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Same FIR sample offsets.....different delays?? 5 years 4 weeks ago #27254

  • captgnarly
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OpenDRC -DA.

Comparing two FIR files, one on Config 1, second on Config 2................
Both files made with rePhase, both have 6144 taps, middle centering, closest perfect impulse, and both show same 3072 sample, 64ms offset.

I get a measured delay difference of 0.65ms between the two files (measured with smaartlive at the OpenDRC's XLR output).

These files are for a mid freq driver, 100 to 650hz, so the difference is material as it requires time realignment with adjacent bands to be able to make any sonic evaluation...

Any ideas why?

Thx, Mark

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Same FIR sample offsets.....different delays?? 5 years 4 weeks ago #27260

  • john.reekie
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Are you using a timing reference?
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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Same FIR sample offsets.....different delays?? 5 years 4 weeks ago #27263

  • captgnarly
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Are you using a timing reference?


Hi John,

Yes, my timing reference is a x-32 mixer analog out. The mixer's AES output feed the miniDSPs.
I've never noticed any anomalies with timing across two OpenDRC 2x2s, and one DA-8.....tuning a 4-way...
...until I got around to trying to set up more than one Config...

Config 1 reads what I expect...Config 2 has the (unexpected) extra delay..

I mean, I've made boatloads of timing measurements, outdoors too. Scratching my head :unsure:

Hey, as I was typing this, I just thought of a error checking path.........I will load the same FIR file in Config 1 & 2 and check delays...
Will return with results ....

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Same FIR sample offsets.....different delays?? 5 years 4 weeks ago #27283

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Ok, loading the same FIR file into both Config 1 & 2 slots, I get the same timing.
Yea, as expected, good news ! No prob with OpenDRC !

So I guess now I have to figure out why two different rePhase files with the same tap count and centering give such different timing.
One was Hann, and one was Nuttall...can that have anything to do with it?
Do different tap structures somehow need different processing time?

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Same FIR sample offsets.....different delays?? 5 years 4 weeks ago #27288

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I hope everyone will pardon me from starting a worthless questioning thread....

I found the timing difference...I forgot I put in -700us timing offset in rePhase on the Config1 file , when doing some phase flattening...

Sorry folks...
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Same FIR sample offsets.....different delays?? 5 years 3 weeks ago #27380

  • devteam
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Glad you figured it out. :-) That's a common mistake in building FIR filters.. It happens .. :-)
Thanks for sharing with the community to hopefully make sure others find this.

DevTeam
miniDSP, building a DSP community one board at a time.

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Same FIR sample offsets.....different delays?? 5 years 3 weeks ago #27414

  • captgnarly
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Glad you figured it out. :-) That's a common mistake in building FIR filters.. It happens .. :-)
Thanks for sharing with the community to hopefully make sure others find this.

DevTeam


Thanks DevTeam, ,,,,,,,,very kind words from those who are constantly facing questions spawned by user error :cheer:

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