Using REW and rephase to generate amplitude and time domain corrections

[SwissBear]

Hi everyone,

I wanted to share a new feature of REW/rePhase which makes combining the two pieces of software to make amplitude corrections in the frequency domain very easy.

Since v5.17 Beta 12, REW incorporates a rePhase EQ filters set, which makes it easy to generate amplitude correction filters aimed at being used with rePhase. In the EQ tab of REW, select rePhase as an equalizer and generate your filters. You can then export these filters as text.

You filters file should look like this:

Then, in rePhase, you can easily import these filters:

in order to apply them as your correction:

You can now make detailed adjustments:

in order to obtain a final correction in amplitude:

You can also look at the time domain and make some adjustments in this field, in order to compensate for your speakers filters.

and you end-up with a correction impulse, which, applied to your system, gives you a corrected impulse which is as nice as what you could get from a commercial software (like Dirac or Acourate):

For more details on rePhase, you can visit here: https://sourceforge.net/projects/rephase/

or here: rePhase, a loudspeaker phase linearization, EQ and FIR filtering tool - diyAudio

 

REW is better known, but available here: http://www.roomeqwizard.com/

 

A warm thank you to Pos, the author of rePhase and to John, the author of REW, for making these huge pieces of software available to us free of charge (on a personal contribution basis).

[SwissBear]

A short update to mention that, starting with REW 5.17 Beta 14, an XML interface has been substituted to the text file format.

 

To save the filters to the .xml format, just use this function:

The rest of the procedure is unchanged, Pos having changed in rePhase the format of the expected file from REW.

[SwissBear]

Hello,

 

Today, I would like to illustrate a slightly different use of REW / rePhase, in the field of simulation, adapted to pedagogy or design of systems.

 

But how can we achieve simulations with rePhase ?

 

It's very simple starting from a blank page, we create a filter, for example high pass like this:

 

 

This filter is a minimum phase filter, and we can generate a pulse from it, for example, with the characteristics on the left of the screen.

 

We will do the same with a linear phase filter of the same characteristics:

 

 

The corresponding pulses are generated and imported into REW by the 'Import Impulse Response' function.

 

From there, we have two filters available in REW, which we can compare the characteristics:

SPL: identical in both cases

 

Phase: we observe that the phase of the linear phase filter (green on the graph) is equal to zero, which is not the case of the minimum phase filter (red on the graph)

 

Step: we find the pre-ringing in the case of the linear phase

 

ETC: we find the limit of audibility that I commented on the rePhase forum and which shows that the pre-ringing of the linear filter is probably not audible

 

Finally, if we represent the excess phase (filter's phase in excess with respect to the minimal phase of the curve), it is observed that the filter in minimal phase behaves better than that in the linear phase, which was expected.

 

 

 

With this method, even if you are not at all interested in active correction, but just wanting to simulate the behavior of your speakers, you can go far enough.

 

To illustrate, here is a simulation of the phase of my speakers, with a 2nd order filter at 350Hz and a second at 4000Hz. This is fairly realistic;)

 

 

Hope this is useful for some

[SwissBear]

Hi everyone,

 

Then last version of rePhase, which is implementing the interface with REW, is available: rePhase, a loudspeaker phase linearization, EQ and FIR filtering tool - Page 135 - diyAudio

 

Thanks again to Pos and John for making this happen.

[SwissBear]

Last year, Pos the author of rePhase and JohnMP the author of REW, have implemented an interface in order to allow usage of amplitude correction filters generated inside REW in rePhase, and improve the possibilities to use rePhase as a tool to generate room corrections. Since the 5.18 beta version of REW, JohnMP has implemented some new features which allow: to simplify the averaging of measurements (time alignment and vector averaging) to generate a minimum phase and an excess phase versions of any measurement, which allow to greatly simplify the possibility to use rePhase in order to generate a minimum phase correction of any system. I have updated a short 'How To' guide in order to illustrate these features. This manual is available here: https://www.dropbox.com/s/10xdhh83jokzbxv/REW_rePhase_tuto.pdf?dl=0 Thanks again to JohnMP and to Pos for making this interface so easy to use

[SwissBear]

Hi @pkane2001,

Thanks for your interest in REW/rePhase.

The excess phase is the difference between the minimum phase and the phase actually produced by your system. This difference should effectively be brought back to close to zero in order for your system to behave as a minimum phase system.

As a general rule, you should mainly use the Filters Linearization tag, select the frequencies of your LS crossovers and adjust the slope for each of them. After this step, there should only be some light adjustments to make in the Paragraphic Phase EQ, mainly gentle adjustments in the area of the cross-overs.

If you need help on this, I invite you to join the very friendly and dedicated community which is supporting rePhase here: http://www.diyaudio.com/forums/multi-way/221434-rephase-loudspeaker-phase-linearization-eq-fir-filtering-tool-217.html

[SwissBear]

17 hours ago, pkane2001 said:

 

Just as a follow up, here's the corrected speaker output with phase closely matching minimum phase response. I also corrected my HD650 headphone output. Sounds great!

 

 

 

Congratulations ! You did a great job ! Must sound awesomely .

[SwissBear]

15 hours ago, lasker98 said:

I'm trying to follow along with SwissBear's pdf tutorial linked above in this thread. I'm having a problem with convolving the rePhase correction impulse to my REW measurement. When I do the convolution with the settings shown (A*B) I end up with a new measurement at 152.9 dB, which is about double the original measurement. At this point, I don't know whether this is wrong (I'm assuming it is) or if it's ok how to I work with it at such an increase amplitude.

 

I've attached a screenshot that should help explain better.

 

Thanks in advance for any help.

Nothing wrong here. Just add (in this case subtract) the level which is necessary to obtain a simulated measurement comparable with the original one. On my own system, I subtract 110 db in REW after convolution, but I suspect this is dependent on the level used to make measurements.

[SwissBear]

9 hours ago, lasker98 said:

Thanks SwissBear. I assume I do that adjustment in the same window as the convolution? Using the "offset data" setting? That's how I've done it for now.

Yes.