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HOLMImpulse: Measuring Frequency- & Impulse-Response
HOLMImpulse: Measuring Frequency- & Impulse-Response
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Old 28th April 2019, 02:30 PM   #1091
critofur is offline critofur  United States
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Quote:
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Could we keep this thread on topic please?
I would love to see HolmImpulse actively maintained again, and if there is a chance for this to happen let's not miss it!
Has the author ever talked about reasons for development stopping? (Or the possibility of releasing the source code to be open source?) Just too busy with other things in life I imagine? I would guess that while some of us would very much like to see an update, perhaps the "market" is not that large, and even if we tried something like a "go fund me" it wouldn't gain enough participants to really be worth while?
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Old 1st May 2019, 09:06 PM   #1092
Defo is offline Defo  Norway
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I read an article by ARTA (http://www.artalabs.hr/AppNotes/AP4_...d-Rev03eng.pdf) where you can see measurements done at 0 cm, 3 cm, 6 cm, 12 cm, 24 cm, 48 cm, and 96 cm.

Although the industry standard is 1 meter, it seems to me that 1/2 meter is a "good enough" middle ground between near field and far field.

Any thoughts on this?
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Old 1st May 2019, 11:19 PM   #1093
gedlee is offline gedlee  United States
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Quote:
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Has the author ever talked about reasons for development stopping?
He left the company and no one could handle taking it up again.
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Old 1st May 2019, 11:20 PM   #1094
gedlee is offline gedlee  United States
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Quote:
Originally Posted by Defo View Post
I read an article by ARTA (http://www.artalabs.hr/AppNotes/AP4_...d-Rev03eng.pdf) where you can see measurements done at 0 cm, 3 cm, 6 cm, 12 cm, 24 cm, 48 cm, and 96 cm.

Although the industry standard is 1 meter, it seems to me that 1/2 meter is a "good enough" middle ground between near field and far field.

Any thoughts on this?

I believe farther is always better. The near field has things going on that don't get top the far field. You don;t want to measure those. But you do need to gate, otherwise you have altogether another problem.
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Old 8th May 2019, 07:06 AM   #1095
Juhazi is offline Juhazi  Finland
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Quote:
Originally Posted by Defo View Post
I read an article by ARTA (http://www.artalabs.hr/AppNotes/AP4_...d-Rev03eng.pdf) where you can see measurements done at 0 cm, 3 cm, 6 cm, 12 cm, 24 cm, 48 cm, and 96 cm.

Although the industry standard is 1 meter, it seems to me that 1/2 meter is a "good enough" middle ground between near field and far field.

Any thoughts on this?
It depends on what you want to see in the measurement. A single driver's spl-response with typical narrow speaker baffle is ok at 50cm. Wider baffle and multpiple drivers summing up needs more distance. Also reliable off-axis measurements should be done at at least 1m, preferably 2m distance.

Reflections start to show in measurements only after a few milliseconds, depending on distace to boundaries and by ratio of direct vs. reflected sound energy. FFT analysis with variable impulse response gating enables the user to see reflections in impulse response and help to decide IR gating for spl/F, short gating doesn't show spl well in low freq. So, it is always a compromise.

Distortion is typically measured very close to a single driver, but the problem is to be able to use high enough voltage/spl, because mic easily gets overdriven. At 1m distance spl should be at least 95dB, preferably 100dB, depending on the level of ambient noise.

For an amateur measuring her/his own project, it is very easy to get blind to artefacts. It is a bit more difficult to learn to "see through" those artefacts!

Comparing measurements done by others is always problematic, because we don't know excact conditions of the measurement
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Old 8th May 2019, 07:11 AM   #1096
Defo is offline Defo  Norway
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Quote:
Originally Posted by Juhazi View Post
A single driver's spl-response with typical narrow speaker baffle is ok at 50cm. Wider baffle and multpiple drivers summing up needs more distance. Also reliable off-axis measurements should be done at at least 1m, preferably 2m distance.
Should've mentioned I was indeed referencing single driver measurements for XO simulation and so forth

Doing measurements at 1m I actually usually don't get much different results with and without gating (typically 3ms)
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Old 8th May 2019, 10:02 AM   #1097
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Why is it always refered to the baffle width when to set measurement distance? Why not the baffle height?
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Old 8th May 2019, 10:16 AM   #1098
Juhazi is offline Juhazi  Finland
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^Because in most cases the widht is narrower than height. And that dictates the baffle step/diffraction behaviour for the most.

Easy to test this with The Edge! You can also test how mic distance changes the simulated response.
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Old 8th June 2019, 11:26 AM   #1099
marabella is offline marabella  Germany
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Default Very strange results after importing a mic-calibration file.

Hello

I need some help or advice. Am I doing something wrong?

E888F_dir_00d.mic is the original calibration file done by professionals.
It's working in ARTA as expected.

When I imported it in HolmImpulse the results were very strange as you can see in the picture (green = FR with cal-file, red =FR without cal-file)

I have replaced all tabs with semicolons (E888F_dir_00d.cal) but nothing changed.

At least I found the cause. In C:\user\...Holmimpulse a new calibration file had been created (CalibrationMic.cal). And HI uses this file for FR-correction.

The values obviously have changed in a way, I can't explain and I do not understand.

Does someone know what is happening here?
Did I something wrong?


Thanks in advance
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File Type: jpg FR-Cal.jpg (149.3 KB, 85 views)
Attached Files
File Type: txt E888F_dir_00d.mic.txt (2.2 KB, 3 views)
File Type: txt E888F_dir_00d.cal.txt (2.2 KB, 2 views)
File Type: txt CalibrationMic.cal.txt (2.2 KB, 2 views)
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Old 8th June 2019, 04:00 PM   #1100
gedlee is offline gedlee  United States
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It appears that the mic EQ contains almost 10 dB of boost at the high end. Not a very good mic I would say. Or the cal file is wrong.
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