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Low Earth Orbit
DIY Audio
New DIY Mid High (90deg) - AKA PM90
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<blockquote data-quote="Mark Wilkinson" data-source="post: 204118" data-attributes="member: 8989"><p>Andy, one thing we both found out...a speaker on the ground with the mic above it doesn't work....unless the speaker is in a hole in the ground, and then supposedly it works. And I ain't gonna dig no hole ! </p><p>I tried speaker on ground, mic in air, to try to verify some REW harmonic distortion measurements at high volume. I was rattling my house and thought getting away from the house would help. Frankly, the REW traces looked very alien. I wish I had tried the mic on ground.......</p><p></p><p>......as Peter and Mark both say, box on ground, mic on ground, works. I've always figured floor bounce would screw up middle thru higher freqs. But I guess the on-ground measurement is more about measuring the low end. </p><p>Maybe 1m on the ground, with the box standing up is too close for the two mids, making too much distance variation to them ? Why not lay it on its side so you can center the mic? Or back the mic up? Or tilt the upright box to aim to mic?</p><p></p><p>I have a pretty good setup for measuring in-air, reflection wise. What I've found comparing inside measurements to outside, is that with the DIY on a sub or something, in the middle of a fair sized room, and as far away from everything as possible...with the mic centered on the horn about 2 ft away...I get results that tie pretty OK. Magnitude and timing will both be off some, but not that bad really for straight on axial.</p><p></p><p>Also found it was much easier to divide and conquer, ie tune the bms first by itself, then the mid, and then try to put them together...</p><p>(It's real easy to toy with the bms alone, inside without reflection probs.)</p><p></p><p>I'm left thinking in-air works best above some given freq. On-ground helps confirm, or adjust in-air meas below said freq.</p><p>Maybe the guys can confirm or kill this idea....</p></blockquote><p></p>
[QUOTE="Mark Wilkinson, post: 204118, member: 8989"] Andy, one thing we both found out...a speaker on the ground with the mic above it doesn't work....unless the speaker is in a hole in the ground, and then supposedly it works. And I ain't gonna dig no hole ! I tried speaker on ground, mic in air, to try to verify some REW harmonic distortion measurements at high volume. I was rattling my house and thought getting away from the house would help. Frankly, the REW traces looked very alien. I wish I had tried the mic on ground....... ......as Peter and Mark both say, box on ground, mic on ground, works. I've always figured floor bounce would screw up middle thru higher freqs. But I guess the on-ground measurement is more about measuring the low end. Maybe 1m on the ground, with the box standing up is too close for the two mids, making too much distance variation to them ? Why not lay it on its side so you can center the mic? Or back the mic up? Or tilt the upright box to aim to mic? I have a pretty good setup for measuring in-air, reflection wise. What I've found comparing inside measurements to outside, is that with the DIY on a sub or something, in the middle of a fair sized room, and as far away from everything as possible...with the mic centered on the horn about 2 ft away...I get results that tie pretty OK. Magnitude and timing will both be off some, but not that bad really for straight on axial. Also found it was much easier to divide and conquer, ie tune the bms first by itself, then the mid, and then try to put them together... (It's real easy to toy with the bms alone, inside without reflection probs.) I'm left thinking in-air works best above some given freq. On-ground helps confirm, or adjust in-air meas below said freq. Maybe the guys can confirm or kill this idea.... [/QUOTE]
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