HOLMImpulse: Measurements in practice

[Pano]

Both very good ideas - thanks!

I did have to reset the gain on all these HP filters. It always came out ~2dB higher than the LP.
And it would be nice to be able to set the vertical scaling in the impulse. As you see, they didn't all come out the same.

[banana]

Very nice software.

Can I splice nearfield bass response into farfield response?
It would be nice to have SPL calibration function, so as to measure absolute loudness.

[KSTR]

Hi Ask,

After measuring a few electrical circuits to check if all is well I measured my coax nearfields today at ~25cm distance (but with a VERY crude "measurement" mic and q&d setup, you don't wanna know. Look at the low sensivity and the ~3% THD which is 2nd-HD mostly, dominated by the "mic pre" -- there wasn't any, that is --, the speakers themselves are not *that* bad, same for the mag response ).

Looks pretty nice, the 360° deg phase shift (centered to ~1.6kHz, which is the XO freq of these 2-ways) is clearly visible.

Some small issues I found:

- Impulse start estimation goes wrong. But then again, the shifter works well (a bit slow, though) and is a needed feature anyway. You have addressed that already, I see. EDIT: Sample offset isn't remembered between runs, although the display is fine. No deal, since it's a "relative" value anyway.

- I'd prefer to have a "not always in foreground" option, regarding some displayed windows.

- A initial delay would be a nice option (say 10sec, checkbox) to get out of the room etc before the sweep starts.

All in all, thumbs up! Stuff like the markers to locate the harmonics is really nice.

- Klaus

[askbojesen]

Originally posted by KSTR
Looks pretty nice, the 360� deg phase shift (centered to ~1.6kHz, which is the XO freq of these 2-ways) is clearly visible.

Yes! Exactly my point even with a Quick and dirty measurement you learn a lot

- Impulse start estimation goes wrong. But then again, the shifter works well (a bit slow, though) and is a needed feature anyway. You have addressed that already, I see. EDIT: Sample offset isn't remembered between runs, although the display is fine. No deal, since it's a "relative" value anyway.

Yes I know that... I have a new version ready later this evening handling this issue with time zero much better. A bit slow? if you set the measurement save length down it will be faster, but you will loose some data.

- A initial delay would be a nice option (say 10sec, checkbox) to get out of the room etc before the sweep starts.

Are you measuring lethal high volumes? - or why do you want to leave the room?

/Ask

[askbojesen]

http://www.holmacoustics.com/downloa.../ChangeLog.txt

The time zero detection failures in above measurements made by Klaus and panomaniac should be fixed now.
(Try measure again with the new default settings)


NB: If you start HOLMImpulse while online the autoupdater detects new version available

Version 1.1.5.6 (2009-06-16)

Features/Changes:
* 0dB Normalization optional (Enabled by default)
* Time window auto-apply optional (Enabled by default)
* Stich measurement with phase and gain optional
* Match measurement with phase optional
* Detection of time zero improved and configurable
* LogSweep highpass of the resulting impulse response

Bugfixes:
* Impulse domain: Autozoom for not normalized measurements
* Normalization (Shift dB did not include pregain)

Notes:
* Code-cleanup for normalization
* Remake of detection of time zero

[KSTR]

Thanks again, Ask!

I'll try it later today with a real measurement.

And I already have another (not so) silly "option/display request" (I can hear you yelling "OMG, please, not HE again" ) : Group delay, obtained from a reasonably smoothed phase response (to avoid the typical increase in "roughness" from the numerical derivation of gd(omega) = -d(phi)/d(omega)).

- Klaus

[KSTR]

To illustrate what the now featured binary export of the pulse response is good for (in terms of less overhead), look at this S-transform display of the measurement I've shown in post #23



The white line shows the maxima and resembles pretty well the shape of a LR24 group delay.

- Klaus

[dlr]

I've been curious, so I tried it a bit today. After some fumbling around with XP and one of the sound cards installed, I got a measurement. The card is a Turtle Beach Fiji (44.1K sampling limit) that I still use with LAUD for measurements. It has a built-in high quality mic pre-amp. I use a dual-boot setup for Win98/XP Home Edition.

I tried to do a calibrate of the card, but could get no further measurements afterwards. Other apps that used the card would not output, either. After unistalling/reinstalling it cleared up. I also made sure that windows was set to no sounds (it was blank in the setting). The card shouldn't need a calibration andyway as it should be down at most 0.5db at 20K.

The driver is mounted on a 2m x 2m baffle with the mic at 0.5m on-axis.

The problem I have is that below 1K, I don't get good agreement. It likely has to do with the window as this area changes more with the window selected. I believe that I used a half Blackman-Harris in LAUD. It would be good to have options for type of window (or have I missed that?).

The measurement capture:



Overlay of LAUD and HOLMImpulse (using Praxis for display only):



Dave

[EarlK]

Hi All,

- I downloaded the first version ( when the first thread came into existance ) & successfully ran the software for some time .

- This morning I "unintalled it" as preparation for installing the latest version being offered ( 1.1.6.6 ) .

- Well, I downloaded the installer / but it won't run ( & install the newer version ).
- I also tried running the installer ( not downloaded ) from within my browser ( IE8 ) .
- I am online when I attempt either insall approach.
- I get an official message box telling me the program is not a valid installer ( this box appears after the first official warning that the installer program is “unpublished” )

- I'm running Windows XP SP3 .
- I've turned off all aspects of Norton & rebooted ( just in case that's necessary )

- NOTE: I'm really a long-time Mac guy so I'm out here in lala land when it comes to installation problems such as this .

Can anyone help me out here ? Thanks Muchos for your time !

>, EarlK

[Pano]

Strange that it wouldn't work. I downloaded the 1st version and every one since has been an automatic update. Never unistalled anything. It just updates when I start the software.

So you still have the original version to try again? If that works, the software should take care of updating by itself when you start it.