HOLMImpulse: Measuring Frequency- & Impulse-Response

[Pano]

Spagetti Code?



Arrggh!!

[fb]

Thanks for free software!!!

[Shaun]

Originally posted by fb
Thanks for free software!!!

+1

It's not only free: it's also high quality. Thanks for sharing it with us.

[gedlee]

Hi Ask

Had a chance today to use the software a lot. Comments and bug list:

1) it is very hard to figure out the gain settings to get the maximum SNR and to drive the speaker at a given level. The system kept telling me that there was digital clipping but yet, another piece of software with the same levels settings in Windows, reported a very low level. Its baffling to me how I get exactly 2.83 volts into the system and then get all the gains set so that everbody (your software and others) are happy. In my other software SpectraLab, I can always see the waveform directly from the sound card. I can see cliping etc. and there is a meter at the bottom for setting the levels. In your software its a pure guess.

2) it gets the cleanest impulse responses that I have ever obtained - thats great

3) on my system there is an impulse at about -280 samples. I'm guessing that this is crosstalk or something bleading through the electronics. Normally this would not be a problem - just set it outside of the window - but you have to do this in "impulse" every time. The system always resets back to "auto window" setting that starts well ahead of 280 samples. You have to go in and turn off "Locked" each and every time you take a measurement. It doesn't stay "unlocked" and the window doesn't stay were you set it.

4) when saving the impulse responses you have to set the number of samples to export each time. It should remeber these settings.

Works pretty good otherwise. I like to do more myself than your "auto everything" approach however. I would prefer that the system let me set the window and not have the software find what it "thinks" that it should be.

[Pano]

I had a little trouble setting the levels, too. But as my sound card mic input has actual knobs on it, it didn't take long. I just ran a few sweeps and looked at the resulting levels.

The line input doesn't have a knob, just a -10dB or +4dB switch. In the +4dB position, I see a -10 level input as -10, so that seems to work well.

As for setting the window, you might try unchecking the "Auto apply time window" button on the lower right of the Setting tab. I never have, but maybe it will do what you want.

Great software - features getting better and better.
Next up - the distortion graphs!

[gedlee]

Originally posted by panomaniac

As for setting the window, you might try unchecking the "Auto apply time window" button on the lower right of the Setting tab. I never have, but maybe it will do what you want.

Exactly, and every time you make a measurement you have to go back and uncheck it. It doesn't stay unchecked.

[Pano]

Ah, I see. There are a number of settings like that.

[domtw]

I think it is an excellent way that the software development is going together with users' feedback.
In a while, it will be a great piece of software.
Thanks again!

[Shaun]

Originally posted by gedlee
1) it is very hard to figure out the gain settings to get the maximum SNR and to drive the speaker at a given level. The system kept telling me that there was digital clipping but yet, another piece of software with the same levels settings in Windows, reported a very low level. Its baffling to me how I get exactly 2.83 volts into the system and then get all the gains set so that everbody (your software and others) are happy. In my other software SpectraLab, I can always see the waveform directly from the sound card. I can see cliping etc. and there is a meter at the bottom for setting the levels. In your software its a pure guess.

I am using my SoundEasy hardware setup with HOLMimpulse. It includes attenuators to reduce the input signal to levels manageable by the sound card. In my sound card's mixer panel I am able to save particular mixer setting profiles. I believe that this is the common way to do it.

I think that having a level meter with clipping indicator in the software will be very helpful.

[askbojesen]

Originally posted by gedlee
1) it is very hard to figure out the gain settings to get the maximum SNR and to drive the speaker at a given level. The system kept telling me that there was digital clipping but yet, another piece of software with the same levels settings in Windows, reported a very low level. Its baffling to me how I get exactly 2.83 volts into the system and then get all the gains set so that everbody (your software and others) are happy. In my other software SpectraLab, I can always see the waveform directly from the sound card. I can see cliping etc. and there is a meter at the bottom for setting the levels. In your software its a pure guess.

You don't have to be guessing... See attachment
When I measure logsweep I use a full scaled PCM-signal - if you want a lower output you will need to adjust this using your windows mixer.

2) it gets the cleanest impulse responses that I have ever obtained - thats great

3) on my system there is an impulse at about -280 samples. I'm guessing that this is crosstalk or something bleading through the electronics. Normally this would not be a problem - just set it outside of the window - but you have to do this in "impulse" every time. The system always resets back to "auto window" setting that starts well ahead of 280 samples. You have to go in and turn off "Locked" each and every time you take a measurement. It doesn't stay "unlocked" and the window doesn't stay were you set it.

Point taken - will not auto window anything if you choose not to

4) when saving the impulse responses you have to set the number of samples to export each time. It should remeber these settings.

I'll keep it this way, I set the impulses to the maximum possible length, that is available

Works pretty good otherwise. I like to do more myself than your "auto everything" approach however. I would prefer that the system let me set the window and not have the software find what it "thinks" that it should be.

I'll try to make my "auto everything" optional for you experts

Thanks again for the feedback