port placement

is it ok to build my port to fire in the opposite direction of my subs?in other words in the back of my box.

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THE JEFF RETURNS

Yes it's perfectly fine to do that.  That issue is far down on the priorities checklist.  Issues that rank above it in importance include:  the right combination of box air space and port air space; a large enough port opening; a straight vs. multi-turned port structure; space at both ends of the port of at least the diameter of the port; the firing direction of the driver re: the car's acoustics; phase matching of the sub to the rest of the system; a well-constructed and braced box...and more.  But make sure both the driver and port fire into the same general air space, such as both into the trunk...not something like driver into the trunk cavity and port into the cabin.

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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

Thanks Stevdart for confirming why I like building sealed .


oh yeah.. the qualitys good too

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99 Blazer LT.   Yellow Top. Big 3. Infinity Kappa Speakers All Around. Jensen CD/DVD flip out. 2 Infinity Kappa Perfect 12DVQs powered by a Alpine PDX600.1 (in one custom box, building a FG box)

Stevdart, what is the difference of having the driver and port fire into the different air spaces? & Does the port have to be completely inside of the box? or can it stick out of the box. For example, Can 5 inches of a 9 inch port be outside of the box?

Thanx

A trunk, a room, a cab of a truck...all have a common airspace.  When the port produces sound, which it will at various degrees throughout most of the freq range, that sound needs to blend with the sound coming directly from the driver itself.  It's the same way, in a manner of speaking, that the sound from a sealed box blends with the sound of the driver.  The total sound is a blend of driver and box sounds.  If one were to purposely port the vented box through the rear parcel shelf while the driver fired into the trunk cavity, he would hear the sound from the port at a different time and db level than it should be.  But if both driver and port fired into the trunk cavity, he would hear the result of the mixture of sound...even if the port were open to the rear of the box.

The way to open up the trunk to the cabin with a ported box in the trunk is the same way  you'd do it with a sealed box.  Fashion a hole, or large opening, through the parcel shelf or seat back.

A port can extend from the box, yes.  There are often ways that one could have avoided having such a long port, though.  Usually, it's using too small of an airspace for the driver which resulted in an overly long port, or it's porting a driver that would probably have been better off used in a sealed box.  In car audio installation, customization to fit the vehicle is a primary concern.  One may have just enough space in the car to design a box but with the added displacement of the port it becomes too huge for the space.  In a case like that he could extend the port from the box and fit the contours of the car better without compromising the amount of airspace he wants in the box itself.  It's important to leave an amount of free airspace on both ends of the physical port structure, shown below in red.  Those spaces are actually part of the acoustical port properties (don't end your port opening against a wall).

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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

The reason for the prot sticking out of the box is not an airspace issue. It is the right amount of airspace. The reason is for the looks of the box. Here is a picture of what I'm planning on my box. The amp will be flush mounted on top of the box which is where the ports will be facing.

Creative.  Looks like a nice design.

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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.