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whats the ideal setup for (2) JL 12W0? trunk space is no concern. my buddy at the car shop has suggested to wedge them inward in a ported box similar to the factory JL boxes. justified it with somethin about the acoustics making a 'cone' to hit a little harder than just front firing or whatever.

should i point the box, if your design provides for it, toward the back seat or away from it?

since styles of music determine somewhat box design, i want it to perform best with rock with tight hits, but still be able to sink low for rap. a happy medium i suppose. forgive me if im wrong, but i think sealed is best for rock and ported for rap. suggestions made to me are too unclear. thanx in advance.

 
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If you're building it, go to JL's site and build it to the specs they provide. If you're buying it, buy one of the JL Power wedge premade boxes. Oh, and the box that you're describing, if I'm thinking of the right JL box is a bandpass box. I'd probably go with either slot ported or sealed.

 
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And if you are building it, the specs JL give will probably have a range for volume. Stay to the lower side for rock and the higher side for rap for the most part. IF someone without a lot of experience is building the box, stay with a sealed box anyway.

 
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Personally I like to use a lot of port area. Some say match the surface area (cross section) of your port and cone area. For example, if your woofers combined have 250 sq. in. of surface area, design a port that has 250 sq. in. of surface area and play with the port length to achieve the desired tuning.

One trick I like to use to make a really solid box is to put a rectangular port between the woofers that runs from the top to bottom of the box and as far back as possible so that you can screw the top and bottom into it to create a massive brace.

Other than that, it's really up to you to decide how you want it to sound and whether you want it optimized for sound quality or SPL. But space wise, sticking to the manufacturers spec is a good idea, they tend to know best.

 
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Like that?

 
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Exactly! Isn't it a wicked technique?

 
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Designing a ported a.k.a. vented enclosure will not only give you added output, but can give you more low-frequency extension. This means louder and lower! Since the speaker system is the least efficient part of the whole audio chain, would it not make sense to make it as efficient as possible? Of coarse it does.

This is why venting is basically free output, and free sound quality. Local shops tell you that a small sealed box is the best way to go? Hit up your local hi-end home audio store and find out how many of those $20,000.00 pairs of speakers are sealed designs. You won't find many. This is why i personally never go with a small sealed enclosure.

Think of a box port not as a vent in the terms of a venting path for air to travel into and out of a box, but rather as extra cone area that is propagating acoustic energy from the enclosure to the cabin. The air in a port is fixed; it is trapped within the confines of the port walls. When the cone moves there is a corresponding change to the pressure in the box, that pressure change then causes the trapped air in the port to move either forward or backward. It moves as a solid unit, just like a speaker cone does.

Passive radiator and a vented port work on the same theory. When a port mass moves back and forth, a pressure wave (sound wave) is sent into the cabin. The larger the port, the larger the radiating area is that creates the pressure. Tuning a port is tuning the mass of the trapped air in the port to the air mass in the box volume.

For all out no holds barred SPL efficiency, rule of thumb is the larger the box, the higher the output. The larger the box, the larger the ports can be for a given frequency tuning range. There is no substitute for cubic inches.
The port area must be commensurate with cone area. If the port velocity gets too high, the port no longer functions as a port, you end up with a leaky sealed box, double bad.

Lets say we have a 12 inch speaker in a box, roughly 100 sq inches of surface area. Many programs and manufacturer sites will suggest a 4" diameter port for a 12" vented box. A 4" diameter port has about 12 sq inches of area. This is about an 8-1 ratio of cone area to port area. If the 12 inch cone moves 0.25", the port *Edit* AIR must move 2.0". It can handle this, but when the cone is moving 1.0", the port *Edit* AIR must move 8 inches! Now you've got a leaky sealed box.

You need more port area for a clean sounding, high output system. The best port formula is this: 16 sq inches of port area per cubic foot of box volume. The port should be 13 inches long. Remember, the port is tuned to the box volume, not the sub(s). This rule of thumb will tune your box if it were in an open area to 45hz but with the small size and air pressure load of the interior space of a vehicle effectively tuning your box down to 30-35hz which is lower than most all cd's (except for specifically made bass cd's) play down to.

Hope this helps

PS i'm going to make a separate post for all to read since most people dont know how to properly port.

 
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editI'm sure for an SPL competition thats ok but a bit large for an actual ported box for most subs under daily driving conditions. Unless you have an ungodly huge box or a VERY long port your tuning frequency will be very high.

When you tune to a high frequency it will play that requency just fine and frequencies above that ok also, but your sub will lose efficency dramastically below that point. I'm sure MHZ know this but for all you rookies

 
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maybe its just me but when did ports start moving?

 
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smart

good catch i'll edit it.