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Measuring Holm Impulse ... need help
Measuring Holm Impulse ... need help
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Old 12th February 2018, 10:45 PM   #1
Flaxxer is offline Flaxxer  United States
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Default Measuring Holm Impulse ... need help

I'm measuring a two way, on a baffle. But I have a couple of questions.
I understand measuring the drivers independently. But when I measure them together, without xovers, do I need TWO channels of power to do so? Or do I hook both woofer and tweeter leads together on one channel?

I see I need to set gains ... and that is ALL it says. Okay ... set them to what level exactly? How do I set them, BEFORE I measure them ? It says to set the gains first, but the sweep sound, or blip sound, etc comes after I set the gains, according to instructions.

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Old 13th February 2018, 05:04 AM   #2
Zvu is offline Zvu  Serbia
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Extracting Z offset i guess.

I usually limit the sweep frequency first at 300Hz. Set the volume to get good S/N ratio (dependent on suroundings). Then i measure tweeter, then tweeter and woofer in parallel and then i meaaure woofer with and without 300Hz constraint. I do at least 3 sweeps of each. When you do the first sweep, the volume and speaker/microphone positions are not to be touched.
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Old 13th February 2018, 02:30 PM   #3
Flaxxer is offline Flaxxer  United States
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Thank you much. I have everything set up, and ready to measure this afternoon. See everyone after work, and measurements will be finished.
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Old 13th February 2018, 04:47 PM   #4
Draki is offline Draki  Macedonia
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Quote:
Originally Posted by Zvu View Post
Extracting Z offset
How do you do that in Holm? Is there a delay function (that I - obviously - can't locate or understand?) to help offset a driver? I have never used this with Holm, but would like to know. Thanks.
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Old 13th February 2018, 05:45 PM   #5
Zvu is offline Zvu  Serbia
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Nothing like that. I use Holm to derive files for the simulator. Z offset is derived in simulator. Importing midwoofer and tweeter responses and then i enter X and Y offset of midwoofer in regard to tweeter. Then i import captured response of tweeter and midwoofer in parallel. I start adding Z axis distance untill i get perfect match between overlay and sum curve from simulator.
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Last edited by Zvu; 13th February 2018 at 05:49 PM.
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Old 13th February 2018, 06:54 PM   #6
Draki is offline Draki  Macedonia
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Ah, OK then. I thought that it could be done in Holm, and couldn't figure out how. Clear now. Thanks.
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Old 13th February 2018, 10:56 PM   #7
Flaxxer is offline Flaxxer  United States
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Slight delay ... I can not find my USB A to B connector. I need one, to connect my two long USB cables for the mic. I guess I can break out the soldering gear, and absolutely MOLEST two perfectly fine USB cables, to make one long one.

I will get that done tonight. And will measure after work tomorrow.

I'm not sure about not moving the microphone "when I do the first sweep". I didn't think I had to move it at all for the three measurements, woofer tweeter, and summed? Zvu ... did you mean "after" the first measurement, do not move the mic?

When measuring outdoors, is it okay to have a wall about 15 feet BEHIND the speakers? That shouldn't affect the measurements, should it?

Last edited by Flaxxer; 13th February 2018 at 11:07 PM.
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Old 14th February 2018, 04:45 AM   #8
Zvu is offline Zvu  Serbia
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Wall that far away will not affect the measurements. Yes, i meant after the first measurement.
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