germanyt Posted August 5, 2015 Report Posted August 5, 2015 I'm trying to calculate port length for the front chamber of a 4th order. My net volume is almost dead on 15 cubic feet assuming I allow .5 cubes worth of the port to say inside the box (rest will be external). I've used 3 different calculators and done the math myself and none are the same and all are giving me negative numbers. Trying to get 48hz in 15 cubic feet with 224 sq in of port area. What am I doing wrong? Current Setup : Nothing2014 Ford Focus SE Hatch Future looking like: Singer / XS power Crescendo BC3500D CT EXO 15 Pioneer 80PRS CDT HD-61PRO CT Sounds M75.4 CT Sounds AT60.4 Something along those lines.
Triticum Agricolam Posted August 5, 2015 Report Posted August 5, 2015 Basically you can't tune that high with that combination of net volume and port area. You need to increase your port area, which is probably a good thing anyway, or decrease your net volume. Weren't you looking at 12 cubes for the ported side on this box anyway? "Nothing prevents people from knowing the truth more than the belief they already know it.""Making bass is easy, making music is the hard part."Builds:
germanyt Posted August 5, 2015 Author Report Posted August 5, 2015 Basically you can't tune that high with that combination of net volume and port area. You need to increase your port area, which is probably a good thing anyway, or decrease your net volume. Weren't you looking at 12 cubes for the ported side on this box anyway? I've done several drawings and am now on 4.97 sealed and 15 ported. I was using 15sq in port per cube. How much is too much? I know port velocity is key but don't know how to figure it. Current Setup : Nothing2014 Ford Focus SE Hatch Future looking like: Singer / XS power Crescendo BC3500D CT EXO 15 Pioneer 80PRS CDT HD-61PRO CT Sounds M75.4 CT Sounds AT60.4 Something along those lines.
germanyt Posted August 5, 2015 Author Report Posted August 5, 2015 Wow just adding 15 sq inches of area lengthened the port to nearly 6 inches. Current Setup : Nothing2014 Ford Focus SE Hatch Future looking like: Singer / XS power Crescendo BC3500D CT EXO 15 Pioneer 80PRS CDT HD-61PRO CT Sounds M75.4 CT Sounds AT60.4 Something along those lines.
germanyt Posted August 5, 2015 Author Report Posted August 5, 2015 Back to frustration. Math gives me 1.22 inches port length. Online calculator says 6.69 inch for same. The site I'm getting the formula from says 8.76 inches. edit. Found a thread on accuracy of online calculators. Apparently 12 volt matches up to within 1% of Winisd and mobileinformationlabs also matches it. Seems to be the most reliable source and in line with what I was expecting the length to be for that frequency. Current Setup : Nothing2014 Ford Focus SE Hatch Future looking like: Singer / XS power Crescendo BC3500D CT EXO 15 Pioneer 80PRS CDT HD-61PRO CT Sounds M75.4 CT Sounds AT60.4 Something along those lines.
Triticum Agricolam Posted August 5, 2015 Report Posted August 5, 2015 Port area per cube rules are dumb and really don't apply to bandpass boxes. They don't take any consideration for how much power you are going to run. How much power is going to be used for this box? With that info I can give you a suggestion for appropriate port area. FYI, it's really, really hard to have too much port area, especially with bandpass boxes. Different port calculators are going to give you different numbers. Its not an exact science unfortunately. I would suggest making the port long, testing it out, and then trimming down to get the tuning where you want. It would really help you to use WinISD so you can see what effect design changes have. "Nothing prevents people from knowing the truth more than the belief they already know it.""Making bass is easy, making music is the hard part."Builds:
germanyt Posted August 5, 2015 Author Report Posted August 5, 2015 Port area per cube rules are dumb and really don't apply to bandpass boxes. They don't take any consideration for how much power you are going to run. How much power is going to be used for this box? With that info I can give you a suggestion for appropriate port area. FYI, it's really, really hard to have too much port area, especially with bandpass boxes. Different port calculators are going to give you different numbers. Its not an exact science unfortunately. I would suggest making the port long, testing it out, and then trimming down to get the tuning where you want. It would really help you to use WinISD so you can see what effect design changes have. Power is coming from an Audiopipe 3000 with sufficient electrical. Maybe 13.5 volts. I imagine it's getting 2500 to the subs. Yea I wish I had these programs but since I haven't had my own setup in quite a few years and this is the first box i've built since 2007 I'm not really up on my software. If a guy at work hadn't asked for my advice I wouldn't have even considered a new setup for myself but I got the bug back. Current Setup : Nothing2014 Ford Focus SE Hatch Future looking like: Singer / XS power Crescendo BC3500D CT EXO 15 Pioneer 80PRS CDT HD-61PRO CT Sounds M75.4 CT Sounds AT60.4 Something along those lines.
germanyt Posted August 5, 2015 Author Report Posted August 5, 2015 Just saw your post in my other thread btw. Interesting stuff. Though I feel like everytime I have a good idea it gets squashed by someone with more advice. I appreciate the help though. Current Setup : Nothing2014 Ford Focus SE Hatch Future looking like: Singer / XS power Crescendo BC3500D CT EXO 15 Pioneer 80PRS CDT HD-61PRO CT Sounds M75.4 CT Sounds AT60.4 Something along those lines.
CleanSierra Posted August 5, 2015 Report Posted August 5, 2015 If you TRULY get 2500W(in the real world, like on an AD-1 or AMM-1 or new clamp for a Term-lab), I'll eat my hat. My 4K(Crossfire), wired at half ohm nominal makes 3200W rising to 2 ohms. 2500W, real world in a musical install out of that amp...no. Im not the one you want to try to troll. Just a fyi for you.
germanyt Posted August 5, 2015 Author Report Posted August 5, 2015 If you TRULY get 2500W(in the real world, like on an AD-1 or AMM-1 or new clamp for a Term-lab), I'll eat my hat. My 4K(Crossfire), wired at half ohm nominal makes 3200W rising to 2 ohms. 2500W, real world in a musical install out of that amp...no. Never clamped an amp before so all I have to go on is input voltage and what I know about the accuracy of the amps rating. I assume an Audiopipe is a tad overrated and the voltage not being 14.4 makes me say 2500. I have no idea what it's really putting out. Current Setup : Nothing2014 Ford Focus SE Hatch Future looking like: Singer / XS power Crescendo BC3500D CT EXO 15 Pioneer 80PRS CDT HD-61PRO CT Sounds M75.4 CT Sounds AT60.4 Something along those lines.
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