sherwiboy gp Posted June 25, 2015 Report Posted June 25, 2015 hi guys i am sherwin from south africa and i am very involved in the sound scene here i just need some help when it comes to designing the octo port box as i want to attempt building one up this weekend for a single 15" subwoofer i have looked at a lot of pictures and watched videos relating to the box and also worked out the measurments taking in to consideration what amount of volume my woofer likes to play in but i am having a hard time calculating the port length i just wanted to find out if i am on the right path so far my box will be 450mm all around and i will be using a 160mm pvc pipe as the port but i want to tune the box high for spl looking at 57hz as thats my cars frequency what i need to know is does the port lenght work the same as a normal spl box were the shorter the port the higher the frquency response?
bigmizzle99 Posted June 25, 2015 Report Posted June 25, 2015 Your post is a little confusing.. You first mention "octo port", which to me means an 8-sided wooden port, then you say you're going to use 160mm PVC pipe. If you are using PVC pipe, its not an octo port. I also don't understand the statement "... the same as a normal spl box.... ". However, if the question is does a shorter port length tune a box higher, then I will say yes it does. Typically, when using tools like Bass Box and Torres, for a given port diameter, as you lengthen the port, the tuning frequency will be lowered. Camaro SS Build Altima build 2.0 Altima build 1.0
Joe X Posted June 25, 2015 Report Posted June 25, 2015 In any case a single 6" round port will be low port area for a 15" SPL woofer specially at that very high tuning.
sherwiboy gp Posted June 26, 2015 Author Report Posted June 26, 2015 hi guys thank you for the input appreciate it hi Joe i am going to be using a street series subwoofer and not my spl woofer in the box and my current box has a 6" round port and i average a 147dbs as 57hz with that setup this is why i was thinking that the same port size would be fine. please let me know what your sugesstions are for the box plan as i will be competing with the box next weekend at db drags
Joe X Posted June 26, 2015 Report Posted June 26, 2015 A 45x45x45 box (18mm wood) will be ~2,3 cubic feet inside if the driver displacement is 0.2 cubic feet, a 54Hz tuning will have the box peaking at 57Hz, to do that, assuming the internal diameter of the port is 6"(15.24 cm) a FULLY external port would need to be 17.25 centimeters long to achieve that tuning, usually you start cutting it a bit longer than 17,25 and once built, test and then take out a little length and test again, keep doing this until it stops getting louder.
sherwiboy gp Posted June 29, 2015 Author Report Posted June 29, 2015 thank you joe we did a few tests with the box this weekend and i was amazed at its frequency range it sounds deep and very solid being the 1st time i tried the design out. i will get the port length to what you have given me and will test it out before the show thank you for your assistance much appreciated
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