HOLMImpulse: Measuring Frequency- & Impulse-Response

Hi,

I have developed a freeware program called HOLMImpulse for speaker gain and phase response measurement.

HOLMImpulse is Non-Commercial freeware with full functionality (No limitations or trial periods) running on Windows XP/Vista

Download HOLMImpulse here

The purpose of the application is to:
- Work with any soundcard
- Easy and fast to use
- Measure Frequency-response (gain and Phase)
- Measure Impulse-response
- Dynamically/Automaticly adjust the time window (Gating)
- Use cross-correlation techniques with logsweep, chirp or MLS
- Very good signal/noise ratio (Due to cross-correlation)
- Make bandwitdh limited measurements with no phase-errors
- Measure Harmonic distortion (THD)
- Compare measurements (50 slots, and 3 shown at a time)
- Easy open/save import/export measurements in any format
- Be freeware with full functionality (Up to 192KHz, 24 bit)
- Manipulate measurements (Lowpass, highpass, etc...)

I would like your response
I know that there is no manual, but we are all geeks who rather want features than manuals - right?
- Simply define select your soundcard and click measure
- I would like you to reply in this post and tell me if you have had any success with the program
- And of course post your measurements ;-)
- If you have any difficulties getting this to work, then I'll assist you in this thread

NB I am working for
HOLM Acoustics (A new small Danish Company),
but I have no commercial interest in HOLMImpulse, which is mostly developed in my spare time. The core libraries used in HOLMImpulse are the same as in
HOLMFIR, which is a program used to configure the commercial product DSPre

An externally hosted image should be here but it was not working when we last tested it.
 
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It sounds good! I haven't had much luck with taking measurements in the past, but perhaps this will be better for me. Thanks for providing this software!


Not to be too OT, but could I use the panasonic capsule mics, connected to a normal mixer and powered with phantom power, to take measurements? Leaving EQ and high pass off naturally. I have built mics like this in the past for recording, all i'd need to change is the mounting of the capsule (placing it on a wand) :)
 
Microphone calibration

Dr.EM said:

Not to be too OT, but could I use the panasonic capsule mics, connected to a normal mixer and powered with phantom power, to take measurements? Leaving EQ and high pass off naturally. I have built mics like this in the past for recording, all i'd need to change is the mounting of the capsule (placing it on a wand) :)

As I posted in DIY measurement mic
We have a calibration file for the wm61a:
http://www.holmacoustics.com/downloads/MicrophoneCalibration/Mic_WM61A.cal

But of course any microphone calibration can be used in HOLMImpulse
  • Exspects data in columns:
    Frequency <seperator> dB <seperator> phase <eol>
  • Ignores lines not starting with a number
  • Accepts the following seperators: space, semicolon, tabular
  • Accepts , and/or . as decimal point

Import microphone calibration
An externally hosted image should be here but it was not working when we last tested it.


Three different wm61a capsules
An externally hosted image should be here but it was not working when we last tested it.
 
That's excellent! Yes, those are the capsules I used. The Linkwitz mod doesn't make any difference to the frequency response does it, just to the max SPL handled? I have some unmodified and some modified, but heard that during the mod it is possible to break the seal and upset the low frequency response, so I'd sooner trust my unmodified capsules :)
 
Askbojesen

I have not tried it, but before I do, I have some questions.

When the log sweep is used does the impulse response that is calculated from the cross-correlation yield the impulse response of the higher harmonics preceding the main impulse as the theory says it should?

Is the signal file that is cross-correlated with the measured data corrected to give the proper phase and amplitude as is required per Farina?

Can the impulse response be written out to be read by another program? What about OLE?

Is 64 bit VISTA a problem?

In any case thanks for this valuable addition to the technology. Hopefully more people will do measurements and quite making decisions "by ear".
 
I decided to test my soundcard, since I don't have my mics or speakers here. It's evidently not great! Creative Audigy thing. It'll work for frequency response measuring though, which is really what I need :)
 

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Dr.EM said:
I decided to test my soundcard, since I don't have my mics or speakers here. It's evidently not great! Creative Audigy thing. It'll work for frequency response measuring though, which is really what I need :)

Your soundcard is out of phase with itself. Check of the "Invert recorded signal" under device settings. At the impulse response it is very clear that the impulse is going down instead of up.
 
gedlee said:
I have not tried it, but before I do, I have some questions.

When the log sweep is used does the impulse response that is calculated from the cross-correlation yield the impulse response of the higher harmonics preceding the main impulse as the theory says it should?
Yes that is how I calculate 2-9th harmonics and sum them to THD
I have tested the magnitudes with a normal steady state sinus + FFT afterwards.

Is the signal file that is cross-correlated with the measured data corrected to give the proper phase and amplitude as is required per Farina?
Yes I know that a logsweep needs an inverse crosscorrelator (Unlike MLS sequences, that are they own inverse)

Can the impulse response be written out to be read by another program? What about OLE?
The measurements can be exported to text file in custom format (See attachment)
OLE - No.

Is 64 bit VISTA a problem?
If VC++ crosscompiler works then no. I have crosscompiled but not yet tested on 64bit HOLMImpulse now with 64 bit

In any case thanks for this valuable addition to the technology. Hopefully more people will do measurements and quite making decisions "by ear".

I agree that more people should measure more - They would be able to pinpoint what they like / dislike. We would have more quantities to talk about instead of just words like smooth/tight/warm/hard/cold/sloppy,... Ore maybe link those words to quantities
 

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askbojesen said:

Yes that is how I calculate 2-9th harmonics and sum them to THD
I have tested the magnitudes with a normal steady state sinus + FFT afterwards.


Yes I know that a logsweep needs an inverse crosscorrelator (Unlike MLS sequences, that are they own inverse)


The measurements can be exported to text file in custom format (See attachment)
OLE - No.


You misundertood a lot of the questions, so lets start again.

Does the program export the impulse response WITH the pre impulses of the harmonics? If it does this then I am very interested, if it doesn't then I am not. Frequency response with THD is not very interseting.

Farina talks about several things that have to be done to the "inverse crosscorrelator " to get rid of some artifacts. Its all in his latest AES paper. Do you do these things?
 
gedlee said:
Does the program export the impulse response WITH the pre impulses of the harmonics?
Not as it is now - it would give huge amount of data.
But if you are interested I can easily make "special save" button with the direct cross-correlation in binary format.
(Sent me a direct message if of any interest)
If it does this then I am very interested, if it doesn't then I am not. Frequency response with THD is not very interseting.
With a timewindow I disregard the harmonics. so the THD is not included.
Farina talks about several things that have to be done to the "inverse crosscorrelator " to get rid of some artifacts. Its all in his latest AES paper. Do you do these things?
Not sure that I have read the latest (I am a AES member, but not subscriber), so sent me a link to the article.
I have tested with digital loopback and electric loopback to ensure I have no artifacts. But I might have forgotten something - I have an open mind :)
 
BDP said:
Any sound card? I selected my sound card and then selected measure and my computer rebooted :( . The computer I tried it on is 5 years old with a SB live sound card running XP. Any tips?
PS: You are working with a 1/2 geek!

No errors before reboot? sounds weird :xeye:
HOLMImpulse is using the .Net 2.0 windows framework
which is running in protected mode in windows.

Have you run a windows-update lately ?
http://update.microsoft.com/windowsupdate/