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Old 6th December 2018, 09:17 PM   #781
montana1 is offline montana1  United States
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Thanks kimmosto,
That did the trick. I'm cooking with gas now!


Best Regards,
Rich
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Old 7th December 2018, 06:23 AM   #782
kimmosto is offline kimmosto  Finland
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^Very good.
I just made small change that driver instance in the crossover is linked automatically to driver data in Drivers tab as long as number of driver instances is smaller or equal to number of drivers in Drivers tab. In other cases linking should be done manually. This could be helpful in practice, but not always. Feature is available in the latest built.

Basically Drivers tab is just storage for measurement data. Actual/physical driver instances are added to crossover schematic, and they could be linked to any driver in Drivers tab. For example, you can have 20 full-range drivers in a project (added in the crossover) and all of those are using the same measurement set (Driver #1) in Drivers tab.
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Old 8th December 2018, 03:12 AM   #783
montana1 is offline montana1  United States
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Thanks kimmosto,
I appreciate your detailed explanation. It makes perfect sense now. I'm starting to wrap my head around your fabulous software. Still need to read the help manual from start to finish. Your YouTube videos are also a great help in learning more about the program. Could you at some point make a video(s) detailing your steps to designing a successful Xover? It would be very much appreciated from newbies like myself. Love your program and the hard work you put into it!

Happy Holidays,
Rich
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Old 9th December 2018, 05:42 PM   #784
kimmosto is offline kimmosto  Finland
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Rev. 2.0.9.0 (2018-12-09)

Enclosure
* Added calculation of T/S parameters with added mass or sealed box method. Feature integrated into same window with extended impedance model solver. Window opens with 'Calculate T/S...' button in 'Edit parameters'/'Add new driver' window. Two impedance responses, Re and Dd/Sd are needed. Z1k and Z10k of basic Z model are detected from free air impedance response.
* Extended impedance model solver uses loaded free air response as a reference within 1-20 kHz with 1/6 oct. resolution. Manual target points (4) are used if free air response is not loaded.

This feature is normally in measurement programs, but might be useful in VCAD because works with txt/zma impedance responses files i.e. does not require original mls/sin/lim/mdat files.
Added mass and sealed box methods are for cone drivers only but that could be quite adequate for a while.
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Old 10th December 2018, 08:37 AM   #785
kimmosto is offline kimmosto  Finland
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^Detection of driver's fs is slightly improved in the latest build few minutes ago. It's more tolerant for impedance ripples below fs, and fs is calculated by impedance peak and polarity change of phase (if phase column exists).

Last edited by kimmosto; 10th December 2018 at 09:04 AM.
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Old 10th December 2018, 09:24 AM   #786
JohnPM is offline JohnPM  United Kingdom
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Not forgetting that the frequency at which the phase crosses zero will be a little offset from fs due to the effect of the voicecoil impedance...
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Old 10th December 2018, 10:45 AM   #787
kimmosto is offline kimmosto  Finland
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^That's so true. I tested few different methods to specify fs (before knowing L). Quite common system is to detect frequencies f1,f2 where Z=sqrt(Zmax*Re), and then fs=sqrt(f1*f2). This could give a bit strange result if symmetry of Z peak is not expected. Also for drivers with very low inductance.
We could also boost this basic formula with frequency at measured peak: fs=(f1*fpeak*f2)^(1/3), or include also frequency where polarity changes: fs=(f1*fpolar*fpeak*f2)^(1/4).
Current method is that f1 and f2 are skipped and possible small offset down is accepted. Looks more stable than with f1 and f2, imo.
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Old 10th December 2018, 10:57 AM   #788
JohnPM is offline JohnPM  United Kingdom
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Might find it better to fit your drive unit impedance model to the data and determine the fs values from the model fit values of LCES and CMES. Although a little old now there is lots of interesting info in Claus Futtrup's DPC manual. Claus has done a lot of work on various impedance models since.
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Old 10th December 2018, 12:17 PM   #789
kimmosto is offline kimmosto  Finland
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Extended Z model solver in the same window would be fully capable to fit also any number of T/S-parameters to measured impedance curve within 10...20000 Hz. But excessive focusing to fs is probably overshoot in this case. VCAD is using impedance response as interpolated to 1/48 oct. resolution. Original file exported with measurement program has some other resolution which is also interpolated from constant frequency step FFT data. In addition, expected <0.5 Hz error in VCAD is probably less than tolerance of individual drivers.
So, T/S-calculation with measurement program is recommended to make science with much better accuracy.
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Old 14th December 2018, 12:33 PM   #790
kimmosto is offline kimmosto  Finland
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Rev. 2.0.9.1 (2018-12-14)

Enclosure
* Added Mms and BL checkboxes to T/S Calculation. Parameters can be calculated with free air impedance response if Mms or BL is known and trusted.
* Manual target points of extended Z model removed, assuming that free air impedance response is always available for Z-curve fitting.
* Lossy inductance is subtracted from impedance responses before detection of fs and Q-factors.


This feature should be quite final now. I've also tested curve fitting for T/S parameters, but advantages are not so significant. Iteration would be okay for fine tuning with free air response when Mms or BL is known.
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