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Junior Varsity
Subwoofer comparison SRX728 vs Vertec 4883
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<blockquote data-quote="Art Welter" data-source="post: 59406" data-attributes="member: 52"><p>Re: Subwoofer comparison SRX728 vs Vertec 4883</p><p></p><p></p><p>TJ,</p><p></p><p>The Fb is likely to be the same as the impedance minima, but as you can see the sensitivity falls rapidly below 50 Hz.</p><p>The chart would indicate a 1 watt one meter sensitivity of about 101 dB in the 50 to 100 range, not out of line for a box rolling off so high.</p><p></p><p>DJK’s post #75 and a recent post by FE3T:</p><p><a href="http://www.diyaudio.com/forums/subwoofers/80833-jbl-2268hpl-opossed-jbl2242h.html" target="_blank">JBL 2268HPL as opossed to JBL2242H - diyAudio</a></p><p></p><p>explain how the 23 mm figure is Xmech, not Xmax, as FE3T says in post # 93 </p><p>“The most usually speced Xmax for the 2268 from reputable resellers are 8mm.”</p><p></p><p>Phil Lewandowski tested the JBL SRX 718 which also uses the 2268 in his thread "Basic Distortion Testing"</p><p><a href="http://srforums.prosoundweb.com/index.php/m/553054/19717/#msg_553054" target="_blank">ProSoundWeb Community - Index</a></p><p></p><p>His tests confirm that the 2268 Xmax is indeed only around 8mm, he had to reduce the drive level on the 718 to 49 v at 35Hz, and 23 V at 30 Hz to keep the excursion and distortion down to the 10 % level. </p><p></p><p>I have tested a JBL SRX 728 and can confirm JBL’s frequency response and sensitivity specs are accurate for half space.</p><p></p><p>The 4883 uses the 2263H-1 which also mistakenly reports the Xmech of 23 mm as Xmax.</p><p></p><p>Both transducers use the 75 mm (3 in) Dual Coil Dual Magnet , neodymium Differential Drive®. </p><p>The 2268 Sd is 1269, the 4883 only 552, therefore it would take 2.3 of the 12” to equal the displacement of the 18”. </p><p>However with an Fs of 41.2 for the 12” and 33 for the 18” the 18 can support a lower box tuning and put out more LF.</p><p></p><p>At any rate, there are many drivers with far more Xmax than either of these JBL drivers.</p><p></p><p>The B&C 18SW115 has 15 mm Xmax (30mm Xmech), almost double the X max of the JBL 2268 or 2263.</p><p></p><p>Doubling Xmax results in 6 dB more output.</p><p>The far cheaper Eminence Lab 12 has a real 13 mm Xmax, a pair of those can blow away an old school 18” in the 30-40 Hz range.</p><p></p><p>In tests using the B&C 18SW115-4 I found that a tapped horn of only slightly larger dimensions (still smaller than a JBL SRX 728) than a bass reflex had 6 dB more output with the same drive level.</p><p><a href="http://www.diyaudio.com/forums/subwoofers/184992-tapped-horn-vs-bass-reflex-case-study.html" target="_blank">Tapped Horn Vs. Bass Reflex Case Study - diyAudio</a></p><p></p><p>At any rate, with a good tapped horn such as the DSL TH-118 (or my Keystone design) using a single B&C 18SW115-4 there is no doubt that it has around 5 dB more output potential (and a similar LF extension) than an SRX 728 in a smaller size (and weight) package.</p><p>And if you don't care about low bass, the TH mini has a similar response, sensitivity and Xmax as the 4883 in an even smaller (but 12 pound heavier) package.</p><p></p><p>Art Welter</p></blockquote><p></p>
[QUOTE="Art Welter, post: 59406, member: 52"] Re: Subwoofer comparison SRX728 vs Vertec 4883 TJ, The Fb is likely to be the same as the impedance minima, but as you can see the sensitivity falls rapidly below 50 Hz. The chart would indicate a 1 watt one meter sensitivity of about 101 dB in the 50 to 100 range, not out of line for a box rolling off so high. DJK’s post #75 and a recent post by FE3T: [url=http://www.diyaudio.com/forums/subwoofers/80833-jbl-2268hpl-opossed-jbl2242h.html]JBL 2268HPL as opossed to JBL2242H - diyAudio[/url] explain how the 23 mm figure is Xmech, not Xmax, as FE3T says in post # 93 “The most usually speced Xmax for the 2268 from reputable resellers are 8mm.” Phil Lewandowski tested the JBL SRX 718 which also uses the 2268 in his thread "Basic Distortion Testing" [url=http://srforums.prosoundweb.com/index.php/m/553054/19717/#msg_553054]ProSoundWeb Community - Index[/url] His tests confirm that the 2268 Xmax is indeed only around 8mm, he had to reduce the drive level on the 718 to 49 v at 35Hz, and 23 V at 30 Hz to keep the excursion and distortion down to the 10 % level. I have tested a JBL SRX 728 and can confirm JBL’s frequency response and sensitivity specs are accurate for half space. The 4883 uses the 2263H-1 which also mistakenly reports the Xmech of 23 mm as Xmax. Both transducers use the 75 mm (3 in) Dual Coil Dual Magnet , neodymium Differential Drive®. The 2268 Sd is 1269, the 4883 only 552, therefore it would take 2.3 of the 12” to equal the displacement of the 18”. However with an Fs of 41.2 for the 12” and 33 for the 18” the 18 can support a lower box tuning and put out more LF. At any rate, there are many drivers with far more Xmax than either of these JBL drivers. The B&C 18SW115 has 15 mm Xmax (30mm Xmech), almost double the X max of the JBL 2268 or 2263. Doubling Xmax results in 6 dB more output. The far cheaper Eminence Lab 12 has a real 13 mm Xmax, a pair of those can blow away an old school 18” in the 30-40 Hz range. In tests using the B&C 18SW115-4 I found that a tapped horn of only slightly larger dimensions (still smaller than a JBL SRX 728) than a bass reflex had 6 dB more output with the same drive level. [url=http://www.diyaudio.com/forums/subwoofers/184992-tapped-horn-vs-bass-reflex-case-study.html]Tapped Horn Vs. Bass Reflex Case Study - diyAudio[/url] At any rate, with a good tapped horn such as the DSL TH-118 (or my Keystone design) using a single B&C 18SW115-4 there is no doubt that it has around 5 dB more output potential (and a similar LF extension) than an SRX 728 in a smaller size (and weight) package. And if you don't care about low bass, the TH mini has a similar response, sensitivity and Xmax as the 4883 in an even smaller (but 12 pound heavier) package. Art Welter [/QUOTE]
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