EASY FIR crossover PC based+DRC

[thierry38efd]

Making your own house target and create the FIR filter equalization file

open rePhase

create with filters and EQ the house curve you need.(slopes,low frequency boost ,subsonic filter )



export the target with target.txt for holm
export the target with target.wav for REW.
open HOLM or REW

A slot import the target.txt you've created with rephase.
B slot import the measurement (right or left at the listenning spot ).

change offset to merge the two curves,it will avoid high positive corr.

C=A/B
it gives the global equalization.



the green curve (C) is the result of difference between measurement and target.

the limitation of positive correction.
C=A x B
create with rephase an IR with negative EQ to reduce the too positive ones



export as .WAV,and make a stereo file with an another measurement.

same work can be done with REW or HOLM.

[thierry38efd]

correction in green,simulated with REW
next,i'll sown measurement in room with this method

[natehansen66]

Have you used linear filters generated by rePhase in J River convolution?

I just got my speakers setup using linear phase crossovers generated in rePhase. Horrible clicks and pops. I upped the latency on my interface to 1024 samples from 512 and it helped a bit (sounded like the woofers were clipping at 512 but they were nowhere near that). Still, the clicks pops and dropouts make it unlistenable as is.

[thierry38efd]

Have you used linear filters generated by rePhase in J River convolution?

not me,few people are running with rephase,jriver and config file for crossover.it's ok.(DRC and FIR crossover ).

using the same sampling frequency is very important,48 kHz seems to be a good choice.
frequency of the source and Impulse must be the same.(otherwise it gonna troncate with the kind of phenomem you've describe ).

i can try with j river jukebox (freeware ).i gonna check...

in rephase,how any taps (samples) did you set for generation ?
default is 8192 taps,you can check with lower value.
in rephase,when you generate,take a look at the bottom right,it gives the lenght of impulse in second (taps/sampling frequency)

with J.river,be careful if you're using DRC convolver (like SIR) with crossover convolver.
you have to reorder plugin to set DRC before crossover.

[natehansen66]

Thanks, I'm running JR's convolver and everything is at 48khz. It's working fine now. I've been doing a lot of audio stuff the last couple days on this PC getting these speakers setup and didn't do the obvious........reboot the machine It's all good now.

Thanks again for your in-depth tutorials.

[thierry38efd]

good new.

did you insert a DRC file before convolver crossover ?
what software are using to create your DRC file ?

[natehansen66]

I'm not doing any DRC yet, I wanted to get this going before adding anything else. I'm only using rePhase to build the crossover filters, and I do eq with JR's parametric equalizer. I'm not real crazy about rePhase's eq abilities and it's easier to make changes on the fly using the PEQ in JR. Phase comes out nice and flat this way so I'm happy.

I'm still having some issues with the audio stuttering though. I like to use the loopback function in JR for Netflix, Spotify, etc. In order to get the loopback to work without pops and clicks (at least when I was doing my eq and crossovers exclusively in JR's PEQ) I have to set the buffer super low, about .05 seconds. I can get clean playback from my hard drive in JR doing convolution with a higher buffer (2.5 seconds), but the loopback suffers. The loopback function doesn't work all that well with a low buffer and convolution though either. Gotta look into that.

[thierry38efd]

rephase EQ is intend to correct definitvely direct field measurement.once done,no reason to change it
also you can add bass boost and subsonic filter in the crossover.
J River eq is not linear phase EQ,but it does not affect sound .(i do not listen difference phase linear and minimum phase ).


did you try less taps for IR.
the longest one is define by the lower frequency ,slope and ripple level.
depend of your sound card.
after this, apply the same number of taps for all impulse,band pass,high pass.
you may need only 1000 taps.(21 ms)
did you increase partitions in the convolver,paralleling process reduce delay.

[natehansen66]

Originally Posted by thierry38efd

rephase EQ is intend to correct definitvely direct field measurement.once done,no reason to change it

I understand that......it's getting it done that is the problem. Typically I build my eq filters in REW and copy them to the parametric eq in J River. Measurements confirm that REW's simulated eq'd response follows the actual output fairly close. On the fly changes are easy to make. The same set of filters plugged into rePHase's eq don't produce anywhere near the same result. The A + B trick gets kind of close to the actual result, but gets tiresome when you're working with 20+ filters . The eq in rePhase is a bit buggy as well, at least in the Gain Bank.

J River says they're working on convolution latency handling for the loopback function. I've set a second zone for now with min phase filters to use the loopback, but I'm going to look into the number of taps for the filters.

I don't know anything about how these FIR filters are built so this is a learning experience. I'm playing around with different numbers of taps in rePhase, and I'm wondering what the threshold for quality is (I suppose that's subjective). I've got a 35hz hi-pass (250 low pass), so right away I understand that's going to require more than a hi-pass at 80 would. The default 8192 taps shows a textbook roll-off and a nice continued slope as far down as the graph will go. At 5000 taps I'm getting ripple and a greatly reduced slope for the low pass starting around -100. For the 35hz high pass the slope starts transitioning to a shallower one around -40 and at 10hz -52 has transitioned to flat (no slope).

Any "rules" on whats acceptable here? I'm thinking anything greater than -50 or so wouldn't be audible at all or have any negative effect........but then I'm just guessing and like I said I don't know anything about linear phase filters.

[Boden]

Bonjour Thierry,

What are the minimal PC Hardware requirements to run your setup?

Also, is the SB Audigy working satisfactory sound quality wise pr would you rather recommend a different soundcard?

Merci,

Eelco