Home sub DIY

Hi there,

Can anyone advise me on the correct sealed internal volume for my sub Im building?? Im using it mainly for music but 30% HT too. I like a flat response down to -3db @ 30 to 35ish Hz. Any advice would be so much appreciated ;-)),

Driver: JL Audio 12w0-4 12"
Fs 22.1
Qts .430
Qes .451
Qms 8.974
Vas 160L or 5.65ft
Xmax 8.6mm
Efficiency 87.9Db
Sd .0531 m2
Re 3.86 ohm
Nominal Impedance 4ohm
Power handling 125w

Amp used BK 300wRMS @ 4ohm

Room size 65m3

I love building sub enclosures but I'm not too good at the design, At the moment im using the winISD software but it does not have any excursion/thermal graphs, So far I have determined a volume of 2.2 cu.ft. with a Qtc of .80 but I don't know if the driver will over excurt or burn out first with my chosen amp power. It takes a while to start understanding box design :-(

Any help much appreciated!!

Stewart.
 
Hi,

Since it's also for HT, a ported box is what I'd build, especially with such a driver with only 8mm Xmax. 140l tuned to 18Hz should provide satisfying results (use flared ports). If you want to go sealed, a 70l box would be a good starting point and it would give an f3 of 35Hz - 40Hz (anechoic), which would most probably extend down to your requirement of -3dB at 30Hz in-room.

Anyway, these are just (very) quick simulations... try some numbers with UNIBOX, which you can find at http://www.pvconsultants.com/audio/frdgroup.htm UNIBOX will give a lot more information compared to winISD.

Good luck! :)

Isaac
 
Unless you're willing to have a signifigantly larger enclosure than 2.2 cu ft a ported enclosure is unlikely to yield response superior to a sealed woofer. Usable extension starts at about 3 cu ft ported. And as usual, the bigger, the deeper the bass. Group delay is going to get very high with larger ported enclosures.

Personally, I'd use a 3.3 cu ft sealed enclosure and extend the bass slightly with something like a 3dB shelving boost at 30Hz. Sealed subwoofers always offer cleaner bass, but generally lose out in the very low frequency response without signifigant equalization. A ported enclosure will certainly be more efficient.
 
#2 is here.

f4ier said:
You're welcome :)

But unless it was measured by DUMAX, I'd still get a second opinion :)

Good luck!

isaac

one should be cautious, but if you're running music and not 10hz - 30hz sweeps, you'll likely be okay. (just ease into your favorite DVD passages- don't blow it at the first bombblast)

but i put 250-300 watts RMS into a 10w0 from a Zapco Competition (Z series) amp. It took it all day long. (sealed enclosure)

Granted, there was compression and the volume did not increase significantly over the 150 Aura Watts, nor much past the the 130 Zapco watts (another amp). the W0 handled it all fine.