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<blockquote data-quote="Art Welter" data-source="post: 203727" data-attributes="member: 52">Randy,When it comes to sub-woofers (or internal combustion engines) there is no replacement for displacement.Displacement in loudspeakers is measured by the one way linear stroke, Xmax, generally in mm (milimeters). The linear stroke peak to peak is twice Xmax.A woofer with twice the displacement, given 6 dB more power, will put out 6 dB more output.Your K151 Xmax is only 2.54mm, similar to some 3&quot; speakers, modern PA 18&quot; woofers such as the B&amp;C18SW115 have more than 6 times that displacement, 18dB more output. Some competition car drivers have as much as 30mm Xmax!A 10 dB increase in SPL sounds &quot;twice as loud&quot; to average ears at 1000 Hz, it takes less at lower frequencies, around 5 dB at 20 Hz sounds &quot;twice as loud&quot;, though with a 40Hz Fb, your boxes won&#039;t do much below 35 Hz.You could purchase new drivers and get four times the sound in the roughly the same cabinet volume (though port size would probably need to be larger, reducing cabinet volume and sensitivity a bit), or &quot;upgrade&quot; your sub amps and hear the sound of your K151 distort like pigs- Xmax is also the displacement at which THD is 10%, once driven beyond Xmax (probably only a few hundred watts with your very sensitive K151s) the speaker rapidly will exceed 100% distortion.Cheers,Art</blockquote>

[QUOTE="Art Welter, post: 203727, member: 52"] Randy, When it comes to sub-woofers (or internal combustion engines) there is no replacement for displacement. Displacement in loudspeakers is measured by the one way linear stroke, Xmax, generally in mm (milimeters). The linear stroke peak to peak is twice Xmax. A woofer with twice the displacement, given 6 dB more power, will put out 6 dB more output. Your K151 Xmax is only 2.54mm, similar to some 3" speakers, modern PA 18" woofers such as the B&C18SW115 have more than 6 times that displacement, 18dB more output. Some competition car drivers have as much as 30mm Xmax! A 10 dB increase in SPL sounds "twice as loud" to average ears at 1000 Hz, it takes less at lower frequencies, around 5 dB at 20 Hz sounds "twice as loud", though with a 40Hz Fb, your boxes won't do much below 35 Hz. You could purchase new drivers and get four times the sound in the roughly the same cabinet volume (though port size would probably need to be larger, reducing cabinet volume and sensitivity a bit), or "upgrade" your sub amps and hear the sound of your K151 distort like pigs- Xmax is also the displacement at which THD is 10%, once driven beyond Xmax (probably only a few hundred watts with your very sensitive K151s) the speaker rapidly will exceed 100% distortion. Cheers, Art [/QUOTE]

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