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Discussion Starter #1
I hope to keep things as simple as possible so anyone like myself can complete reasonable gated measurements of their drivers / speakers.


Equipment


Notebook or PC running Vista or XP

M-audio Mobilepre USB sound card (other sound cards will work too, I like this one because it has the phatom power for the mic built in)

ECM8000 Mic with calibration file (Dayton Mic EMM-6 would be fine too, it has a .cal file also).


Software


HOLMImpluse ( http://www.diyaudio.com/forums/multi...-response.html )

ARTA ( http://www.fesb.hr/~mateljan/arta/ )



Im going to go through HOLM first then ARTA.


Warning!! I have never figured out how to configure the sound card on ARTA or calibration the dBs on ARTA so that the dB Axis values are legit....everything else works and we can still measure not doing those two things.



Thanks goes out to HTGuide members Saurav, Dennis (catapult) and Brandon (Augerpro) for their incredible input in helping me do it right!
 

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Discussion Starter #2
mobilepre loop back calibration


Make sure phatom power is off. (red light on the front)




I use a 1/4" plug, its plugged into 1/L output (on back) and into ch1 inst/line input (on front).





HOLM at startup (Device and Signal tag)



- Make sure the input device and output device both have the mobilepre sound card selected.


- I use the Left channel (its default)


The rest of the options are all default.


I then click on the "Make" button beside "DAC-ADC calibration"




Click OK



Opps, signal too low



I go into Windows Vista Control panel and pull up the MobilePre control/properties program.



I adjust the "output Volume" to what I need...I had to adjust it down pretty low not to clip originally.


Now measure again, I get this result



HOLM will ask you if you want to use that Calibration, just say YES.


SoundCard calibration done!


Mic calibration....


Click on "import" button beside "Microphone Calibration" and select your .cal file. You should have a file for your Mic.
 

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Discussion Starter #3
Measurements...


I think the speaker should be atleast 4 feet from any wall, if that can not happen then we should have some accoustical absorption. I have 4" thick DIY panels behind my speaker and on the floor in front of the speaker. This definitely helps with reflections.


Rember to turn on the phantom power so that the mic works. Plug in the mic to Ch1 also if it wasnt already.


I use a stand for my mic and I place it 1 meter from the speaker and I try to center it between the Woofer and tweeter (Catapult's recommendations).


Check the "Device & Signal" tab to insure the calibrations are active.


You can also set the Start frequency on that tab..for tweeters you can always run up > 500Hz if you want.

Its at 10Hz in the picture.



In the Data analysis tab, use the "detect time zero" option and select "Causal Impulse" in the drop down.


Everything else is default



Also click on the "Options' menu item and change, Impulse Axis to "Impulse as time [millisec]"




You might want to change the starting Hz for tweeter measurements from 10Hz to 500Hz or so! Its in the Device & signal tab (shown earlier).


Now go to the Measurements tab



A, B, C should show Empty0 , Empty 1, Empty 2 respectively. NO measurements shown yet. Click on the Measure button under A.


This is our first measurements and its usually done on the tweeter alone so that we can set the zero time for the impulse. This is used to figure out the time delays between the tweeter and the woofer.


You should see something like this....



The Gate is easy to move and we will get into that later.


Next step is to lock the time alignment and measure the tweeter again then woofer.
 

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Discussion Starter #4
Locking Time aligment




- Goto the Data Analysis tab

- Click on "Time Zero Locked (time alignment)

- Click on "USE" next to "Last Dectected"


Now go back to the measurement tab and click on "measurement" button again for the "A". You are still measuring the tweeter and it will overwrite the last measurement.


You should have the same tweeter measurement as before with the impulse starting at 0.


Okay, tweeter measurement done for now. Lets measure the woofer! Make sure you set the starting frequency back down. Not to low though if you have ported speakers and you want to protect the drivers. Even 100Hz is fine since all LOW frequency measurements are going to be skewed in room.


Now go back to the measurement tab and click on "measurement" button again for the "B". HOLM will overlay the woofer measurement with the tweeter measurement.


like this




Congrats, you have done your first set of measurements
 

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Discussion Starter #5
Details on how to measure multiple positions in room to get an averaged response.

Quote:
Originally Posted by jtalden /forum/post/18449010


Yes, I use HOLMImpulse


Example:

Key elements:

1- take a measurement at 6 mic positions

use meas location 11,12,13 for mic positions 1,2,3 (I name them 1,2,3 to keep track)

use meas location 16,17,18 for mic positions 4,5,6 (I name them 4,5,6 to keep track)

2- display in A,B,C: locations 11,12,13 and set options to raw, select Highest Positive Peak, then autoselect

3- confirm that the 3 impulse responses are all aligned with each other as shown below (important)




4- now Change C to L14 (location 14)

5- select manipulation, Sum C = A+B

6- change A to L13, B to L14, C to L15

7- select manipulation, Sum A+B=C

You now have the sum of 3 impulse responses in L15 like this:




[Now we repeat for the other 3 mic positions]

8- display in A,B,C: locations 16,17,18 and set options to raw, select Highest Positive Peak, then autoselect

9- confirm that the 3 impulse responses are all aligned with each other as shown below (important)

10- Change C to L19

11- select manipulation, Sum C = A+B

12- change A to L18, B to L19, C to L20

13- select manipulation, Sum A+B=C

[You now have the sum of all 3 impulse responses in L20]

14- change A to L15, B to L20, C to L2 (or anyplace you want)

15- confirm that the 2 impulse responses are aligned and you are still set to raw like this:




16- select manipulation, Sum C = A+B

You now have the summed impulse response saved in L2. You can now rename it and filter it as you like.


I believe this summed 6-pos impulse response provides the correct average amplitude and phase response except that it is increased in amplitude by approximately 15.563 dB [20*LOG(6)]. You can just scale down again if you like, but I see no reason as the amplitude scale is arbitrary to start with.


This process sounds long and complicated and it goes slowly at first. With some practice it goes quickly. I complete a 6 measurement average in maybe 3-5 minutes so it’s not really so bad. I use HOLM as it carries along the phase response. REW is a little easier to use but just provides amplitude response.


I did this “guide” quickly and mostly off the top of my head. There are many little details to watch and I may have forgotten to mention one or two. Let me know if you have questions.
 

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Seriously though I'm working with these 2 programs lately and a thread like this could be helpful. Holm seems very easy to use, but there are a few things that I wish it would do that it doesn't seem to, or I haven't figured out yet. ARTA seems more powerful and advanced, but the user interface seems very confusing. It sometimes takes 15min and a trip through the help manual to figure out how to set up a measurement.
 

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Discussion Starter #12

I have always wanted this thread to exist somewhere and since I have been finally successful at doing gated measurements (the right way) I figured I would create something that should be easy to follow.
 

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Thanks! I'm looking forward to this thread (and I'll contribute if possible).


Absolute SPLs require a meter (preferably an accurate one) so that levels can be set. Though I have a little bit of experience with HolmImpulse, I have no direct measurement experience with either of these packages yet. If all goes well, I should be doing quite a bit of measurements in the next few weeks.
 

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Discussion Starter #14

Quote:
Absolute SPLs require a meter (preferably an accurate one) so that levels can be set

Neither package calibrates based on an SPL meter like REW does.


HOLM does not have a dB axes actually, It simply sets the start at 0 dB change.



ARTA calibrates based on Voltages and I do not have a clue about that.
 

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Quote:
Originally Posted by penngray /forum/post/18335887


Neither package calibrates based on an SPL meter like REW does.


HOLM does not have a dB axes actually, It simply sets the start at 0 dB change.



ARTA calibrates based on Voltages and I do not have a clue about that.

That's one of my gripes with Holm actually. No spl scale. I've not tried to calibrate ARTA yet either.
 

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Quote:
Originally Posted by Ricci /forum/post/18336052


That's one of my gripes with Holm actually. No spl scale. .

There's really no major need for it. I take a reading with a meter at 100Hz and use that as my calibration figure, tweaking the measurement level to end up with 0dB at 100Hz.
 

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Quote:
Originally Posted by Bill Fitzmaurice /forum/post/18336422


There's really no major need for it. I take a reading with a meter at 100Hz and use that as my calibration figure, tweaking the measurement level to end up with 0dB at 100Hz.

"Absolute SPLs require a meter (preferably an accurate one) so that levels can be set."


We're saying the same thing here. I do my measurements similarly.


Any relative measurement can be referenced to reality (and should be - as a sanity check), so long as the results are presented in units we can directly measure.
 

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Discussion Starter #18

Quote:
Originally Posted by Ricci /forum/post/18336052


That's one of my gripes with Holm actually. No spl scale. I've not tried to calibrate ARTA yet either.

Its not a big deal, I can do sensitivity measurements with WT3. All other measurements have no SPL requirements.
 

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Quote:
Originally Posted by penngray /forum/post/18337263


Its not a big deal, I can do sensitivity measurements with WT3.

In the box? I don't have it but I thought WT3 only did a calculated base sensitivity from the measured specs.
 

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Discussion Starter #20

Quote:
Originally Posted by Bill Fitzmaurice /forum/post/18338335


In the box? I don't have it but I thought WT3 only did a calculated base sensitivity from the measured specs.

Yes, that is what it does.
 
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