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post #41 of 45 Old 09-30-12, 03:19 PM
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Re: simple impulse wave question

I've zipped up a Word doc on phase. This is much easier for composing with pictures and links. Otherwise I will post up bits and pieces.

Windowing technique is best gained through practice/experimentation. This is especially true when working with real signals. Time references for signal and windowing are crucial. In many software packages window lengths are limited to powers of 2. REW allows many choices. Tweaking sizes and references for particular situation is useful. With time alignment, it is important that windows for observing two signals be of same type, size, and time reference.

Let me know if attached doc makes sense.

Regards,

Andrew
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post #42 of 45 Old 10-01-12, 04:42 PM
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Re: simple impulse wave question

Looks like a useful document, but I would suggest one correction: in the document you quote Steven Smith as saying "Several different windows are available, most of them named after their original developers in the 1950s. Only two are worth using, the Hamming window and the Blackman window." but you omit the context in which his comment was made, which was regarding the choice of windows for designing windowed sinc filters. Other windows have advantages in other applications, with various tradeoffs in frequency resolution and sideband suppression.
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post #43 of 45 Old 10-04-12, 02:56 PM Thread Starter
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Re: simple impulse wave question

Quote:
Barleywater wrote: View Post
I've zipped up a Word doc on phase. This is much easier for composing with pictures and links. Otherwise I will post up bits and pieces.

Windowing technique is best gained through practice/experimentation. This is especially true when working with real signals. Time references for signal and windowing are crucial. In many software packages window lengths are limited to powers of 2. REW allows many choices. Tweaking sizes and references for particular situation is useful. With time alignment, it is important that windows for observing two signals be of same type, size, and time reference.

Let me know if attached doc makes sense.

Regards,

Andrew
Hi Andrew,
Your windowing approach surelly does make sense for me too. The resulting plots speaks for themself.
I would like to be able to duplicate the same but I need some REW technics advices to realize that.
I am not able to plot phase curve in the same format. This must be a really simple REW option that I overlooked somewhere?

I've joined an anoted copy of your word file.

Just to be sure, do you suggest that I could do the same with REW alone? I can only use real signals going through Jriver with system delays.

The uses of this proceedure must be more usefull for lower frequency crossovers since a tiny microphone position changes these very fine time delay settings and phase relationship.

regards
jacques
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post #44 of 45 Old 10-04-12, 04:26 PM Thread Starter
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Re: simple impulse wave question

Are these settings are suitables BH4 ?
Attached Thumbnails
simple impulse wave question-jpg-image-pref_-bh4.jpg  

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post #45 of 45 Old 10-05-12, 10:20 AM
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Re: simple impulse wave question

Preferences settings sets window type and length for new measurements and for imported measurements.

IR Windows is used for changing windowing of open measurements.

Loopback timing reference maintains relative timing of multiple measurements, but propagation delays add excess phase. Same amount of excess phase is removed from all measurements. This reduces slope of phase display. Short windows may be thought of as providing time dependent smoothing.

I set REW up on my screen like this:

simple impulse wave question-rew-work-layout-2.jpg

Switching between phase and impulse in overlays panels allows easy viewing of waveform relative timing.
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