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<blockquote data-quote="Art Welter" data-source="post: 148036" data-attributes="member: 52">Re: No compromises front loaded double 18” cabThe B6 is basically a &quot;too small&quot; bass reflex needing a 6 dB LF boost to flatten out the response. Turns out that my last cabinet re-build, cramming two 15&quot; in a slot loaded push-pull arrangement in the the same box previously used for 2 Lab 12&quot; (the design in the stickies in this DIY section) is &quot;kinda&quot; a B6 (QTS is too high), well more a B10...<a href="http://www.diyaudio.com/forums/subwoofers/255010-compact-2x15-ppsl-using-dayton-pa385-8-drivers.html" target="_blank">http://www.diyaudio.com/forums/subwoofers/255010-compact-2x15-ppsl-using-dayton-pa385-8-drivers.html</a>To quote DJK:&quot;Take a driver with a Qts=0.312 and put it in a sealed box sized to make it a D2 alignment. Now vent it to Fs and it becomes an SBB4, with the best transient response of all the vented alignments. Now add a Q=2 high-pass filter at Fs, and you now have a B6. It still has the transient response of the SBB4 because the box volume and tuning have not changed, you have just applied some EQ, mechanically it is the same. Fb=Fs=Faux.The Qts=0.312 is the intercept of two equations determining box size and low-frequency cut-off. The box size equation says that the size is proportional to the square of the Qts, so a Qts=0.3 can run in a box about half the size of a Qts=.4 driver. The problem is the bass response rolls off at a higher frequency the lower the Qts is. The two equations have an intercept at Qts=0.312, yielding the best bass extension and minimum box size, and allowing you to build a B6 alignment.&quot;Higher-order bandpass boxes are different, there is no direct output of the driver, only output from 1 or more tuned resonant chambers.Their bandwidth is limited, and the rapid phase change at the top of the bandpass does make alignment to the top cabinets &quot;difficult&quot;.Art</blockquote>

[QUOTE="Art Welter, post: 148036, member: 52"] Re: No compromises front loaded double 18” cab The B6 is basically a "too small" bass reflex needing a 6 dB LF boost to flatten out the response. Turns out that my last cabinet re-build, cramming two 15" in a slot loaded push-pull arrangement in the the same box previously used for 2 Lab 12" (the design in the stickies in this DIY section) is "kinda" a B6 (QTS is too high), well more a B10... [url]http://www.diyaudio.com/forums/subwoofers/255010-compact-2x15-ppsl-using-dayton-pa385-8-drivers.html[/url] To quote DJK: [I]"Take a driver with a Qts=0.312 and put it in a sealed box sized to make it a D2 alignment. Now vent it to Fs and it becomes an SBB4, with the best transient response of all the vented alignments. Now add a Q=2 high-pass filter at Fs, and you now have a B6. It still has the transient response of the SBB4 because the box volume and tuning have not changed, you have just applied some EQ, mechanically it is the same. Fb=Fs=Faux. The Qts=0.312 is the intercept of two equations determining box size and low-frequency cut-off. The box size equation says that the size is proportional to the square of the Qts, so a Qts=0.3 can run in a box about half the size of a Qts=.4 driver. The problem is the bass response rolls off at a higher frequency the lower the Qts is. The two equations have an intercept at Qts=0.312, yielding the best bass extension and minimum box size, and allowing you to build a B6 alignment."[/I] Higher-order bandpass boxes are different, there is no direct output of the driver, only output from 1 or more tuned resonant chambers. Their bandwidth is limited, and the rapid phase change at the top of the bandpass does make alignment to the top cabinets "difficult". Art [/QUOTE]

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