HOLMImpulse: Measuring Frequency- & Impulse-Response - Page 14 - diyAudio
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Old 18th June 2009, 04:20 PM   #131
doug20 is offline doug20  United States
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Thanks my Mic (ECM8000) has been professionally calibraeted and I think it has the sensitivity in it but when Im measuring the levels shown on my RS meter do not match the program levels so Im assuming something isnt done yet or my file isnt right.
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Old 18th June 2009, 04:22 PM   #132
doug20 is offline doug20  United States
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Quote:
Originally posted by KSTR
Doug,

You could use a simple Radio-Shack SPL-meter nearby (as close as possible to) the mic position to check the sensivity of the mic+ADC-chain before the actual measurement, say with at 400Hz test tone. Don' use any weighting for the level-meter (or C-weighting if that is an option).

Then shift the response in the FR graph at 400Hz to that level --> scaling is then in absolute dB-SPL. Is is more robust when you use a set of frequencies (not to high, say 250, 400, and 600Hz or something). Alas, at the moment Ask has restricted the top range to 20dB, so shift to 0dB instead (will be pretty close anyway) -- not to the SPL reading --, and then just add that value to everything with your brain (or photo-chop the graph output accordingly).

Otherwise I don't know if any mic sensivity given in a calibration file is used by Ask, so we better ask Ask

- Klaus

Thank you, I will do as you suggested.
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Old 19th June 2009, 05:31 PM   #133
jcga is offline jcga  France
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Quote:
Originally posted by askbojesen


Future
I'll implement two options for absolute SPL.

A. Enter sensitivity for one frequency

B. Simply have absolute values in the mic-cal file

OK?
May I humbly suggest a third option :

C. Use of a calibrator (pistophone)

Jen-Claude
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Old 19th June 2009, 06:41 PM   #134
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Default Calibration using a pistonphone

Quote:
Originally posted by jcga
May I humbly suggest a third option :
C. Use of a calibrator (pistophone)
Jen-Claude
Using a pistonphone gives you sensitivity for one frequency (Typical 250 Hz)
So that A. "Enter sensitivity for one frequency" covers this

http://www.google.com/search?q=pistonphone+250+Hz

Then how is this one frequency sensitivity measured?
I could of course make a bandpassed levelmeter to make this calibration
good idea!
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Old 19th June 2009, 10:52 PM   #135
Pano is offline Pano  United States
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Thanks very mmuch for the new features! You've been working hard. I like the DS and ASIO support. Below you will find my M-Audio USB Duo in loop-back with all 3 modes. Don't know why the THD shows lower in ASIO, as the impulses look identical - at any zoom.

The zero time works very well now, too. Even with filters. Great!

I did manage to export the wave in 32bit floating, but ARTA does not like it. Had to run it thru a wave editor and go to 16 bit PCM. Anyone else find that?

Important Question
The 3 measurement modes -
Swept Sine
Chirp
MLS

Shouldn't they sound different? They all sound the same to me now - all are a log sweep sine. Am I doing something wrong?
Attached Images
File Type: png duo impulse.png (36.9 KB, 492 views)
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Old 19th June 2009, 10:57 PM   #136
Pano is offline Pano  United States
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Here's a cool feature request. Don't know if it's possible, but it would be nice to see all of the harmonics graphed at once.

It's nice to see the harmonics/freq graph. Getting to see each broken out into its own graph line ought to be very interesting. Might relate to the "sound" of a certain driver or other DUT.
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Old 20th June 2009, 02:45 AM   #137
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Default Bugs an future features

Quote:
Originally posted by panomaniac
Thanks very mmuch for the new features! You've been working hard. I like the DS and ASIO support. Below you will find my M-Audio USB Duo in loop-back with all 3 modes. Don't know why the THD shows lower in ASIO, as the impulses look identical - at any zoom.
Not at any zoom? - Try the dB scale in the impulse domain and scale to lets say -130 db and zoom out like I have done in:
Click the image to open in full size.
(Notice the harmonic distortion pre-impulses, that are marked)
Quote:
The zero time works very well now, too. Even with filters. Great!
Thanks! can you post your DCX2496 filters meaurement again?
(Just one filter at a time perhaps)
Quote:
I did manage to export the wave in 32bit floating, but ARTA does not like it. Had to run it thru a wave editor and go to 16 bit PCM. Anyone else find that?
Yes I tested myself in ARTA. In next release you can save as:
- 32 bit float wave
- 64 bit double wave
- 16 bit PCM wave (ARTA compatible)
- 24 bit PCM wave (ARTA compatible)
- 32 bit PCM wave
Quote:
Important Question
The 3 measurement modes -
Swept Sine
Chirp
MLS
Shouldn't they sound different? They all sound the same to me now - all are a log sweep sine. Am I doing something wrong?
That's a bug I have introduced somewhere while making features - sorry... that is how software development works - its called Regression Testing


Thanks for telling me

I'll be back with a fix soon
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Old 20th June 2009, 03:06 AM   #138
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Default The "Sound"

Quote:
Originally posted by panomaniac
It's nice to see the harmonics/freq graph. Getting to see each broken out into its own graph line ought to be very interesting. Might relate to the "sound" of a certain driver or other DUT.
Yes, I thought about that also. We also want the phase of the distortion
Let us study the phase of the harmonic distortions - it's not irrelevant if considering the masking effects, that Earl are taking talking about also - or...?

My problem is how to visualize this in a consistent way so the plot is not overcrowded by curves.
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Old 20th June 2009, 06:14 AM   #139
Thawach is offline Thawach  Thailand
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hi...askbojesen


i never translate the page more than 3 pages. but in this time i think its sure more than 100 pages. i would like to cry really...kiki(thai baby has a litle lol) ok i just install it. askbojesen i have a question. i want to know this program can export the the txt file(freq and phase respond)? my xo loudsoft wants the txt file to work with.


askbojesen thanks for all your post.

kiki
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Old 20th June 2009, 11:59 AM   #140
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I had no problem with the Wave export into ARTA. Although The old measurments had a DC offset, but I can't reproduce that now so it might have been an old glitch.
The Lister plugin in Total Commander had some problem playing it, sometimes it would sometimes not. So it might be a problem with the header?

Here is a burst decay with all 7 B&C 15PE40 combined. Mic was 1m in front of the speaker. The volume was turned up "enough".

Click the image to open in full size.

Any comments?
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