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<blockquote data-quote="Tim McCulloch" data-source="post: 58490" data-attributes="member: 67">Re: Voicing/tuning a 3-way home brew speaker cabHi John-I&#039;m not familiar with REW, and I downloaded (but never installed) Holm Impulse.&nbsp; I&#039;ve been a Smaart user for a few years and I&#039;ve made hundreds of bad measurements.&nbsp; I still do, but I can usually spot them now. :blush:&nbsp; At any rate, I think Bennett assumed that Holm Impulse only did &quot;impulse alignment&quot;.What all the cool kids do these days is attempt to get consistent summation, both in amplitude and pattern, throughout the acoustic crossover region.That said, all your LF measurements should be ground plane.&nbsp; That might mean laying a trap box on it&#039;s side and blocking it up so the front is 90° to the &quot;ground.&quot;&nbsp; Likewise, your measurement mic should be as close to the ground plane as practical.&nbsp; Your measuring distance should be at least 3x the longest (diagonal) dimension of the enclosure.The different loading of the 2 15&quot; speakers will create an interesting acoustic crossover between them and I suspect this is part of what doesn&#039;t work well with an impulse response alignment.&nbsp; I&#039;m also presuming you are driving both 15&quot; from the same amp channel, which may (or may not) be possible depending on what you figure out about their behavior.I suggest you drive and measure each 15&quot; separately, using the same stimulus.&nbsp; Each speaker gets its own amp channel (at least for now).&nbsp; If Holm will let you save traces to the screen, you&#039;ll want to save both the magnitude and phase traces AND the impulse response.&nbsp;&nbsp; The reason for the impulse response is to look at group delay; it will be different for each loudspeaker loading.&nbsp; Next power the 15&quot;s from separate amp channels.&nbsp; Bring up the first channel and look at the magnitude and phase, then bring up the other amp channel and see what happens and at what relative levels.&nbsp; Now experiment with delaying the earliest-arriving 15&quot; to match the later speaker.&nbsp; What happens to the phase trace where the energy contribution of both speakers is within 6dB of equal?&nbsp; What do your ears tell you as you try these various evaluations?Once you have the 15s playing nice with each other, we can deal with getting the uppermost 15 to play nice with Mr. Horn.</blockquote>

[QUOTE="Tim McCulloch, post: 58490, member: 67"] Re: Voicing/tuning a 3-way home brew speaker cab Hi John- I'm not familiar with REW, and I downloaded (but never installed) Holm Impulse. I've been a Smaart user for a few years and I've made hundreds of bad measurements. I still do, but I can usually spot them now. :blush: At any rate, I think Bennett assumed that Holm Impulse only did "impulse alignment". What all the cool kids do these days is attempt to get consistent summation, both in amplitude and pattern, [I]throughout the acoustic crossover region[/I]. That said, all your LF measurements should be ground plane. That might mean laying a trap box on it's side and blocking it up so the front is 90° to the "ground." Likewise, your measurement mic should be as close to the ground plane as practical. Your measuring distance should be at least 3x the longest (diagonal) dimension of the enclosure. The different loading of the 2 15" speakers will create an interesting acoustic crossover between them and I suspect this is part of what doesn't work well with an impulse response alignment. I'm also presuming you are driving both 15" from the same amp channel, which may (or may not) be possible depending on what you figure out about their behavior. I suggest you drive and measure each 15" separately, using the same stimulus. Each speaker gets its own amp channel (at least for now). If Holm will let you save traces to the screen, you'll want to save both the magnitude and phase traces AND the impulse response. The reason for the impulse response is to look at group delay; it will be different for each loudspeaker loading. Next power the 15"s from separate amp channels. Bring up the first channel and look at the magnitude and phase, then bring up the other amp channel and see what happens and at what relative levels. Now experiment with delaying the earliest-arriving 15" to match the later speaker. What happens to the phase trace where the energy contribution of both speakers is within 6dB of equal? What do your ears tell you as you try these various evaluations? Once you have the 15s playing nice with each other, we can deal with getting the uppermost 15 to play nice with Mr. Horn. [/QUOTE]

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