HOLMImpulse: Measuring Frequency- & Impulse-Response
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diyAudio Member

Join Date: Mar 2003
Location: Denmark, Copenhagen
Quote:
 Originally posted by KSTR I think I cannot give a satisfying answer for the fading issue... but I share a few thoughts and observations, adding to what I already wrote in an earlier post. The "problem" lies in the way you define the inverse as the inverse of the sweep in the freq domain regardless of its shape (enevelope), which gives by definition a true dirac unless you run into numerical issues.
I really don't see this as a "problem", the inverse of a sequence is uniquely defined. When not using the inverse you will introduce artifacts. I will rather LP, HP the result.

We really need a numerical example to justify the faded inverses used by DRC and others. I have tried several transfer functions that all validates my method

- Power expansion like y = 0.5x + 0.1x^2 + 0.2x^3 + 0.1x^4 +...
- Clipping to amplitude en after multiplied buy 1.25
- Introducing echoes y[i] = 0.5x[i] + 0.2x[i-100] - 0.2x[i-1000]

My problem is that they use intuitive arguments for fading the inverse. We need a transfer function / filter that will prove that using the real inverse is not working.

 6th July 2009, 10:04 AM #282 JohnPM   diyAudio Member   Join Date: Oct 2008 Fade in/out is only beneficial for people using the Farina method to generate the inverse as it reduces the transients at the beginning/end that otherwise cause errors in deconvolution. When the inverse is derived from the FFT of the stimulus fading in/out offers only cosmetic benefit, i.e. the FFT of the stimulus looks nicer and there is no possibility of an audible click at the end of a band limited sweep.
diyAudio Member

Join Date: Mar 2003
Location: Denmark, Copenhagen
Quote:
 Originally posted by JohnPM Fade in/out is only beneficial for people using the Farina method to generate the inverse as it reduces the transients at the beginning/end that otherwise cause errors in deconvolution. When the inverse is derived from the FFT of the stimulus fading in/out offers only cosmetic benefit, i.e. the FFT of the stimulus looks nicer and there is no possibility of an audible click at the end of a band limited sweep.
So you agree that fade in/out should be removed from HOLMImpulse?
(since I use FFT to create the exact inverse)

NB: When making LP/HP measurements in HOLMImpulse there is indirectly fading to the signal since the logsweep is convolved with a LP/HP FIR filter. The inverse is still the inverse of the full-range logsweep. Så the LP/HP is "simulating" a digital filter in the speaker.

JohnPM
diyAudio Member

Join Date: Oct 2008
Quote:
 Originally posted by askbojesen So you agree that fade in/out should be removed from HOLMImpulse?
Depends on how you plan to handle band limited sweeps. Personally I start the sweep at a frequency lower than the desired start and end it higher and apply fading to those parts outside the desired range, as I don't like a stimulus that can cause clicks.

 6th July 2009, 12:30 PM #285 tbrooke   diyAudio Member     Join Date: Apr 2007 Location: China Grove, NC Vista I have been following this thread but I have been unable to get HolmImpulse to run on my Vista system. Does anyone else have trouble? I have updated it several times and it updates but then won't load Tom
diyAudio Member

Join Date: Mar 2003
Location: Denmark, Copenhagen
Re: Vista

Quote:
 Originally posted by tbrooke I have been following this thread but I have been unable to get HolmImpulse to run on my Vista system. Does anyone else have trouble? I have updated it several times and it updates but then won't load
- Vista 32 or 64 ?
- Does the msi-package install?
- Any erros when starting?

diyAudio Member

Join Date: Mar 2003
Location: Denmark, Copenhagen
Quote:
 Originally posted by JohnPM Depends on how you plan to handle band limited sweeps. Personally I start the sweep at a frequency lower than the desired start and end it higher and apply fading to those parts outside the desired range, as I don't like a stimulus that can cause clicks.
Yes I get the idea now. so when I start the unfaded logsweep at 10 Hz, then I in fact start it at let us say 8 Hz and fade in. The real logsweep will still have a length of 2^N then extended with in-out-tfading. I might try this. Right now I have now frequency end - sweeping to Fs, so outfade is not relevant.

 6th July 2009, 03:15 PM #288 ilardi   diyAudio Member   Join Date: Mar 2006 Location: Westchester County, NY New Release 1.2.0.2 First, thanks for this great software. I find it works very well and has (I think) an intuitive interface. After struggling to perform measurements with SpeakerWorkshop for several years this is a huge improvement. Unfortunately, one of the two machines I use this on is a rather old desktop that does not include SSE2 (the other is an SSE2 enabled laptop). Thus I have what may seem to be a bit of an odd request. I downloaded the latest version and of course it does not work on my non SSE2 enabled desktop. Unless there is some way to make the new version run on my ancient hardware, I would really appreciate it if someone could please send me the install file for the previous version so that I could at least continue to use the desktop for measurements until I upgrade this machine in the fall. TIA Again, thanks for a really intriguing and useful piece of software!
diyAudio Member

Join Date: Mar 2003
Location: Denmark, Copenhagen
SSE2

Quote:
 Originally posted by ilardi Unfortunately, one of the two machines I use this on is a rather old desktop that does not include SSE2 (the other is an SSE2 enabled laptop). Thus I have what may seem to be a bit of an odd request. I downloaded the latest version and of course it does not work on my non SSE2 enabled desktop. Unless there is some way to make the new version run on my ancient hardware, I would really appreciate it if someone could please send me the install file for the previous version so that I could at least continue to use the desktop for measurements until I upgrade this machine in the fall.
Previous without SSE2:
http://www.holmacoustics.com/downloa...se-1.2.0.0.msi

I'll introduce the specific SSE2 version again from 1.2.0.4

tbrooke
diyAudio Member

Join Date: Apr 2007
Location: China Grove, NC
Re: Re: Vista

Quote:
 Originally posted by askbojesen - Vista 32 or 64 ? - Does the msi-package install? - Any erros when starting?
Vista 32 - I completely uninstalled and then installed it again and it does fine

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