Measuring comparisons with two mics - Page 4 - Home Theater Forum and Systems - HomeTheaterShack.com

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post #31 of 36 Old 09-22-12, 10:41 PM Thread Starter
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Re: Measuring comparisons with two mics

Quote:
Barleywater wrote: View Post
To get full range:

Measure Center or Floorstander <9 inches. Use measure or other method to insure each microphone is located in same position, hopefully to within 1/16th of an inch.

Repeat measurements using Sub. For Sub place each microphone about 1/2 inch to 1 inch from center of driver. Run Sub fairly loud. Idea is to get good excursion from driver, while keeping microphone from being hit.

Small differences in microphone placement have less impact on results with long wavelengths.

Since you've got 3-way Floorstander?, you may want to do measurements first with microphone (still <9 inch) located midway between mid and tweeter, and then at <1" for woofer of main. If main is run full range woofer may produce enough signal to get low end, otherwise do sub measurements too.

Results from measurements are level adjusted to match, at desired merge frequencies and merge function used to combine results. Merge frequencies are chosen where frequency responses of measurements ( sub v woofer, woofer v mid/tweeter) are both smooth, and hopefully similar in shape.

Using A/B math, level matching and merging may be used to produce calibration data. Saved data as text become calibration file.

Regards,

Andrew


Hi Andrew thank you.

Yes my speakers are 3 way Floorstanders (Energy Veritas 2.3i).
I run them full range.

Do i have to turn off the e.g. woofer or can i measure with all speakers operating, but different mic position?

Thanks again
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post #32 of 36 Old 09-22-12, 11:09 PM
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Re: Measuring comparisons with two mics

The less going on with each measurement, the better.

You are comparing now Omnimic V1 v V2? They have identical bodies? The closer they are to exact same location for each measurement, the better the A/B math works.

Do Energy Veritas have bi-amp terminal setup? Or by woofer are you referring to sub?

Andrew
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post #33 of 36 Old 09-25-12, 10:20 PM Thread Starter
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Re: Measuring comparisons with two mics

Hi Andrew

Yes hopefully will be able to.

The Veritas are bi-wired currently.

I have moved REW on to another laptop.

I am trying to do a soundcard calibration file for the other laptop.

I have attached some print/screen shots of the settings, please can you advise.

Thanks again


Laptop Settings.zip

Last edited by Phillips; 09-25-12 at 10:29 PM.
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post #34 of 36 Old 09-26-12, 05:27 AM
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Re: Measuring comparisons with two mics

Laptop Settings.zip is second Laptop? Does it have separate line in and mic input as seen in recording controls?

Master Volume Control: This is output. Master: not muted, wave out: not muted, line: muted.

Loopback calibration shows good signal management, and gross behavior, but is combo of output amplifier and input amplifier, actual input for measurement is USB and the amplifier built into Omnimic.

Andrew
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post #35 of 36 Old 09-26-12, 03:30 PM Thread Starter
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Re: Measuring comparisons with two mics

Quote:
Barleywater wrote: View Post
Laptop Settings.zip is second Laptop? Does it have separate line in and mic input as seen in recording controls?

Master Volume Control: This is output. Master: not muted, wave out: not muted, line: muted.

Loopback calibration shows good signal management, and gross behavior, but is combo of output amplifier and input amplifier, actual input for measurement is USB and the amplifier built into Omnimic.

Andrew

Hi Andrew yes it is the second laptop.

No it is only single in and out.

Looking last night there was stereo mix and mono mix as well (hidden in the advanced settings)

The laptop is XP and about 8-10 years old. I run it on power not battery.

Would it pay to download the Realtek High Definition Drivers, currently using ALi, old?

The general error i get is Excess Variation

You mentioned that Omnimic might have "different equalization", what do you mean, the calibration file?

Any thoughts?

Thanks again.

Last edited by Phillips; 09-26-12 at 04:17 PM. Reason: Add text
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post #36 of 36 Old 10-04-12, 03:45 PM Thread Starter
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Re: Measuring comparisons with two mics

Quote:
Barleywater wrote: View Post
if we sort out Omnimic response mystery

Andrew

Hi Andrew i have attached a mdat file with a REW measurement + Imported Omni Wav file 32 bit and a imported Omni software FRD file, all labelled.

All measurments were taken with the same mic / position, just different software.

Please could you look at these, very interesting, the REW + Omni Wav files look similar.

It is a generic mic.

I have seen something about response correction/calibration and not having sample clocks locked. Would this make a difference?

Thanks in advance

REW Comparison.zip

Last edited by Phillips; 10-04-12 at 05:40 PM. Reason: Add text
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