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Low Earth Orbit
DIY Audio
15" hornloaded coax
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<blockquote data-quote="Mark Wilkinson" data-source="post: 209249" data-attributes="member: 8989"><p>I'd go back outside and measure each of the drivers individually.</p><p></p><p>I'm guessing either the 1464 horn in the throat of your 15" is giving you the ripples like you're thinking,</p><p>or you have a timing issue between the 15" and the CD.</p><p></p><p>If the 15" alone still measures with the ripples, well.....dammit...... huh?</p><p>But if it measures cleaner, you have to think it's driver interaction problems.....which I'm guessing is no more than a timing problem...</p><p></p><p>For digging into timing/xover, I'd compare REW's Estimated Impulse Response shift for each section. (assuming you're using loopback or acoustic ref)</p><p>If the Estimated IR shifts are not the same, they most likely need to be (with the use of delay)</p><p></p><p>To see what getting equal IR shifts does, you can measure the 15" again, and apply the same impulse response shift used for the BMS CD. </p><p>Then you'll have individual phase traces for both sections, and you can compare how they would overlay when time aligned.....</p><p></p><p>To dig further without having to add delay, you can then sum the two measurements (that have the same Impulse Response shift applied) under All SPL, </p><p>and see how that computer summation compares to the whole speaker measurements.........</p><p>The All SPL summation should be much cleaner than the measurement of the entire box (if timing is a prob)</p><p></p><p>I see the xover is only 2nd order so I guess maybe it's possible summation could be an issue down to 600Hz apart from timing???...</p><p>but those ripples look pretty deep...my bet is timing...</p><p></p><p>Hope this helps...good luck</p><p></p><p>Edit...I said to use the Est IR shift from the CD on both....I should have said use whichever section gives the longest Est IR shift on both.</p><p>(with the idea you'll end up delaying to longest...)</p></blockquote><p></p>
[QUOTE="Mark Wilkinson, post: 209249, member: 8989"] I'd go back outside and measure each of the drivers individually. I'm guessing either the 1464 horn in the throat of your 15" is giving you the ripples like you're thinking, or you have a timing issue between the 15" and the CD. If the 15" alone still measures with the ripples, well.....dammit...... huh? But if it measures cleaner, you have to think it's driver interaction problems.....which I'm guessing is no more than a timing problem... For digging into timing/xover, I'd compare REW's Estimated Impulse Response shift for each section. (assuming you're using loopback or acoustic ref) If the Estimated IR shifts are not the same, they most likely need to be (with the use of delay) To see what getting equal IR shifts does, you can measure the 15" again, and apply the same impulse response shift used for the BMS CD. Then you'll have individual phase traces for both sections, and you can compare how they would overlay when time aligned..... To dig further without having to add delay, you can then sum the two measurements (that have the same Impulse Response shift applied) under All SPL, and see how that computer summation compares to the whole speaker measurements......... The All SPL summation should be much cleaner than the measurement of the entire box (if timing is a prob) I see the xover is only 2nd order so I guess maybe it's possible summation could be an issue down to 600Hz apart from timing???... but those ripples look pretty deep...my bet is timing... Hope this helps...good luck Edit...I said to use the Est IR shift from the CD on both....I should have said use whichever section gives the longest Est IR shift on both. (with the idea you'll end up delaying to longest...) [/QUOTE]
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