Help: Sealed vs Ported vs Passive [Graph Included]

[okazar]

Hey guys,

I'm just about to enter the world of DIY subwoofers because my friend is providing me with 2 JL 12" W3V3-4ohm cones to use those woofers in a Home Theater application.

I've attempted at doing as much research possible and I've come up with 3 scenarios but cannot decide which route to go. When plotting these graphs a couple of inconsistencies came up (or phenomenons which I cannot describe).

A) The port for the vent seem either too big/too small
B) The passive cone has a hump @ 16hz

Could anyone provide me with any insights as to which way to go? The passive radiator will be the Dayton 12" Reference PR.

Please and thank you!

An externally hosted image should be here but it was not working when we last tested it.

 

[chris661]

Qts of 0.44 means you'll need to go for a fairly large ported (or passive radiator) box, or a smallish sealed box.

A pair of sealed 12"s can move a useful amount of air, but that's very dependent on your requirements for this build.

Chris

 

[Sonce]

A) The port for the vent seem either too big/too small
B) The passive cone has a hump @ 16hz

Could anyone provide me with any insights as to which way to go?

A) Port long 28.74 cm is not too big. Diameter of 10.2 cm looks OK, too.
B. Actually, there is a dip at 20 Hz - that is normal for a Passive Radiator box.

Designing good PR box require more effort and knowledge than simple bass-reflex box. Besides own resonant frequency (which can be tuned with different weights), compliance of the PR (which can't be tuned) affect the overall frequency response. If this is your first sub building, make simple bass-reflex enclosure.

 

[GM]

A) Port long 28.74 cm is not too big. Diameter of 10.2 cm looks OK, too.

Designing good PR box require more effort and knowledge than simple bass-reflex box.

Hmm, at what frequency/power? At 500 W, HR calcs a vent mach peaking at 80+ m/s and ~35 Hz/17+ m/s, so as long as his music is rolling off below ~40 Hz will it likely be OK.

Right, a 12" driver needs at least a 15" PR and preferably dual 12" with a high Xmax driver, so need to either buy more parts or skip the PR.

GM

 

[Sonce]

Hmm, at what frequency/power? At 500 W, HR calcs a vent mach peaking at 80+ m/s and ~35 Hz/17+ m/s, so as long as his music is rolling off below ~40 Hz will it likely be OK.

Agreed, with 500 W air velocity is high, so bigger tube diameter is better. Tube will be long, so 90-deg. "elbow" is a must for fitting the tube inside the enclosure.

 

[whgeiger]

For an at home venue, a servo controlled driver in a sealed box yeilds a small footprint subwoofer that delivers superior performance, particularly when three such units are used. WHG
For example see Rythmikaudio.com