I was gonna build a box like this for my 15L7. Its gonna be 3.0 cu ft ported to 48hz. I have 2 L7s but I want to build 2 boxes for them. This design works the best for fit in my car. but i want to know if this design sounds like crap before I do it.
Not to start a battle....but I have a bit of a physics background as well. Though your point about even distrobution is well taken, I disagree that a port is not intended to move air. With your physics background I am sure you understand that the port is simply a open ended tube with a fixed length. Given the fixed demension, you also understand that only a limited number a frequencies are able to resonate at that length (more than one because of first, second third harmonics /resonate frequencies. Since we know that only a few out of the hundreds of frequencies have a potential to resonate, I find it hard to belive that soooo many people would see increases in spl over a range of frequencies if the port was not also intended to move air through it. Thought i need bit more time to think about it, most manufacteres suggest the port be firing paralell with the driver. Now if you point about even distrobution is correct (and it very well may be), this person could fix that by simply bending the port inside the box, correct? Please correct me if I made a mistake in my logic, again not trying start a battle, just having a civl discution.Originally posted by SPLThunder The rule of thumb is based on the physics of the pressure that sound waves create. You dont want the head on pressure from a cone pushing directly into the port. It will not have distributed evenly inside the box. You are also more likely to get air moving in and out of the port Which we all know is not what a port is used for. Air inside the port is just suppose to resonate. In fact if you had a perfect port you shouldnt be able to feel and air move in or out at all.
When a port is aimed in a different direction than the cone the pressure should have (i say should based on design) distributed itself through the whole box first which is why we make the boxes a certian size.
Agreeed, We use a port pretty much to hear the back side of the cone as well as the front. Generally a 3db gain is achieved from just having a port. Wave dynamics is not my thing. I am more interested in electrical engineering. (by the way i am a physics undergrad) However from the professors i have talked to this seems to be my conclusion. When a frequency resonates it becomes very loud in a port however dont you still hear other frequencies even if they arent at a certian harmonic. If a port is tuned to 30HZ the longest wave to resonate will be 30 hz. You will still hear (just not as loud) higher than that even if the end doesnt catch on a node or antinode of the wave.Originally posted by evo2k3 Not to start a battle....but I have a bit of a physics background as well. Though your point about even distrobution is well taken, I disagree that a port is not intended to move air. With your physics background I am sure you understand that the port is simply a open ended tube with a fixed length. Given the fixed demension, you also understand that only a limited number a frequencies are able to resonate at that length (more than one because of first, second third harmonics /resonate frequencies. Since we know that only a few out of the hundreds of frequencies have a potential to resonate, I find it hard to belive that soooo many people would see increases in spl over a range of frequencies if the port was not also intended to move air through it. Thought i need bit more time to think about it, most manufacteres suggest the port be firing paralell with the driver. Now if you point about even distrobution is correct (and it very well may be), this person could fix that by simply bending the port inside the box, correct? Please correct me if I made a mistake in my logic, again not trying start a battle, just having a civl discution.