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Gold Member Username: InsearchofbassPost Number: 2278 Registered: Jun-04 | Heres what i came up with from this guys site tell me if you agree with my theorys and conclusions http://www.cardomain.com/id/kennywrx these are the calculators i used http://www.carstereo.com/help/Articles.cfm?id=31 http://www.linearteam.dk/default.aspx?pageid=ventcalculator 32 hz and 45 hz tuning points is what he claims they are at .80 is at 31.76 hz on the square port calculator at 20.69 inches long each .40 is at 44.92 hz on the square port calculator at 20.69 inches long each 1.20 comes out to 36.68 hz at 20.69 inches on the square port calculator he seems to have picked the 37 hz port at 1.20 cf for for two reasons one being it raised the curve slightly down to 33 hz and more at the frequencies above that the second reason is because he wanted to target a specific frequency (45 hz) The sacrifice was accuracy was slightly affected by the higher box volume above the optimum box size of what i came up with of 1.03 cf. points to watch for ...at his port sizes the port volocity is fine on linear team at two ports at 1.20 cf but not at .80 at one port the same length of 20.69 and .40 at the same length 20.69 using the .66666 percent large chamber to .33333 percent small chamber...larger ports to linear team .15 and under would prob be necessary at rater rms power applied minimun impedances while tested with frequency sweeps was achieved at 32.5 hz and 64.5 hz all but exactly an octave apart as he mentioned in the article note.. lower impedances equal more power recieved to the 6.5 subwoofers highest impedance peaks seem to start at 37 hz to 62.5 hz slight peak at 67 hz 79hz highest impedance peaks were up to 41 ohms in resistance rough guestamation of about 22 watts rms at that resistance theory... doubling the power by reducing the resistance in half would not only increase efficiency of the amplifier but also produce a 3 db gain in spl of this box. The maximum potential to drop resistance is by 2 from 41 ohms to 20.5 ohms to 10.25 ohms at the amps 8ohm bridged connection....a maximum total spl increase potential of 6 db (a 136 db potential at 50 hz from 130.3 with 100 watts rms in that same car) theory... the raise in impedance at 37 hz to 62.5 hz seems to be due to the the wide speard of frequencies. From what i understand the point of least resistance in a ported box is at the tuning frequency (in this case its 32 hz) so if thats true it makes sense that the further you go from it the higher the impedance becomes. next theory...to reduce the the wide frequency span and higher impedances in the above metioned you would want a chamber in between these two. I also believe the smaller risistance hump at 66 to 80 hz may be due to the 45 hz port tune of the second chamber 90 hz being an octave apart (check the chart it seems to hold true) next problem to solve design a box for these 6.5s adding a third chamber to test this theory out in real world ts specs are fs= 35 qts= .37 vas= .52 |
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Gold Member Username: InsearchofbassPost Number: 2279 Registered: Jun-04 | ok heres what i came up with to run three chambers with two 6.5 inch subwoofers box with 3 ports at 1.80 cf 20.69 inches at same tune and length 36.68 hz 20.69 length adding 50.00 percent to total original box size and adding another port instead of 2 like the original 29.945 first chamber at .90 cf 36.68 second chamber at .60 third chamber 44.92 at .40 = 1.90 cf for two 6.5s note...i may have to adjust to fit all this plus raise the first port tune and adjust for port volocity |
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Gold Member Username: InsearchofbassPost Number: 2280 Registered: Jun-04 | the comment "box with 3 ports at 1.80 cf 20.69 inches at same tune and length 36.68 hz 20.69 length" was a mental note for me disreaguard that |
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Gold Member Username: InsearchofbassPost Number: 2281 Registered: Jun-04 | 29.945 36.68 and 44.92 are hz port tunes |
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Silver Member Username: Tdeaton1021Near Tampa, Florida USA Post Number: 419 Registered: Sep-04 | i wish i was as smart at sean..... |
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Gold Member Username: InsearchofbassPost Number: 2282 Registered: Jun-04 | lol you are |
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Silver Member Username: RhasslerGilford, NH Post Number: 267 Registered: Dec-04 | hey Sean! i just looked at your post, and i don't have time to comprehend all waht it says, im leaving town for the weekend, and i will be back on monday. So you can wait (i don't suggest lol) till i get back and i'll try to understand all that stuff. If you could, could you start to work on the RE XXX 15" abc box. Sorry to leave you hangin over the weekend though lol Thanks! |
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Gold Member Username: InsearchofbassPost Number: 2284 Registered: Jun-04 | sure thing man triple chamber for you coming up less the box gets to big them ill do you a double |
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Gold Member Username: InsearchofbassPost Number: 2285 Registered: Jun-04 | in case anyone wants to know the demensions first chamber 12 high x 12 deep x 11 wide= .91666 cf second chamber 12 high x 12 deep x 8 wide = .66666 cf. third chamber 12 high x 12 deep x 6 wide = .50 cf. internal so external measurements are 13.5 high by 13.5 deep by 28 (two .75 pieces add to the width for the chambers plus the outer walls gives you your outer walls at 28 inches wide) some width will be needed to account for displacements for the ports and subs but most cars should be able to fit this 3 chamber model |
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Gold Member Username: InsearchofbassPost Number: 2324 Registered: Jun-04 | disreguard the post above this i made a mistake...i will post the new results later |
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Gold Member Username: InsearchofbassPost Number: 2327 Registered: Jun-04 | post speaking " optimum box size of what i came up with of 1.03 cf." is incorrect it should read .81 cf at 37.82 hz |
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Gold Member Username: FishyTamarac Ft.Laud, FL USA Post Number: 1372 Registered: Sep-04 | So whats the biggest advantage of using an ABC box? SPL? Almost every non-mainstream enclosure design I've examined usually sacrifices SQ when going for SPL or visa versa. Seems like most of the time a good ported enclosure is best when one wants a combination of the two. -Fishy |
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Gold Member Username: InsearchofbassPost Number: 2335 Registered: Jun-04 | actually the abc box has the the best of both worlds the low end response of a ported and the high end of a sealed ...some say the abc lacks high end but i think its all about how you design the abc box......i want to try it with the triple chamber because i feel it will distribute the frequencies across the whole bandwidth better .....and from what ive seen it will lower the resistance while being played delivering more power to the speaker per frequency.....the abc box that guy built had lowest points in resistance all but exactly and octave apart and highest where he hit the hardest (41 ohms about 22 watts on that 100 rms amp) lowering it to 20.5 ohms would up hit by 3db assuming he has the excursion capability and another 3 db at 10.25 ohms assuming he has the excursion capability again.....at least thats my theories. Waht do you think? |