Mid-Hi crossover time aligning with REW ? - Home Theater Forum and Systems - HomeTheaterShack.com

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post #1 of 14 Old 03-24-17, 04:16 AM Thread Starter
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Mid-Hi crossover time aligning with REW ?

I was trying to display multiple measurements / phases to align a mid-hi crossover, based on a selectable common measurement minimum phase display,
and wasn't successfull…
Can someone point me in the right direction ?
( Sorry to say, I'm used to Smaart 5 )
Thank you very much
and best regards

Klaus


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post #2 of 14 Old 03-25-17, 04:39 AM
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Re: Mid-Hi crossover time aligning with REW ?

Not really sure what you mean by based on a selectable common measurement minimum phase display. If there's a process you regularly use worth running through what it is to see if REW has something similar to offer.

There have been a number of threads about time alignment with REW lately, also worth a look through some of those.
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post #3 of 14 Old 03-25-17, 11:20 AM Thread Starter
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Re: Mid-Hi crossover time aligning with REW ?

Sorry if I was unclear…
I am trying to use REW instead of other software because the support for the DCX2496 filters…*at the same time*

If I display the overlay window, is there a way to show 'minimum phase' for selected measurements based on an individual measurement / time base of these ?
I.e. I show a minimum phase of the midrange system, and also display the highrange system minimum phase in the overlay window

> for time aligning 'thru crossover'

Thank you very much
and best regards

Klaus


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Last edited by redmountain; 03-25-17 at 11:34 AM.
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post #4 of 14 Old 03-25-17, 12:02 PM
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Re: Mid-Hi crossover time aligning with REW ?

Minimum Phase traces have had Excess Phase stripped out ( removed ) .

Excess Phase has all the "time of flight" information contained within it.
- TOF is what's needed for determining Time Offsets .

I just don't see a pair of minimum phase traces being of much use for time-aligning when they are now missing that key element of flight time .

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post #5 of 14 Old 03-25-17, 12:14 PM Thread Starter
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Re: Mid-Hi crossover time aligning with REW ?

I don't get it…
you mean in overlay, the phase isn't correlated between each measurement ?
Or how can I do that ?

Klaus


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post #6 of 14 Old 03-25-17, 12:36 PM
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Re: Mid-Hi crossover time aligning with REW ?

Quote:
redmountain wrote: View Post
I don't get it…
you mean in overlay, the phase isn't correlated between each measurement ?
Or how can I do that ?

Klaus

Klaus,

Are you asking me ( the above ) ?

REW traces are only referenced to a time Zero ( correlated I suppose ) if one first sets up a T=0, reference channel ( via a cabled loopback of output to input, using an unused soundcard chnl ).


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post #7 of 14 Old 03-25-17, 01:08 PM
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Re: Mid-Hi crossover time aligning with REW ?

Quote:
EarlK wrote: View Post
Klaus,

Are you asking me ( the above ) ?

REW traces are only referenced to a time Zero ( correlated I suppose ) if one first sets up a T=0, reference channel ( via a cabled loopback of output to input, using an unused soundcard chnl ).


Once a trace is captured with a T=0 reference point, then one can look within the IR ( Impulse ) window to see time of flight info .

Compare the TOC's of 2 traces to calculate the offset between the two ( easier said than done considering the large units that REW uses for display ).

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post #8 of 14 Old 03-25-17, 01:21 PM Thread Starter
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Re: Mid-Hi crossover time aligning with REW ?

I use the same rig as with Smaart,
1 soundcard ch = reference, 1 soundcard channel = measuring output / input.
So this should be ok…. not ? ( all measurements are then correlated time / phase wise, not ? )
Do I have to set anything else ?
> the wrapped phases in overlay woud be nice to be displayed as minimal phases so one can overlap phases in the processor settings on regions or crossover points…
Aligning 'just' by IR isn't what I'm trying to do, but exact phase overlapping…
Thanks a lot

Klaus


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post #9 of 14 Old 03-25-17, 01:44 PM
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Re: Mid-Hi crossover time aligning with REW ?

Klaus,
Main Steps:
> Set REW 'loopback timing'/'Acoustic timing' depending on XLR/USB mic.
> Measure MR driver and TW driver
> Select the TW measurement/impulse chart
> Open the 'controls' panel
> Select 'Estimate IR Delay' Record the delay that is offered (ms).
> Select 'Shift IR' [The TW impulse will shift that amount back to near 0 ms]
> Select the MR measurement/impulse chart. In the 'controls' panel and enter the recorded offset value used for the TW IR into the 't=0 offset(ms):' entry box and select 'Apply'
[The MR IR will shift the same amount as the TW. The relative timing will be unchanged as they were both shifted the same distance.]

REW settings for phase analysis:
> Open the 'overlay/phase' graph panel.
> Set 1/48 octave filtering for both measurements.
> Activate the 'IR Windows' popup.
  • Enter 0.00 into the 'Window Reference Time' box
  • Check 'Add Frequency Dependent Window'
  • Enter '5' into 'Width in cycles' [A greater number often works fine. Using a lower number will start to distort the trace tails.]
  • Select 'Apply Windows to All'

The phase overlay graph now displays the correct relative phase between the MR and TW and should be easily read. If it is not clear then there was an error in this process.

If you shift the MR impulse location to find the offset need for proper phase tracking then it is necessary to again enter 0.00 into the 'Window Reference Time' box and select 'Apply'. Any IR shift requires resetting the 'window reference time' to 0.00 to assure the phase relationship will be correct.
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post #10 of 14 Old 03-25-17, 01:51 PM
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Re: Mid-Hi crossover time aligning with REW ?

Thanks for chiming in John!

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