Robby Posted July 19, 2017 Report Share Posted July 19, 2017 I am currently in the process of trying to choose a pair of 12" subwoofers to put in the trunk of my Nissan Altima. I currently have one 12" subwoofer in a ported box tuned to 32 hz. I am not having any issues with it, I am wanting to go another route and try to design a proper sealed box. I like to change things up from time to time. I will be feeding each 12" sub 500 watts. They will be dual 4 ohm voice coil subs. I just need to know if I'm going about this all the wrong way using the proper calculations. SUBWOOFER 1 Fs 34hz Vas 44L Qes .60 Qts .57 Xmax 15mm RESULTS Qtc of .707 = Vb 2.86 ft^3 Qtc of 1.0 = Vb .75 ft^3 EBP = 57 SUBWOOFER 2 Fs 26hz Vas 66.24L Qes .437 Qts .396 Xmax 12mm RESULTS Qtc of .707 = Vb 1.07 ft^3 Qtc of 1.0 = Vb .44 ft^3 EBP = 57 SUBWOOFER 3 Fs 37hz Vas 29L Qes .662 Qts .584 Xmax 12.5mm RESULTS Qtc of .707 = Vb 2.18 ft^3 Qtc of 1.0 = Vb .53 ft^3 EBP = 57 SUBWOOFER 4 Fs 36hz Vas 30.8L Qes .53 Qts .47 Xmax 14mm RESULTS Qtc of .707 = Vb .87 ft^3 Qtc of 1.0 = Vb .31 ft^3 EBP = 69 In summary, am I going about this all the wrong way when trying to build a proper sealed enclosure? I know everything changes once you place the subwoofer in the trunk of a car or in the cabin of a vehicle to do cabin gain, etc. I also know you can just be simple and build a sealed box and give each 12" subwoofer 1 net cubic foot and roll with it. I'm just wondering if it were your choice of the above 4 subwoofers, which would you choose and if I'm way off base with my calculations and reasoning. Thank you for any advice. Link to comment Share on other sites More sharing options...
Triticum Agricolam Posted July 19, 2017 Report Share Posted July 19, 2017 Can you tell us specifically what subs you are looking at so we can get the full specs? What kind of music do you listen to? "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...
Robby Posted July 19, 2017 Author Report Share Posted July 19, 2017 Sure, and these are not high end subs at all. I'm just trying something different. I listen to a range of music. Jazz, classical, bass, hip hop, old country, alternative, 90's grunge. I prefer good recordings and I rip all my music into .FLAC and put them on a thumb drive. The subs listed above in order are: 1. Alpine SWS 12D4 2. NVX VSW124v2 3. CT Sounds Tropo 4. Sundown E-12 V3 Link to comment Share on other sites More sharing options...
twalker182 Posted July 19, 2017 Report Share Posted July 19, 2017 You're not going to be happy with that Sundown in a sealed box. Very low output in a sealed enclosure. 2010 Accord Sedan XS D3400R Clarion HU Sundown mids and highs Incriminator amps Incriminator Lethal Injection 12" Link to comment Share on other sites More sharing options...
Robby Posted July 19, 2017 Author Report Share Posted July 19, 2017 I forgot to add the sensitivity of each sub. Alpine 86.5 dB NVX 90 dB CT Tropo 85.6dB Sundown E-12 86.4 dB Link to comment Share on other sites More sharing options...
Triticum Agricolam Posted July 19, 2017 Report Share Posted July 19, 2017 1 hour ago, Robby said: I forgot to add the sensitivity of each sub. Alpine 86.5 dB NVX 90 dB CT Tropo 85.6dB Sundown E-12 86.4 dB Sensitivity numbers are pretty much irrelevant for car audio subwoofers, FYI. There is no standardized way to measure them and every manufacturer does it differently. How much space do you have available? "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...
Robby Posted July 19, 2017 Author Report Share Posted July 19, 2017 I have about 3 cubic feet available in the trunk for an enclosure. There is something about the way the NVX is lining up with a Qtc of .707 and Vb of about 1 ft^3 that I like. But the Qts of 0.396 has me concerned about placing it in a sealed box. I'm trying to figure out why most websites, sellers, dealers of most subwoofers list 1 cubic ft as the ideal recommended size for a 12" sub sealed enclosure.... Link to comment Share on other sites More sharing options...
Triticum Agricolam Posted July 19, 2017 Report Share Posted July 19, 2017 17 minutes ago, Robby said: I have about 3 cubic feet available in the trunk for an enclosure. There is something about the way the NVX is lining up with a Qtc of .707 and Vb of about 1 ft^3 that I like. But the Qts of 0.396 has me concerned about placing it in a sealed box. I'm trying to figure out why most websites, sellers, dealers of most subwoofers list 1 cubic ft as the ideal recommended size for a 12" sub sealed enclosure.... A QTC of .707 gives the flattest response (in a open space) but that doesn't mean its the best for every situation. I compared those four subs in WinISD all using 1 cu ft of box volume per sub. The Sundown and the CT Sounds have nearly identical performance. The NVX has slightly flatter response with a little more low frequency output. Due to its higher QTC the Alpine has the most output in the mid-bass range, but the steepest rolloff below 40 hz. If it were me I'd pick either the NVX or the Alpine. They are all good choices though. "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...
Robby Posted July 20, 2017 Author Report Share Posted July 20, 2017 Thank you so much. I tried the free download of WinISD about a month ago and had some issues with it. Maybe I found it confusing or had a bad download. I'm not sure. I've looked at the different graphs using AJDesigner. It has been helpful, but thank you for running the graphs on WinISD. I have to admit, I'm a sucker for low frequency output, thus the reason I have a 1000 watt dual 2 ohm sub tuned to 32 hz. Sometimes it can be a bit much. I'm just experimenting with something different. Link to comment Share on other sites More sharing options...
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