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Thanks LastButNotLeast, I ended up muddling around the site last month when I posted this and finding that link.

I've ended up with 2 of the ECM8000's that I've had professionally calibrated, 2 boom stands and an Alesis iO2 USB interface. I'm experimenting with ARTA, REWv.5, TrueRTA and ETFv.5 software.

I do a bit of speaker modding as well as solving mode problems, and with 2 mics I'm able to take Stereo Listening Position measurments as well as standard Nearfield and 1Meter/1Watt measurements. I'm having a blast experimenting with this gear and am really pleased with the cost/performance ratio.
 

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hi im looking for a mic for a mini lap acer.. im trying to use it in car audio.. i live in mexico and my lap burns when i try to use it with the mic it has... but then i read i cant use it with it... so i need one.. has anyone a mic it wont use anymore?.. i cant pay much for it.. but if you tell me how much i save the money to get it... thnks..
 

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Hi Beto,

The only cheap mic that can be used with REW (assuming that’s what you want it for) is the Radio Shack SPL meter. If your computer has a line input. If it doesn’t you’ll also need a USB sound card.

But the Radio Shack meter is only good for low frequency (subwoofer) measurements. If you want full range measurements, there is no cheap option. Even if you use our generic calibration file, the ECM8000 mic with a suitable sound card that has a pre-amp and phantom power will cost at least $100.

Regards,
Wayne
 

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Hi again.. thanks for the info.. look i dont know english so much but i just read abouot be a moderator.. what this mean? i dont under stand.. besides..how can i help you if you are kings in this work? you are the bible fro all knowlege.. i dont even know how to fix my pc.. or how to calibrate a car.. sorry i cant help you because i dont know all you do know.. thnks..
 

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The Basic + adds calibration for 45° and 90° mic orientations, in addition to the 0° orientation of the Basic calibration package. However, for frequency response measurements you typically want 0° orientation – i.e., pointed at the signal source. More reading as to the “whys” and “wherefores” here.

Regards,
Wayne
 

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The Basic + adds calibration for 45° and 90° mic orientations, in addition to the 0° orientation of the Basic calibration package. However, for frequency response measurements you typically want 0° orientation – i.e., pointed at the signal source. More reading as to the “whys” and “wherefores” here.

Regards,
Wayne
Thanks Wayne.

The more you go into EQ the deeper it gets that's for sure, it's like, just as you learn how to open one door another comes along with a bigger lock, 'so to speak'. :eek:



The short answer for subwoofer measurements is, it doesn’t matter.

If you’re doing full-range measurements (your main-channel speakers), the short answer is, you only point the mic towards the ceiling if you’re using a 90-degree incident (vertical) calibration file.

Horizontal orientation with the mic on-axis to the sound source (0-degrees incident) has been the traditional method for full-range, free-field measurement, where the room was an open space relatively free of reflections. However, that’s mainly because most stand-alone RTAs (which until several years ago was about the only thing available) came with mics that were calibrated for on-axis measurements.

Some RTA manufacturers offered the option of 90-degree orientation for random incident measurements (aka diffuse field), where the sound arrives from all directions more or less simultaneously, with equal probability and level. In other words, an exceedingly reverberant environment. Random-incident measurements required a different capsule for the measurement mic (which the manufacturer made available), for reason of the specific calibration as well as a housing better suited for 90-degree orientation.

That just refers to the mic’s position during its calibration, however. Everything I’ve seen for actual “in the field” measurements says the standard protocol for horizontal (on-axis) measuring is 20 degrees, and 70 degrees for vertical (i.e., angled slightly forwards towards the sound source). This may have something to do with compensating for interference from the mic’s housing with the sound waves, I forget exactly why.

The ready availability these days of mics with 90-degree calibration certainly opens up more measurement options. Others have their opinions, and maybe they’ll weigh in, but mine is that you will generally get the best results with on-axis measurements. It should be a no brainer to figure out that the home theater environment, while certainly not totally free of reflections and reverberation, more closely resembles a free-field environment than a random-incident environment.

Vertical orientation may add more upper-frequency information from ceiling reflections than you’d get with on-axis, and as such will probably influence what the RTA displays. How much so will depend on your particular room – how “live” it is, the height of the ceiling in relation to the distance between the sound source (speaker) and measurement mic (i.e. inside or outside the “first reflection” zone), etc. Even though the ECM8000 is omnidirectional, its capsule is rather large for a measurement mic. As a result, its off-axis response (compared to on-axis) starts skewing as low as 3 kHz. So differences >3 kHz are what you might see with horizontal vs. vertical readings. (Smaller-capsule omni mics typically retain uniform 0 vs. 90-degree response at least an octave higher.)

Regards,
Wayne
 

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Hi.

I have just received my ECM800 'Basic' Mic from Cross Spectrum. It comes with two Mic Cal files. I was wandering which Cal file I load into REW, either the 'narrow band response 0 degree', or the 'one third octave band response 0 degree'.
:scratch:
 

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There should have been a “Read me” file on the calibration disc that includes the following:

The narrow-band-response.FRD files are designed for use with measurement and analysis programs like Room EQ Wizard, ARTA, and FuzzMeasure Pro that can make use of fine-tuned correction curves. The one-third-octave-response.FRD files are designed for applications where additional smoothing is warranted or for comparision with criteria given in terms of 1/3-octave bands.
Regards,
Wayne
 

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There should have been a “Read me” file on the calibration disc that includes the following:



Regards,
Wayne
Thanks Wayne, this is what mine reads:

Frequency Response Files:
The narrow band response x degree.FRD files contain the narrowband (FFT) frequency response response
calibration files for the microphone at an angle of 0 degree incidence (microphone pointed directly at the sound
source), 45 degrees incidence (microphone pointed diagonally with respect to the sound propagation path of the
source) and 90 degrees incidence (microphone perpendicular to the sound propagation path of the source).

The one third octave band response x degree.FRD files contain the one-third octave band frequency response
response calibration files for the microphone at an angle of 0 degree incidence (microphone pointed
directly at the sound source), 45 degrees incidence (microphone pointed diagonally with respect to the sound
propagation path of the source) and 90 degrees incidence (microphone perpendicular to the sound propagation
path of the source).
P.
 

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Thanks Wayne, this is what mine reads:

Frequency Response Files:
The narrow band response x degree.FRD files contain the narrowband (FFT) frequency response response
calibration files for the microphone at an angle of 0 degree incidence (microphone pointed directly at the sound
source), 45 degrees incidence (microphone pointed diagonally with respect to the sound propagation path of the
source) and 90 degrees incidence (microphone perpendicular to the sound propagation path of the source).

The one third octave band response x degree.FRD files contain the one-third octave band frequency response
response calibration files for the microphone at an angle of 0 degree incidence (microphone pointed
directly at the sound source), 45 degrees incidence (microphone pointed diagonally with respect to the sound
propagation path of the source) and 90 degrees incidence (microphone perpendicular to the sound propagation
path of the source).
P.
The part Wayne quoted is on Page 2.
 

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The part Wayne quoted is on Page 2.
:doh:

Sorry to continue sounding thick:

So in the REW/Preferences/Analysis

When running REW with no smoothing then use 'The narrow band response'

And use the one third octave band response when applying only the 1/3rd. What about the other smoothing frequency responces?
 

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:doh:

Sorry to continue sounding thick:

So in the REW/Preferences/Analysis

When running REW with no smoothing then use 'The narrow band response'

And use the one third octave band response when applying only the 1/3rd. What about the other smoothing frequency responces?
For REW, just use the narrow band correction curve, no matter the smoothing you're using.
 

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Hi guys,

I don't know if this has been discussed before (not that I haven't searched) but in my quest in finding an affordable and convenient microphone calibration (by substitution) solution I stumbled across this:


(I don't know why the images are not showing up, maybe it's the forum censorship, just do a google on "rockwool tube")
It's rockwool tube used for plumbing purposes, it can be acquired in all kinds of thickness, diameter, density, with or without the foil shell. The idea is that it can be used as a anechoic chamber for high frequencies (best case scenario 1kHz and up) between the tweeter and the microphone.

Now while this is obviously an anechoic "chamber" at certain frequencies, the fact that it's quite narrow will inevitably affect the frequency response (some sort of high-pass filter?). On the positive side, reflections may get attenuated, compared to free air measurements, resulting in smoother overall response.

Also, correct me if I'm wrong but a very reliable and precise method of low end calibration should be nearfield measurement, as described in Claudio Negro's page.

Any comments appreciated
K.
 

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My Cross Spectrum ''Basic Plus'' ECM8000 will arrive next week. I want to make measurements with this mic+REW+my Tascam 122 MKII. Can you guys tell me what I need to do FIRST with the ECM8000 before I can start making measurements? I only know that I will need to plug in the ECM8000 to the L or R xlr input of my Tascam 122 MKII but that s all I know :)

Thanks guys!
 

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The first thing you'll need to do is copy the calibration files from the disc that will come with the mic to the REW Calibration Files folder on your computer. Then, open REW and go to Preferences/Mic-Meter and open the "narrow_band_response_0_degree.cal" file.

If you're still lost at this point, then you obviously haven't studied the Help Files. :)

Regards,
Wayne
 
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