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Low Earth Orbit
DIY Audio
Comparing LF drivers
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<blockquote data-quote="Art Welter" data-source="post: 106417" data-attributes="member: 52"><p>Re: Comparing LF drivers</p><p></p><p></p><p>The biggest advantage is in linear displacement, the Xmax or Xvar. </p><p>Just like in engines, there is no replacement for displacement, for low frequencies we need to "move some air".</p><p>The JBL 2242H has only 7.87 mm Xmax, the B&C 18SW115 has 14mm Xmax, 16mm Xvar. </p><p>Doubling the displacement nets a 6 dB increase in output, but also requires 6 dB more power, hence the greater power handling.</p><p>Given the same Xmax, a 21" has about 28% more displacement than an 18", so can put out almost 2 dB more SPL.</p><p>The increased displacement and power handling require heavier cones and voice coils, which reduces efficiency a bit, so given limited power many of the old cones will outperform the new crop.</p><p>With amplifiers exceeding 90% efficiency, and power available for about 25 cents a watt, loosing a few dB in speaker efficiency to gain 6 dB output from the same enclosure size is a compromise I'm certainly willing to pay.</p><p></p><p>The B&C 18SW115 gets rid of heat better than many older designs, which reduces power compression. </p><p></p><p>The heavy, stiff cones also can handle the high compression ratios used in horn loaded designs with far less distortion than lighter cones.</p><p>Horn enclosures can increase the output of a capable driver by 6 dB. As an example, my single B&C 18SW115 Keystone tapped horn design, a bit smaller than a dual 18 JBL SRX728, has slightly higher sensitivity, but due to the increased excursion capability, has more output potential.</p><p></p><p>Art</p></blockquote><p></p>
[QUOTE="Art Welter, post: 106417, member: 52"] Re: Comparing LF drivers The biggest advantage is in linear displacement, the Xmax or Xvar. Just like in engines, there is no replacement for displacement, for low frequencies we need to "move some air". The JBL 2242H has only 7.87 mm Xmax, the B&C 18SW115 has 14mm Xmax, 16mm Xvar. Doubling the displacement nets a 6 dB increase in output, but also requires 6 dB more power, hence the greater power handling. Given the same Xmax, a 21" has about 28% more displacement than an 18", so can put out almost 2 dB more SPL. The increased displacement and power handling require heavier cones and voice coils, which reduces efficiency a bit, so given limited power many of the old cones will outperform the new crop. With amplifiers exceeding 90% efficiency, and power available for about 25 cents a watt, loosing a few dB in speaker efficiency to gain 6 dB output from the same enclosure size is a compromise I'm certainly willing to pay. The B&C 18SW115 gets rid of heat better than many older designs, which reduces power compression. The heavy, stiff cones also can handle the high compression ratios used in horn loaded designs with far less distortion than lighter cones. Horn enclosures can increase the output of a capable driver by 6 dB. As an example, my single B&C 18SW115 Keystone tapped horn design, a bit smaller than a dual 18 JBL SRX728, has slightly higher sensitivity, but due to the increased excursion capability, has more output potential. Art [/QUOTE]
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