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Pulseaudio Crossover Rack - multi-way crossover design & implementation with linux
Pulseaudio Crossover Rack - multi-way crossover design & implementation with linux
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Old 12th January 2019, 07:24 PM   #71
DWP13 is offline DWP13
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It'll be awhile before I can but looking forward to it! (geek incarnate)
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Old 13th January 2019, 05:57 PM   #72
Tfive is offline Tfive  Germany
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I just released version 1.12 with the following changelog:

Code:
pulseaudio-crossover-rack (1.12) stable; urgency=low
  * features:
    - added second order low-/highpass filters with variable Q
    - added dialog to load FRD frequency response files and look at the speaker
      response, both standalone and combined with the filter response
    - added dialog to show summed up responses of loaded FRD+filter responses
      plus their sums
      ATTENTION: This dialog does not yet account for phase shifts introduced
                 by delay filters, this is kind of complicated :/
    - changed all lower frequency parameter limits to 2Hz and all
      upper limits to 20kHz
    - made connection curves look nicer by using antialiasing
    - added dividers in EditFilterDialog to group parameters of ParamEq
    - added inverting filter
  * bugfixes:
    - insert/remove modules threw an error when no file was loaded
-- Jürgen Herrmann <t-5@t-5.eu> 2019-01-13
Regarding the missing calculation of phase shifts of delay filters I will have to first wrap my head around it...

Question for the experts: won't you have to measure the summed response anyways as the single driver measurements don't have timing information embedded into them, i.e. don't know about the driver<->microphone distance? Will probably be a lot smarter once I have a microphone available and can do some hands on testing...
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Old 13th January 2019, 06:52 PM   #73
Boden is offline Boden  Netherlands
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Yes, the summed response will enable you to establish the relative distance, i.e. the distance between the acoustic centres of the drivers, a.k.a. the offset in the Z plane at the x/o frequency. That distance is not the same as the physical distance between the voicecoils of, say, a tweeter and a midwoofer.



In a conventional 25mm dome/16 cm midwoofer, the tweeter is located at Z=0 and the woofer some 30 mm behind that. I suppose for your software you have to convert the distance into milliseconds.



Good Luck and keep up the good work: I haven't tried it yet, but the GUI looks superb!


Eelco
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Old 13th January 2019, 07:03 PM   #74
Tfive is offline Tfive  Germany
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Quote:
Originally Posted by Boden View Post
Yes, the summed response will enable you to establish the relative distance, i.e. the distance between the acoustic centres of the drivers, a.k.a. the offset in the Z plane at the x/o frequency. That distance is not the same as the physical distance between the voicecoils of, say, a tweeter and a midwoofer.

In a conventional 25mm dome/16 cm midwoofer, the tweeter is located at Z=0 and the woofer some 30 mm behind that. I suppose for your software you have to convert the distance into milliseconds.
How would you go about this when doing the measurements? Do you change the delay until you don't have dips in the summed response?

Quote:
Originally Posted by Boden View Post
Good Luck and keep up the good work: I haven't tried it yet, but the GUI looks superb!

Eelco
Thanks, very much appreciated
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Old 13th January 2019, 09:28 PM   #75
Boden is offline Boden  Netherlands
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The delay is experimentally established in any x/o simulation program . First a measurement is made of the woofer separately without any crossover, then, without moving the microfone the tweeter is measured. Thirdly both drivers are simultaneusly measured without moving the mic. The non filtered summed curve will show a lot of valleys and peaks, but that is not problematic.

In the simulation program, LspCad 5.2 in my case, the summed curve of both drivers is overlaid with the combined measurement. This usually start with some discrepancies between both curves. After experimentally adding delay to the woofer in small steps, after some 30 mm or so both curves start to converge.
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Old 13th January 2019, 09:32 PM   #76
Boden is offline Boden  Netherlands
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To be accurate also x and y placement of the drivers relative to each other must be defined.


You may want to take a look at VituiCad, XSim or Boxsim, all freeware.
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Old 13th January 2019, 11:13 PM   #77
Tfive is offline Tfive  Germany
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So as far is I understand it the establishment of a correct delay between a pair of speakers is more the job of the speaker measurement software suite?! Actually I have some ideas already for such a program, but more on that once I have my mic and can do some initial testing. Of course it will then be tightly integrated with PaXoverRack and there will be no need to import/export FRD files anymore. Once i get going on this topic I will probably have another metric ton of questions but that shall be topic of another thread.

As far as I'm concerned I'm pretty happy with the state PaXoverRack is in right now, but we'll see how the new FRD feature is picked up by the audience that actually will use it...

That's it for now folks, I'm off to bed

Last edited by Tfive; 13th January 2019 at 11:15 PM.
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Old 14th January 2019, 08:26 AM   #78
Boden is offline Boden  Netherlands
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Well, the establishment of the correct delay is more a job of the x/o simulation and optimization software than the measurement software. So far, those jobs mostely have been been separated softwarewise - albeit with a few exceptions e.g. SoundEasy/LspCad- but there is no reason why the different jobs could not be integrated in one suite. Actually, that would be an excellent idea.
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Old 14th January 2019, 05:44 PM   #79
Tfive is offline Tfive  Germany
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just a minor cleanup release:

Code:
pulseaudio-crossover-rack (1.13) stable; urgency=low
  * features:
    - delays now show the offset in millimeters
  * bugfixes:
    - removed formatter with 3 decimal places for float values (otherwise a
      precise delay value for example would be truncated)
    - removed some debug statements
    - reverted delay biquad filter coefficients to short form for
      performance reasons
-- Jürgen Herrmann <t-5@t-5.eu> 2019-01-14
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Old 15th January 2019, 03:27 PM   #80
Tfive is offline Tfive  Germany
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Sorry for the noise, but some improvements were in order

Code:
pulseaudio-crossover-rack (1.15) stable; urgency=medium
  * features:
    - added checkbox to ignore phase values in FRD files and replace them
      by calculated phase responses (minimum phase model, hilbert transform)
    - added checkbox to sync up the dB values by which FRD responses get
      shifted towards 0dB
    - added spinBox to manually shift phase responses. this enables exploration
      of different phase shifts needed to gain proper summation at crossover
      frequencies. phase shifts then have to be converted to delays in the
      crossover filter chain.
  * bugfixes:
    - switched internal data structures completely to complex representation
      of magnitude/phase responses. In the process a summation error was
      detected and fixed
-- Jürgen Herrmann <t-5@t-5.eu> 2019-01-15
pulseaudio-crossover-rack (1.17) stable; urgency=medium
  * bugfixes:
    - resized edit fields for filter parameters to accomodate new precision
-- Jürgen Herrmann <t-5@t-5.eu> 2019-01-15
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