15" Mofo Enclosure

[theCybe 5,000+ posts]

My MOFO should be here tomorrow.

PA recommends 3.5 @ 40 - I say blasphemy, I want 33hz.

Should I be adjusting the volume?

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[Goldtaz1 10+ year member]

Manufacturer recommendations are just that; Recommendations. You can build your box (within reason) to almost whatever you feel like. I'm not saying to try to build a ported enclosure for a 15" driver with only 2 cubic foot, but you could use their recommendation of 3.5 cubes and tune your box to 33 Hz. Besides, 40 Hz and higher is almost getting to the point of straight SPL rather than daily music listening. A good musical tuning is usually between 30 and 35 Hz. Just remember net cubic volume and tuning greatly detertermine power handling of the woofer.

 

[theCybe 5,000+ posts]

[ blink, blink. ]

 

[Goldtaz1 10+ year member]

Does that mean you did not understand my comment?

 

[skeptikal Premium Member]

those things will handle whatever power you plan to throw at it as long as you gain it correctly. dave's got his in 4.5 cubes each @ 36Hz (iirc) and gots an a3000db on each one.

 

[theCybe 5,000+ posts]

Well, my condition is this.

The maximum outer dimensions for a box that I can actually fit through the trunk opening are:

35 x 13 x 19.

I already have such a box, and it's sealed.

We'll call it 4 cubes after bracing and the woofer's displacement;

The box also has two 3" diameter holes, for ports.

How long should the ports be for 30hz? 35? 40?

That's my dilemna.

the12volt.com reports a portlength of just over three inches, for a single 3" diameter port.

I realize the ports will eat up some of the box volume, which is fine by me - the manufacturer suggests a 3.4 cube, tuned to 40Hz; Their port information is something like two 3" dia ports @ ~10 inches.

the12volt.com's calculator reports a single 3" port at only .75 inches for 40Hz; Which is equal to the depth of the wood;

What am I missing?

How long should each port be, to achieve 30-35 Hz?

 

[req 5,000+ posts]

WAY more port cross sectional area. take the SD of the woofer, cut it in half. thats roughly what you wanna shoot for if you can.

what are the specs of the mofo 15. i will be building one at porlly like 36hz for it because its a 60\40 install.

 

[theCybe 5,000+ posts]

I misread; PA's recommendations are for two 4 inch ports at 8.25" each.

So given a box volume of 4 cubes after driver displacement, how's 1.5x13.5x11 for a slotport?

The specs are available at http://www.poweracoustik.com/SUPPORT/wooferspecs/PAWooferSpecs2003_pg2.html