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Low Earth Orbit
DIY Audio
60 Degree DIY Mid Hi - AKA PM60
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<blockquote data-quote="Mark DeArman" data-source="post: 145408" data-attributes="member: 950"><p>Re: 60 Degree DIY Mid Hi</p><p></p><p>Peter, I wouldn't be to worried about your loopback measurement there. Any good measurement system which is band-limited, will produce a loopback impulse response which looks like that of an FIR filter (symmetric and asymptotically decreasing side-lobes). That is because it is band-limited and has some finite delay.</p><p></p><p> On some systems I've used, this will be the IR of the envelope function applied to the stimulus. Some systems, do their delay correction by just doing a circular move on the IR back to zero.</p><p></p><p>The only time I calibrate that out in my system, is if I need to do absolute delay (phase) measurements. Once calibrated, you end up with a loopback response which looks more like you would expect, flat line with one sample at unity ( ie. exact delta function ). If you don't care about really low frequency, reaally high frequency (near Fs/2), or absolute group delay then it doesn't really matter. </p><p></p><p>Mark.</p></blockquote><p></p>
[QUOTE="Mark DeArman, post: 145408, member: 950"] Re: 60 Degree DIY Mid Hi Peter, I wouldn't be to worried about your loopback measurement there. Any good measurement system which is band-limited, will produce a loopback impulse response which looks like that of an FIR filter (symmetric and asymptotically decreasing side-lobes). That is because it is band-limited and has some finite delay. On some systems I've used, this will be the IR of the envelope function applied to the stimulus. Some systems, do their delay correction by just doing a circular move on the IR back to zero. The only time I calibrate that out in my system, is if I need to do absolute delay (phase) measurements. Once calibrated, you end up with a loopback response which looks more like you would expect, flat line with one sample at unity ( ie. exact delta function ). If you don't care about really low frequency, reaally high frequency (near Fs/2), or absolute group delay then it doesn't really matter. Mark. [/QUOTE]
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60 Degree DIY Mid Hi - AKA PM60
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