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rplace

Active, DSP, REW, Xilica 101

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9 minutes ago, Chris A said:

If you select a single ramping filter on a channel, like a high shelf or a low shelf, you'll notice that the phase doesn't return to zero.  This is also the effect of crossover filters--they shift phase between channels (which is usually not desirable).  That's why I have advocated PEQs instead of ramping filters (and REW's EQ facility doesn't handle ramping filters, either). 

 

Every answer yields 10 more questions. When I started down the zero order cross over I did it with PEQs. I thought the idea was go get rid of the named (Bessel, LR, Butterworth) crossovers for phase reasons discussed in numerous posts. Then I became aware of shelf filters in the Xilixa from @Rudy81. I decided to give that a go for no other reason than it was another thing to learn about on my Xilica. *IF* I am understanding you correctly the shelf filters mess with my phase which is what we were trying to avoid. Is that correct?

 

Some screen captures to follow. One using Shelf filters 1 low and 2 high. The other uses only PEQs. I tried to look at the individual wrap of phase for the HF and LF and pick a point where they overlapped and were within in 90 degrees....but I'm still trying to figure this all out.

 

Side Note, attempts to cross around 500-800 (Shelf and PEQ) always seem to give worse Phase/GD than attempts around 200-350 but I get a better spectrogram with the 500-800 range. Is it just a matter of striking a balance?

 

Should I give my "shelved" preset a switch over to PEQs?

 

Here is the relevant screen shots for the Shelf Filtering to attenuate:

Shelf1.thumb.JPG.d4d9e7ed38cb1d0c95ef00ad22d56cd0.JPG

 

Shelf2.JPG.aaca30ed5ed1cd5c6b43cb036b0d1e91.JPG

 

 

And here is the relevant screen shots for the PEQ attenuation:PEQ1.thumb.JPG.34ff5199c0f53451d3da419eb9c5c00b.JPG

 

PEQ2.thumb.JPG.a264f839d73a2c54ab70dab601b82211.JPG

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7 minutes ago, Chris A said:

While you're here, can you recall an instance where you used an all-pass to correct phase?  Or a ramping filter...

 

Yes, allpass compensation is necessary in any Linkwitz-Riley crossover having more than two passbands. See response from Greg Berchin (who is actually me) here: https://www.dsprelated.com/showthread/comp.dsp/112896-1.php

 

As for a ramping filter, not sure what you mean. Is that commonly called a shelving filter? If so, then I use them occasionally in place of peaked-highpass filters to boost bass, because they have better phase response.

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1 hour ago, rplace said:

*IF* I am understanding you correctly the shelf filters mess with my phase which is what we were trying to avoid. Is that correct?

Yes, if you're looking for phase flattening.

 

1 hour ago, rplace said:

Is it just a matter of striking a balance?

That's been my experience.

 

1 hour ago, rplace said:

Should I give my "shelved" preset a switch over to PEQs?

Try them both ways and look as the resulting phase response overall.  I've seen instances where it might be advantageous to use shelving filters (which I referred to as ramping filters above because they really do ramp instead of creating shelves).

 

Chris

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