.10
42.00 4.04 119.03
43.00 3.96 118.95
44.00 3.87 118.86
45.00 3.77 118.76
46.00 3.67 118.66
47.00 3.56 118.55
48.00 3.45 118.44
49.00 3.34 118.33
50.00 3.24 118.23

Number of drivers : 1
Box type : Vented
Box size : 4.000 ft^3
Tuning frequency : 28.00 Hz
Vent : 1 vent(s)
7.66 in length for each
4.00 in round


Relative
Freq Gain SPL
[Hz] [dB] [dB]
20.00 -9.68 105.31
21.00 -8.47 106.52
22.00 -7.33 107.66
23.00 -6.25 108.74
24.00 -5.24 109.75
25.00 -4.27 110.72
26.00 -3.35 111.64
27.00 -2.48 112.51
28.00 -1.65 113.34
29.00 -0.87 114.12
30.00 -0.15 114.84
31.00 0.53 115.52
32.00 1.14 116.13
33.00 1.69 116.68
34.00 2.18 117.17
35.00 2.60 117.59
36.00 2.96 117.95
37.00 3.25 118.24
38.00 3.48 118.47
39.00 3.65 118.64
40.00 3.78 118.77
41.00 3.86 118.85
42.00 3.90 118.89
43.00 3.91 118.90
44.00 3.89 118.88
45.00 3.85 118.84
46.00 3.80 118.79
47.00 3.73 118.72
48.00 3.66 118.65
49.00 3.58 118.57
50.00 3.49 118.48


As you can see, the 5cu. ft box shifts the low end just a tad bit lower and spikes a little harder right around 38-42Hz, but only by .3-.4dB. I'm starting to think that the 4cu. ft box might be the way to go, just not sure what to do.

Help

 

Model another couple at 3 and 3.5 as well. I wouldn't go any larger than 4. Also try a coupel tuned to 30/31 hz. Try using WinISD so you can compare graphs between boxes. The .5 DB will not be noticeable. However the weight and gas consumption will be.

 

Are you looking for rip your head off SPL or more for it to drop deeeeep. If the latter, I would give consideration to two 15s in an IB configuration.