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Low Earth Orbit
DIY Audio
B&C DCX464 vs DCX 354
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<blockquote data-quote="Art Welter" data-source="post: 218174" data-attributes="member: 52"><p>Kevin,</p><p></p><p>A constant directivity horn like the 90x50 Limmer 250M sensitivity will be around -5 to-10dB at 18kHz compared to 1000 Hz, regardless of the driver used. Chasing a "flat " response at the very high frequencies any driver can run out of headroom quickly due to air (atmospheric) absorption on top of constant directivity EQ compensation.</p><p>[ATTACH=full]209851[/ATTACH]</p><p>At 50 feet, in addition to the inverse distance loss, around 4 times more power (-6dB loss) is required to flatten the VHF at 18kHz compared to 1200Hz. </p><p>The problem gets worse at lower humidity levels than this example:</p><p>[ATTACH=full]209850[/ATTACH]</p><p>[URL unfurl="true"]http://www.sengpielaudio.com/calculator-air.htm[/URL]</p><p></p><p>Usually a 3" should have no problem being "fully relaxed" with a single 10" at 1200 Hz if using a 24dB/octave crossover, unless the low-mid horn is very narrow dispersion.</p><p>You say the crossover "will be" active FIR, what are you using now?</p><p>Have you verified the low mid and high horns are acoustically in phase through the crossover region?</p><p>What midhorn (350-1100Hz) is the JBL 2012 on?</p><p></p><p>Art</p></blockquote><p></p>
[QUOTE="Art Welter, post: 218174, member: 52"] Kevin, A constant directivity horn like the 90x50 Limmer 250M sensitivity will be around -5 to-10dB at 18kHz compared to 1000 Hz, regardless of the driver used. Chasing a "flat " response at the very high frequencies any driver can run out of headroom quickly due to air (atmospheric) absorption on top of constant directivity EQ compensation. [ATTACH type="full"]209851[/ATTACH] At 50 feet, in addition to the inverse distance loss, around 4 times more power (-6dB loss) is required to flatten the VHF at 18kHz compared to 1200Hz. The problem gets worse at lower humidity levels than this example: [ATTACH type="full"]209850[/ATTACH] [URL unfurl="true"]http://www.sengpielaudio.com/calculator-air.htm[/URL] Usually a 3" should have no problem being "fully relaxed" with a single 10" at 1200 Hz if using a 24dB/octave crossover, unless the low-mid horn is very narrow dispersion. You say the crossover "will be" active FIR, what are you using now? Have you verified the low mid and high horns are acoustically in phase through the crossover region? What midhorn (350-1100Hz) is the JBL 2012 on? Art [/QUOTE]
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B&C DCX464 vs DCX 354
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