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JBL M2 crossover with the openDRC 6 years 2 months ago #24618

  • kallis
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im also considering building these. i have the 2x4HD. it only got 1024 taps per channel so when i copy FIR settings rephase cuts the corners. it looks somewhat like the original but not quite there.
i tried inputting IIR settings from the document but it looks nothing like the reference.

not too picky on a few variations being that big of a deal in practice, as long as the compression driver doesnt get a higher load etc.
any pointers? thanks

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Last edit: by kallis.

JBL M2 crossover with the openDRC 6 years 2 months ago #24620

  • john.reekie
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Pointers for what? Maybe post some info or screenshots or something.

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JBL M2 crossover with the openDRC 6 years 2 months ago #24621

  • pos
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Hello kallis

1024 taps at 96kHz is not going to cut it for the woofer, and even possibly not for the compression driver either.
How many biquads per do you have at your disposal?
I will try to find a usable/elegant solution for the 2x4HD by mixing FIR and IIR at the right places, and add it to the google document (and here).

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JBL M2 crossover with the openDRC 6 years 2 months ago #24622

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that was fast.
im not that familier with the workings, and compared to DRC etc, but the 2x4HD plugin has 10 parametric IIR EQ bands per channel. so i was just trying to find out if its doable or not with it as i dont have complete perspective on it. :laugh:

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JBL M2 crossover with the openDRC 6 years 2 months ago #24625

  • pos
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Ok, it looks like 10 PEQ will complement the FIR quite nicely.

So, here is how to do it:
- take both presets and change the sampling rate to 96kHz and the number of taps to 1024.
- re increase the FFT length to 32768 to ensure good good precision, and leave all other impulse parameters as is.
- the HF part does not need any further modification and will work entirely within the FIR.
- the LF part requires the 8 lowest paragraphic EQ points to be zeroed and transferred to the IIR section in the 2x4HD using the "parametric Q" values from the google doc (miniDSP products do not use "constant Q" conventions).

7 of these EQ points are in bank 2, and the last one (500Hz) is in bank 1.

I reported these 8 EQ points and the values to enter in the 2x4HD in the attached picture.


Hope this helps!
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JBL M2 crossover with the openDRC 6 years 2 months ago #24640

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thanks alot :) even though the CD is FIR i still need all the input settings right? and i can disregard XO settings for both channels?
i feel like a idiot, the new software with external windows is more confusing than the regular 2x4 and with FIR in i wouldnt know the full picture without measuring the output. :silly:

btw, minidsp only has one decimal for Q and Hz so i had to choose the closest equivalent.

FIR and PEQ looks like this for now:





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Last edit: by kallis.

JBL M2 crossover with the openDRC 6 years 2 months ago #24651

  • pos
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The rephase presets from the google doc include both input ant output EQs (input EQs are put on the output), as well as the crossover, level offsets and time offsets.
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Last edit: by pos.

JBL M2 crossover with the openDRC 6 years 2 months ago #24948

  • johoo
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Kallis: How did it work out with the 2x4HD and M2? Im considering to trying it out myself as a complete preamp/dac/dsp solution.

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JBL M2 crossover with the openDRC 6 years 2 months ago #24965

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have not gotten that far yet :laugh: but as pos suggests it should work in theory. one thing you have to watch out for is clipping the unit on lower gain amps, and the volume control with the current firmware is a bit rough on higher gain. too much per click of the remote.
i supoce the opendrc-da8 will work also? 3x FIR + PEQ.
someone smarter than me might chime in. :silly:

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JBL M2 crossover with the openDRC 5 years 10 months ago #26863

  • iansr
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Dummy question: if you have a digital source such as a streaming device that has a digital output, how do you feed the 2 separate open DRC devices?

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JBL M2 crossover with the openDRC 5 years 10 months ago #26864

  • pos
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Here is what I am currently using:

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Last edit: by pos.

JBL M2 crossover with the openDRC 5 years 10 months ago #26868

  • iansr
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Thanks pos. Next question. Given that the openDRC DI unit only has digital inputs I can't see how you would set things up if you have both digital and analog sources. Am I missing something?

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JBL M2 crossover with the openDRC 5 years 10 months ago #26869

  • pos
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Correct, no analog source unless you add an ADC in front of one of the existing digital inputs.
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JBL M2 crossover with the openDRC 5 years 10 months ago #26881

  • planetti
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For splitting the signal for the two (and up to three) opendrc DI or DA I suggest the behringer src 2496 (see www.music-group.com/Categories/Behringer...aces/SRC2496/p/P0141). Although it is not very chic, it brings high value to the boxes:
Analog input ADC with +20db, 96kHz or alternatively digital input up to 192kHz SRC which is better than the SRC of the opendrc, particularly if the digital signal is not excellent. Then there are 3 digital outputs which are absolutely synchronized to 96kHz,24dB which provides a very clean signal for the opendrc and improves their "musical timing". Under 100€ on ebay auctions.

Before, I tried the passive TOSlink splitter which degraded the optical signal severly. I also tried the best active Marmite TOS-splitter 1 to 4, 192kHz which cleaned and amplified the signal a bit, but there were glitches every minute due to digital synchronizing problems.

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Last edit: by planetti.

JBL M2 crossover with the openDRC 5 years 10 months ago #26882

  • iansr
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For splitting the signal for the two (and up to three) opendrc DI or DA I suggest the behringer src 2496 (see www.music-group.com/Categories/Behringer...aces/SRC2496/p/P0141). Although it is not very chic, it brings high value to the boxes:
Analog input ADC with +20db, 96kHz or alternatively digital input up to 192kHz SRC which is better than the SRC of the opendrc, particularly if the digital signal is not excellent. Then there are 3 digital outputs which are absolutely synchronized to 96kHz,24dB which provides a very clean signal for the opendrc and improves their "musical timing". Under 100€ on ebay auctions.

Before, I tried the passive TOSlink splitter which degraded the optical signal severly. I also tried the best active Marmite TOS-splitter 1 to 4, 192kHz which cleaned and amplified the signal a bit, but there were glitches every minute due to digital synchronizing problems.


Interesting, thanks.

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