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TOPIC: rePhase 0.9.8

rePhase 0.9.8 5 years 10 months ago #15920

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After more than a year without any update, here is rePhase 0.9.8

sourceforge.net/projects/rephase/
0.9.8 2014-09-28
    - minimum-phase filters tab with common IIR filter types:
        * 1st order
        * 2nd order with arbitrary Q
        * Butterworth with slopes ranging from 6dB/oct to 996dB/oct in 6dB
          increments
        * Linkwitz-Riley with slopes ranging from 12dB/oct to 996dB/oct in
          12dB increments
    - 'compensate' mode for generalized arbitrary order Linkwitz
      Transform-like manipulations in minimum-phase filters tab
    - new centering options expressed as a percentage to easily obtain
      matched delays
    - default to "middle" centering instead of "energy" to avoid delay
      mismatch problems for the unaware user (principle of least surprise)
    - praxis measurement format handling, scientific notation in frequency
      column
    - smaller executable, new installation method
    - bug correction: crash on impulse generation with some specific filter
      settings
    - directory handling bug correction
    - measurements can now be loaded from the command line or drop on exe,
      similarly to settings
    - revamped file extension handling (settings)
    - revamped icon
    - smoothed out taps/fft size calultation
https//wavetracing.com | rephase.org
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rePhase 0.9.8 5 years 10 months ago #15923

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Hi pos,
great to see the continued excellent work and improvement on this. I have implemented 3-way Horbach-Keele crossovers for my MTMW system using rePhase.

I notice a bug in this latest build. A routine crashes for every Box compensation of the Closed type, other than Q=0.5.

Cheers.
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rePhase 0.9.8 5 years 10 months ago #15925

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Hi micfre

Thanks for the bug report, version 0.9.8c now online.

I am happy to hear that at least one person is using the Horbach-Keele feature in rePhase :D
Is it not too cumbersome having to calculate the fc and R values yourself?
https//wavetracing.com | rephase.org
Last Edit: 5 years 10 months ago by pos.
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rePhase 0.9.8 5 years 10 months ago #15951

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@ Pos,

Keeping the great spirit of rephase! Great stuff to see these upgrades and the whole miniDSP community want to thank you for this great software.. very neat! :-)
miniDSP, building a DSP community one board at a time.
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rePhase 0.9.8 5 years 9 months ago #16332

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Hey Pos,

Great to see that you are continuing to add to Rephase, thanks for all your efforts.

I've only just noticed that you've had this new build. I notice that you've got a minimum phase filters tab and that is what I'm posting about here. I can't really get my head around what the point is? When I've used rephase to make filters in the past i've used the linear filters to take advantage of the neutral phase nature of them, If I've already used IIR filters (say set up in the minidsp XO interface or jriver et al) I use the filters linearization tab to correct. Can you point me in the right direction concerning where I might want to use this new tab please.

Ta.

Stefan
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rePhase 0.9.8 5 years 9 months ago #16333

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Hi Stefan

Here are a few reasons, in no particular order:
- minimum-phase FIR filters can do what IIR filters do (including zero delay when direct convolution is used, like in the openDRC/miniSHARC) without any risk of quantization noise. The only form of distortion you can get is linear distortion if the number of taps is too low for the task (ie amplitude and/or phase target is not met, and this shows in the result curves), whereas IIR can (and will) bring you non linear distortion in the form of quantization noise down low, the amount being dependent on the implementation and resolution. I think FIR is the future and might become the de facto standard, even for minimum-phase only filtering (and sometimes of course minimum-phase is the way to go...)
- depending on the situation and configuration, you might want or need to implement an all FIR crossover, and you might want to have minimum-phase filters for some crossover points. If you want to replicate a known crossover setting (and then possibly linearize its phase afterward and see if it makes a difference) it is interesting to have all the classic slopes available.
- combining minimum-phase filters to the ones of your system (from the drivers and boxes themselves for example) to obtain a given target, and then use the linearization tab to lineaize them is a simple and efficient way of building linear phase crossovers. "compensate" mode (generalized Linkwitz transforms of arbitrary order) also come in handy for this

Regards
Thomas
https//wavetracing.com | rephase.org
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rePhase 0.9.8 5 years 9 months ago #16345

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Hi Thomas,

Thanks for the prompt reply, it continues to amaze me that devs of freeware / donation ware / opensource continue to our class commercial developers of software, thanks again.

with regard to your first point, what do you mean by direct convolution? compared presumably to indirect? is the sharc setup direct because it is hardware whereas doing this in a convolution engine like that in a DAW or J RIver isn't or is there another reason? With regards to the delay, I'd always thought that was a function of the amount of taps used for a filter, but reading between the lines a bit here that is only the case for linear phase filters generated this way? If that is the case for latency sensitive applications using the minimum phase filters would work well? Presumably if the phase of those resultant filters was corrected in the filters linearization tab the net result on the amount of taps needed and the delay caused would be the same as just using the linear filters tab in the first place?

I don't think I understand the 'compensate mode' at all!! Loading a measurement an setting a filter in compensate mode seems to have the exact opposite effect of no compensate and I can't think of any situation where I would use this, what do you use it for personally?

Lastly, If I could add a feature request to you list? it would be very hand to achieve other linear filter types as well, I quite often use a linkwitz transform or a shelving filter, or of course baffle step, any chance of getting those added, or at least a way of correcting for them?

Cheers

Stefan
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rePhase 0.9.8 5 years 9 months ago #16361

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Hi Stefan
orangeart wrote:
with regard to your first point, what do you mean by direct convolution? compared presumably to indirect? is the sharc setup direct because it is hardware whereas doing this in a convolution engine like that in a DAW or J RIver isn't or is there another reason?
It is direct/Time domain convolution vs FFT/frequency domain convolution.
The miniSHARC (and many other DSP based solution) tend to use time domain convolution because they do not have a lot of memory.
Time domain convolution is a very strait forward approach that brings no additional delay beside the one caused by the impulse itself (the position of the peak inside the impulse).
On the other hand frequency domain convolution uses buffers and FFT to do the convolution, which reduces CPU load but uses more memory, and also introduce an additional delay due to the buffering. Methods exists to reduce this buffering time (partitioning, etc.) but you get the idea.
This kind of convolution is typically used in software tools, and of course those introduce other sources of delay (soudcard buffers, etc.).
With regards to the delay, I'd always thought that was a function of the amount of taps used for a filter, but reading between the lines a bit here that is only the case for linear phase filters generated this way? If that is the case for latency sensitive applications using the minimum phase filters would work well?
Yes, the delay implied by the impulse is dependent on the position of the peak inside the impulse.
Most FIR software will simply center the peak, but rephase has a "enregy" mode that will try to find the best position for the peak, and also options to manually center the impulse using % values (and the coming version will be much more flexible in the regard).
For linear phase correction the peak will typically be centered because the impulse is symmetrical, so the delay will be the time to read half of the samples of the impulse.
For phase linearization (of a phase minimum crossover) the peak will tend to be on the right, and the delay will be maximal
For minimum phase corrections the peak will be on the left and the delay will be minimal (could even be almost 0 sample)
Presumably if the phase of those resultant filters was corrected in the filters linearization tab the net result on the amount of taps needed and the delay caused would be the same as just using the linear filters tab in the first place?
That's correct.
I don't think I understand the 'compensate mode' at all!! Loading a measurement an setting a filter in compensate mode seems to have the exact opposite effect of no compensate and I can't think of any situation where I would use this, what do you use it for personally?

Lastly, If I could add a feature request to you list? it would be very hand to achieve other linear filter types as well, I quite often use a linkwitz transform or a shelving filter, or of course baffle step, any chance of getting those added, or at least a way of correcting for them?
The composite mode is supposed to be combined with another "normal" filter.
For example if your system has a 2nd order high pass at 50Hz with a Q=1.0 and you want to turn it into a 20Hz Q=0.707 one you simply enter the forst high pass in compensate mode, and the second in normal mode, and voilĂ .
This is a Linkwitz Transform, but you are not limited to second order filter, nor are you limited to high passes only...

As for shelving EQ, it is coming in the next release :D
Currently you can do linear-phase shelving using the raised cosine EQs, and minimum-phase shelving by combining compensate and and normal minimum phase filters with same Q and different frequencies.

As for baffle step, this is something you have to measure and correct -or most likely leave alone) in situ, so normal minimum-phase EQ is the way to go.

And of course all these corrections are to be done in minimum-phase mode rather than linear phase mode most of the time...
https//wavetracing.com | rephase.org
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rePhase 0.9.8 5 years 9 months ago #16369

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Hi Thomas,

Thanks for the explanations, it's given me a lot to think about and to research more, it never ends does it???

Now you've explained the compensate mode in terms of a Linkwitz transform the penny has dropped! I can't think of any software that makes altering system knee and Q anywhere near that easy, I'll definitely be using that function. I mainly make sealed speakers and have used a linkwitz transform rarely but now I should be able to control far more precisely what is happening, thanks.

As for baffle step, I mostly don't correct as I have a small room so speakers normally go near the wall anyway, lately however I am experimentally with designs that are 2pi down to the lower XO frequency by virtue of wider baffles so still no real need for them but it's always good to have options :-)

Why do you way that these types of correction should be performed minimum phase rather than linear phase? As an example say I was using the compensated tool which is obviously only minimum phase to do the aforementioned linkwitz transform and it's associated phase shifts, what benefit does that have over providing the same tool in the linera tab and thus producing no phase shifts? I guess I'm missing something fundamental here....

Thanks again

Stefan
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rePhase 0.9.8 5 years 9 months ago #16399

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Hi Stefan,
orangeart wrote:
Now you've explained the compensate mode in terms of a Linkwitz transform the penny has dropped! I can't think of any software that makes altering system knee and Q anywhere near that easy, I'll definitely be using that function.
Yes I was quite happy when I found this little trick :D
Why do you way that these types of correction should be performed minimum phase rather than linear phase? As an example say I was using the compensated tool which is obviously only minimum phase to do the aforementioned linkwitz transform and it's associated phase shifts, what benefit does that have over providing the same tool in the linera tab and thus producing no phase shifts? I guess I'm missing something fundamental here....
You want to correct minimum-phase systems using minimum-phase correction, so that the resulting systems stays minimum-phase.
Any acoustical "filter" you could think of *is* minimum-phase.
https//wavetracing.com | rephase.org
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rePhase 0.9.8 5 years 8 months ago #16841

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POS

When I try to download RePhase from miniDSP using Chrome it is labeled "malicious" and is blocked.

I m running Win 7 Pro.

What is happening here?
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rePhase 0.9.8 5 years 8 months ago #16842

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Hello

I just tried downloading it with chrome on Win XP and Win 8.1 without any issue.
I can try with Win 7 Pro tomorrow but I doubt it will give different results.
What message do you get? Is it from chrome or from an antivirus software?
When exactly do you get that message?
From what address are you downloading it?
The only valid source is sourceforge: sourceforge.net/projects/rephase/
https//wavetracing.com | rephase.org
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rePhase 0.9.8 5 years 8 months ago #16844

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POS

Thanks!

I downloaded it successfully, and I am eagerly looking forward to using it.
Last Edit: 5 years 8 months ago by mdbuck. Reason: typo
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rePhase 0.9.8 5 years 8 months ago #16845

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mdbuck wrote:
POS

When I try to download RePhase from miniDSP using Chrome it is labeled "malicious" and is blocked.

I m running Win 7 Pro.

What is happening here?

Probably just your internet properties security setting. I use Win 7 Pro and Chrome and it downloads without a problem with my setting on "medium high."

Regardless, if downloading from the valid site mentioned by pos, you should fine overriding the malicious message.

Dave.
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