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Author Topic: Phase shift using PEQ  (Read 1396 times)

BayensF

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Phase shift using PEQ
« on: June 13, 2013, 03:05:10 pm »

Hi,

I am using J River to send filtered signals through a 6 channel AMP to may 3 way stereo speakers. More about it including graphs created through REW on http://home.xmsnet.nl/bayens/.

Concrete questions, what will happen with the phase if I use PEQ filters? Do they "act" as when using caps and coils?
When using 12dB slopes at Bass, MID and High transducer I need to use Reverse Polarity for the MID, sure but what is the influence on the phase when using High Shelf and Low Shelf filters?

When I measure with REW I see the phase shifting, is it the sum of High Pass and Low Shelf for example or is it only caused by the High Pass?

Anyone?
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natehansen66

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Re: Phase shift using PEQ
« Reply #1 on: June 13, 2013, 05:14:19 pm »

The PEQ uses IIR (infinite impulse response) filters, aka "warped phase" filters. They will change the phase in the same way as an analog component would in a passive crossover.
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mwillems

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Re: Phase shift using PEQ
« Reply #2 on: June 13, 2013, 05:47:35 pm »

Hi,

I am using J River to send filtered signals through a 6 channel AMP to may 3 way stereo speakers. More about it including graphs created through REW on http://home.xmsnet.nl/cba/.

Concrete questions, what will happen with the phase if I use PEQ filters? Do they "act" as when using caps and coils?
When using 12dB slopes at Bass, MID and High transducer I need to use Reverse Polarity for the MID, sure but what is the influence on the phase when using High Shelf and Low Shelf filters?

When I measure with REW I see the phase shifting, is it the sum of High Pass and Low Shelf for example or is it only caused by the High Pass?

Anyone?

Nate's right all of the PEQ filters (shelf, high pass, EQ, etc.) all affect phase more or less as the equivalent analogue circuit would.  However, you can design PEQ filter schemes that wouldn't really be possible in analog (or at least not possible cheaply or easily), and there's no easy way (that I know of) to model what's going to happen with phase in advance once you get beyond basic topographies.

In my experience the only way to get a handle on what the PEQ filters are doing to your phase is to measure each element separately  (HF separately from MID and LF) , adding the filters (checking them) one at a time.  Otherwise it can be easy to miss interactions, etc.
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BayensF

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Re: Phase shift using PEQ
« Reply #3 on: June 14, 2013, 01:25:11 am »

 ;)Thanks for the reply. This is exactly what I am doing. I had hopped some kind of "user-guide" was available.

Anyway let's continue the "tweaking" it's a lot of fun because with MC PEQ it's so easy (and cheap). Every hour I spend is fun and almost always finetuning my speakers a bit more. Only room acoustics is killing sometimes the end result.

With kind regards,

FB Netherlands
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