# Help with PR box for SDX15



## scotthulbs (Jan 11, 2009)

Hey everyone, I am a frequent reader of this forum, which is GREAT, I rarely post but I have been having a problem I think you guys can help me with. I have 3 SDX15's I am currently running 2 of them in 22" cube boxes with 1 1821 PR per box. I am am wanting to go with dual PR's per box. I cannot get any of these modeling programs to work properly, or at least it doesn't seem right to me, I thought adding a second PR would raise the tuning, but the program shows the tuning around 4-5hz?? I used bassbox pro to model the current boxes I have. I was using it on a windows XP machine at the time. Now that I got a new pc the software is giving me different results than before. IIRC my current boxes were tuend around 15hz, of course that is assuming the software was working correctly. This has been driving me crazy, I want to build new boxes but I want to be sure I will get the result I a looking for. If anyone can help me out and plot my current boxes (20.5x19x20.5 internal dimensions) vs. a 24" (21.75x21x22.5 internal dimensions) cube with dual 1821 PR's I would really appreciate it. I would like to be tuned around 16-17hz.


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## Mike P. (Apr 6, 2007)

Post the parameters for the 1821 PR's.


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## scotthulbs (Jan 11, 2009)

FS - 3.65 Hz
QMS - 67.72
VAS - 1,840 litre
CMS - 0.9
MMS - 2100g
RMS - 0,714
SD - 186 in^2 / 0.1200 m^2


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## Mike P. (Apr 6, 2007)

21.75x21x22.5 internal is about 5.5 cu.ft net volume. 2 PR's as is would tune the box to 17.8 hz. Adding 350 grams of mass to each PR would lower the tuning to 16.5 hz.


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