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TOPIC: DRC-DA8 FIR filter for phase only correction

DRC-DA8 FIR filter for phase only correction 3 years 5 months ago #25177

Hi guys. I have recently finished making a 3-way crossover using the IIR and PEQ capabilities of my MiniDSP DRC-DA8. The result is a flat amplitude response (using appropriately gated measurement to elimate reflections) at the measuring point, 1m from the baffle at tweeter level. The gated phase response is not linear, but integrates well between drivers and has an overall gradual slope from +180deg to -360deg from left to right over the frequency range.

I want to use the FIR phase only correction filters for each driver on my DRC-DA8 to linearise the overall phase of the loudspeaker while leaving my current IIR crossovers and PEQ filters in place. To do this, do I measure the individual response of each driver with the current IIR filter and PEQ filters applied (as shown in screenshots below)? Each driver is measured individually from the same point (1m from baffle and in line with the tweeter) as is the overall system response. Once this is done, import the results individually into rePhase, then use the phase EQ tabs to change the phase of each individual driver to be a flat line over the usable frequency band. Then, use the rePhase generated output for each and put this into the FIR filter for each individual driver on the DRC-DA8 plugin.

Presumably once this is done, I would measure the response of each driver again and the overall combined response and hopefully find that the response is still linear in amplitute but now also linear in phase.

Is this correct or am I not understanding the concept of phase correction correctly using FIR filters?

Note all measurements attached are gated to 3.2ms to remove reflections so low frequencies <300hz are inaccurate.

Many thanks in advance.

OVERALL SYSTEM


WOOFERS (2x scanspeak revelators 6.5")


MID (Morel EM428)


TWEETER (Scanspeak D2905/9500)


Solidworks Render of my speakers
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DRC-DA8 FIR filter for phase only correction 3 years 5 months ago #25187

  • sly
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Adjusting only the phase response in rePhase will do exactly what you suggest. However you may find that by improving the phase response, your amplitude response changes. Some harmonics will be affected as you improve the phase linearity. You may have to go back and tweak your IIR filters slightly, especially around the crossover regions.

I personally don't use IIR crossovers anymore. The DRC has an FIR section, as you know, and with FIR you can implement linear phase crossovers using rePhase. For me, it's easier to create linear phase crossovers with FIR than it is to create minimum phase crossovers using IIR and then use FIR to even them back out.
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DRC-DA8 FIR filter for phase only correction 3 years 5 months ago #25191

Hi sly, thanks for clarifying that. I understand as you say by improving the phase it may impact the amplitude response around the crossover regions slightly. This will hopefully not be a problem as I will tweak the IIR filters if required as you suggest.

I chose to start with IIR and PEQ because I was new to DSP and it seemed the easiest progression coming from traditional crossover design. I would like to try implement a complete FIR linear phase crossover once I am completely satisfied with my current effort using IIR and FIR for phase correction. The best bit is I can run both crossover types on separate configs on the DRC-DA8, such a great bit of kit!

Thanks again Sly.
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DRC-DA8 FIR filter for phase only correction 3 years 5 months ago #25193

  • john.reekie
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The FIR linear phase crossover is really easy. Easier than what you are doing.
I am not miniDSP support.

"You must ask the right questions." - Dr. Alfred Lanning's hologram.
-> Have you read the User Manual??
-> Have you drawn and posted a diagram?
-> Have you posted a screenshot?
-> Have you posted your config file?
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DRC-DA8 FIR filter for phase only correction 3 years 5 months ago #25196

  • john.reekie
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I am not miniDSP support.

"You must ask the right questions." - Dr. Alfred Lanning's hologram.
-> Have you read the User Manual??
-> Have you drawn and posted a diagram?
-> Have you posted a screenshot?
-> Have you posted your config file?
The administrator has disabled public write access.
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