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Old 19th November 2012, 05:18 PM   #11
pos is offline pos  Europe
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Quote:
Originally Posted by CopperTop View Post
I've downloaded it, and look forward to playing with it. Thanks.

The phase thing in general is very interesting, and something I don't yet feel I entirely understand.

In the second illustration down, the phase goes through several 'wraps' of 360 degrees. This might be explained by a constant delay caused by, say, the distance between driver and mic, with the true phase shift of the speaker riding up and down on top of the linearly descending line, presumably(?). If we somehow infer what the constant delay is and remove it, and yet the phase still goes through several 'wraps', can we still linearise it? Am I really talking about 'minimum phase' vs. 'excess phase'? (two terms whose meanings I don't think I fully understand yet). Programs like REW allow you to export what they call a minimum phase version of the impulse response. How do they separate the minimum from excess phase, and does your program implicitly do the same thing, Thierry?

Thanks!
Hi,
Holm Impulse will generally lock the offset of the impulse to the highest peak, so that the phase ends up at 0° at the end of the band and the delay is suppressed. In some case it will need some manual fine tuning (like when measuring a speaker with a high order and high frequency crossover) but Holm generally copes with this problem quite well.

Thierry is showing two different uses of rephase here: filter generation (which require one convolution per channel) and filter linearization (which only require a stereo convolution, in front of an existing crossover, passive or active).
In this second approach rephase is very similar to phase arbitrator:
DSP Loudspeaker Phase Arbitrator. Transient Perfect loudspeaker processor
http://www.thuneau.com/Loudspeaker%2...er%20Guide.pdf

In all cases it will only generate the correction impulse (embodying a filter or a simple phase or gain eq, etc.) and you then need a convolution engine to "run" it through inside your signal pass.
You can use a PC like Thierry is showing here, or an external convolution engine such as the mini DSP openDRC (limited to stereo for now, but it looks like it will envolve soon).
If you only wants to linearize and existing crossover you can use a simple plugin with your media player, such as foobar convolver.

There is a thread about rephase in the multi-way section of this forum:
rePhase, a loudspeaker phase linearization, EQ and FIR filtering tool
Questions and suggestions are most welcome.

If you read french here is another tutorial, explaining how to use rephase with jriver convolution engines for complete speaker filtering, similar to what Thierry is achieving here with a VST host:
http://jimmy.thomas.free.fr/Jriver/T...olmImpulse.pdf

And some measurements of speaker (with existing crossovers, both passive and active) linearization listed here:
rePhase: linéarisation de phase, EQ et filtrage FIR - Enceintes

Last edited by pos; 19th November 2012 at 05:21 PM.
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Old 21st November 2012, 11:50 AM   #12
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here an example of a stereo+sub file config to import with vst convolver

Click the image to open in full size.

example for a stereo+2 subwoofer

Click the image to open in full size.

example for 2ways FIR cossover + 1 subwoofer

Click the image to open in full size.

Last edited by thierry38efd; 21st November 2012 at 12:04 PM.
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Old 21st November 2012, 01:14 PM   #13
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an example for stereo to 5 loudspeakers
i've omit to apply .5 coefficient (-6dB ) to channel 3,due to the sum of the right and left channel.

Click the image to open in full size.

just generate a flat response with rePhase.(all the impulse response are MONO ),only for the use of VSTconvolver which use mono impulse.
nothing to change when opening rePhase,just set the file name (i.e flat-response on the graph below ) and mono+wav

Click the image to open in full size.

Last edited by thierry38efd; 21st November 2012 at 01:21 PM.
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Old 21st November 2012, 06:20 PM   #14
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using rePhase.

open software and create a Hpf and a Lpf filter
advices for setting IR are done in the window

Click the image to open in full size.

generate IR (16 or 24 bits )
.wav for convolver and REW simulation
.txt for HOLM simulation

open REW-->file-->import impulse response-->choose IR generated by rephase

import lpf.wav and import hpf.wav
all spl-->controls tab-->generate A+B (lpf.wav+hpf.wav)

Click the image to open in full size.

you can apply the filter IMPULSE to speaker measurement.convolution are LPF x woofer and HPF x tweeter in this case.
generate the sum filtered_woofer + filtered_tweeter

Click the image to open in full size.

Last edited by thierry38efd; 21st November 2012 at 06:32 PM.
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Old 21st November 2012, 10:36 PM   #15
pos is offline pos  Europe
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Thank you Thierry for this very interesting tutorial!
I did not know REW could do A*B and A+B manipulations!
Holm also does, but is somewhat picky (to say the least) when it comes to importing impulses and doing manipulations between them, especially on windows7...
I will have to give it a try!
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Old 22nd November 2012, 04:16 PM   #16
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Hello,

Quote:
I did not know REW could do A*B and A+B manipulations
same as you,i've just discover it few days ago




the graph below shows how simple is the FIR crossover+DRC processing.

Click the image to open in full size.


only two files

-a stereo file for DRC and phase linearization
-config.txt for VSTconvoler

more simple ?
never seen.

to generate DRC impulse:
two ways:
-DRC/align http://www.ohl.to/audio/downloads/align2.zip

Click the image to open in full size.


-using personnal measurement
a long MS sequence (30 sec min )
moving micro around the listening spot (random movement during sequence )
create a personal curve rePhase and REW in simulation.

export the DRC.wav in the SIR v1.011 convolver
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Old 24th November 2012, 03:30 AM   #17
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Thanks for the tutorials! I'm going to be using rePhase for a 3-way active linear phase xo soon so this should help.

I'd like to add that J River Media Center can also do convolution (64 bit processing) and supports the config file format. It also has a loopback function that works similar to virtual audio cable. At this point I'm not sure if it can do multiple convolution tasks like multi-way config + global DRC.
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Old 24th November 2012, 08:30 AM   #18
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Quote:
Quote:
I'd like to add that J River Media Center can also do convolution (64 bit processing) and supports the config file format. It also has a loopback function that works similar to virtual audio cable. At this point I'm not sure if it can do multiple convolution tasks like multi-way config + global DRC.
yes,you can do the same work with Jriver,only one software.
the config file is the same.(i believe that Jriver is using vstconvolver)

you can add convolution plug in to Jriver,SIR v1.011,leCAB2...
otherwise,to add DRC file in he config file:

44100 2 6 0
0 0
0 0 0 0 0 0
c:\DRC-left.wav
0
0.0 ;convolution to channel front left
0.0
c:\DRC-right.wav
0
1.0 ;convolution to ch front right
1.0
...
...
and continue with crossover convolution for each channel.DRC convolution will be add the filter convolution.for each way

no limit of convolution in the config.file

you can add crosstalk...
just prepare all the impulse before (with rephase,and align2 for DRC)
here for drc software

be careful not to swap sub IR with hpf IR
tweeter may not appreciate low frequency (without capacitor on tweeter )

you can do it manualy
import DRC.wav with REW
import hpf.wav
use a x B tool to convoluate the IR,export the new IR as hpf-drc.wav
etc....
this is eavy to do

just add a convolution plug in to jriver (sir v1.011)
and load every DRC.wav you need.

Last edited by thierry38efd; 24th November 2012 at 08:42 AM.
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Old 24th November 2012, 09:11 AM   #19
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see at bottom left,plug-in tab for each channel
insert sir v1.011 for each one
you can use multiple instance of SIR without issue.

Click the image to open in full size.
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Old 24th November 2012, 02:56 PM   #20
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Cool thanks!
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