Chad Willey Posted August 7, 2014 Report Share Posted August 7, 2014 I have been racking my head around the numbers on this one. Using a combination of Bassbox pro, WinISD, and Google Sketchup to get the design that "mathematically" seems correct. PLEASE C&C WELCOME! I need to be sure this is appropriate before I move forward. This design seems promising. The design I decided to go with is going to be a TC Sounds Epic 8" Subwoofer wired in parallel being ran by 500W. The ONLY thing that I may have an issue with is my Transfer Function Magnitude as there is a point where it is almost 6.2 dB. The graph itself doesn't seem to have much issue as the Group Delay and the Rear Air Port Velocity seem to be within range of what's necessary. My limits are as follows according to both WinISD and Bassbox Pro. .69 cu. ft. 37 Hz tuning 1 port: 8"x 2"x 42.15" using 3/4" MDF Transfer Function Magnitude: 6.161 dB @ 40.37 Hz Rear Air Port Velocity: 23.243 m/s @ 36.93 Hz Group Delay: 28.5 ms @ 37.81 Hz F0: 32 Hz F3: ~29.94 Hz In the sketchup model the total port area with wood excluded (including braces) is 671.56 in 3 total area of actual subwoofer box inside (excluding all port area) is 571.61 in 3 2005 Dodge Ram 1500 Quad Cab Alpine IVA-D901 7" Single DIN Infinity 3.5" Front Tweeters 6.5" Toxik Audio SST65 5.25" Toxik Audio SST525 100W Goldwood Tweeters Eclipse DA6213 500Wx2 Alpine MRP-M250 Link to comment Share on other sites More sharing options...
Chad Willey Posted August 12, 2014 Author Report Share Posted August 12, 2014 bump please 2005 Dodge Ram 1500 Quad Cab Alpine IVA-D901 7" Single DIN Infinity 3.5" Front Tweeters 6.5" Toxik Audio SST65 5.25" Toxik Audio SST525 100W Goldwood Tweeters Eclipse DA6213 500Wx2 Alpine MRP-M250 Link to comment Share on other sites More sharing options...
Triticum Agricolam Posted August 12, 2014 Report Share Posted August 12, 2014 The tough thing about small, low-tuned boxes with enough port area is the port ends up being a mile long, as you found out. You have four 180 degree bends and one 90 degree bend in that port. If it were me I'd try to find another way to orient the port internally to try to get rid of some of those bends. What are the external dimensions of your enclosure? "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: Link to comment Share on other sites More sharing options...
Chad Willey Posted August 14, 2014 Author Report Share Posted August 14, 2014 Externals: 22.77" x 15.41" x 9.65" using 3/4" MDF. Do you believe that the bends will really affect the overall SQ of the system/box? I have been told that it can cause a sort of "muffling" effect that may lower the overall dB output. Thank you for your info/input. 2005 Dodge Ram 1500 Quad Cab Alpine IVA-D901 7" Single DIN Infinity 3.5" Front Tweeters 6.5" Toxik Audio SST65 5.25" Toxik Audio SST525 100W Goldwood Tweeters Eclipse DA6213 500Wx2 Alpine MRP-M250 Link to comment Share on other sites More sharing options...
CleanSierra Posted August 14, 2014 Report Share Posted August 14, 2014 Externals: 22.77" x 15.41" x 9.65" using 3/4" MDF. Do you believe that the bends will really affect the overall SQ of the system/box? I have been told that it can cause a sort of "muffling" effect that may lower the overall dB output. Thank you for your info/input. It makes an already inefficient port, even MORE inefficient. Yes, the difference can be heard. Those multiple 180° turns you have make a hell of an inefficient port design. Im not the one you want to try to troll. Just a fyi for you. Link to comment Share on other sites More sharing options...
CleanSierra Posted August 14, 2014 Report Share Posted August 14, 2014 Also, your model isn't showing you the truth(in more ways than one). Your model that you have is taking ONLY the port area and length into account for the graph have you. If you had a way of telling the program, "the port made 5 180° turns in this design", the program would respond with, "WTF bruh?" Im not the one you want to try to troll. Just a fyi for you. Link to comment Share on other sites More sharing options...
Triticum Agricolam Posted August 14, 2014 Report Share Posted August 14, 2014 Externals: 22.77" x 15.41" x 9.65" using 3/4" MDF. Do you believe that the bends will really affect the overall SQ of the system/box? I have been told that it can cause a sort of "muffling" effect that may lower the overall dB output. Thank you for your info/input. It makes an already inefficient port, even MORE inefficient. Yes, the difference can be heard. Those multiple 180° turns you have make a hell of an inefficient port design. Yup. Anything that creates air resistance in a port is going to eat up your output to a varying degree. The higher your port velocities are, the worse it will be. All those little brace pieces you have in your port are only going to make matters worse too. With the size of enclosure you have they are completely unnecessary. While I'm not completely against labyrinth style ports, what you have in your design is pretty extreme. The lower you are able to get your port velocities, the less an inefficient port will hurt you, but to do that you need more port area, which results in even a longer port, so that's probably not an option for you. "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: Link to comment Share on other sites More sharing options...
philrab Posted August 14, 2014 Report Share Posted August 14, 2014 Just throwing another idea out there: what about having the port follow the perimeter of the enclosure, start about midway, make two 90 degree turns, then one more 90 and exit the box about 1/3 up from the bottom. Or, port the enclosure and do an extermal slot port that wraps around the enclosure like a squared off spiral. Just thinking, a couple of 90's wouldn't jack up airflow as much as those 180's do. Is that making sense, or is the visual getting across? 2015 Toyota Tacoma Build Thread 2007 Mazda 3; 5000K HID's, Kenwood Excelon KDC-X997, Infinity Reference 6.5 comps in front and coaxials in the rear doors, JL 320.4 four channel, Rab Designs built ported enclosure with an SA12, Kenwood monoblock, Redline Leater shift boot/e-brake boot/center console cover, JBR short shifter/shifter bushings/rear motor mount. Build Thread 1996 Mazda Miata: Kenwood Excelon HU, Alpine speaker in the doors, Clearwater (miata specific) headrest speakers. 1994 Mazda Protege: Kenwood Excelon HU, Infinity Reference 2 ways all around, 2x RF Punch 10's in ported boxes. Link to comment Share on other sites More sharing options...
hispls Posted August 14, 2014 Report Share Posted August 14, 2014 Have you considered buying or building a 12" passive radiator? Low tuning in a tiny box is difficult without eating up a ton of volume if you want adequate port area and not a rat's maze of port. Link to comment Share on other sites More sharing options...
Triticum Agricolam Posted August 14, 2014 Report Share Posted August 14, 2014 I took at try at your enclosure. Here is what I came up with: Same external dimensions as you listed. .8 cu ft internal space, which should put you pretty close to .7 after you factor in sub displacement. 17.75 sq in of port area WinISD doesn't properly calculate port length for 3 common wall slot ports, it will tune you lower than you want. The layout I made took this into account. "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: Link to comment Share on other sites More sharing options...
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