Why place the enclosure facing backwards ?

[gstokes]

Everything i have read says to place the enclosure firing backwards in the vehicle, this defies logic for me because you are creating delay, does this apply to both sealed and ported or just one in particular ?

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[Beatin' 10+ year member]

cancellation is the issue. Subs should always face away from the cabin. Preferably right up against the trunk lid/door, but not so close that the cone hits the trunk during play.

If you want the subs facing the cabin, they have to be sealed off from the trunk as to not allow air flow between the trunk and cabin.

 

[gstokes]

cancellation is the issue. Subs should always face away from the cabin. Preferably right up against the trunk lid/door' date=' but not so close that the cone hits the trunk during play.
If you want the subs facing the cabin, they have to be sealed off from the trunk as to not allow air flow between the trunk and cabin.[/quote']

Ah hah, my vehicle is a full size van and the subs are on the floor facing forward about 6ft behind the front seats, am i doing it right ?

 

[Beatin' 10+ year member]

Ah hah, my vehicle is a full size van and the subs are on the floor facing forward about 6ft behind the front seats, am i doing it right ?

try different positions in the trunk area of the van and see which position gives the most output. I'm particularly interested in what happens if you put it in the corner with the sub facing the trunk door. //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

 

[T3mpest 10+ year member]

Everything i have read says to place the enclosure firing backwards in the vehicle, this defies logic for me because you are creating delay, does this apply to both sealed and ported or just one in particular ?

The key is that your actually increasing delay, but it's all the same delay.. Subwoofer waves are very long, 40 feet in some cases, as you approach 20hz or so.. A soundwave will bend around any object that is smaller than the wavelength. This is why bass carries so well, it's longer wavelengths allow it to bend around most obects. This also means when you fire a subwoofer, the waves go not only the way you'd expect, but they also bend backwards behind the enclosure. If you face your woofer into your cabin and close to you, then the waves are also bending behind, travelling to the back of the car and then finally going forwards again once they have no choice. This makes that part of the soundwave very delayed vs the inital wave that was "aimed" at you.. Beacuse of this you'll get a null in your upper bass where the wavelengths are shorter. By placing the sub facing rear and very close to the back of the car, the waves that are aimed at the back and reflect off aren't that far out of phase vs the wave that bends behind and immediately go forward, it's only off by depth of your box, more or less, that pushes the null up much higher in frequency.

If that doesn't make sense, look at your avatar. imagine the blue wave facing the other direction, that is the wave that isn't reflecting off the trunk and heading towards you.. If you want the red wave that goes the wrong direction to stay in phase with that, it needs to hit a barrier and start heading the right direction, as fast as possible.

 

[fatboytyler]

Its also really cabin dependent. My subs face and fire up. My buddies car had the subs facing the front with the port facing the side of the vehicle next to the trunk. Like its been said, experiment around.

 

[gstokes]

outstanding explanation that has me convinced i need to turn the enclosure around and slide it ALL the way to the back so it reflects off the back doors, many thanks for putting it in a language i can understand..

 

[T3mpest 10+ year member]

outstanding explanation that has me convinced i need to turn the enclosure around and slide it ALL the way to the back so it reflects off the back doors, many thanks for putting it in a language i can understand..

That is most of the time, the best way to do things.. The other option is to fire forward, but seal off everything behind the woofer, so the wave has no choice but to go the right direction. This cuts down on rattle and is generally more or less as loud as rear firing (some cases more some cases a bit less) BUT is a pita to do.. For a daily driver it's much easier to rear fire and deaden the trunk as needed.