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TOPIC: miniSHARC + rePhase

miniSHARC + rePhase 6 years 4 months ago #12531

  • Ken Tripp
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Anybody using a miniSHARC board with the 96khz plugin and using rePhase to correct the phase of individual filter sections. Not sure what I'm doing wrong but even trying to correct just one filter isn't working. In this case a 1khz LR 24db/oct.

Start with this...



Apply...



And end up with this...

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miniSHARC + rePhase 6 years 4 months ago #12535

  • dreite
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Ken,

I'm not sure of your measuring setup, but remember you're introducing a 5.33mS (in your example) delay into your modified channel. If you're making a two-channel measurement you'd need to introduce an equivalent delay into your reference channel as well.
However, in your case, it seems you have something else going on also.

It will work though. Here's a measured phase plot from my miniSHARC implementing a three-way LR4 phase linearization filter.

Dave.
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miniSHARC + rePhase 6 years 4 months ago #12543

  • Ken Tripp
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Thanks Dave,

I've used both REW and HolmImpulse, same result and whilst the delay might mess up the phase response it's the ripples and attenuation of the amplitude response that's really got me confused.

At this stage I don't know whether it's something I'm doing wrong in rePhase or getting the the file into the miniSHARC 4X8 plugin or to the board itself.

Perhaps some decent documentation for rePhase or the miniSHARC plugin would be helpful!

As you've got it working would you care to step me (and no doubt others) through what should be a simple process?

For a start should the way I've got rePhase setup work and output the correct file for the miniSHARC plugin to work with?

And a question on your measured phase plot.

It's the summed output of 3 channels of the board?

A LP, a matching HP and another LP (a bandpass) and a HP so the output of any individual channel should be a flat line at 0 or 360 degrees?

Cheers,

Ken
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miniSHARC + rePhase 6 years 4 months ago #12547

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Your rePhase setup looks okay to me, but your measuring results are clearly puzzling. If you make an electrical measurement only your amplitude response should be ruler flat just as in your rePhase display screen. In Holmimpulse it should look just as it does for a loopback measurement.....except for the phase response which will be wrapping at your selected 1000Hz frequency.

The measurement I posted is not a summed response, that's a single output with that phase response implemented. However, a summed response from three associated (LP, BP and HP) outputs would look identical.

Cheers,

Dave.
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miniSHARC + rePhase 6 years 4 months ago #12548

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So if I have bandbass filter section (IIR) at say 110hz and 1.7khz (channel 2) I just need to apply Phase Linearization with two corrections for 110hz and 1700hz for that filter section (channel 2). So something like this...



And then do a matching 110hz correction for channel 1 and another 1700hz for channel 3.

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miniSHARC + rePhase 6 years 4 months ago #12550

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Yeah, that would be one way to do it. That would be the preferable way if you were using the OpenDRC hardware/plugin.
Since you're using the miniSHARC plugin and you can't implement a phase correction upstream of the crossover, I think I might just use the Linear Filters tab in rePhase.

Dave.
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miniSHARC + rePhase 6 years 4 months ago #12551

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"Since you're using the miniSHARC plugin and you can't implement a phase correction upstream of the crossover"

So if I'm understanding this correctly if you're using IIR filters in the 4x8 96khz plugin you can't use FIR as well!!!

Or at least not to correct any phase errors the IIR filters cause?
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miniSHARC + rePhase 6 years 4 months ago #12552

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Sure, you could use both...if you want to. However, if you use the FIR sections to create your main filters then you won't have any phase shifts to correct.
I don't see any point in creating the main filters with the IIR sections and then linearizing their phase with the FIR sections. Might as well kill two birds with one stone.

Dave.
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miniSHARC + rePhase 6 years 4 months ago #12553

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I was under the impression that filters implemented in IIR and then phase corrected in FIR was more efficient, ie. used less TAPS than using FIR to implement the filters directly.

Getting back to your previous post, can you use IIR filters on the 4x8 plugin and then use FIR as well to correct the phase shifts? Your last two posts are slightly at odds with each other.

And someone from the development team, feel free to join the conversation at any time.
Last Edit: 6 years 4 months ago by Ken Tripp.
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miniSHARC + rePhase 6 years 4 months ago #12559

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No, I don't think they're at odds. Maybe I just didn't explain correctly.
The way the miniSHARC plugin is configured, the FIR sections are applied to each output. You can't apply a "global" FIR correction at the input. This means you have to correct phase response with individual/different filters on each output vice using a single one upstream. (It's not as convenient and logical....IMHO.)
This is what I'm referring to with this posting:

www.minidsp.com/forum/opendrc-series-sup...in-minisharc-plugins

Regarding the "hybrid" approach......just fine to do it either way. It's not like you have a shortage of horsepower with this platform. :)

Cheers,

Dave.
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miniSHARC + rePhase 6 years 4 months ago #12567

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Thanks Dave now understood.

So (and assuming rePhase is spitting out the correct stuff) what am I doing wrong at the 4x8 plugin end.

Care to walk me through the process...



I'm assuming you click on the Unload FIR then the Browse button, select the .BIN file and then Send to DSP.

Which is what I'm doing now without success.

As for horsepower, doesn't go far at 96kz and doing a 4 way.

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miniSHARC + rePhase 6 years 4 months ago #12568

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How about posting your midfir.bin file and let me try it on mine?

Dave.
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miniSHARC + rePhase 6 years 4 months ago #12569

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Here it is, should be a single 1000hz 4th order LR correction.

Edit. Well it would be if the file attached.
Last Edit: 6 years 4 months ago by Ken Tripp.
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miniSHARC + rePhase 6 years 4 months ago #12570

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Here it is, should be a single 1000hz 4th order LR correction.

Edit. Well it would be if the file attached.

Edit: Nor can I send you a PM.

Edit: Put it on a web site at...

tripp.com.au/share/midfir.bin
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miniSHARC + rePhase 6 years 4 months ago #12588

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Sorry, had to get some sleep. :)
You can attach files to your messages, but you'll need to rename them with a .txt extension because this forum won't support .bin extensions.

So that .bin file looks just fine when measured on my setup. (See attached photo.)
Since my miniSHARC is setup for 48khz operation it's showing the phase wrap at 500Hz vice 1000Hz, and I had to add 10.66mS (vice 5.33mS) of delay to my reference channel to make the two-channel measurement.

It seems like your rePhase process is perfectly fine, but the issue is with your measuring setup.

Cheers,

Dave.
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