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Ben Building

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  1. If you need a lower tuning, you will need to make the port incrementally longer. If you can't squeeze the port length you need into the space you have, then you have to go with a smaller port. The 16-18 in2/cf thing is just a guide; use it to get yourself into the ballpark. Feel free to diverge from the formula when you are able to mitigate losses from area reduction.

    Keep in mind that your port shape has a lot to do with how well the port resists pressure loss. The box shown above for the HC3 sub has a slot port that is rectangular in shape. The rectangular/slot port shape creates more pressure loss than either square or round ports of the same port area because it has more surface area inside the port.

    Do the math:

    For a Rectangular Port that is 18" x 4." For our example port, we will make it 10 inches long. That port has 72 square inches of area (a =l x w = 18 x 4 = 72). The perimeter of this port is 44 inches (P = s+s+s+s = 18+4+18+4 = 44). Since the port is 10" long with a perimeter of 44 inches, it has a total of 440 square inches of surface area inside the port.

    For a Square Port that is 8.5"(W) x 8.5"(H), we know that the port has 72.25 square inches of port area (8.5 x 8.5 = 72.25). Even with more port area than the Slot Port, the Perimeter of the Square Port at 34 inches, however, is much less than that of the Slot Port (P = 8.5 + 8.5 + 8.5 + 8.5 = 34). The Square Port thus has an internal surface area of 340 square inches; 100 square inches less than the Slot Port.

    A Round Port that is 9.6 inches across has an area of 72.35 square inches, more than either the Slot or Square ports above. Nevertheless, it has a Circumference of 30.14 inches (C=2(pie)r = (2)(3.14)(4.8) = 30.14. Thus, at 10 inches in length, our Round Port has 301.4 square inches of surface area inside the port; less than either the Slot or Square ports. Actually, the Round Port may be demonstrated to have 31.5% less surface area than the Slot Port.

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  3. I would make a left turn, a right turn, a right and another left. Any car behind me would have had to make 4 turns behind me just to get back on the same road in the same direction. If you think you are being followed, it is not advisable to let on that you know immediately.

    If you are alone and unarmed, do not even think of confronting anybody following you. There are many ways to lose people in other cars including classics such as:

    The Red Light Trick: Wait until there is another car between your car and the one following you and simply (but SAFELY) run a red light. The middle car will block your bad guys for a while, giving you time to take evasive action before they can follow.

    The U-Turn Trick: Make a sudden (but SAFE) U-Turn, timing traffic so as not to allow time for a second car to do the same.

    The 911 Trick: Assuming someone wants to kill or rob you and you can't get away, keep driving and call people with guns.

    The Homeboy Trick: Drive as normal until you pull into the dead end street where your allies are waiting with small arms.

  4. not true. maybe not quite as deep as a box with less port area, but my box has about 16 sq inches of port like this one and almost the same tuning...and mine gets plenty deep

    measure down the middle of the port to get port length. if you do it the way you say, measuring on the outer walls would be much longer. so measuring down the middle of the port will get you correct numbers

    a 45 in the vent would be nice. bracing i say is always a good idea. but 45's in the box arent as necessary

    Your box looks much better with the corner added.

    If you tune your box to 36 hertz, then the port will unload on notes deeper than that. "Unloading" means your port acts more like a giant hole in the enclosure instead of an output-augmenting device. Below tuning, response rolls off at up to 18 db/octave and the woofer sees no mechanical resistance from the port. It just plays in free-air. On music, there is no-telling what kind of note the sub will get thrown at it. It is better to design an enclosure that plays ALL the notes and not just the higher ones.

    Don't listen to this guy^^. Tune deeper, even if you have to increase overall size a little bit.

  5. Why not change the tuning on your current box? What kind of port do you have, round or square?

    To lower the tuning of an enclosure of a given volume, you would need to add length (air mass) to the port. The design and shape of your current port will determine whether this is even practical, but extending the port is a viable option if you don't want to rebuild the whole box right now.

  6. A port on the side of the box will sound great provided you give the port enough room to flow.

    The reason a side port works well is that you get a little extra "bump" from the side of the truck pushing back against the port. Some guys swear by the port on the driver's side, but I think you need to play with in you truck a little bit for best results.

  7. If you plan on using a lot of power (BTLs) you shouldn't use L-shaped ports at all. The reason for this is that, at higher port pressure/velocity that comes with extreme power, it is simply too hard for the air to move around that 90 degree bend. Imagine water trying to vibrate back and forth around a 90 degree bend. It will play, of course; but you will sacrifice efficiency over a straight(er) port. Try to use a true 45 if you must bend the port.

    As far as port shapes go, a round port is more efficient than one with corners (square, rectangle, etc.) because it has less internal surface area than a 4-sided port of the same area. This means less friction (heat) that your subs have to overcome. For similar reasons, a square port is better than a rectangular one because it has less internal surface area. If you have to use a 4-sided port, try and make it a square as opposed to a slot/retangle.

    Hope this helps you. :hairtrick:

  8. I was just curious as to what SMD are Mechanical Engineers (or ME students). Other techs or engineers feel free to chime in too! :drinks:

    In working on a new port design, the question of boundary layer separation in smooth pipes (aka Ports :hairtrick: ) in the presence of 90, 45, and 0 degree bends came up. Due to the diffuculty of calculating seperating/ divergent flows; I was contemplating an experiment postulating the connection between the reynold's numbers at different phases of subwoofer stroke to the total head losses for the system. Also, as a logical tangent, it would be interesting to see the connection between velocity and the Reynolds numbers present in transient, turbulent flow.

    Basically, I am looking for a way to reduce port pressure losses in space-limited environments when port bends are unavoidable.

  9. Where are you thinking of locating the controls? There is nothing stopping you from making any layout you want if you have enough time and patience.

    As for moving the controls, like any mobile electronics install, the first thing you need to know is where you plan to locate your physical components. This is so you know how long make your wires.

    Those AC harnesses don't come with a lot of extra wire, so you will likely need to extend it. Simply cut the harnesses and solder wire for wire on them to your new AC control location.

    The vents can be re-constructed relatively with good ol' fashioned Dremel, cardboard, and duct tape patience. If you relocate them up high, it will clear that middle space out and stilll look semi-factory. Have you sketched out what look you intend to acheive?

  10. actually im kinda looking around for a couple 10" or 12" RE SE's.... and 12's or smaller because the tacoma has a shallow bed... its 14" from the bed floor to the bottom of the rail.... i know a guy that has a couple 10" se's for sale but i havent been able to get ahold of him today...

    man scottiej's offer keeps burning my skull...lol... i could use an upgrade on my highs stage.. but i kinda want to focus on the things that i dont have yet...

    What if you designed the box to carry the sub face up or down?

    Did I mention that my sub comes with a FREE 4th order box design? Can you get some actual dimensions?

  11. A new 2009 RE Audio SEX 15 would be perfect on that amp.

    Did I mention that I happen to have a brand new one? :01nocomment8so:

    Seriously though, I know it is a conflict of interest, but the RE 15 would sound great in the right box. Is there a particular reason you wanted to stick to 12s or smaller?

  12. You should take a look at the Chevy HHR if space, fuel efficiency, and price are your main considerations. The car has a funky shape for a reason you would understand by looking inside. It is extremely good on gas and can be found for cheap.

    The Toyota Scion Xb is also a good choice for similar reasons, but is a little more expensive than the HHR.

    Besides that, both little cars take bass like champs!! :hairtrick: vs. :hairtrick:

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