Need help building a Fusion FEW-12 12" subwoofer box

DovydasSpec

Member
2016-05-20 12:16 pm
Hello. I have an old Fusion FEW-12 subwoofer and want to make an enclosure for it but have no experience in calculating sizes of the boxes :D . Subwoofer will be used in a car. Here is the link to the subwoofer and Thiele stats of it :

Subwoofer

Product Name: FEW-12 FUSION ENCOUNTER SUBWOOFER
VAS 100 L
QTS .343
QMS 4.155
QES .374
RMS Power 200 Watts
Peak Power 400 Watts
Sens (1W/1M) 91dB
Xmax (Pk to Pk) 22.5mm
Xmax (1 way) 11mm
Freq. Response 23Hz - 3KHz
Fs 27Hz
Voice Coil 2" Kapton SVC
Impedence 4 Ω
Mounting Diameter: 10.09" / 277mm
Mounting Depth: 5.02" / 127.5mm
Outside Diameter: 12.24" / 311mm

The box should be closed or ported?

Also, does the Kenwood KAC-821 amp have enough juice to power the subwoofer?

I would be very thankful if you could help me with this project :)
 

DovydasSpec

Member
2016-05-20 12:16 pm
I tried to use WinISD but as I said I dont have any experience calculating the size of the boxes or using the program :D

What size of the box do you think is big? Around 60 or 100-120 liters? Because I have read on other forum that 120 liters is mostly used for 2 12" subs but when I calculate using the program, I get that around 100 liters should be pretty good for me, unless I am doing something stupid and going over the top with the size.

So what do you think, 100, 80 or 60 liters should be enough?

Edit: adding images of the program. Thought could be useful for you :)

IMAGES
 
Last edited:
For normal use, you want to aim for a frequency response that's pretty much flat down to however low you want the bass to go.

In a car, its better to aim for a sloping down response (ie, 20Hz is quieter than 100Hz), as cabin gain tends to really boost the bottom end. Sealed boxes tend to match this quite well with minimal work.

Ported boxes will go louder around the port tuning, but need to be protected from signals below port tuning, as you can easily damage drivers by driving them too low. Not a problem in sealed boxes.

Chris
 

Lunchietey

Member
2009-07-06 11:11 am
I had four in a giant flat reflex box at the rear of a van many years ago in 180L tuned to 38hz. I wanted a bit of a bump and used a variable highpass at 38hz with a q of 2 to boost output at tuning(because the woofers could take a lot of power at that frequency).

They have poor xmax(cone travel) but with the above design I could feed 1.2kw to them all day and flex the steel sides of the undamped van around 20mm. Was making a comfortable 145db at 40 hz or so when driven by old Orion HCCA amps. Stupidly loud but you won't get much more(deeper) from them any other way unless you only use low power.
 
Inside a car, you're going to have the acoustics of the car far overshadowing your box. Just build a smallish box and give it a 7cm diameter port about 25cm long. I currently have a 10" in a box about 27 litres and a tiny port about 5cm diameter and 20cm long, and it absolutely thunders. You could even mount it on the dividing wall between the boot and the cabin (but that requires some cutting of the car itself).

If you want a decently designed box, you can go with 52 litres (35 x 35 x 44 cm internal = 54 litres - 1L for the port and some for the driver = ~52L), and the 7cm port I mentioned above, and you should have big bass (box will take you to 30Hz at -6dB). Tune your amplifier's LPF to the minimum if the rest of your sound does a good job handling >80Hz. And then play with the phase!

And then what Chris said about damaging the driver below port frequencies - but if your driver can take the power, then it shouldn't be a problem. Anyway, a ported box will in most cases be much more efficient.